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{{Short description|Human-caused changes to climate on Earth}}
]
{{About|the present-day human-induced rise in global temperatures|natural historical climate trends|Climate variability and change}}
'''HEYHEYHEY'''
{{Redirect|Global warming||Climate change (disambiguation)|and|Global warming (disambiguation)}}
'''''Global warming''''' is a term used to describe an increase over ] of the ] of ] and ]s. Global warming theories attempt to account for the rise in average global temperatures since the late ] <!-- The following is an approximate 95% confidence interval, please DO NOT replace by 0.4-0.8 -->(0.6 ± 0.2°C) and assess the extent to which the effects are due to human causes. The most common global warming theories ] temperature increases to increases in the ] caused primarily by anthropogenic (human-generated) ] (CO<sub>2</sub>) and to possible increases in ].
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] over the past 50 years.<ref>{{Cite web |title=GISS Surface Temperature Analysis (v4) |url=https://data.giss.nasa.gov/gistemp/maps/index_v4.html |access-date=12 January 2024 |website=NASA}}</ref> The ] has warmed the most, and temperatures on land have generally increased more than ]s.]]
]s, driven by estimates of increasing CO<sub>2</sub> and to a lesser extent by generally decreasing sulfate aerosols, predict that temperatures will increase (with a range of 1.4°C to 5.8°C for change between 1990 and 2100 ]). Much of this uncertainty results from not knowing future CO<sub>2</sub> emissions, but there is also uncertainty about the accuracy of climate models. ] predict that even if levels of greenhouse gases and solar activity were to remain constant, the global climate is committed to 0.5°C of warming over the next one hundred years due to the lag in warming caused by the oceans.
]. Natural forces cause some variability, but the 20-year average shows the progressive influence of human activity.<ref>{{harvnb|IPCC AR6 WG1 Summary for Policymakers|2021|loc=SPM-7}}</ref>]]
<!--Please do not change the content in the lead section without first proposing the change on the talk page, and please limit overall length to under 500 words.-->
Present-day '''climate change''' includes both '''global warming'''—the ongoing increase in ]—and its wider effects on ]. ] also includes previous long-term changes to Earth's climate. The current rise in global temperatures is ], especially ] burning since the ].<ref>{{harvnb|Forster|Smith|Walsh|Lamb|2024|p=2626}}: "The indicators show that, for the 2014–2023 decade average, observed warming was 1.19 °C, of which 1.19 °C was human-induced."</ref><ref name=Lynas_2021>{{cite journal |last1=Lynas |first1=Mark |last2=Houlton |first2=Benjamin Z. |last3=Perry |first3=Simon |title=Greater than 99% consensus on human caused climate change in the peer-reviewed scientific literature |journal=] |date=19 October 2021 |volume=16 |issue=11 |page=114005 |doi=10.1088/1748-9326/ac2966 |bibcode=2021ERL....16k4005L |s2cid=239032360 |doi-access=free |issn = 1748-9326}}</ref> Fossil fuel use, ], and some ] and ] practices release ]es.<ref name="Our World in Data-2020">{{harvnb|Our World in Data, 18 September|2020}}</ref> These gases ] that the Earth ] after it warms from ], warming the lower atmosphere. ], the primary greenhouse gas driving global warming, ] and is at levels not seen for millions of years.<ref>{{harvnb|IPCC AR6 WG1 Technical Summary|2021|p=67}}: "Concentrations of {{CO2}}, methane ({{CH4}}), and nitrous oxide ({{N2O}}) have increased to levels unprecedented in at least 800,000 years, and there is high confidence that current {{CO2}} concentrations have not been experienced for at least 2 million years."</ref>


Climate change has an increasingly large ]. ], while ]s and ]s are becoming more common.<ref>
Although the discussion of global warming often focuses on temperature, global warming or any climate change may cause changes in other things as well, including the ], ], weather patterns, etc. These may impact on human activity via floods, droughts, heat waves, declining agricultural yields, etc.
* {{harvnb|IPCC SRCCL|2019|p=7}}: "Since the pre-industrial period, the land surface air temperature has risen nearly twice as much as the global average temperature (high confidence). Climate change... contributed to desertification and land degradation in many regions (high confidence)."
* {{harvnb|IPCC AR6 WG2 SPM|2022|p=9}}: "Observed increases in areas burned by wildfires have been attributed to human-induced climate change in some regions (medium to high confidence)"</ref> ] has contributed to thawing ], ] and ].<ref>{{harvnb|IPCC SROCC|2019|p=16}}: "Over the last decades, global warming has led to widespread shrinking of the cryosphere, with mass loss from ice sheets and glaciers (very high confidence), reductions in snow cover (high confidence) and Arctic sea ice extent and thickness (very high confidence), and increased permafrost temperature (very high confidence)."</ref> Higher temperatures are also causing ], droughts, and other ].<ref>{{Harvnb|IPCC AR6 WG1 Ch11|2021|p=1517}}</ref> Rapid environmental change in ], ]s, and ] is forcing many species to relocate or ].<ref>{{cite web|author=EPA|date=19 January 2017|title=Climate Impacts on Ecosystems|url=https://19january2017snapshot.epa.gov/climate-impacts/climate-impacts-ecosystems_.html#Extinction|url-status=live|archive-url=https://web.archive.org/web/20180127185656/https://19january2017snapshot.epa.gov/climate-impacts/climate-impacts-ecosystems_.html#Extinction|archive-date=27 January 2018|access-date=5 February 2019|quote=Mountain and arctic ecosystems and species are particularly sensitive to climate change... As ocean temperatures warm and the acidity of the ocean increases, bleaching and coral die-offs are likely to become more frequent.}}</ref> Even if efforts to minimize future warming are successful, some effects will continue for centuries. These include ], ] and ].<ref>{{harvnb|IPCC SR15 Ch1|2018|p=64}}: "Sustained net zero anthropogenic emissions of {{CO2}} and declining net anthropogenic non-{{CO2}} radiative forcing over a multi-decade period would halt anthropogenic global warming over that period, although it would not halt sea level rise or many other aspects of climate system adjustment."</ref>


Climate change ] with increased ], extreme heat, increased ] and ] scarcity, more disease, and ]. ] and conflict can also be a result.<ref>
==Terminology==
* {{harvnb|Cattaneo|Beine|Fröhlich|Kniveton|2019}}
* {{harvnb|IPCC AR6 WG2 SPM|2022|p=15}}
* {{harvnb|IPCC AR6 WG2 Technical Summary|2022|p=53}}</ref> The ] calls climate change one of the biggest threats to ] in the 21st century.<ref name=WHO_Nov_2023>{{harvnb|WHO, Nov|2023}}</ref> Societies and ecosystems will experience more severe risks without ].<ref>{{harvnb|IPCC AR6 WG2 SPM|2022|p=19}}</ref> ] through efforts like ] measures or ] partially reduces climate change risks, although some limits to ] have already been reached.<ref>
* {{harvnb|IPCC AR6 WG2 SPM|2022|pp=21–26}}
* {{harvnb|IPCC AR6 WG2 Ch16|2022|p=2504}}
* {{harvnb|IPCC AR6 SYR SPM|2023|pp=8–9}}: "Effectiveness<sup>15</sup> of adaptation in reducing climate risks<sup>16</sup> is documented for specific contexts, sectors and regions (high confidence) ... Soft limits to adaptation are currently being experienced by small-scale farmers and households along some low-lying coastal areas (medium confidence) resulting from financial, governance, institutional and policy constraints (high confidence). Some tropical, coastal, polar and mountain ecosystems have reached hard adaptation limits (high confidence). Adaptation does not prevent all losses and damages, even with effective adaptation and before reaching soft and hard limits (high confidence)."</ref> Poorer communities are responsible for ], yet have the least ability to adapt and are most ].<ref>{{cite web |last1=Tietjen |first1=Bethany |title=Loss and damage: Who is responsible when climate change harms the world's poorest countries? |url=https://theconversation.com/loss-and-damage-who-is-responsible-when-climate-change-harms-the-worlds-poorest-countries-192070 |website=] |access-date=30 August 2023 |date=2 November 2022}}</ref><ref>{{cite web |title=Climate Change 2022: Impacts, Adaptation and Vulnerability |url=https://www.ipcc.ch/report/sixth-assessment-report-working-group-ii/ |publisher=] |access-date=30 August 2023 |date=27 February 2022}}</ref>
<noinclude>{{multiple image
| perrow = 1 / 2
| total_width = 310
| image1 = Bobcat Fire, Los Angeles, San Gabriel Mountains.jpg
| alt1 = Bobcat Fire in Monrovia, CA, September 10, 2020
| image2 = Bleached colony of Acropora coral.jpg
| alt2 = Bleached colony of Acropora coral
| image4 = California Drought Dry Lakebed 2009.jpg
| alt4 = A dry lakebed in California, which is experiencing its worst megadrought in 1,200 years.<ref>{{cite web |url=https://www.cbsnews.com/amp/news/water-cutbacks-california-6-million-people-drought/ |title=California is rationing water amid its worst drought in 1,200 years |first=Irina |last=Ivanova |publisher=] |date=June 2, 2022}}</ref>
| footer = Examples of some ]: ] intensified by heat and drought, ] occurring more often due to ]s, and worsening ]s compromising water supplies.
}}
</noinclude>
Many climate change impacts have been observed in the first decades of the 21st century, with 2023 the warmest on record at +{{convert|1.48|C-change}} since regular tracking began in 1850.<ref>{{cite web |title=2023 confirmed as world's hottest year on record |url=https://www.bbc.com/news/science-environment-67861954 |publisher=] |first1=Mark |last1=Poynting |first2=Erwan |last2=Rivault |access-date=13 January 2024 |date=10 January 2024}}</ref><ref>{{Cite web |date=21 April 2023 |title=Human, economic, environmental toll of climate change on the rise: WMO|url=https://news.un.org/en/story/2023/04/1135852 |access-date=11 April 2024 |publisher=United Nations |language=en}}</ref> Additional warming will increase these impacts and can trigger ], such as melting all of the ].<ref>{{harvnb|IPCC AR6 WG1 Technical Summary|2021|p=71}}</ref> Under the 2015 ], nations collectively agreed to keep warming "well under 2&nbsp;°C". However, with pledges made under the Agreement, global warming would still reach about {{convert|2.8|C-change}} by the end of the century.<ref name="UNEP2024">{{harvnb|United Nations Environment Programme|2024|p=XVIII}}: "The full implementation and continuation of the level of mitigation effort implied by unconditional or conditional NDC scenarios lower these projections to 2.8&nbsp;°C (range: 1.9–3.7) and 2.6&nbsp;°C (range: 1.9–3.6), respectively. All with at least a 66 per cent chance."</ref> Limiting warming to 1.5&nbsp;°C would require halving emissions by 2030 and achieving ] emissions by 2050.<ref>{{harvnb|IPCC SR15 Ch2|2018|pp=95–96}}: "In model pathways with no or limited overshoot of 1.5&nbsp;°C, global net anthropogenic {{CO2}} emissions decline by about 45% from 2010 levels by 2030 (40–60% interquartile range), reaching net zero around 2050 (2045–2055 interquartile range)"</ref><ref>{{harvnb|IPCC SR15|2018|loc=SPM C.3|p=17}}: "All pathways that limit global warming to 1.5&nbsp;°C with limited or no overshoot project the use of carbon dioxide removal (CDR) on the order of 100–1000 Gt{{CO2}} over the 21st century. CDR would be used to compensate for residual emissions and, in most cases, achieve net negative emissions to return global warming to 1.5&nbsp;°C following a peak (high confidence). CDR deployment of several hundreds of Gt{{CO2}} is subject to multiple feasibility and sustainability constraints (high confidence)."</ref>


] by ] and switching to energy sources that do not produce significant carbon pollution. These energy sources include ], ], ], and ].<ref>
Use of the term "global warming" generally implies a human influence &mdash; the more neutral term ] is usually used for a change in climate with no presumption as to cause and no characterization of the kind of change involved, such as the ]s. Note, however, that there is one important exception to this: the ] uses "climate change" for human caused change and "climate variability" for non-human caused change . Sometimes the term "anthropogenic climate change" is used to indicate the presumption of human influence.
* {{harvnb|IPCC AR5 WG3 Annex III|2014|p=1335}}
* {{harvnb|IPCC AR6 WG3 Summary for Policymakers|2022|pp=24–25}}
* {{harvnb|IPCC AR6 WG3 Technical Summary|2022|p=89}}</ref> Cleanly generated electricity can replace fossil fuels for ], ], and running industrial processes.<ref>{{harvnb|IPCC AR6 WG3 Technical Summary|2022|p=84}}: "Stringent emissions reductions at the level required for 2°C or 1.5°C are achieved through the increased electrification of buildings, transport, and industry, consequently all pathways entail increased electricity generation (high confidence)."</ref> Carbon can also be ], for instance by ] and farming with methods that ].<ref>
* {{harvnb|IPCC SRCCL Summary for Policymakers|2019|p=18}}
* {{harvnb|IPCC AR6 WG3 Summary for Policymakers|2022|pp=24–25}}
* {{harvnb|IPCC AR6 WG3 Technical Summary|2022|p=114}}</ref>


{{TOC level|3}} <!--Please do not uncollapse the TOC without prior discussion (see discussion on talk page from May 2022).-->
== Scientific opinion ==
{{seemain|scientific opinion on climate change}}
The current ] on global warming might be summarized by the findings of the ] (IPCC). In their ], they concluded that "most of the warming observed over the last 50 years is ]". Naomi Oreskes 2004 survey of scientific literature concluded


== Terminology ==<!--An excerpt of this section has been added to ] in September 2022.-->
The IPCC does not commission or carry out research itself, but rather brings together hundreds of scientists to review and interpret previously published research. This group then issues reports to summarize the state of climate change science and, when possible, expresses the consensus of IPCC participants. The 1995 IPCC report concluded that ''"The balance of evidence suggests a discernible human influence on global climate"''; this was strengthened in the 2001 ] to ''"There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities"''. The Fourth Assessment Report of the IPCC is scheduled for November 2007.


Before the 1980s it was unclear whether the warming effect of ] was stronger than the ] in ]. Scientists used the term ''inadvertent climate modification'' to refer to human impacts on the climate at this time.<ref name="Conway 2008">{{harvnb|NASA, 5 December|2008}}.</ref> In the 1980s, the terms ''global warming'' and ''climate change'' became more common, often being used interchangeably.<ref>{{harvnb|NASA, 7 July|2020}}</ref><ref>{{Harvnb|Shaftel|2016}}: "{{thinsp}}'Climate change' and 'global warming' are often used interchangeably but have distinct meanings.&nbsp;... Global warming refers to the upward temperature trend across the entire Earth since the early 20th century&nbsp;... Climate change refers to a broad range of global phenomena&nbsp;... include the increased temperature trends described by global warming."</ref><ref>{{harvnb|Associated Press, 22 September|2015}}: "The terms global warming and climate change can be used interchangeably. Climate change is more accurate scientifically to describe the various effects of greenhouse gases on the world because it includes extreme weather, storms and changes in rainfall patterns, ocean acidification and sea level.".</ref> Scientifically, ''global warming'' refers only to increased surface warming, while ''climate change'' describes both global warming and its effects on Earth's ], such as precipitation changes.<ref name="Conway 2008"/>
In 2004 Naomi Oreskes published a survey of 928 peer-reviewed scientific abstracts on climate change, concluding that there is a scientific consensus on the reality of anthropogenic climate change .


''Climate change'' can also be used more broadly to include ] that have happened throughout Earth's history.<ref>{{Harvnb|IPCC AR5 SYR Glossary|2014|p=120}}: "Climate change refers to a change in the state of the climate that can be identified (e.g., by using statistical tests) by changes in the mean and/or the variability of its properties and that persists for an extended period, typically decades or longer. Climate change may be due to natural internal processes or external forcings such as modulations of the solar cycles, volcanic eruptions and persistent anthropogenic changes in the composition of the atmosphere or in land use."</ref> ''Global warming''—used as early as 1975<ref name=Science_Broecker_19750808>{{cite journal |last1=Broecker |first1=Wallace S. |title=Climatic Change: Are We on the Brink of a Pronounced Global Warming? |journal=] |date=8 August 1975 |volume=189 |issue=4201 |pages=460–463 |doi=10.1126/science.189.4201.460 |jstor=1740491 |pmid=17781884 |bibcode=1975Sci...189..460B |s2cid=16702835 |url=https://www.jstor.org/stable/1740491}}</ref>—became the more popular term after ] climate scientist ] used it in his 1988 testimony in the ].<ref name="history.aip.org2">{{harvnb|Weart "The Public and Climate Change: The Summer of 1988"}}, .</ref> Since the 2000s, ''climate change'' has increased usage.<ref>{{harvnb|Joo|Kim|Do|Lineman|2015}}.</ref> Various scientists, politicians and media may use the terms '']'' or '']'' to talk about climate change, and may use the term ''global heating'' instead of ''global warming''.<ref>{{harvnb|Hodder|Martin|2009}}</ref><ref>{{harvnb|BBC Science Focus Magazine, 3 February|2020}}</ref>
==Temperature records==


== Global temperature rise ==
]
{{Further|Global surface temperature}}
The period of ''time'' over which the change has been observed may vary according to the focus of the user of the term: sometime since the ], or since the beginning of an approximately global ] in about ]; or over the past century; or the most recent 50 years.


=== Temperatures prior to present-day global warming ===
Over the past century or so the global (land and sea) temperature has increased by approximately 0.6 ± 0.2°C . Over the past 1-2 thousand years the temperature has been relatively stable, with various (possibly local) fluctuations, such as the ] or the ].
{{Main|Climate variability and change|Temperature record of the last 2,000 years|Paleoclimatology}}
] reconstruction over the last 2000 years using proxy data from tree rings, corals, and ice cores in blue.<ref>{{harvnb|Neukom|Barboza|Erb|Shi|2019b}}.</ref> Directly observed data is in red.<ref name="nasa temperatures">{{cite web |title=Global Annual Mean Surface Air Temperature Change |url=https://data.giss.nasa.gov/gistemp/graphs_v4/ |access-date=23 February 2020 |publisher=]}}</ref>]]
Over the last few million years the climate cycled through ]. One of the hotter periods was the ], around 125,000 years ago, where temperatures were between 0.5&nbsp;°C and 1.5&nbsp;°C warmer than before the start of global warming.{{sfn|IPCC AR6 WG1 Ch2|2021|pp=294, 296}} This period saw sea levels 5 to 10 metres higher than today. The most ] 20,000 years ago was some 5–7&nbsp;°C colder. This period has sea levels that were over {{convert|125|m|ft}} lower than today.{{sfn|IPCC AR6 WG1 Ch2|2021|p=366}}


Temperatures stabilized in the current interglacial period beginning ].<ref>{{cite journal |last1=Marcott |first1=S. A. |last2=Shakun |first2=J. D. |last3=Clark |first3=P. U. |last4=Mix |first4=A. C. |title=A reconstruction of regional and global temperature for the past 11,300 years |journal=] |year=2013 |volume=339 |issue=6124 |pages=1198–1201 |doi=10.1126/science.1228026|pmid=23471405 |bibcode=2013Sci...339.1198M }}</ref> This period also saw the start of agriculture.{{sfn|IPCC AR6 WG1 Ch2|2021|p=296}} Historical patterns of warming and cooling, like the ] and the ], did not occur at the same time across different regions. Temperatures may have reached as high as those of the late 20th century in a limited set of regions.<ref>{{harvnb|IPCC AR5 WG1 Ch5|2013|p=386}}</ref><ref>{{harvnb|Neukom|Steiger|Gómez-Navarro|Wang|2019a}}</ref> Climate information for that period comes from ], such as trees and ]s.<ref name="SR15 Ch1 p57">{{harvnb|IPCC SR15 Ch1|2018|p=57}}: "This report adopts the 51-year reference period, 1850–1900 inclusive, assessed as an approximation of pre-industrial levels in AR5&nbsp;... Temperatures rose by 0.0&nbsp;°C–0.2&nbsp;°C from 1720–1800 to 1850–1900"</ref><ref>{{harvnb|Hawkins|Ortega|Suckling|Schurer|2017|p=1844}}</ref>
For details of changes during various periods:
* General discussion of Temperature records see: ''']'''
* Record of past century see: ''']'''
* Record of recent millenia see: ''']'''
* For attribution see: ''']'''


=== Warming since the Industrial Revolution ===
] of the lower atmosphere for the 25 years; others show up to three times as much warming]]
]
] during recent decades as the oceans absorb over 90% of the ].<ref name=NOAA_NASA_OHC_1957_>''Top 700 meters:'' {{cite web |last1=Lindsey |first1=Rebecca |last2=Dahlman |first2=Luann |title=Climate Change: Ocean Heat Content |url=https://www.climate.gov/news-features/understanding-climate/climate-change-ocean-heat-content |website=climate.gov |publisher=National Oceanic and Atmospheric Administration (NOAA) |archive-url=https://archive.today/20231029171303/https://www.climate.gov/news-features/understanding-climate/climate-change-ocean-heat-content |archive-date=29 October 2023 |date=6 September 2023 |url-status=live }} ● ''Top 2000 meters:'' {{cite web |title=Ocean Warming / Latest Measurement: December 2022 / 345 (± 2) zettajoules since 1955 |url=https://climate.nasa.gov/vital-signs/ocean-warming/ |website=NASA.gov |publisher=National Aeronautics and Space Administration |archive-url=https://web.archive.org/web/20231020033606/https://climate.nasa.gov/vital-signs/ocean-warming/ |archive-date=20 October 2023 |url-status=live}}</ref>]]
Around 1850 ] records began to provide global coverage.<ref name="AR5 WG1 SPM p4-5">{{Harvnb|IPCC AR5 WG1 Summary for Policymakers|2013|pp=4–5}}: "Global-scale observations from the instrumental era began in the mid-19th century for temperature and other variables&nbsp;... the period 1880 to 2012&nbsp;... multiple independently produced datasets exist."</ref>
Between the 18th century and 1970 there was little net warming, as the warming impact of greenhouse gas emissions was offset by cooling from ] emissions. Sulfur dioxide causes ], but it also produces ] aerosols in the atmosphere, which reflect sunlight and cause ]. After 1970, the increasing accumulation of greenhouse gases and controls on sulfur pollution led to a marked increase in temperature.<ref>{{cite news |url=https://www.washingtonpost.com/climate-environment/2023/12/26/global-warming-accelerating-climate-change/ |title=Is climate change speeding up? Here's what the science says. |last1=Mooney |first1=Chris | last2=Osaka |first2=Shannon |date=26 December 2023 |newspaper=The Washington Post |access-date=18 January 2024}}</ref><ref name="NASA2007">{{cite news |date=15 March 2007 |title=Global 'Sunscreen' Has Likely Thinned, Report NASA Scientists |url=http://www.nasa.gov/centers/goddard/news/topstory/2007/aerosol_dimming.html |publisher=]}}</ref><ref name="Quaas2022" />
]
Ongoing changes in climate have had no precedent for several thousand years.<ref>{{harvnb|IPCC AR6 WG1 Technical Summary|2021|p=43}}</ref> Multiple independent datasets all show worldwide increases in surface temperature,<ref>{{harvnb|EPA|2016}}: "The U.S. Global Change Research Program, the National Academy of Sciences, and the Intergovernmental Panel on Climate Change (IPCC) have each independently concluded that warming of the climate system in recent decades is "unequivocal". This conclusion is not drawn from any one source of data but is based on multiple lines of evidence, including three worldwide temperature datasets showing nearly identical warming trends as well as numerous other independent indicators of global warming (e.g. rising sea levels, shrinking Arctic sea ice)."</ref> at a rate of around 0.2&nbsp;°C per decade.<ref>{{Harvnb|IPCC SR15 Ch1|2018|p=81}}.</ref> The 2014–2023 decade warmed to an average 1.19&nbsp;°C compared to the pre-industrial baseline (1850–1900).<ref>{{harvnb|Forster|Smith|Walsh|Lamb|2024|p=2626}}</ref> Not every single year was warmer than the last: internal ] processes can make any year 0.2&nbsp;°C warmer or colder than the average.<ref name="Samset2020">{{cite journal |last1=Samset |first1=B. H. |last2=Fuglestvedt |first2=J. S. |last3=Lund |first3=M. T. |title=Delayed emergence of a global temperature response after emission mitigation |journal=Nature Communications |date=7 July 2020 |volume=11 |issue=1 |page=3261 |doi=10.1038/s41467-020-17001-1 |pmid=32636367 |pmc=7341748 |bibcode=2020NatCo..11.3261S |quote=At the time of writing, that translated into 2035–2045, where the delay was mostly due to the impacts of the around 0.2 °C of natural, interannual variability of global mean surface air temperature |hdl=11250/2771093 |hdl-access=free }}</ref> From 1998 to 2013, negative phases of two such processes, ]<ref name="SeipGrønWang2023PacificDecadalOscillation">{{Cite journal |last1=Seip |first1=Knut L. |last2=Grøn |first2=ø. |last3=Wang |first3=H. |date=31 August 2023 |title=Global lead-lag changes between climate variability series coincide with major phase shifts in the Pacific decadal oscillation |journal=] |volume=154 |issue=3–4 |language=en |doi=10.1007/s00704-023-04617-8 |issn=0177-798X |pages=1137–1149 |bibcode=2023ThApC.154.1137S |s2cid=261438532 |doi-access=free |hdl=11250/3088837 |hdl-access=free }}</ref> and ]<ref>{{Cite journal |last1=Yao |first1=Shuai-Lei |last2=Huang |first2=Gang |last3=Wu |first3=Ren-Guang |last4=Qu |first4=Xia |date=January 2016 |title=The global warming hiatus—a natural product of interactions of a secular warming trend and a multi-decadal oscillation |url=http://link.springer.com/10.1007/s00704-014-1358-x |journal=] |language=en |volume=123 |issue=1–2 |pages=349–360 |doi=10.1007/s00704-014-1358-x |bibcode=2016ThApC.123..349Y |s2cid=123602825 |issn=0177-798X |access-date=20 September 2023}}</ref> caused a short slower period of warming called the "]".<ref>{{Cite journal |last1=Xie |first1=Shang-Ping |last2=Kosaka |first2=Yu |date=June 2017 |title=What Caused the Global Surface Warming Hiatus of 1998–2013? |url=http://link.springer.com/10.1007/s40641-017-0063-0 |journal=Current Climate Change Reports |language=en |volume=3 |issue=2 |pages=128–140 |doi=10.1007/s40641-017-0063-0 |bibcode=2017CCCR....3..128X |s2cid=133522627 |issn=2198-6061 |access-date=20 September 2023}}</ref> After the "hiatus", the opposite occurred, with years like 2023 exhibiting temperatures well above even the recent average.<ref name="Copernicus2023">{{Cite web |date=21 November 2023 |title=Global temperature exceeds 2&nbsp;°C above pre-industrial average on 17 November |url=https://climate.copernicus.eu/global-temperature-exceeds-2degc-above-pre-industrial-average-17-november |website=] |access-date=31 January 2024 |quote=While exceeding the 2&nbsp;°C threshold for a number of days does not mean that we have breached the Paris Agreement targets, the more often that we exceed this threshold, the more serious the cumulative effects of these breaches will become.}}</ref> This is why the temperature change is defined in terms of a 20-year average, which reduces the noise of hot and cold years and decadal climate patterns, and detects the long-term signal.<ref name="IPCC_AR6_WGI_SPM">IPCC, 2021: . In: . Cambridge University Press, Cambridge, United Kingdom and New York, New York, US, pp. 3−32, doi:10.1017/9781009157896.001.</ref>{{rp|5}}<ref>{{Cite web |last=McGrath |first=Matt |date=17 May 2023 |title=Global warming set to break key 1.5C limit for first time |url=https://www.bbc.com/news/science-environment-65602293 |website=] |access-date=31 January 2024 |quote=The researchers stress that temperatures would have to stay at or above 1.5C for 20 years to be able to say the Paris agreement threshold had been passed. }}</ref>


A wide range of other observations reinforce the evidence of warming.<ref>{{harvnb|Kennedy|Thorne|Peterson|Ruedy|2010|p=S26}}. Figure 2.5.</ref>{{sfn|Loeb et al.|2021}} The upper atmosphere is cooling, because ]es are trapping heat near the Earth's surface, and so less heat is radiating into space.<ref>{{cite web |url=https://earthobservatory.nasa.gov/features/GlobalWarming |title=Global Warming |date=3 June 2010 |publisher=] |access-date=11 September 2020 |quote=Satellite measurements show warming in the troposphere but cooling in the stratosphere. This vertical pattern is consistent with global warming due to increasing greenhouse gases but inconsistent with warming from natural causes.}}</ref> Warming reduces average snow cover and ]. At the same time, warming also causes ], leading to more ], more and heavier ].<ref>{{harvnb|Kennedy|Thorne|Peterson|Ruedy|2010|pp=S26, S59–S60}}</ref><ref>{{harvnb|USGCRP Chapter 1|2017|p=35}}</ref> Plants are ] earlier in spring, and thousands of animal species have been permanently moving to cooler areas.<ref>{{harvnb|IPCC AR6 WG2|2022|pp=257–260}}</ref>
The temperature increase has not been uniform over the globe or over time . Recent research (Peterson ]; Parker ]) indicates that estimates of temperature trends may not be much influenced by the ] effect. While the accuracy of collected station data is not in dispute, the records suffer from incomplete coverage, geographically and historically, making the conclusions drawn from the data subject to disagreement.


==== Differences by region ====
Temperatures in the lower ] have increased at somewhere between 0.08 and 0.22&nbsp;°C per decade since 1979 (see ''']'''). Just like the surface record, the average temperature rise is not linear, but has rises and falls superimposed on it due to natural variability, most notably ]'s. Over the same period the ''']''' shows a warming of approximately 0.15&nbsp;°C/decade.
Different regions of the world ]. The pattern is independent of where greenhouse gases are emitted, because the gases persist long enough to diffuse across the planet. Since the pre-industrial period, the average surface temperature over land regions has increased almost twice as fast as the global average surface temperature.<ref>{{harvnb|IPCC SRCCL Summary for Policymakers|2019|p=7}}</ref> This is because oceans lose more heat by ] and ].<ref>{{Harvnb|Sutton|Dong|Gregory|2007}}.</ref> The thermal energy in the global climate system has grown with only brief pauses since at least 1970, and over 90% of this extra energy has been ].<ref name="ocean heat absorption">{{cite web|title=Climate Change: Ocean Heat Content |newspaper=Noaa Climate.gov |publisher=] |year=2018 |url=https://www.climate.gov/news-features/understanding-climate/climate-change-ocean-heat-content|archive-url=https://web.archive.org/web/20190212110601/https://www.climate.gov/news-features/understanding-climate/climate-change-ocean-heat-content|archive-date=12 February 2019 |url-status=live|access-date=20 February 2019}}</ref><ref name="Harvipccar5">{{Harvnb|IPCC AR5 WG1 Ch3|2013|p=257}}: "] dominates the global energy change inventory. Warming of the ocean accounts for about 93% of the increase in the Earth's energy inventory between 1971 and 2010 (high confidence), with warming of the upper (0 to 700 m) ocean accounting for about 64% of the total.</ref> The rest has heated the ], melted ice, and warmed the continents.<ref name=EarthSysSciData_20200907>{{cite journal |last1=von Schuckman |first1=K. |last2=Cheng |first2=L. |last3=Palmer |first3=M. D. |last4=Hansen |first4=J. |last5=Tassone |first5=C. |last6=Aich |first6=V. |last7=Adusumilli |first7=S. |last8=Beltrami |first8=H. |last9=Boyer |first9=T. |last10=Cuesta-Valero |first10=F. J. |display-authors=4 |title=Heat stored in the Earth system: where does the energy go? |journal=Earth System Science Data |date=7 September 2020 |doi=10.5194/essd-12-2013-2020 |doi-access=free |url=https://essd.copernicus.org/articles/12/2013/2020/ |volume=12 |issue=3 |pages=2013–2041|bibcode=2020ESSD...12.2013V |hdl=20.500.11850/443809 |hdl-access=free }}</ref>


The ] and the ] have warmed much faster than the ] and ]. The Northern Hemisphere not only has much more land, but also more seasonal snow cover and ]. As these surfaces flip from reflecting a lot of light to being dark after the ice has melted, they start ].<ref>{{harvnb|NOAA, 10 July|2011}}.</ref> Local ] deposits on snow and ice also contribute to Arctic warming.<ref>{{harvnb|United States Environmental Protection Agency|2016|p=5}}: "Black carbon that is deposited on snow and ice darkens those surfaces and decreases their reflectivity (albedo). This is known as the snow/ice albedo effect. This effect results in the increased absorption of radiation that accelerates melting."</ref> Arctic surface temperatures are increasing ] than in the rest of the world.<ref name="3X2021">{{cite web |date=20 May 2021 |title=Arctic warming three times faster than the planet, report warns |url=https://phys.org/news/2021-05-arctic-faster-planet.html |website=] |language=en |access-date=6 October 2022}}</ref><ref name="Rantanen2022">{{Cite journal |last1=Rantanen |first1=Mika |last2=Karpechko |first2=Alexey Yu |last3=Lipponen |first3=Antti |last4=Nordling |first4=Kalle |last5=Hyvärinen |first5=Otto |last6=Ruosteenoja |first6=Kimmo |last7=Vihma |first7=Timo |last8=Laaksonen |first8=Ari |date=11 August 2022 |title=The Arctic has warmed nearly four times faster than the globe since 1979 |journal=Communications Earth & Environment |language=en |volume=3 |issue=1 |page=168 |doi=10.1038/s43247-022-00498-3 |s2cid=251498876 |issn=2662-4435|doi-access=free |bibcode=2022ComEE...3..168R |hdl=11250/3115996 |hdl-access=free }}</ref><ref name="4X2021">{{cite web |date=14 December 2021 |title=The Arctic is warming four times faster than the rest of the world |url=https://www.science.org/content/article/arctic-warming-four-times-faster-rest-world |language=en |access-date=6 October 2022}}</ref> Melting of ]s near the poles weakens both the ] and the ] limb of ], which further changes the distribution of heat and ] around the globe.<ref>{{Cite journal |last1=Liu |first1=Wei |last2=Fedorov |first2=Alexey V. |last3=Xie |first3=Shang-Ping |last4=Hu |first4=Shineng |date=26 June 2020 |title=Climate impacts of a weakened Atlantic Meridional Overturning Circulation in a warming climate |journal=Science Advances |volume=6 |issue=26 |pages=eaaz4876 |doi=10.1126/sciadv.aaz4876 |pmid=32637596 |pmc=7319730 |bibcode=2020SciA....6.4876L }}</ref><ref name="PearceYale3602023">{{cite web |last=Pearce |first=Fred |date=18 April 2023 |title=New Research Sparks Concerns That Ocean Circulation Will Collapse |url=https://e360.yale.edu/features/climate-change-ocean-circulation-collapse-antarctica |language=en |access-date=3 February 2024 }}</ref><ref name="Lee2023">{{Cite journal |last1=Lee |first1=Sang-Ki |last2=Lumpkin |first2=Rick |last3=Gomez |first3=Fabian |last4=Yeager |first4=Stephen |last5=Lopez |first5=Hosmay |last6=Takglis |first6=Filippos |last7=Dong |first7=Shenfu |last8=Aguiar |first8=Wilton |last9=Kim |first9=Dongmin |last10=Baringer |first10=Molly |date=13 March 2023 |title=Human-induced changes in the global meridional overturning circulation are emerging from the Southern Ocean |journal=Communications Earth & Environment |volume=4 |issue=1 |page=69 |doi=10.1038/s43247-023-00727-3 |bibcode=2023ComEE...4...69L |doi-access=free }}</ref><ref name="NOAA2023">{{cite web |date=29 March 2023 |title=NOAA Scientists Detect a Reshaping of the Meridional Overturning Circulation in the Southern Ocean |url=https://www.aoml.noaa.gov/noaa-scientists-detect-reshaping-of-the-meridional-overturning-circulation-in-southern-ocean/ |publisher=] }}</ref>
A new reconstruction by Moberg, et al, published in ] ])] shows both the ] and ] anomalies (although not by name) and concludes that the temperatures around 1000 and 1100 AD were comparable to those of the 20th century before 1990. "Moberg's reconstruction will help to put the record straight in one of the most contested issues in palaeoclimatology," says ]. "But it does not weaken in any way the hypothesis that recent observed warming is a result mainly of human activity.". Moberg's results are consistent with those of Von Storch, et al, who conducted a modeling analysis that showed the variability to be about twice as great as previously published .


=== Future global temperatures ===
Mann concedes that past climate variations may be larger than thought, but that "The contrarians would have us believe that the entire argument of anthropogenic climate change rests on our hockey-stick construction. But in fact some of the most compelling evidence has absolutely nothing to do with it, and has been around much longer than our curve" .
] multi-model projections of ] changes for the year 2090 relative to the 1850–1900 average. The current trajectory for warming by the end of the century is roughly halfway between these two extremes.<ref name="UNEP2024" /><ref name="Schuur2022">{{Cite journal |last1=Schuur |first1=Edward A. G. |last2=Abbott |first2=Benjamin W. |last3=Commane |first3=Roisin |last4=Ernakovich |first4=Jessica |last5=Euskirchen |first5=Eugenie |last6=Hugelius |first6=Gustaf |last7=Grosse |first7=Guido |last8=Jones |first8=Miriam |last9=Koven |first9=Charlie |last10=Leshyk |first10=Victor |last11=Lawrence |first11=David |last12=Loranty |first12=Michael M. |last13=Mauritz |first13=Marguerite |last14=Olefeldt |first14=David |last15=Natali |first15=Susan |year=2022 |title=Permafrost and Climate Change: Carbon Cycle Feedbacks From the Warming Arctic |journal=Annual Review of Environment and Resources |volume=47 |pages=343–371 |bibcode=2022ARER...47..343S |doi=10.1146/annurev-environ-012220-011847 |quote="Medium-range estimates of Arctic carbon emissions could result from moderate climate emission mitigation policies that keep global warming below 3&nbsp;°C (e.g., RCP4.5). This global warming level most closely matches country emissions reduction pledges made for the Paris Climate Agreement..." |doi-access=free |last16=Rodenhizer |first16=Heidi |last17=Salmon |first17=Verity |last18=Schädel |first18=Christina |last19=Strauss |first19=Jens |last20=Treat |first20=Claire |last21=Turetsky |first21=Merritt}}</ref><ref name="Phiddian2022">{{Cite web |last=Phiddian |first=Ellen |date=5 April 2022 |title=Explainer: IPCC Scenarios |url=https://cosmosmagazine.com/earth/climate/explainer-ipcc-scenarios/ |website=] |access-date=30 September 2023 |quote="The IPCC doesn't make projections about which of these scenarios is more likely, but other researchers and modellers can. ], for instance, released a report last year stating that our current emissions trajectory had us headed for a 3&nbsp;°C warmer world, roughly in line with the middle scenario. ] predicts 2.5 to 2.9&nbsp;°C of warming based on current policies and action, with pledges and government agreements taking this to 2.1&nbsp;°C.}}</ref>]]
The ] estimates there is an 80% chance that global temperatures will exceed 1.5&nbsp;°C warming for at least one year between 2024 and 2028. The chance of the 5-year average being above 1.5&nbsp;°C is almost half.{{sfn|WMO|2024b|p=2}}


The IPCC expects the 20-year average global temperature to exceed +1.5&nbsp;°C in the early 2030s.<ref>{{Cite web |date=7 August 2021 |title=Climate Change 2021 - The Physical Science Basis |url=https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Full_Report.pdf#page=955 |url-status=live |archive-url=https://web.archive.org/web/20240405072633/https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Full_Report.pdf#page=955 |archive-date=5 April 2024 |website=Intergovernmental Panel on Climate Change |id=IPCC AR6 WGI}}</ref> The ] (2021) included projections that by 2100 global warming is very likely to reach 1.0–1.8&nbsp;°C under a ], 2.1–3.5&nbsp;°C under an ],
==Theories to explain temperature change==
or 3.3–5.7&nbsp;°C under ].<ref>{{harvnb|IPCC AR6 WG1 Summary for Policymakers|2021|p=SPM-17}}</ref> The warming will continue past 2100 in the intermediate and high emission scenarios,<ref name="Meinshausen2011">{{Cite journal |last1=Meinshausen |first1=Malte |last2=Smith |first2=S. J. |last3=Calvin |first3=K. |last4=Daniel |first4=J. S. |last5=Kainuma |first5=M. L. T. |last6=Lamarque |first6=J-F. |last7=Matsumoto |first7=K. |last8=Montzka |first8=S. A. |last9=Raper |first9=S. C. B. |last10=Riahi |first10=K. |last11=Thomson |first11=A. |last12=Velders |first12=G. J. M. |last13=van Vuuren |first13=D.P. P. |year=2011 |title=The RCP greenhouse gas concentrations and their extensions from 1765 to 2300 |journal=Climatic Change |language=en |volume=109 |issue=1–2 |pages=213–241 |doi=10.1007/s10584-011-0156-z |bibcode=2011ClCh..109..213M |issn=0165-0009|doi-access=free }}</ref><ref name="Lyon2021">{{cite journal |last1=Lyon |first1=Christopher |last2=Saupe |first2=Erin E. |last3=Smith |first3=Christopher J. |last4=Hill |first4=Daniel J. |last5=Beckerman |first5=Andrew P. |last6=Stringer |first6=Lindsay C. |last7=Marchant |first7=Robert |last8=McKay |first8=James |last9=Burke |first9=Ariane |last10=O'Higgins |first10=Paul |last11=Dunhill |first11=Alexander M. |last12=Allen |first12=Bethany J. |last13=Riel-Salvatore |first13=Julien |last14=Aze |first14=Tracy |year=2021 |title=Climate change research and action must look beyond 2100 |journal=Global Change Biology |language=en |volume=28 |issue=2 |pages=349–361 |doi=10.1111/gcb.15871 |issn=1365-2486 |pmid=34558764 |s2cid=237616583 |doi-access=free|hdl=20.500.11850/521222 |hdl-access=free }}</ref> with future projections of global surface temperatures by year 2300 being similar to millions of years ago.<ref>{{harvnb|IPCC AR6 WG1 Technical Summary|2021|pp=43–44}}</ref>


The remaining ] for staying beneath certain temperature increases is determined by modelling the carbon cycle and ] to greenhouse gases.<ref>{{harvnb|Rogelj|Forster|Kriegler|Smith|2019}}</ref> According to ], global warming can be kept below 1.5&nbsp;°C with a 50% chance if emissions after 2023 do not exceed 200 gigatonnes of {{CO2}}. This corresponds to around 4 years of current emissions. To stay under 2.0&nbsp;°C, the carbon budget is 900 gigatonnes of {{CO2}}, or 16 years of current emissions.{{sfn|United Nations Environment Programme|2024|pp=XI, XVII}}
The climate system varies both through natural, "internal" processes as well as in response to variations in "external forcing" from both human and non-human causes, including changes in the Earth's orbit around the Sun (]), ], and volcanic emissions as well as greenhouse gases. See ''']''' for further discussion of these forcing processes.


== Causes of recent global temperature rise ==
Climatologists accept that the earth has warmed recently. Somewhat more controversial is what may have caused this change. See ''']''' for further discussion.
{{Main|Causes of climate change}}
] of global warming that has happened so far. Future ] for long lived drivers like carbon dioxide emissions is not represented. Whiskers on each bar show the possible ].]]


The climate system experiences various cycles on its own which can last for years, decades or even centuries. For example, ] events cause short-term spikes in surface temperature while ] events cause short term cooling.<ref>{{cite journal |last1=Brown |first1=Patrick T. |last2=Li |first2=Wenhong |last3=Xie |first3=Shang-Ping |title=Regions of significant influence on unforced global mean surface air temperature variability in climate models: Origin of global temperature variability |journal=Journal of Geophysical Research: Atmospheres |date=27 January 2015 |volume=120 |issue=2 |pages=480–494 |doi=10.1002/2014JD022576 |doi-access=free |hdl=10161/9564 |hdl-access=free }}</ref> Their relative frequency can affect global temperature trends on a decadal timescale.<ref>{{cite journal |last1=Trenberth |first1=Kevin E. |last2=Fasullo |first2=John T. |title=An apparent hiatus in global warming? |journal=Earth's Future |date=December 2013 |volume=1 |issue=1 |pages=19–32 |doi=10.1002/2013EF000165 |bibcode=2013EaFut...1...19T |doi-access=free }}</ref> Other changes are caused by an ] from ].<ref>{{Harvnb|National Research Council|2012|p=9}}</ref> Examples of these include changes in the concentrations of ]es, ], ] eruptions, and ] around the Sun.<ref>{{Harvnb|IPCC AR5 WG1 Ch10|2013|p=916}}.</ref>
===Greenhouse gas theory===


To determine the human contribution to climate change, unique "fingerprints" for all potential causes are developed and compared with both observed patterns and known internal ].<ref>{{harvnb|Knutson|2017|p=443}}; {{Harvnb|IPCC AR5 WG1 Ch10|2013|pp=875–876}}</ref> For example, solar forcing—whose fingerprint involves warming the entire atmosphere—is ruled out because only the lower atmosphere has warmed.<ref name="USGCRP-2009" /> Atmospheric aerosols produce a smaller, cooling effect. Other drivers, such as changes in ], are less impactful.<ref>{{harvnb|IPCC AR6 WG1 Summary for Policymakers|2021|p=7}}</ref>
In the late 19th century the Swedish chemist and ] ] ] used the measured infrared absorption of carbon dioxide to calculate that increases in ] concentration would lead to higher global mean temperatures while decreases would lead to colder global mean temperatures. The idea arose largely as Arrhenius' attempt to explain ]s. At the time his peers largely rejected this theory.


=== Greenhouse gases ===
Arrhenius' colleague ] was one of the first to study the ]. Through him Arrhenius was aware that in ] emission and absorption of CO<SUB>2</SUB> were roughly in balance. Their best estimates were that burning of fossil fuels would not be a future problem, but this was based on coal consumption at the end of the 19th century.
{{Main|Greenhouse gas|Greenhouse gas emissions|Greenhouse effect|Carbon dioxide in Earth's atmosphere}}]
Greenhouse gases are transparent to ], and thus allow it to pass through the atmosphere to heat the Earth's surface. The Earth ], and greenhouse gases absorb a portion of it. This absorption slows the rate at which heat escapes into space, trapping heat near the Earth's surface and warming it over time.<ref>{{cite web|title=The Causes of Climate Change|author=NASA |url=https://climate.nasa.gov/causes|website=Climate Change: Vital Signs of the Planet|access-date=8 May 2019|archive-url=https://web.archive.org/web/20190508000022/https://climate.nasa.gov/causes/|archive-date=8 May 2019|url-status=live}}</ref>


While ] (≈50%) and clouds (≈25%) are the biggest contributors to the greenhouse effect, they primarily change as a function of temperature and are therefore mostly considered to be ] that change ]. On the other hand, concentrations of gases such as {{CO2}} (≈20%), ],<ref>Ozone acts as a greenhouse gas in the lowest layer of the atmosphere, the ] (as opposed to the stratospheric ]). {{harvnb|Wang|Shugart|Lerdau|2017}}</ref> ] and ] are added or removed independently from temperature, and are therefore considered to be ] that change global temperatures.<ref>{{harvnb|Schmidt|Ruedy|Miller|Lacis|2010}}; {{harvnb|USGCRP Climate Science Supplement|2014|p=742}}</ref>
The longest sustained measurement of CO<SUB>2</SUB> in the atmosphere is reflected in the ]. Measurements conducted by Dr. Charles David Keeling atop ] in ] show an increase of more than 50 parts per million by volume from 1958 to the present.


Before the ], naturally-occurring amounts of greenhouse gases caused the air near the surface to be about 33&nbsp;°C warmer than it would have been in their absence.<ref>{{Harvnb|IPCC AR4 WG1 Ch1|2007|loc=FAQ1.1}}: "To emit 240 W m<sup>−2</sup>, a surface would have to have a temperature of around −19&nbsp;°C. This is much colder than the conditions that actually exist at the Earth's surface (the global mean surface temperature is about 14&nbsp;°C).</ref><ref>{{cite web|title=What Is the Greenhouse Effect?|author=ACS|author-link=American Chemical Society|url=https://www.acs.org/content/acs/en/climatescience/climatesciencenarratives/what-is-the-greenhouse-effect.html|access-date=26 May 2019|archive-url=https://web.archive.org/web/20190526110653/https://www.acs.org/content/acs/en/climatescience/climatesciencenarratives/what-is-the-greenhouse-effect.html|archive-date=26 May 2019|url-status=live}}</ref> Human activity since the Industrial Revolution, mainly extracting and burning fossil fuels (], ], and ]),<ref>{{Harvnb|The Guardian, 19 February|2020}}.</ref> has increased the amount of greenhouse gases in the atmosphere. In 2022, the ] and methane had increased by about 50% and 164%, respectively, since 1750.<ref>{{Harvnb|WMO|2024a|p=2}}.</ref> These {{CO2}} levels are higher than they have been at any time during the last 14 million years.{{sfn|The Cenozoic CO2 Proxy Integration Project (CenCOPIP) Consortium|2023}} ] are far higher than they were over the last 800,000 years.{{Sfn|IPCC AR6 WG1 Technical Summary|2021|p=TS-35}}
The theory that human greenhouse gas emissions are contributing to the warming of the Earth's atmosphere has gained many adherents and some opponents in the scientific community within the past 25 years. The ], which was established to assess the risk of human-induced climate change, attributes most of the recent warming to human activities. The United States ] also endorsed the theory. Atmospheric physicist ] and other ] oppose aspects of the theory.


] shows how additions to {{CO2}} since 1880 have been caused by different sources ramping up one after another.]]
] and ]es (green and blue) during 420,000 years.]]
There are many subtle aspects to the question. Atmospheric scientists know that adding ] (CO<SUB>2</SUB>) to an atmosphere, with no other changes, will tend to make a planet's surface warmer. But there is a significant amount of water vapor in the Earth's atmosphere in the form of humidity and clouds, and water vapor is a strong greenhouse gas. If adding CO<SUB>2</SUB> to the atmosphere changes processes that regulate the amount of water vapor in the Earth's atmosphere, that could have a profound effect on the climate: more water vapor means more warmth.


Global human-caused greenhouse gas emissions in 2019 were ] 59&nbsp;billion tonnes of {{CO2}}. Of these emissions, 75% was {{CO2}}, 18% was ], 4% was nitrous oxide, and 2% was ].{{sfn|IPCC AR6 WG3 Summary for Policymakers|2022|loc=Figure SPM.1}} {{CO2}} emissions primarily come from burning fossil fuels to provide energy for ], manufacturing, ], and electricity.<ref name="Our World in Data-2020"/> Additional {{CO2}} emissions come from ] and ], which include the {{CO2}} released by the chemical reactions for ], ], ], and ].<ref>{{harvnb|Olivier|Peters|2019|p=17}}</ref><ref>{{harvnb|Our World in Data, 18 September|2020}}; {{harvnb|EPA|2020}}: "Greenhouse gas emissions from industry primarily come from burning fossil fuels for energy, as well as greenhouse gas emissions from certain chemical reactions necessary to produce goods from raw materials."</ref><ref>{{cite web|title=Redox, extraction of iron and transition metals|url=https://www.bbc.co.uk/bitesize/guides/zv7f3k7/revision/2|quote=Hot air (oxygen) reacts with the coke (carbon) to produce carbon dioxide and heat energy to heat up the furnace. Removing impurities: The calcium carbonate in the limestone thermally decomposes to form calcium oxide. calcium carbonate → calcium oxide + carbon dioxide}}</ref><ref>{{harvnb|Kvande|2014}}: "Carbon dioxide gas is formed at the anode, as the carbon anode is consumed upon reaction of carbon with the oxygen ions from the alumina ({{chem2|Al2O3}}). Formation of carbon dioxide is unavoidable as long as carbon anodes are used, and it is of great concern because {{CO2}} is a greenhouse gas."</ref> Methane emissions ], manure, ], landfills, wastewater, and ], as well as ].<ref>{{harvnb|EPA|2020}}</ref><ref>{{harvnb|Global Methane Initiative|2020}}: "Estimated Global Anthropogenic Methane Emissions by Source, 2020: ] (27%), Manure Management (3%), Coal Mining (9%), ] (11%), Oil & Gas (24%), ] (7%), ] (7%)."</ref> Nitrous oxide emissions largely come from the microbial decomposition of ].<ref>{{harvnb|EPA|2019}}: "Agricultural activities, such as fertilizer use, are the primary source of {{N2O}} emissions."</ref><ref>{{harvnb|Davidson|2009}}: "2.0% of manure nitrogen and 2.5% of fertilizer nitrogen was converted to nitrous oxide between 1860 and 2005; these percentage contributions explain the entire pattern of increasing nitrous oxide concentrations over this period."</ref>
The effect of clouds is also critical. Clouds have competing effects on the climate; everyone has noticed that surface temperature drops when a cloud passes overhead on an otherwise hot, sunny summer day. So clouds cool the surface by reflecting sunlight back into space. However, many people have also noticed that clear winter nights tend to be colder than cloudy winter nights. That is because clouds block the radiation of heat away from the surface (and eventually into space), and radiate it back to the surface of the Earth. If CO<SUB>2</SUB> changes the amount or distribution of clouds, it could have various complex effects on the climate. In the 2001 IPCC report on climate change, the possible changes in cloud cover were highlighted as one of the dominant uncertainties in predicting future climate change.


While methane only lasts in the atmosphere for an average of 12 years,<ref>{{cite web |title=Understanding methane emissions |publisher=International Energy Agency |url=https://www.iea.org/reports/global-methane-tracker-2023/understanding-methane-emissions}}</ref> {{CO2}} lasts much longer. The Earth's surface absorbs {{CO2}} as part of the ]. While plants on land and in the ocean absorb most excess emissions of {{CO2}} every year, that {{CO2}} is returned to the atmosphere when biological matter is digested, burns, or decays.<ref name="nasacc">{{cite web|last1=Riebeek|first1=Holli|title=The Carbon Cycle|url=http://earthobservatory.nasa.gov/Features/CarbonCycle/?src=eoa-features|website=Earth Observatory|publisher=NASA|access-date=5 April 2018|date=16 June 2011|archive-url=https://web.archive.org/web/20160305010126/http://earthobservatory.nasa.gov/Features/CarbonCycle/?src=eoa-features|archive-date=5 March 2016|url-status=live}}</ref> Land-surface ] processes, such as ] in the soil and photosynthesis, remove about 29% of annual global {{CO2}} emissions.<ref>{{Harvnb|IPCC SRCCL Summary for Policymakers|2019|p=10}}</ref> The ocean has absorbed 20 to 30% of emitted {{CO2}} over the last two decades.<ref>{{harvnb|IPCC SROCC Ch5|2019|p=450}}.</ref> {{CO2}} is only removed from the atmosphere for the long term when it is stored in the Earth's crust, which is a process that can take millions of years to complete.<ref name="nasacc" />
Given this, it is not correct to imagine that there is a debate between those who "believe in" and "oppose" the theory that adding CO<SUB>2</SUB> to the Earth's atmosphere will result in warmer surface temperatures on Earth, on average. Rather, the debate is about what the ''net'' effect of the addition of CO<SUB>2</SUB> will be, and whether changes in water vapor, clouds, and so on will ''cancel out'' its warming effect. The observed warming of the Earth over the past 50 years appears to be at odds with the skeptics' theory that climate feedbacks will cancel out the warming.


=== Land surface changes ===
Scientists have also studied this issue with computer models of the climate (see below). These models are accepted by the scientific community as being valid only after it has been shown that they do a good job of simulating known climate variations, such as the difference between summer and winter, the ], or ]. All climate models that pass these tests also predict that the net effect of adding CO<SUB>2</SUB> will be a warmer climate in the future. The amount of predicted warming varies by model, however, which probably reflects the way different models depict clouds differently. Skeptics point to the growing evidence that variation in cosmic ray flux represents an indirect effect of changes in solar activity that increases the warming response to increases in solar activity. Climate models that pass the above tests while only modeling the direct effects of increases in solar activity will have attributed too much of the historical warming to greenhouse gas forcing, and will predict larger increases in temperature in the future. Skeptics of global warming point to potential feedbacks that current models poorly understand, such as changes in vegetation and cloud cover, and suggest that these processes reduce the sensitivity of the climate to greenhouse gas forcing. Proponents of established global warming theory argue that the uncertainty could just as easily extend to increases in warming as reductions in it. For example, it has been hypothesized that an increase in average temperature would cause volatilization of ] ]s, which would increase the amount of methane in the atmosphere, causing further warming and hence further volatilization.
]
Around 30% of Earth's land area is largely unusable for humans (]s, ]s, etc.), 26% is ]s, 10% is ] and 34% is ].<ref>{{harvnb|Ritchie|Roser|2018}}</ref> ] is the main ] contributor to global warming,<ref>{{harvnb|The Sustainability Consortium, 13 September|2018}}; {{harvnb|UN FAO|2016|p=18}}.</ref> as the destroyed trees release {{CO2}}, and are not replaced by new trees, removing that ].<ref name="IPCC SRCCL Summary for Policymakers 2019 18">{{harvnb|IPCC SRCCL Summary for Policymakers|2019|p=18}}</ref> Between 2001 and 2018, 27% of deforestation was from permanent clearing to enable ] for crops and livestock. Another 24% has been lost to temporary clearing under the ] agricultural systems. 26% was due to ] for wood and derived products, and ]s have accounted for the remaining 23%.<ref>{{harvnb|Curtis|Slay|Harris|Tyukavina|2018}}</ref> Some forests have not been fully cleared, but were already degraded by these impacts. Restoring these forests also recovers their potential as a carbon sink.<ref name="Duchelle-2022">{{Cite book |author1=Garrett, L. |author2=Lévite, H. |author3=Besacier, C. |author4=Alekseeva, N. |author5=Duchelle, M. |url=https://doi.org/10.4060/cc2510en |title=The key role of forest and landscape restoration in climate action |publisher=FAO |year=2022 |isbn=978-92-5-137044-5 |location=Rome|doi=10.4060/cc2510en }}</ref>


Local vegetation cover impacts how much of the sunlight gets reflected back into space (]), and how much ]. For instance, the change from a dark ] to grassland makes the surface lighter, causing it to reflect more sunlight. Deforestation can also modify the release of chemical compounds that influence clouds, and by changing wind patterns.<ref name="Seymour 2019">{{harvnb|World Resources Institute, 8 December|2019}}</ref> In tropic and temperate areas the net effect is to produce significant warming, and forest restoration can make local temperatures cooler.<ref name="Duchelle-2022"/> At latitudes closer to the poles, there is a cooling effect as forest is replaced by snow-covered (and more reflective) plains.<ref name="Seymour 2019" /> Globally, these increases in surface albedo have been the dominant direct influence on temperature from land use change. Thus, land use change to date is estimated to have a slight cooling effect.<ref name="IPCC Special Report: Climate change and Land p2-54">{{Harvnb|IPCC SRCCL Ch2|2019|p=172}}: "The global biophysical cooling alone has been estimated by a larger range of climate models and is −0.10 ± 0.14&nbsp;°C; it ranges from −0.57&nbsp;°C to +0.06&nbsp;°C&nbsp;... This cooling is essentially dominated by increases in surface albedo: historical land cover changes have generally led to a dominant brightening of land."</ref>
] during the last 400,000 years and the rapid rise since the ]]]
Coal-burning power plants, automobile exhausts, factory smokestacks, and other waste vents of the human environment contribute about 22 billion tons of carbon dioxide (corresponding to 6 billion tons of pure carbon)<!--why is this figure relevant? (coal mass) --> and other ]es into the earth's atmosphere each year. The atmospheric concentration of CO<SUB>2</SUB> has increased by 31% above pre-industrial levels since 1750. This is considerably higher than at any time during the last 420,000 years, the period for which reliable data has been extracted from ]s. From less direct geological evidence it is believed that CO<SUB>2</SUB> values this high were last attained 40 million years ago. About three-quarters of the anthropogenic emissions of CO<SUB>2</SUB> to the atmosphere during the past 20 years is due to ] burning. The rest is predominantly due to land-use change, especially ] .


=== Other factors ===
<br style="clear:both;" />
==== Aerosols and clouds ====
]
Air pollution, in the form of ] on a large scale.<ref>{{Harvnb|Haywood|2016|p=456}}; {{harvnb|McNeill|2017}}; {{harvnb|Samset|Sand|Smith|Bauer|2018}}.</ref> Aerosols scatter and absorb solar radiation. From 1961 to 1990, a gradual reduction in the amount of ] was observed. This phenomenon is popularly known as '']'',<ref>{{harvnb|IPCC AR5 WG1 Ch2|2013|p=183}}.</ref> and is primarily attributed to ] aerosols produced by the combustion of fossil fuels with heavy sulfur concentrations like ] and ].<ref name="Quaas2022" /> Smaller contributions come from ] (from combustion of fossil fuels and biomass), and from dust.<ref>{{harvnb|He|Wang|Zhou|Wild|2018}}; {{Harvnb|Storelvmo|Phillips|Lohmann|Leirvik|2016}}</ref><ref>{{Cite web |date=18 February 2021 |title=Aerosol pollution has caused decades of global dimming |url=https://news.agu.org/press-release/aerosol-pollution-caused-decades-of-global-dimming/ |website=] |access-date=18 December 2023 |archive-url=https://web.archive.org/web/20230327143716/https://news.agu.org/press-release/aerosol-pollution-caused-decades-of-global-dimming/ |archive-date=27 March 2023 }}</ref><ref>{{Cite web |last=Monroe |first=Robert |date=2023-01-20 |title=Increased Atmospheric Dust has Masked Power of Greenhouse Gases to Warm Planet {{!}} Scripps Institution of Oceanography |url=https://scripps.ucsd.edu/news/increased-atmospheric-dust-has-masked-power-greenhouse-gases-warm-planet |access-date=2024-11-08 |website=scripps.ucsd.edu |language=en}}</ref> Globally, aerosols have been declining since 1990 due to pollution controls, meaning that they no longer mask greenhouse gas warming as much.<ref>{{harvnb|Wild|Gilgen|Roesch|Ohmura|2005}}; {{Harvnb|Storelvmo|Phillips|Lohmann|Leirvik|2016}}; {{harvnb|Samset|Sand|Smith|Bauer|2018}}.</ref><ref name="Quaas2022">{{Cite journal |last1=Quaas |first1=Johannes |last2=Jia |first2=Hailing |last3=Smith |first3=Chris |last4=Albright |first4=Anna Lea |last5=Aas |first5=Wenche |last6=Bellouin |first6=Nicolas |last7=Boucher |first7=Olivier |last8=Doutriaux-Boucher |first8=Marie |last9=Forster |first9=Piers M. |last10=Grosvenor |first10=Daniel |last11=Jenkins |first11=Stuart |last12=Klimont |first12=Zbigniew |last13=Loeb |first13=Norman G. |last14=Ma |first14=Xiaoyan |last15=Naik |first15=Vaishali |last16=Paulot |first16=Fabien |last17=Stier |first17=Philip |last18=Wild |first18=Martin |last19=Myhre |first19=Gunnar |last20=Schulz |first20=Michael |date=21 September 2022 |title=Robust evidence for reversal of the trend in aerosol effective climate forcing |url=https://acp.copernicus.org/articles/22/12221/2022/ |journal=Atmospheric Chemistry and Physics |volume=22 |issue=18 |pages=12221–12239 |language=en |doi=10.5194/acp-22-12221-2022 |s2cid=252446168 |hdl=20.500.11850/572791 |hdl-access=free |doi-access=free |bibcode=2022ACP....2212221Q }}</ref>
"Greenhouse gases" get their name because they trap radiant energy from the sun that would otherwise be re-radiated back into space, by analogy with the glass panes in a ]. The analogy, however, is a false one, as the effects are different &mdash; see ]. The natural ] that tempers the earth's climate is not at issue in the debate over global warming. Without it, temperatures would drop by approximately 30°C, the oceans would freeze and life as we know it would be impossible. What climatologists are concerned about, rather, is that increased levels of greenhouse gases in the atmosphere might cause more heat to be trapped.


Aerosols also have indirect effects on the ]. Sulfate aerosols act as ] and lead to clouds that have more and smaller cloud droplets. These clouds reflect solar radiation more efficiently than clouds with fewer and larger droplets.<ref>{{harvnb|Twomey|1977}}.</ref> They also reduce the ], which makes clouds more reflective to incoming sunlight.<ref>{{harvnb|Albrecht|1989}}.</ref> Indirect effects of aerosols are the largest uncertainty in ].<ref name=USGCRP_2017_ch2/>
"The longest continuous instrumental measurement of CO<sub>2</sub> mixing ratios began in 1958 at ]. Since then, the annually averaged value has increased monotonically from 315 ]. <!--is that linear? No --> In fact, it is clear that the increase is faster than linear. On ], ], it was reported that the concentration reached 376ppm in ]. South Pole records show similar growth . The monthly measurements display small seasonal oscillations.


While aerosols typically limit global warming by reflecting sunlight, ] in ] that falls on snow or ice can contribute to global warming. Not only does this increase the absorption of sunlight, it also increases melting and sea-level rise.<ref>{{harvnb|Ramanathan|Carmichael|2008}}; {{harvnb|RIVM|2016}}.</ref> Limiting new black carbon deposits in the Arctic could reduce global warming by 0.2&nbsp;°C by 2050.<ref>{{harvnb|Sand|Berntsen|von Salzen|Flanner|2015}}</ref> The effect of decreasing sulfur content of fuel oil for ships since 2020<ref>{{Cite web|url=https://www.imo.org/en/MediaCentre/HotTopics/Pages/Sulphur-2020.aspx|title=IMO 2020 – cutting sulphur oxide emissions|website=imo.org}}</ref> is estimated to cause an additional 0.05&nbsp;°C increase in global mean temperature by 2050.<ref>{{harvnb|Carbon Brief, 3 July|2023}}</ref>
===Solar variation theory===


==== Solar and volcanic activity ====
Various ] have been proposed to attribute terrestrial temperature variations to ].
{{Further|Solar activity and climate}}
] ("NCA4", USGCRP, 2017) includes charts illustrating that neither solar nor volcanic activity can explain the observed warming.<ref>{{cite journal |title=Climate Science Special Report: Fourth National Climate Assessment, Volume I - Chapter 3: Detection and Attribution of Climate Change |url=https://science2017.globalchange.gov/chapter/3/ |website=science2017.globalchange.gov |publisher=U.S. Global Change Research Program (USGCRP) |archive-url=https://web.archive.org/web/20190923190450/https://science2017.globalchange.gov/chapter/3/ |archive-date=23 September 2019 |year=2017 |pages=1–470 |url-status=live}} Adapted directly from Fig. 3.3.</ref><ref>{{cite journal |last1=Wuebbles |first1=D. J. |last2=Fahey |first2=D. W. |last3=Hibbard |first3=K. A. |last4=Deangelo |first4=B. |last5=Doherty |first5=S. |last6=Hayhoe |first6=K. |last7=Horton |first7=R. |last8=Kossin |first8=J. P. |last9=Taylor |first9=P. C. |last10=Waple |first10=A. M. |last11=Yohe |first11=C. P. |date=23 November 2018 |title=Climate Science Special Report / Fourth National Climate Assessment (NCA4), Volume I /Executive Summary / Highlights of the Findings of the U.S. Global Change Research Program Climate Science Special Report |url=https://science2017.globalchange.gov/chapter/executive-summary/ |url-status=live |publisher=U.S. Global Change Research Program |pages=1–470 |doi=10.7930/J0DJ5CTG |archive-url=https://web.archive.org/web/20190614150544/https://science2017.globalchange.gov/chapter/executive-summary/ |archive-date=14 June 2019 |doi-access=free |website=globalchange.gov}}</ref>]]
As the Sun is the Earth's primary energy source, changes in incoming sunlight directly affect the ].<ref name=USGCRP_2017_ch2>{{harvnb|USGCRP Chapter 2|2017|p=78}}.</ref> ] has been measured directly by ]s,<ref>{{Harvnb|National Academies|2008|p=6}}</ref> and indirect measurements are available from the early 1600s onwards.<ref name=USGCRP_2017_ch2 /> Since 1880, there has been no upward trend in the amount of the Sun's energy reaching the Earth, in contrast to the warming of the lower atmosphere (the ]).<ref>{{cite web|title=Is the Sun causing global warming?|website=Climate Change: Vital Signs of the Planet|url=https://climate.nasa.gov/faq/14/is-the-sun-causing-global-warming|access-date=10 May 2019|archive-url=https://web.archive.org/web/20190505160051/https://climate.nasa.gov/faq/14/is-the-sun-causing-global-warming/|archive-date=5 May 2019|url-status=live}}</ref> The upper atmosphere (the ]) would also be warming if the Sun was sending more energy to Earth, but instead, it has been cooling.<ref name="USGCRP-2009">{{Harvnb|USGCRP|2009|p=20}}.</ref>
This is consistent with greenhouse gases preventing heat from leaving the Earth's atmosphere.<ref>{{Harvnb|IPCC AR4 WG1 Ch9|2007|pp=702–703}}; {{harvnb|Randel|Shine|Austin|Barnett|2009}}.</ref>


] can release gases, dust and ash that partially block sunlight and reduce temperatures, or they can send water vapour into the atmosphere, which adds to greenhouse gases and increases temperatures.<ref>{{cite web |url=https://climate.nasa.gov/news/3204/tonga-eruption-blasted-unprecedented-amount-of-water-into-stratosphere/ |title=Tonga eruption blasted unprecedented amount of water into stratosphere |last=Greicius |first=Tony |date=2 August 2022 |website=NASA Global Climate Change |access-date=18 January 2024 |quote=Massive volcanic eruptions like Krakatoa and Mount Pinatubo typically cool Earth's surface by ejecting gases, dust, and ash that reflect sunlight back into space. In contrast, the Tonga volcano didn't inject large amounts of aerosols into the stratosphere, and the huge amounts of water vapor from the eruption may have a small, temporary warming effect, since water vapor traps heat. The effect would dissipate when the extra water vapor cycles out of the stratosphere and would not be enough to noticeably exacerbate climate change effects.}}</ref> These impacts on temperature only last for several years, because both water vapour and volcanic material have low persistence in the atmosphere.<ref name="USGCRP Chapter 2 2017 79">{{harvnb|USGCRP Chapter 2|2017|p=79}}</ref> ] are more persistent, but they are equivalent to less than 1% of current human-caused {{CO2}} emissions.{{sfn|Fischer|Aiuppa|2020}} Volcanic activity still represents the single largest natural impact (forcing) on temperature in the industrial era. Yet, like the other natural forcings, it has had negligible impacts on global temperature trends since the Industrial Revolution.<ref name="USGCRP Chapter 2 2017 79"/>
In the IPCC TAR, it was reported that volcanic and solar forcings might account for half of the temperature variations prior to ], but that the net effect of such natural forcings was roughly neutral since then . In particular, the change in climate forcing from greenhouse gases since ] was estimated to be 8 times larger than the change in forcing due to ] over the same period .


==== Climate change feedbacks ====
However, a number of studies have suggested that additional ] feedbacks may exist which have not been incorporated in the present models or that the relative importance of solar variation may be underestimated . Such claims are disputed (e.g. ) but form an active area of current research. The outcome of this debate may play a key role in determining how much climate change is ].
{{Main|Climate change feedbacks|Climate sensitivity}}
{{seemain|Solar variation theory}}
].<ref>{{cite web |url=https://nsidc.org/cryosphere/seaice/processes/albedo.html |title=Thermodynamics: Albedo |work=NSIDC |access-date=10 October 2017|archive-url=https://web.archive.org/web/20171011021602/https://nsidc.org/cryosphere/seaice/processes/albedo.html |archive-date=11 October 2017 |url-status=live }}</ref>]]


The climate system's response to an initial forcing is shaped by feedbacks, which either amplify or dampen the change. '']'' or ''positive'' feedbacks increase the response, while '']'' or ''negative'' feedbacks reduce it.<ref>{{cite web |title=The study of Earth as an integrated system |publisher=Earth Science Communications Team at NASA's Jet Propulsion Laboratory / California Institute of Technology |year=2013 |series=Vitals Signs of the Planet |archive-url=https://web.archive.org/web/20190226190002/https://climate.nasa.gov/nasa_science/science/ |archive-date=26 February 2019 |url=https://climate.nasa.gov/nasa_science/science/ |url-status=live}}</ref> The main reinforcing feedbacks are the ], the ], and the net effect of clouds.{{sfn|USGCRP Chapter 2|2017|pp=89–91}}<ref>{{harvnb|IPCC AR6 WG1 Technical Summary|2021|p=58}}: "The net effect of changes in clouds in response to global warming is to amplify human-induced warming, that is, the net cloud feedback is positive (high confidence)"</ref> The primary balancing mechanism is ], as Earth's surface gives off more ] to space in response to rising temperature.{{sfn|USGCRP Chapter 2|2017|pp=89–90}} In addition to temperature feedbacks, there are feedbacks in the carbon cycle, such as the fertilizing effect of {{CO2}} on plant growth.<ref>{{harvnb|IPCC AR5 WG1|2013|p=14}}</ref> Feedbacks are expected to trend in a positive direction as greenhouse gas emissions continue, raising climate sensitivity.<ref>{{harvnb|IPCC AR6 WG1 Technical Summary|2021|p=93}}: "Feedback processes are expected to become more positive overall (more amplifying of global surface temperature changes) on multi-decadal time scales as the spatial pattern of surface warming evolves and global surface temperature increases."</ref>
===Other theories===


These feedback processes alter the pace of global warming. For instance, warmer air ] in the form of ], which is itself a potent greenhouse gas.{{sfn|USGCRP Chapter 2|2017|pp=89–91}} Warmer air can also make clouds higher and thinner, and therefore more insulating, increasing climate warming.{{sfn|Williams|Ceppi|Katavouta|2020}} The reduction of snow cover and sea ice in the Arctic is another major feedback, this reduces the reflectivity of the Earth's surface in the region and ].<ref>{{harvnb|NASA, 28 May|2013}}.</ref><ref>{{harvnb|Cohen|Screen|Furtado|Barlow|2014}}.</ref> This additional warming also contributes to ] thawing, which releases methane and {{CO2}} into the atmosphere.<ref name="Turetsky 2019">{{harvnb|Turetsky|Abbott|Jones|Anthony|2019}}</ref>
Various other hypotheses have been proposed, including but not limited to:


Around half of human-caused {{CO2}} emissions have been absorbed by land plants and by the oceans.<ref>{{harvnb|Climate.gov, 23 June|2022}}: "Carbon cycle experts estimate that natural "sinks"—processes that remove carbon from the atmosphere—on land and in the ocean absorbed the equivalent of about half of the carbon dioxide we emitted each year in the 2011–2020 decade."</ref> This fraction is not static and if future {{CO2}} emissions decrease, the Earth will be able to absorb up to around 70%. If they increase substantially, it'll still absorb more carbon than now, but the overall fraction will decrease to below 40%.<ref>{{harvnb|IPCC AR6 WG1 Technical Summary|2021|p=TS-122|loc=Box TS.5, Figure 1}}</ref> This is because climate change increases droughts and heat waves that eventually inhibit plant growth on land, and soils will release more carbon from dead plants ].<ref>{{harvnb|Melillo|Frey|DeAngelis|Werner|2017}}: Our first-order estimate of a warming-induced loss of 190 Pg of soil carbon over the 21st century is equivalent to the past two decades of carbon emissions from fossil fuel burning.</ref><ref>{{harvnb|IPCC SRCCL Ch2|2019|pp=133, 144}}.</ref> The rate at which oceans absorb atmospheric carbon will be lowered as they become more acidic and experience changes in ] and ] distribution.{{sfn|USGCRP Chapter 2|2017|pp=93–95}}<ref name="Liu2022">{{cite journal |last1=Liu |first1=Y. |last2=Moore |first2=J. K. |last3=Primeau |first3=F. |last4=Wang |first4=W. L. |date=22 December 2022 |title=Reduced CO2 uptake and growing nutrient sequestration from slowing overturning circulation |journal=Nature Climate Change |volume=13 |pages=83–90 |doi=10.1038/s41558-022-01555-7 |osti=2242376 |s2cid=255028552 }}</ref><ref name="PearceYale3602023"/> Uncertainty over feedbacks, particularly cloud cover,<ref>{{harvnb|IPCC AR6 WG1 Technical Summary|2021|pp=58, 59}}: "Clouds remain the largest contribution to overall uncertainty in climate feedbacks."</ref> is the major reason why different climate models project different magnitudes of warming for a given amount of emissions.<ref>{{harvnb|Wolff|Shepherd|Shuckburgh|Watson|2015}}: "the nature and magnitude of these feedbacks are the principal cause of uncertainty in the response of Earth's climate (over multi-decadal and longer periods) to a particular emissions scenario or greenhouse gas concentration pathway."</ref>
# The warming is within the range of natural variation and needs no particular explanation
# The warming is a consequence of coming out of a prior cool period &mdash; the ] &mdash; and needs no other explanation
# The warming trend itself has not been clearly established, and therefore does not need any explanation. See also: '''].'''


== Modelling ==
===Other global warmings===
{{Further|Climate model|Climate change scenario}}
It is thought by some geologists that the Earth experienced global warming in the early ] period, with average temperatures rising by 5° ] (9° ]). Research by the ] published in ''Geology'' (32, 157&ndash;160, 2004 ) indicates that this caused the rate of rock weathering to increase by 400%. As a result of this, carbon dioxide levels dropped back to normal over roughly the next 150,000 years.
] that heats the planet up.]]
A ] is a representation of the physical, chemical and biological processes that affect the climate system.<ref>{{Harvnb|IPCC AR5 SYR Glossary|2014|p=120}}.</ref> Models include natural processes like changes in the Earth's orbit, historical changes in the Sun's activity, and volcanic forcing.<ref>{{harvnb|Carbon Brief, 15 January|2018|loc=}}</ref> Models are used to estimate the degree of warming future emissions will cause when accounting for the ].<ref>{{harvnb|Wolff|Shepherd|Shuckburgh|Watson|2015}}</ref><ref>{{harvnb|Carbon Brief, 15 January|2018|loc=}}</ref> Models also predict the circulation of the oceans, the annual cycle of the seasons, and the flows of carbon between the land surface and the atmosphere.<ref>{{harvnb|Carbon Brief, 15 January|2018|loc=}}</ref>


The physical realism of models is tested by examining their ability to simulate current or past climates.<ref>{{Harvnb|IPCC AR4 WG1 Ch8|2007}}, FAQ 8.1.</ref> Past models have underestimated the rate of ]<ref>{{harvnb|Stroeve|Holland|Meier|Scambos|2007}}; {{harvnb|National Geographic, 13 August|2019}}</ref> and underestimated the rate of precipitation increase.<ref>{{harvnb|Liepert|Previdi|2009}}.</ref> Sea level rise since 1990 was underestimated in older models, but more recent models agree well with observations.<ref>{{harvnb|Rahmstorf|Cazenave|Church|Hansen|2007}}; {{harvnb|Mitchum|Masters|Hamlington|Fasullo|2018}}</ref> The 2017 United States-published ] notes that "climate models may still be underestimating or missing relevant feedback processes".<ref>{{harvnb|USGCRP Chapter 15|2017}}.</ref> Additionally, climate models may be unable to adequately predict short-term regional climatic shifts.<ref>{{cite journal |last1=Hébert |first1=R. |last2=Herzschuh |first2=U. |last3=Laepple |first3=T. |date=31 October 2022 |title=Millennial-scale climate variability over land overprinted by ocean temperature fluctuations |journal=] |volume=15 |issue=1 |pages=899–905 |doi=10.1038/s41561-022-01056-4 |pmid=36817575 |pmc=7614181 |bibcode=2022NatGe..15..899H }}</ref>
Sudden release of ] (a ]) has been hypothesized as a cause of past global warming. Two events possibly linked in this way are the ] and the ]. However, warming at the end of the last ice age is thought to not be due to clathrate release.


A ] add societal factors to a physical climate model. These models simulate how population, ], and energy use affect—and interact with—the physical climate. With this information, these models can produce scenarios of future greenhouse gas emissions. This is then used as input for physical climate models and carbon cycle models to predict how atmospheric concentrations of greenhouse gases might change.<ref>{{harvnb|Carbon Brief, 15 January|2018|loc=}}</ref><ref>{{harvnb|Matthews|Gillett|Stott|Zickfeld|2009}}</ref> Depending on the ] and the mitigation scenario, models produce atmospheric {{CO2}} concentrations that range widely between 380 and 1400 ppm.<ref>{{harvnb|Carbon Brief, 19 April|2018}}; {{harvnb|Meinshausen|2019|p=462}}.</ref>
Using ] data for the last 500 million years (Veizer et al. 2000, Nature 408, pp. 698-701) concluded that long-term temperature variations are only weakly coupled to CO<sub>2</sub> variations. Shaviv and Veizer (2003, ) extended this by arguing that the biggest long-term influence on temperature is actually the ]'s motion around the ]. Afterwards, they argued that over geologic time a change in CO<sub>2</sub> concentrations comparable to doubling preindustrial levels, only results in about 0.75 &deg;C warming rather than the usual 1.5-4.5 &deg;C found by climate models . In turn the Vezier's recent work has been criticised .


==Climate models== == Impacts ==
{{Main|Effects of climate change}}
{{seemain|General circulation model}}
As noted above, climate models have been used by the IPCC to anticipate a warming of 1.4°C to 5.8°C between 1990 and 2100 . They have also been used to help determine the ] by comparing the observed changes to those that the models predict from various natural and ] forcing factors.


]s from the 1850 to 1900 baseline.]]
The most recent climate models can produce a good match to observations of global temperature changes over the last century. These models do not unambiguously attribute the warming that occurred from approximately 1910 to 1945 to either natural variation or human effects; however, they suggest that the warming since 1975 is dominated by man-made ] emissions.


=== Environmental effects ===
Uncertainties in the representation of clouds are a dominant source of uncertainty in existing models, despite clear progress in modeling of clouds . There is also an ongoing discussion as to whether climate models are neglecting important indirect and feedback effects of ]. Further, all such models are limited by available computational power, so that they may overlook changes related to small scale processes and weather (e.g. storm systems, hurricanes). However, despite these and other limitations, the ] considers climate models "to be suitable tools to provide useful projections of future climates" .
{{Further|Effects of climate change on oceans|Effects of climate change on the water cycle}}
The environmental effects of climate change are broad and far-reaching, ], ice, and weather. Changes may occur gradually or rapidly. Evidence for these effects comes from studying climate change in the past, from modelling, and from modern observations.<ref>{{harvnb|Hansen|Sato|Hearty|Ruedy|2016}}; {{harvnb|Smithsonian, 26 June|2016}}.</ref> Since the 1950s, ]s and heat waves have appeared simultaneously with increasing frequency.<ref>{{harvnb|USGCRP Chapter 15|2017|p=415}}.</ref> Extremely wet or dry events within the ] period have increased in India and East Asia.<ref>{{harvnb|Scientific American, 29 April|2014}}; {{harvnb|Burke|Stott|2017}}.</ref> Monsoonal precipitation over the Northern Hemisphere has increased since 1980.<ref>{{Cite journal |last1=Liu |first1=Fei |last2=Wang |first2=Bin |last3=Ouyang |first3=Yu |last4=Wang |first4=Hui |last5=Qiao |first5=Shaobo |last6=Chen |first6=Guosen |last7=Dong |first7=Wenjie |date=19 April 2022 |title=Intraseasonal variability of global land monsoon precipitation and its recent trend |journal=npj Climate and Atmospheric Science |language=en |volume=5 |issue=1 |page=30 |doi=10.1038/s41612-022-00253-7 |bibcode=2022npCAS...5...30L |issn=2397-3722 |doi-access=free }}</ref> The rainfall rate and intensity of ],<ref name="USGCRP-2017">{{Harvnb|USGCRP Chapter 9|2017|p=260}}.</ref> and the geographic range likely expanding poleward in response to climate warming.<ref>{{cite journal |first1=Joshua |last1=Studholme |first2=Alexey V. |last2=Fedorov |first3=Sergey K. |last3=Gulev |first4=Kerry |last4=Emanuel |first5=Kevin |last5=Hodges |url=https://www.nature.com/articles/s41561-021-00859-1 |title=Poleward expansion of tropical cyclone latitudes in warming climates |date=29 December 2021 |journal=] |volume=15 |pages=14–28 |doi=10.1038/s41561-021-00859-1 |s2cid=245540084}}</ref> Frequency of tropical cyclones has not increased as a result of climate change.<ref>{{cite web |title=Hurricanes and Climate Change |url=https://www.c2es.org/content/hurricanes-and-climate-change/ |website=] |date=10 July 2020}}</ref>


]
Global sea level is rising as a consequence of ] and ] and ]. Sea level rise has increased over time, reaching 4.8&nbsp;cm per decade between 2014 and 2023.<ref>{{harvnb|WMO|2024a|p=6}}.</ref> Over the 21st century, the IPCC projects 32–62&nbsp;cm of sea level rise under a low emission scenario, 44–76&nbsp;cm under an intermediate one and 65–101&nbsp;cm under a very high emission scenario.<ref>{{harvnb|IPCC AR6 WG2|2022|p=1302}}</ref> ] processes in Antarctica may add substantially to these values,<ref>{{harvnb|DeConto|Pollard|2016}}</ref> including the possibility of a 2-meter sea level rise by 2100 under high emissions.{{sfn|Bamber|Oppenheimer|Kopp|Aspinall|2019}}


Climate change has led to decades of ].<ref>{{harvnb|Zhang|Lindsay|Steele|Schweiger|2008}}</ref> While ice-free summers are expected to be rare at 1.5&nbsp;°C degrees of warming, they are set to occur once every three to ten years at a warming level of 2&nbsp;°C.<ref>{{harvnb|IPCC SROCC Summary for Policymakers|2019|p=18}}</ref> Higher atmospheric {{CO2}} concentrations cause more {{CO2}} to dissolve in the oceans, which is ].<ref>{{Harvnb|Doney|Fabry|Feely|Kleypas|2009}}.</ref> Because oxygen is less soluble in warmer water,<ref>{{harvnb|Deutsch|Brix|Ito|Frenzel|2011}}</ref> its concentrations in the ocean ], and ] are expanding.<ref>{{harvnb|IPCC SROCC Ch5|2019|p=510}}; {{cite web |title=Climate Change and Harmful Algal Blooms |date=5 September 2013 |url=https://www.epa.gov/nutrientpollution/climate-change-and-harmful-algal-blooms |publisher=] |access-date=11 September 2020}}</ref>
==Theories and criticisms ==


=== Tipping points and long-term impacts ===
Leaving the realm of scientific journals, the debate has spilled out into the public arena, with some politicians making the issue a component of their campaigns for high office. One example of this is ] ] candidate ], author of '']''. Global warming is a more central and sustained issue, however, for the ].
] |access-date=31 January 2024 }}</ref><ref name="ArmstrongMcKay2022" />]]
{{Main|Tipping points in the climate system}}
Greater degrees of global warming increase the risk of passing through ']'—thresholds beyond which certain major impacts can no longer be avoided even if temperatures return to their previous state.<ref>{{Harvnb|IPCC SR15 Ch3|2018|p=283}}.</ref><ref>{{Harvnb|Carbon Brief, 10 February|2020}}</ref> For instance, the ] is already melting, but if global warming reaches levels between 1.7&nbsp;°C and 2.3&nbsp;°C, its melting will continue until it fully disappears. If the warming is later reduced to 1.5&nbsp;°C or less, it will still lose a lot more ice than if the warming was never allowed to reach the threshold in the first place.<ref name="Bochow2023">{{cite journal |last1=Bochow |first1=Nils |last2=Poltronieri |first2=Anna |last3=Robinson |first3=Alexander |last4=Montoya |first4=Marisa |last5=Rypdal |first5=Martin |last6=Boers |first6=Niklas |date=18 October 2023 |title=Overshooting the critical threshold for the Greenland ice sheet |journal=] |volume=622 |issue=7983 |pages=528–536 |bibcode=2023Natur.622..528B |doi=10.1038/s41586-023-06503-9 |pmc=10584691 |pmid=37853149}}</ref> While the ice sheets would melt over millennia, other tipping points would occur faster and give societies less time to respond. The collapse of major ]s like the ] (AMOC), and irreversible damage to key ecosystems like the ] and ] can unfold in a matter of decades.<ref name="ArmstrongMcKay2022">{{Cite journal |last1=Armstrong McKay |first1=David I. |last2=Staal |first2=Arie |last3=Abrams |first3=Jesse F. |last4=Winkelmann |first4=Ricarda |last5=Sakschewski |first5=Boris |last6=Loriani |first6=Sina |last7=Fetzer |first7=Ingo |last8=Cornell |first8=Sarah E. |last9=Rockström |first9=Johan |last10=Lenton |first10=Timothy M. |date=9 September 2022 |title=Exceeding 1.5&nbsp;°C global warming could trigger multiple climate tipping points |url=https://www.science.org/doi/10.1126/science.abn7950 |journal=] |volume=377 |issue=6611 |pages=eabn7950 |doi=10.1126/science.abn7950 |pmid=36074831 |hdl=10871/131584 |s2cid=252161375 |issn=0036-8075|hdl-access=free }}</ref>


The long-term ] include further ice melt, ], sea level rise, ocean acidification and ocean deoxygenation.<ref>{{harvnb|IPCC AR6 WG1 Summary for Policymakers|2021|p=21}}</ref> The timescale of long-term impacts are centuries to millennia due to {{CO2}}'s long atmospheric lifetime.<ref>{{Harvnb|IPCC AR5 WG1 Ch12|2013|pp=88–89|loc=FAQ 12.3}}</ref> The result is an estimated total sea level rise of {{convert|2.3|m/°C|ft/°F}} after 2000 years.<ref>{{harvnb|Smith|Schneider|Oppenheimer|Yohe|2009}}; {{harvnb|Levermann|Clark|Marzeion|Milne|2013}}</ref> Oceanic {{CO2}} uptake is slow enough that ocean acidification will also continue for hundreds to thousands of years.{{sfn|IPCC AR5 WG1 Ch12|2013|p=1112}} Deep oceans (below {{convert|2000|m|ft}}) are also already committed to losing over 10% of their dissolved oxygen by the warming which occurred to date.<ref>{{cite journal |last1=Oschlies |first1=Andreas |title=A committed fourfold increase in ocean oxygen loss |journal=Nature Communications |date=16 April 2021 |volume=12 |issue=1 |page=2307 |doi=10.1038/s41467-021-22584-4 |pmid=33863893 |pmc=8052459 |bibcode=2021NatCo..12.2307O }}</ref> Further, the ] appears committed to practically irreversible melting, which would increase the sea levels by at least {{convert|3.3|m|ftin|abbr=on}} over approximately 2000 years.<ref name="ArmstrongMcKay2022" /><ref name="Lau2023">{{Cite journal |last1=Lau |first1=Sally C. Y. |last2=Wilson |first2=Nerida G. |last3=Golledge |first3=Nicholas R. |last4=Naish |first4=Tim R. |last5=Watts |first5=Phillip C. |last6=Silva |first6=Catarina N. S. |last7=Cooke |first7=Ira R. |last8=Allcock |first8=A. Louise |last9=Mark |first9=Felix C. |last10=Linse |first10=Katrin |date=21 December 2023 |title=Genomic evidence for West Antarctic Ice Sheet collapse during the Last Interglacial |url=https://epic.awi.de/id/eprint/58369/1/science.ade0664%281%29.pdf |journal=] |volume=382 |issue=6677 |pages=1384–1389 |bibcode=2023Sci...382.1384L |doi=10.1126/science.ade0664 |pmid=38127761 |s2cid=266436146}}</ref><ref name="Naughten2023">{{cite journal |last1=Naughten |first1=Kaitlin A. |last2=Holland |first2=Paul R. |last3=De Rydt |first3=Jan |date=23 October 2023 |title=Unavoidable future increase in West Antarctic ice-shelf melting over the twenty-first century |journal=] |volume=13 |issue=11 |pages=1222–1228 |bibcode=2023NatCC..13.1222N |doi=10.1038/s41558-023-01818-x |s2cid=264476246 |doi-access=free}}</ref>
Much about global warming theories is controversial, particularly whether there exists a ] sufficient to justify concerted international action to ameliorate its effects (see ''']''').


===Nature and wildlife===
Proponents of global warming theory express a wide range of opinions. Some merely recognize the validity of the observed increases in temperature. Others support measures such as the ] that are intended to have some near-future climate effects and to lead eventually to further measures. Others believe that the environmental damage will have such severe impact that immediate steps must be taken to reduce CO<SUB>2</SUB> emissions, regardless of the economic costs to advanced nations such as the United States (which has the largest emissions of greenhouse gases of any country in absolute terms, and the second largest emissions per capita after Australia ).
<!-- Warning: Do not change the above title without also changing places where the gallery below is transcluded (this article summary, and effects of climate change article). -->
{{Further|Effects of climate change on oceans|Effects of climate change on biomes}}
Recent warming has driven many terrestrial and freshwater species poleward and towards higher ].<ref>{{harvnb|IPCC SR15 Ch3|2018|p=218}}.</ref> For instance, the range of hundreds of North American ]s has shifted northward at an average rate of 1.5&nbsp;km/year over the past 55 years.<ref>{{Cite journal |last1=Martins |first1=Paulo Mateus |last2=Anderson |first2=Marti J. |last3=Sweatman |first3=Winston L. |last4=Punnett |first4=Andrew J. |date=9 April 2024 |title=Significant shifts in latitudinal optima of North American birds |journal=] |language=en |volume=121 |issue=15 |pages=e2307525121 |doi=10.1073/pnas.2307525121 |issn=0027-8424 |pmc=11009622 |pmid=38557189 |bibcode=2024PNAS..12107525M }}</ref> Higher atmospheric {{CO2}} levels and an extended growing season have resulted in global greening. However, heatwaves and drought have reduced ] productivity in some regions. The future balance of these opposing effects is unclear.{{Sfn|IPCC SRCCL Ch2|2019|p=133}} A related phenomenon driven by climate change is ], affecting up to 500 million hectares globally.<ref>{{Cite journal |last1=Deng |first1=Yuanhong |last2=Li |first2=Xiaoyan |last3=Shi |first3=Fangzhong |last4=Hu |first4=Xia |date=December 2021 |title=Woody plant encroachment enhanced global vegetation greening and ecosystem water-use efficiency |url=https://onlinelibrary.wiley.com/doi/10.1111/geb.13386 |journal=] |language=en |volume=30 |issue=12 |pages=2337–2353 |bibcode=2021GloEB..30.2337D |doi=10.1111/geb.13386 |issn=1466-822X |access-date=10 June 2024 |via=Wiley Online Library}}</ref> Climate change has contributed to the expansion of drier climate zones, such as the ] in the ].<ref>{{harvnb|IPCC SRCCL Summary for Policymakers|2019|p=7}}; {{harvnb|Zeng|Yoon|2009}}.</ref> The size and speed of global warming is making ] more likely.{{Sfn|Turner|Calder|Cumming|Hughes|2020|p=1}} Overall, it is expected that climate change will result in the ] of many species.{{Sfn|Urban|2015}}


The oceans have heated more slowly than the land, but plants and animals in the ocean have migrated towards the colder poles faster than species on land.<ref>{{harvnb|Poloczanska|Brown|Sydeman|Kiessling|2013}}; {{harvnb|Lenoir|Bertrand|Comte|Bourgeaud|2020}}</ref> Just as on land, ] occur more frequently due to climate change, harming a wide range of organisms such as corals, ], and ].<ref>{{harvnb|Smale|Wernberg|Oliver|Thomsen|2019}}</ref> Ocean acidification makes it harder for ] such as ]s, ]s and corals to ]; and heatwaves have ].{{Sfn|IPCC SROCC Summary for Policymakers|2019|p=13}} ] enhanced by climate change and ] lower oxygen levels, disrupt ]s and cause great loss of marine life.<ref>{{harvnb|IPCC SROCC Ch5|2019|p=510}}</ref> Coastal ecosystems are under particular stress. Almost half of global wetlands have disappeared due to climate change and other human impacts.{{Sfn|IPCC SROCC Ch5|2019|p=451}} Plants have come under increased stress from damage by insects.<ref>{{Cite journal |last1=Azevedo-Schmidt |first1=Lauren |last2=Meineke |first2=Emily K. |last3=Currano |first3=Ellen D. |date=18 October 2022 |title=Insect herbivory within modern forests is greater than fossil localities |journal=] |language=en |volume=119 |issue=42 |pages=e2202852119 |doi=10.1073/pnas.2202852119 |doi-access=free |pmid=36215482 |pmc=9586316 |bibcode=2022PNAS..11902852A |issn=0027-8424 }}</ref>
Critics of the global warming theory similarly offer a wide spectrum of opinions. Some, such as ], propose that human influence has warmed the atmosphere yet dispute the conclusion of the ] TAR, which says "here is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities". Others point out that observations of global temperatures over much larger time spans, thousands of years rather than decades, show global temperatures fluctuated wildly in the past long before the introduction of human industrial activity such as the ]. An additional assertion of many critics is that it cannot be possible to ascertain any definitive global temperature trend from the limited temperature record having often been cited &mdash; the Earth is much older than that, they affirm. Other scientists theorize global temperature change may in fact be induced by natural causes, such as ] and ].


{| class="center toccolours"
The above paragraphs might give the impression that belief in the course of past climate change correlates strongly with advocacy for future actions: this is not necessarily so. It is possible, perhaps common, to study the past record and give no counsel on the future.
|+ '''Climate change impacts on the environment'''
|<gallery mode="packed" heights="120" style="line-height:120%">
File:Bleachedcoral.jpg|alt=Underwater photograph of branching coral that is bleached white|]. ] from ] has damaged the ] and threatens ]s worldwide.<ref>{{Cite web |url=https://sos.noaa.gov/datasets/coral-reef-risk-outlook/ |title=Coral Reef Risk Outlook |date=2 January 2012 |access-date=4 April 2020 |publisher=] |quote=At present, local human activities, coupled with past thermal stress, threaten an estimated 75 percent of the world's reefs. By 2030, estimates predict more than 90% of the world's reefs will be threatened by local human activities, warming, and acidification, with nearly 60% facing high, very high, or critical threat levels.}}</ref>
File:Orroral Valley Fire viewed from Tuggeranong January 2020.jpg|alt=Photograph of evening in a valley settlement. The skyline in the hills beyond is lit up red from the fires.|]. Drought and high temperatures worsened the ].<ref>{{harvnb|Carbon Brief, 7 January|2020}}.</ref>
File:National Park Service Thawing permafrost (27759123542).jpg|alt=The green landscape is interrupted by a huge muddy scar where the ground has subsided.|]. ] undermine infrastructure and ], a greenhouse gas.<ref name="Turetsky 2019"/>
File:Endangered arctic - starving polar bear (cropped).jpg|alt=An emaciated polar bear stands atop the remains of a melting ice floe.|]. Many arctic animals rely on sea ice, which has been disappearing in a warming Arctic.<ref>{{harvnb|IPCC AR5 WG2 Ch28|2014|p=1596}}: "Within 50 to 70 years, loss of hunting habitats may lead to elimination of polar bears from seasonally ice-covered areas, where two-thirds of their world population currently live."</ref>
File:Mountain Pine Beetle damage in the Fraser Experimental Forest 2007.jpg|alt=Photograph of a large area of forest. The green trees are interspersed with large patches of damaged or dead trees turning purple-brown and light red.|]. Mild winters allow more ] to survive to kill large swaths of forest.<ref>{{Cite web |url=https://www.nps.gov/romo/learn/nature/climatechange.htm |title=What a changing climate means for Rocky Mountain National Park |publisher=] |access-date=9 April 2020}}</ref>
</gallery>
|}


=== Humans ===
Controversial subjects are discussed further in the article ''']'''.
<!-- Warning: Do not change the above title without also changing places where the gallery below is transcluded (this article summary, and effects of climate change article). -->
{{Main|Effects of climate change}}
[[File:20211109 Frequency of extreme weather for different degrees of global warming - bar chart IPCC AR6 WG1 SPM.svg|thumb|upright=1.35 |Extreme weather will be progressively more common as the Earth warms.<ref name=IPCC6AR_ExtremeEvents>{{harvnb|IPCC AR6 WG1 Summary for Policymakers|2021|loc=Fig. SPM.6
|page=SPM-23}}</ref>]]
The effects of climate change are impacting humans everywhere in the world.<ref>{{cite journal |last1=Lenton |first1=Timothy M. |last2=Xu |first2=Chi |last3=Abrams |first3=Jesse F. |last4=Ghadiali |first4=Ashish |last5=Loriani |first5=Sina |last6=Sakschewski |first6=Boris |last7=Zimm |first7=Caroline |last8=Ebi |first8=Kristie L. |last9=Dunn |first9=Robert R. |last10=Svenning |first10=Jens-Christian |last11=Scheffer |first11=Marten |title=Quantifying the human cost of global warming |journal=] |year=2023 |volume=6 |issue=10 |pages=1237–1247 |doi=10.1038/s41893-023-01132-6 |doi-access=free|bibcode=2023NatSu...6.1237L |hdl=10871/132650 |hdl-access=free }}</ref> Impacts can be observed on all continents and ocean regions,<ref>{{Harvnb|IPCC AR5 WG2 Ch18|2014|pp=983, 1008}}</ref> with low-latitude, ] facing the greatest risk.<ref>{{Harvnb|IPCC AR5 WG2 Ch19|2014|p=1077}}.</ref> Continued warming has potentially "severe, pervasive and irreversible impacts" for people and ecosystems.<ref>{{harvnb|IPCC AR5 SYR Summary for Policymakers|2014|loc=SPM 2|p=8}}</ref> The risks are unevenly distributed, but are generally greater for disadvantaged people in developing and developed countries.<ref>{{harvnb|IPCC AR5 SYR Summary for Policymakers|2014|loc=SPM 2.3|p=13}}</ref>


==== Health and food ====
==Potential effects==
{{Main|Effects of climate change on agriculture#Global food security and undernutrition|Effects of climate change on human health}}
Many public policy organizations, governments, and individuals are concerned that global warming could harm the ] in various ways. As well as the intrinsic value attached by them to the preservation of the environment, there are wide range of possible consequences for humans. These include rising sea levels, declining output of global ], increased extreme weather, and the spread of disease.
The ] calls climate change one of the biggest threats to global health in the 21st century.<ref name=WHO_Nov_2023/> Scientists have warned about the irreversible harms it poses.<ref name=Romanello_et_al_2023>{{harvnb|Romanello|2023}}</ref> ] events affect public health, and ] and ].<ref name=nca2018_ch14>{{harvnb|Ebi et al.|2018}}</ref><ref name=Romanello_et_al_2022>{{harvnb|Romanello|2022}}</ref><ref name=IPCC_AR6_WG2_p9>{{harvnb|IPCC AR6 WG2 SPM|2022|p=9}}</ref> ] lead to increased illness and death.<ref name=nca2018_ch14/><ref name=Romanello_et_al_2022/> Climate change increases the intensity and frequency of extreme weather events.<ref name=Romanello_et_al_2022/><ref name=IPCC_AR6_WG2_p9/> It can affect transmission of ], such as ] and ].<ref name=Romanello_et_al_2023/><ref name=nca2018_ch14/> According to the ], 14.5&nbsp;million more deaths are expected due to climate change by 2050.<ref>{{harvnb|World Economic Forum|2024|p=4}}</ref> 30% of the global population currently live in areas where extreme heat and humidity are already associated with excess deaths.<ref name=Carbon_Brief_2017>{{harvnb|Carbon Brief, 19 June|2017}}</ref><ref>{{harvnb|Mora et al.|2017}}</ref> By 2100, 50% to 75% of the global population would live in such areas.<ref name=Carbon_Brief_2017/><ref>{{harvnb|IPCC AR6 WG2 Ch6|2022|p=988}}</ref>


While total ]s have been increasing in the past 50 years due to agricultural improvements, ].<ref name=IPCC_AR6_WG2_p9/> ] in multiple regions.<ref name=IPCC_AR6_WG2_p9/> While ] has been positively affected in some high ] areas, mid- and low-latitude areas have been negatively affected.<ref name=IPCC_AR6_WG2_p9/> According to the World Economic Forum, an increase in ] in certain regions could cause 3.2&nbsp;million deaths from ] by 2050 and ] in children.<ref>{{harvnb|World Economic Forum|2024|p=24}}</ref> With 2&nbsp;°C warming, global ] headcounts could decline by 7–10% by 2050, as less animal feed will be available.<ref>{{harvnb|IPCC AR6 WG2 Ch5|2022|p=748}}</ref> If the emissions continue to increase for the rest of century, then over 9 million climate-related deaths would occur annually by 2100.<ref>{{harvnb|IPCC AR6 WG2 Technical Summary|2022|p=63}}</ref>
The extent and likelihood of these consequences is a matter of considerable controversy, with ] groups typically emphasizing the possible dangers and groups close to ] questioning the climate models and consequences of global warming &mdash; and funding scientists to do so. A summary of possible effects and our current understanding can be found in the report of the IPCC Working Group II. Much remains to be learned, however.


=== Effects on ecosystems === ==== Livelihoods and inequality ====
{{Further|Economic analysis of climate change|Climate security}}
Secondary evidence of global warming &mdash; lessened snow cover, rising sea levels, weather changes &mdash; provides examples of consequences of global warming that may influence not only human activities but also the ]s. Increasing global temperature means that ecosystems may change; some ] may be forced out of their habitats (possibly to extinction) because of changing conditions, while others may flourish. Few of the ] on Earth could expect to be unaffected.
Economic damages due to climate change may be severe and there is a chance of disastrous consequences.<ref>{{harvnb|DeFries|Edenhofer|Halliday|Heal|2019|p=3}}; {{harvnb|Krogstrup|Oman|2019|p=10}}.</ref> Severe impacts are expected in South-East Asia and ], where most of the local inhabitants are dependent upon natural and agricultural resources.<ref name="FAO-2021">{{Cite book |url=https://doi.org/10.4060/cb7431en |title=Women's leadership and gender equality in climate action and disaster risk reduction in Africa − A call for action |publisher=] & The African Risk Capacity (ARC) Group |year=2021 |isbn=978-92-5-135234-2 |location=Accra |doi=10.4060/cb7431en |s2cid=243488592 }}</ref><ref>{{harvnb|IPCC AR5 WG2 Ch13|2014|pp=796–797}}</ref> ] can prevent outdoor labourers from working. If warming reaches 4&nbsp;°C then labour capacity in those regions could be reduced by 30 to 50%.<ref>{{harvnb|IPCC AR6 WG2|2022|p=725}}</ref> The ] estimates that between 2016 and 2030, climate change could drive over 120 million people into extreme poverty without adaptation.{{Sfn|Hallegatte|Bangalore|Bonzanigo|Fay|2016|p=12}}


Inequalities based on wealth and social status have worsened due to climate change.<ref>{{harvnb|IPCC AR5 WG2 Ch13|2014|p=796}}.</ref> Major difficulties in mitigating, adapting to, and recovering from climate shocks are faced by marginalized people who have less control over resources.<ref name="Grabe-2014">Grabe, Grose and Dutt, 2014; FAO, 2011; FAO, 2021a; Fisher and Carr, 2015; IPCC, 2014; Resurrección et al., 2019; UNDRR, 2019; Yeboah et al., 2019.</ref><ref name="FAO-2021" /> ], who are subsistent on their land and ecosystems, will face endangerment to their wellness and lifestyles due to climate change.<ref>{{Cite web |title=Climate Change {{!}} United Nations For Indigenous Peoples |url=https://www.un.org/development/desa/indigenouspeoples/climate-change.html |access-date=29 April 2022 |website=United Nations Department of Economic and Social Affairs}}</ref> An expert elicitation concluded that the role of climate change in ] has been small compared to factors such as socio-economic inequality and state capabilities.{{Sfn|Mach|Kraan|Adger|Buhaug|2019}}
=== Sea level rise ===
{{seemain|sea level rise}}


While women are not inherently more at risk from climate change and shocks, limits on women's resources and discriminatory gender norms constrain their adaptive capacity and resilience.<ref name="FAO-2023">{{Cite book |url=https://doi.org/10.4060/cc5060en |title=The status of women in agrifood systems - Overview |publisher=FAO |year=2023 |location=Rome |doi=10.4060/cc5060en |s2cid=258145984 |language=EN}}</ref> For example, women's work burdens, including hours worked in agriculture, tend to decline less than men's during climate shocks such as heat stress.<ref name="FAO-2023" />
Another effect of great concern is a ]. Sea levels appear to be rising 1 to 2 mm/y this century, although satellite data show a rate of 3 mm/y since 1992. Some ] island nations, such as ], are concerned about the possibility of an eventual evacuation. For historical reasons to do with ], many of the world's largest and most prosperous cities are on the coast, and the cost of building better ] is likely to be considerable. Some countries will be more affected than others - low-lying countries such as ] and the ] will be worst hit by any sea level rise, in terms of ] or the cost of preventing them.


====Climate migration====
=== More extreme weather ===
{{main|Climate migration}}
]
Low-lying islands and coastal communities are threatened by sea level rise, which makes ] more common. Sometimes, land is permanently lost to the sea.{{Sfn|IPCC SROCC Ch4|2019|p=328}} This could lead to ] for people in island nations, such as the ] and ].<ref>{{harvnb|UNHCR|2011|p=3}}.</ref> In some regions, the rise in temperature and humidity may be too severe for humans to adapt to.{{sfn|Matthews|2018|p=399}} With worst-case climate change, models project that almost one-third of humanity might live in Sahara-like uninhabitable and extremely hot climates.<ref>{{harvnb|Balsari|Dresser|Leaning|2020}}</ref>
As the climate grows warmer, ] will increase. This will cause heavier ] and more ]. Many scientists think that it could result in more extreme ] as global warming progresses. The IPCC TAR says: "...global average water vapour concentration and precipitation are projected to increase during the 21st century. By the second half of the 21st century, it is likely that precipitation will have increased over northern mid- to high latitudes and ] in winter. At low latitudes there are both regional increases and decreases over land areas. Larger year to year variations in precipitation are very likely over most areas where an increase in mean precipitation is projected" .


These factors can drive ] or ], within and between countries.<ref name="Cattaneo-2019">{{harvnb|Cattaneo|Beine|Fröhlich|Kniveton|2019}}; {{harvnb|IPCC AR6 WG2|2022|pp=15, 53}}</ref> More people are expected to be displaced because of sea level rise, extreme weather and conflict from increased competition over natural resources. Climate change may also increase vulnerability, leading to "trapped populations" who are not able to move due to a lack of resources.<ref>{{harvnb|Flavell|2014|p=38}}; {{harvnb|Kaczan|Orgill-Meyer|2020}}</ref>
=== Decline of agriculture ===
{{seemain|Global warming and agriculture}}
For some time it was hoped that a positive effect of global warming would be increased agricultural yields, because of the role of CO2 in photosynthesis. This may still be true in some regions (such as ]), but recent evidence is that global yields will be negatively affected. "Rising atmospheric temperatures, longer droughts and side-effects of both, such as higher levels of ground-level ozone gas, are likely to bring about a substantial reduction in crop yields in the coming decades, large-scale experiments have shown."


{| class="center toccolours"
=== Spread of disease ===
|+ '''Climate change impacts on people'''
It has been claimed that global warming will probably extend the favourable zones for ] conveying ] such as ]. However, it has been pointed out that despite the disappearance of infectious disease most temperate regions, the indigenous mosquitoes that transmitted it were never eliminated and remain common in some areas. Thus, although temperature is important in the transmission dynamics of malaria, many other variables are of equal or greater importance.
|<gallery mode="packed" heights="120" style="line-height:120%">
File:Village Telly in Mali.jpg|Environmental migration. Sparser rainfall leads to ] that harms agriculture and can displace populations. Shown: Telly, Mali (2008).<ref>{{harvnb|Serdeczny|Adams|Baarsch|Coumou|2016}}.</ref>
File:Corn shows the affect of drought.jpg|]. Droughts, rising temperatures, and extreme weather negatively impact agriculture. Shown: Texas, US (2013).<ref>{{harvnb|IPCC SRCCL Ch5|2019|pp=439, 464}}.</ref>
File:Acqua alta in Piazza San Marco-original.jpg|]. Sea-level rise increases flooding in low-lying coastal regions. Shown: ] (2004).<ref name="NOAAnuisance">{{cite web|url=http://oceanservice.noaa.gov/facts/nuisance-flooding.html |title=What is nuisance flooding? |author=] |access-date=April 8, 2020}}</ref>
File:US Navy 071120-M-8966H-005 An aerial view over southern Bangladesh reveals extensive flooding as a result of Cyclone Sidr.jpg|]. Bangladesh after ] (2007) is an example of catastrophic flooding from increased rainfall.<ref>{{harvnb|Kabir|Khan|Ball|Caldwell|2016}}.</ref>
File:Argentina geos5 202211.jpg|Heat wave intensification. Events like the ] are becoming more common.<ref>{{harvnb|Van Oldenborgh|Philip|Kew|Vautard|2019}}.</ref>
</gallery>
|}


== Reducing and recapturing emissions ==
=== Destabilisation of local climates ===
{{detail|Climate change mitigation}}
Global warming might also have other, less obvious effects. The ], for instance, is affected by temperature changes. It seems that it is diminishing as the climate grows warmer, and there has been speculation that areas like ] and ] that are warmed by the drift might face a colder climate in spite of the general global warming. Some even fear that global warming may be able to trigger the type of abrupt massive temperature shifts which bracketed the ] period. (See the discussion of ''']''' for related ideas.). However, in coupled AOGCMs the warming effects outweigh the cooling, even locally: the IPCC TAR notes that ''even in models where the THC weakens, there is still a warming over Europe''.
]
Climate change can be mitigated by reducing the rate at which greenhouse gases are emitted into the atmosphere, and by increasing the rate at which carbon dioxide is removed from the atmosphere.<ref>{{harvnb|IPCC AR5 SYR Glossary|2014|p=125}}.</ref> To limit global warming to less than 1.5&nbsp;°C global greenhouse gas emissions needs to be ] by 2050, or by 2070 with a 2&nbsp;°C target.<ref name="IPCC-2018 p12">{{harvnb|IPCC SR15 Summary for Policymakers|2018|p=12}}</ref> This requires far-reaching, systemic changes on an unprecedented scale in energy, land, cities, transport, buildings, and industry.<ref>{{harvnb|IPCC SR15 Summary for Policymakers|2018|p=15}}</ref>


The ] estimates that countries need to triple their ] within the next decade to limit global warming to 2&nbsp;°C. An even greater level of reduction is required to meet the 1.5&nbsp;°C goal.<ref>{{harvnb|United Nations Environment Programme|2019|p=XX}}</ref> With pledges made under the Paris Agreement as of 2024, there would be a 66% chance that global warming is kept under 2.8&nbsp;°C by the end of the century (range: 1.9–3.7&nbsp;°C, depending on exact implementation and technological progress). When only considering current policies, this raises to 3.1&nbsp;°C.{{sfn|United Nations Environment Programme|2024|pp=33, 34}} Globally, limiting warming to 2&nbsp;°C may result in higher economic benefits than economic costs.<ref>{{harvnb|IPCC AR6 WG3 Ch3|2022|p=300}}: "The global benefits of pathways limiting warming to 2&nbsp;°C (>67%) outweigh global mitigation costs over the 21st century, if aggregated economic impacts of climate change are at the moderate to high end of the assessed range, and a weight consistent with economic theory is given to economic impacts over the long term. This holds true even without accounting for benefits in other sustainable development dimensions or nonmarket damages from climate change (medium confidence)."</ref>
=== Reducing ozone layer ===
One of the lesser-known effects of global warming is a reduction in the thickness of the ], which protects life on Earth from harmful radiation. Global warming appears to be partially countering the improvements in the ozone layer caused by the reduction in the use of ozone-destroying chemicals achieved through the ]. "What appears to have caused the further loss of ozone is the increasing number of stratospheric clouds in the winter, 15 miles above the earth. These clouds, in the middle of the ozone layer, provide a platform which makes it easier for rapid chemical reactions which destroy ozone to take place." A reduced ozone layer has negative impacts on human health (notably ] and eye problems such as ]) and on ecosystems. The ecological impact may have further knock-on effects, as it reduces photosynthesis in plants (with potential impacts on agriculture) and damages the DNA of ], which play a significant role in the world's ].


Although there is no single pathway to limit global warming to 1.5 or 2&nbsp;°C,<ref>{{harvnb|IPCC SR15 Ch2|2018|p=109}}.</ref> most scenarios and strategies see a major increase in the use of renewable energy in combination with increased energy efficiency measures to generate the needed greenhouse gas reductions.<ref name="Teske, ed. 2019 xxiii">{{harvnb|Teske, ed.|2019|p=xxiii}}.</ref> To reduce pressures on ecosystems and enhance their carbon sequestration capabilities, changes would also be necessary in agriculture and forestry,<ref>{{harvnb|World Resources Institute, 8 August|2019}}</ref> such as preventing ] and restoring natural ecosystems by ].<ref>{{harvnb|IPCC SR15 Ch3|2018|p=266}}: "Where reforestation is the restoration of natural ecosystems, it benefits both carbon sequestration and conservation of biodiversity and ecosystem services."</ref>
=== Possible positive effects ===
However, global warming may also have positive effects, since higher temperatures and higher CO<sub>2</sub> concentrations may improve ecosystems' productivity. Satellite data shows that the productivity of the Northern Hemisphere has increased since 1982. On the other hand, an increase in the total amount of ] produced is not necessarily all good, since ] can still decrease even though a smaller number of species are flourishing. Similarly, from the human economic viewpoint, an increase in total biomass but a decrease in crop harvests would be a net disadvantage. In addition, IPCC models predict that higher CO<sub>2</sub> concentrations would only spur growth of flora up to a point, because in many regions the limiting factors are water or nutrients, not temperature or CO<sub>2</sub>; after that, though greenhouse effects and warming would continue there would be no compensatory increase in growth.


Other approaches to mitigating climate change have a higher level of risk. Scenarios that limit global warming to 1.5&nbsp;°C typically project the large-scale use of ] over the 21st century.<ref>{{harvnb|Bui|Adjiman|Bardow|Anthony|2018|p=1068}}; {{harvnb|IPCC SR15 Summary for Policymakers|2018|p=17}}</ref> There are concerns, though, about over-reliance on these technologies, and environmental impacts.<ref>{{harvnb|IPCC SR15|2018|p=34}}; {{harvnb|IPCC SR15 Summary for Policymakers|2018|p=17}}</ref> ] (SRM) is under discussion as a possible supplement to reductions in emissions. However, SRM raises significant ethical and ] concerns, and its risks are not well understood.<ref>{{harvnb|IPCC SR15 Ch4|2018|pp=347–352}}</ref>
A possible counter-argument to this is the claim that suppression of plant growth is caused by a shortage of atmospheric carbon dioxide, which is rare in comparison to oxygen (21%). This carbon dioxide starvation becomes apparent in ], where there is so little carbon dioxide, that oxygen can enter a plant's ] and takes the place where carbon dioxide normally would be in the ]. This causes the sugars being made to be destroyed, badly suppressing growth.


=== Clean energy ===
== The relation between global warming and ozone depletion ==
{{Main|Sustainable energy|Sustainable transport}}
] sources even as ] have begun rapidly increasing.<ref>{{harvnb|Friedlingstein|Jones|O'Sullivan|Andrew|2019}}</ref>]]
]
Renewable energy is key to limiting climate change.<ref name="United Nations Environment Programme 2019 46" /> For decades, fossil fuels have accounted for roughly 80% of the world's energy use.<ref>{{harvnb|IEA World Energy Outlook 2023|pp=18}}</ref> The remaining share has been split between nuclear power and renewables (including ], ], wind and solar power and ]).<ref>{{harvnb|REN21|2020|p=32|loc=Fig.1}}.</ref> Fossil fuel use is expected to peak in absolute terms prior to 2030 and then to decline, with coal use experiencing the sharpest reductions.<ref>{{harvnb|IEA World Energy Outlook 2023|pp=18,26}}</ref> Renewables represented 86% of all new electricity generation installed in 2023.<ref name="IRENA">{{cite web |title=Record Growth in Renewables, but Progress Needs to be Equitable |url=https://www.irena.org/News/pressreleases/2024/Mar/Record-Growth-in-Renewables-but-Progress-Needs-to-be-Equitable |website=IRENA |date=27 March 2024}}</ref> Other forms of clean energy, such as nuclear and hydropower, currently have a larger share of the energy supply. However, their future growth forecasts appear limited in comparison.<ref>{{harvnb|IEA|2021|p=57, Fig 2.5}}; {{harvnb|Teske|Pregger|Naegler|Simon|2019|p=180, Table 8.1}}</ref>


While ] and onshore wind are now among the cheapest forms of adding new power generation capacity in many locations,<ref>{{harvnb|Our World in Data-Why did renewables become so cheap so fast?}}; {{harvnb| IEA – Projected Costs of Generating Electricity 2020}}</ref> green energy policies are needed to achieve a rapid transition from fossil fuels to renewables.<ref>{{cite web |url=https://www.ipcc.ch/2022/04/04/ipcc-ar6-wgiii-pressrelease/ |title=IPCC Working Group III report: Mitigation of Climate Change |date=4 April 2022 |access-date=19 January 2024 |publisher=Intergovernmental Panel on Climate Change}}</ref> To achieve carbon neutrality by 2050, renewable energy would become the dominant form of electricity generation, rising to 85% or more by 2050 in some scenarios. Investment in coal would be eliminated and coal use nearly phased out by 2050.<ref>{{harvnb|IPCC SR15 Ch2|2018|loc=Figure 2.15|p=131}}</ref><ref>{{harvnb|Teske|2019|pp=409–410}}.</ref>
{{seemain|ozone depletion}}
Although they are often interlinked in the popular press, the connection between global warming and ] is not strong. There are four areas of linkage:


Electricity generated from renewable sources would also need to become the main energy source for heating and transport.<ref>{{harvnb|United Nations Environment Programme|2019|loc=Table ES.3|p=XXIII}}; {{harvnb|Teske, ed.|2019|p=xxvii, Fig.5}}.</ref> Transport can switch away from ] vehicles and towards ]s, public transit, and ] (cycling and walking).<ref name="IPCC-2018 p142">{{harvnb|IPCC SR15 Ch2|2018|pp=142–144}}; {{harvnb|United Nations Environment Programme|2019|loc=Table ES.3 & p. 49}}</ref><ref>{{Cite web |year=2016 |title=Transport emissions |url=https://ec.europa.eu/clima/eu-action/transport-emissions_en |access-date=2 January 2022 |website=Climate action |publisher=] |archive-url=https://web.archive.org/web/20211010225533/https://ec.europa.eu/clima/eu-action/transport-emissions_en |archive-date=10 October 2021 |url-status=live}}</ref> For shipping and flying, low-carbon fuels would reduce emissions.<ref name="IPCC-2018 p142" /> Heating could be increasingly decarbonized with technologies like ]s.<ref>{{harvnb|IPCC AR5 WG3 Ch9|2014|p=697}}; {{harvnb|NREL|2017|pp=vi, 12}}</ref>
* Global warming from CO<SUB>2</SUB> radiative forcing is expected (perhaps somewhat surprisingly) to ''cool'' the ]. This, in turn, would lead to a relative ''increase'' in ozone depletion and the frequency of ozone holes.


There are obstacles to the continued rapid growth of clean energy, including renewables.<ref>{{harvnb|Berrill|Arvesen|Scholz|Gils|2016}}.</ref> Wind and solar produce energy ]. Traditionally, ] and fossil fuel power plants have been used when variable energy production is low. Going forward, ] can be expanded, ] can be matched, and long-distance ] can smooth variability of renewable outputs.<ref name="United Nations Environment Programme 2019 46">{{harvnb|United Nations Environment Programme|2019|p=46}}; {{harvnb|Vox, 20 September|2019}}; {{cite journal |title=The Role of Firm Low-Carbon Electricity Resources in Deep Decarbonization of Power Generation |year=2018 |last1=Sepulveda |first1=Nestor A. |last2=Jenkins |first2=Jesse D. |last3=De Sisternes |first3=Fernando J. |last4=Lester |first4=Richard K. |journal=] |volume=2 |issue=11 |pages=2403–2420 |doi=10.1016/j.joule.2018.08.006 |doi-access=free|bibcode=2018Joule...2.2403S }}</ref> Bioenergy is often not carbon-neutral and may have negative consequences for food security.<ref>{{harvnb|IPCC SR15 Ch4|2018|pp=324–325}}.</ref> The growth of nuclear power is constrained by controversy around ], ], and ].<ref>{{Citec|last1=Gill |first1=Matthew |last2=Livens |first2=Francis |last3=Peakman |first3=Aiden |in=Letcher |year=2020 |pages=147–149 |chapter=Nuclear Fission}}</ref><ref>{{Cite journal |last1=Horvath |first1=Akos |last2=Rachlew |first2=Elisabeth |date=January 2016 |title=Nuclear power in the 21st century: Challenges and possibilities |journal=] |volume=45 |issue=Suppl 1 |pages=S38–49 |doi=10.1007/s13280-015-0732-y |issn=1654-7209 |pmc=4678124 |pmid=26667059|bibcode=2016Ambio..45S..38H }}</ref> Hydropower growth is limited by the fact that the best sites have been developed, and new projects are confronting increased social and environmental concerns.<ref>{{cite web |title=Hydropower |url=https://www.iea.org/reports/hydropower |website=iea.org |publisher=] |access-date=12 October 2020 |quote=Hydropower generation is estimated to have increased by over 2% in 2019 owing to continued recovery from drought in Latin America as well as strong capacity expansion and good water availability in China (...) capacity expansion has been losing speed. This downward trend is expected to continue, due mainly to less large-project development in China and Brazil, where concerns over social and environmental impacts have restricted projects.}}</ref>
* Conversely, ozone depletion represents a radiative forcing of the climate system. There are two opposed effects: reduced ozone allows more solar radiation to penetrate, thus warming the ]. But a colder stratosphere emits less long-wave radiation, tending to cool the troposphere. Overall, the cooling dominates: the ] concludes that ''observed stratospheric ] losses over the past two decades have caused a negative forcing of the surface-troposphere system'' of about –0.15 ± 0.10 W m–2 .


] improves human health by minimizing climate change as well as reducing air pollution deaths,<ref>{{harvnb|Watts|Amann|Arnell|Ayeb-Karlsson|2019|p=1854}}; {{harvnb|WHO|2018|p=27}}</ref> which were estimated at 7 million annually in 2016.<ref>{{harvnb|Watts|Amann|Arnell|Ayeb-Karlsson|2019|p=1837}}; {{harvnb|WHO|2016}}</ref> Meeting the Paris Agreement goals that limit warming to a 2&nbsp;°C increase could save about a million of those lives per year by 2050, whereas limiting global warming to 1.5&nbsp;°C could save millions and simultaneously increase ] and reduce poverty.<ref>{{harvnb|WHO|2018|p=27}}; {{harvnb|Vandyck|Keramidas|Kitous|Spadaro|2018}}; {{harvnb|IPCC SR15|2018|p=97}}: "Limiting warming to 1.5&nbsp;°C can be achieved synergistically with poverty alleviation and improved energy security and can provide large public health benefits through improved air quality, preventing millions of premature deaths. However, specific mitigation measures, such as bioenergy, may result in trade-offs that require consideration."</ref> Improving air quality also has economic benefits which may be larger than mitigation costs.<ref>{{harvnb|IPCC AR6 WG3|2022|p=300}}</ref>
* One of the strongest predictions of the GW theory is that the stratosphere should cool. However, although this is observed, it is difficult to use it for ] (for example, warming induced by increased solar radiation would not have this upper cooling effect) because similar cooling is caused by ozone depletion.


=== Energy conservation ===
* Ozone depleting chemicals are also greenhouse gases, representing 0.34 ± 0.03 W/m2, or about 14% of the total radiative forcing from well-mixed GHG's .
{{Main|Efficient energy use|Energy conservation}}
Reducing energy demand is another major aspect of reducing emissions.<ref>{{harvnb|IPCC SR15 Ch2|2018|p=97}}</ref> If less energy is needed, there is more flexibility for clean energy development. It also makes it easier to manage the electricity grid, and minimizes ] infrastructure development.<ref>{{harvnb|IPCC AR5 SYR Summary for Policymakers|2014|p=29}}; {{harvnb|IEA|2020b}}</ref> Major increases in energy efficiency investment will be required to achieve climate goals, comparable to the level of investment in renewable energy.<ref>{{harvnb|IPCC SR15 Ch2|2018|p=155|loc=Fig. 2.27}}</ref> Several ] related changes in energy use patterns, energy efficiency investments, and funding have made forecasts for this decade more difficult and uncertain.<ref>{{harvnb|IEA|2020b}}</ref>


Strategies to reduce energy demand vary by sector. In the transport sector, passengers and freight can switch to more efficient travel modes, such as buses and trains, or use electric vehicles.<ref>{{harvnb|IPCC SR15 Ch2|2018|p=142}}</ref> Industrial strategies to reduce energy demand include improving heating systems and motors, designing less energy-intensive products, and increasing product lifetimes.<ref>{{harvnb|IPCC SR15 Ch2|2018|pp=138–140}}</ref> In the building sector the focus is on better design of new buildings, and higher levels of energy efficiency in retrofitting.<ref>{{harvnb|IPCC SR15 Ch2|2018|pp=141–142}}</ref> The use of technologies like heat pumps can also increase building energy efficiency.<ref>{{harvnb|IPCC AR5 WG3 Ch9|2014|pp=686–694}}.</ref>
== The relation between global warming and global dimming ==
{{seemain|global dimming}}
Some scientists now consider that the effects of the recently recognized phenomenon of ] (the reduction in sunlight reaching the surface of the planet, possibly due to aerosols) may have masked some of the effect of global warming. If this is so, the indirect aerosol effect is stronger than previously believed, which would imply that the climate sensitivity to CO<sub>2</sub> is also stronger. Concerns about the effect of aerosol on the global climate were first researched as part of concerns over ] in the 1970s.


=== Agriculture and industry ===
==Attempts to combat global warming==
{{See also|Sustainable agriculture|Green industrial policy}}
===Mitigating temperature rise===
] Agriculture and forestry face a triple challenge of limiting greenhouse gas emissions, preventing the further conversion of forests to agricultural land, and meeting increases in world food demand.<ref>{{harvnb|World Resources Institute, December|2019|p=1}}</ref> A set of actions could reduce agriculture and forestry-based emissions by two-thirds from 2010 levels. These include reducing growth in demand for food and other agricultural products, increasing land productivity, protecting and restoring forests, and reducing greenhouse gas emissions from agricultural production.<ref>{{harvnb|World Resources Institute, December|2019|pp=1, 3}}</ref>
*]
*] / ]
*]
*]
*]


On the demand side, a key component of reducing emissions is shifting people towards ].<ref>{{Harvnb|IPCC SRCCL|2019|p=22|loc=B.6.2}}</ref> Eliminating the production of livestock for ] would eliminate about 3/4ths of all emissions from agriculture and other land use.<ref>{{Harvnb|IPCC SRCCL Ch5|2019|pp=487,488|loc=FIGURE 5.12}} Humans on a vegan exclusive diet would save about 7.9 Gt{{CO2}} equivalent per year by 2050 {{harvnb|IPCC AR6 WG1 Technical Summary|2021|p=51}} Agriculture, Forestry and Other Land Use used an average of 12 Gt{{CO2}} per year between 2007 and 2016 (23% of total anthropogenic emissions).</ref> Livestock also occupy 37% of ice-free land area on Earth and consume feed from the 12% of land area used for crops, driving deforestation and land degradation.<ref>{{Harvnb|IPCC SRCCL Ch5|2019|pp=82, 162|loc=FIGURE 1.1}}</ref>
===Mitigating the effects of global warming===
*]
*]


Steel and cement production are responsible for about 13% of industrial {{CO2}} emissions. In these industries, carbon-intensive materials such as coke and lime play an integral role in the production, so that reducing {{CO2}} emissions requires research into alternative chemistries.<ref>{{cite web|title=Low and zero emissions in the steel and cement industries|url=https://www.oecd.org/greengrowth/GGSD2019_IssuePaper_CementSteel.pdf|pages=11, 19–22}}</ref> Where energy production or {{CO2}}-intensive ] continue to produce waste {{CO2}}, technology can sometimes be used to capture and store most of the gas instead of releasing it to the atmosphere.<ref name=":22">{{Cite web |last1=Lebling |first1=Katie |last2=Gangotra |first2=Ankita |last3=Hausker |first3=Karl |last4=Byrum |first4=Zachary |date=2023-11-13 |title=7 Things to Know About Carbon Capture, Utilization and Sequestration |url=https://www.wri.org/insights/carbon-capture-technology |publisher=] |language=en}}] Text was copied from this source, which is available under a ]</ref> This technology, ] (CCS), could have a critical but limited role in reducing emissions.<ref name=":22" /> It is relatively expensive<ref>{{harvnb|IPCC AR6 WG3 Summary for Policymakers|2022|p=38}}</ref> and has been deployed only to an extent that removes around 0.1% of annual greenhouse gas emissions.<ref name=":22" />
==References==
* Naomi Oreskes, 2004 - The author discussed her survey of 928 peer-reviewed scientific abstracts on climate change. Retrieved ], ]. Also available as a


=== Carbon dioxide removal ===
==External links==
{{Main|Carbon dioxide removal|Carbon sequestration}}
]s, including plant growth, soil uptake, and ocean uptake (]).]]
Natural carbon sinks can be enhanced to sequester significantly larger amounts of {{CO2}} beyond naturally occurring levels.<ref>{{harvnb|World Resources Institute, 8 August|2019}}: {{harvnb|IPCC SRCCL Ch2|2019|pp=189–193}}.</ref> Reforestation and ] (planting forests where there were none before) are among the most mature sequestration techniques, although the latter raises food security concerns.<ref>{{harvnb|Kreidenweis|Humpenöder|Stevanović|Bodirsky|2016}}</ref> Farmers can promote sequestration of ] through practices such as use of winter ], reducing the intensity and frequency of ], and using compost and manure as soil amendments.<ref>{{harvnb|National Academies of Sciences, Engineering, and Medicine|2019|pp=95–102}}</ref> Forest and landscape restoration yields many benefits for the climate, including greenhouse gas emissions sequestration and reduction.<ref name="Duchelle-2022" /> Restoration/recreation of coastal wetlands, ] and ]s increases the uptake of carbon into organic matter.<ref>{{harvnb|National Academies of Sciences, Engineering, and Medicine|2019|pp=45–54}}</ref><ref>{{Cite journal |last1=Nelson |first1=J. D. J. |last2=Schoenau |first2=J. J. |last3=Malhi |first3=S. S. |date=1 October 2008 |title=Soil organic carbon changes and distribution in cultivated and restored grassland soils in Saskatchewan |url=https://doi.org/10.1007/s10705-008-9175-1 |journal=Nutrient Cycling in Agroecosystems |language=en |volume=82 |issue=2 |pages=137–148 |doi=10.1007/s10705-008-9175-1 |bibcode=2008NCyAg..82..137N |s2cid=24021984 |issn=1573-0867}}</ref> When carbon is sequestered in soils and in organic matter such as trees, there is a risk of the carbon being re-released into the atmosphere later through changes in land use, fire, or other changes in ecosystems.<ref>{{harvnb|Ruseva|Hedrick|Marland|Tovar|2020}}</ref>


The use of bioenergy in conjunction with carbon capture and storage (]) can result in net negative emissions as {{CO2}} is drawn from the atmosphere.<ref>{{harvnb|IPCC AR5 SYR|2014|p=125}}; {{harvnb|Bednar|Obersteiner|Wagner|2019}}.</ref> It remains highly uncertain whether carbon dioxide removal techniques will be able to play a large role in limiting warming to 1.5&nbsp;°C. Policy decisions that rely on carbon dioxide removal increase the risk of global warming rising beyond international goals.<ref>{{harvnb|IPCC SR15|2018|p=34}}</ref>
===Data===
* NOAA CO<sub>2</sub> data
* carbon levels and flows
* Climatic Research Unit, University of East Anglia, Norwich, UK. Philip D. Jones and other.
*


== Adaptation ==
====Carbon dioxide "production"====
{{main|Climate change adaptation}}
*
Adaptation is "the process of adjustment to current or expected changes in climate and its effects".<ref name="IPCC-2022">IPCC, 2022: . In: . Cambridge University Press, Cambridge and New York, pp. 3–33, {{doi|10.1017/9781009325844.001}}.</ref>{{rp|5}} Without additional mitigation, adaptation cannot avert the risk of "severe, widespread and irreversible" impacts.{{sfn|IPCC AR5 SYR|2014|p=17}} More severe climate change requires more transformative adaptation, which can be prohibitively expensive.{{sfn|IPCC SR15 Ch4|2018|pp=396–397}} The ] is unevenly distributed across different regions and populations, and developing countries generally have less.<ref>{{Harvnb|IPCC AR4 WG2 Ch19|2007|p=796}}.</ref> The first two decades of the 21st century saw an increase in adaptive capacity in most low- and middle-income countries with improved access to basic ] and electricity, but progress is slow. Many countries have implemented adaptation policies. However, there is a considerable gap between necessary and available finance.{{sfn|UNEP|2018|pp=xii–xiii}}
*
*
* (Metric tons of carbon dioxide can be converted to metric tons of carbon equivalent by multiplying by 12/44)
* (includes "Greenhouse Gas Spectral Overlaps and Their Significance")
*] ]] (temp. data)
*


Adaptation to sea level rise consists of avoiding at-risk areas, learning to live with increased flooding, and building ]s. If that fails, ] may be needed.<ref>{{Cite journal |last1=Stephens |first1=Scott A. |last2=Bell |first2=Robert G. |last3=Lawrence |first3=Judy |year=2018 |title=Developing signals to trigger adaptation to sea-level rise |journal=] |volume=13 |issue=10 |at=104004 |doi=10.1088/1748-9326/aadf96 |bibcode=2018ERL....13j4004S |issn=1748-9326 |doi-access=free}}</ref> There are economic barriers for tackling dangerous heat impact. Avoiding strenuous work or having ] is not possible for everybody.{{sfn|Matthews|2018|p=402}} In agriculture, adaptation options include a switch to more sustainable diets, diversification, erosion control, and genetic improvements for increased tolerance to a changing climate.{{sfn|IPCC SRCCL Ch5|2019|p=439}} Insurance allows for risk-sharing, but is often difficult to get for people on lower incomes.<ref>{{Cite journal |last1=Surminski |first1=Swenja |last2=Bouwer |first2=Laurens M. |last3=Linnerooth-Bayer |first3=Joanne |year=2016 |title=How insurance can support climate resilience |url=https://www.nature.com/articles/nclimate2979 |journal=] |volume=6 |issue=4 |pages=333–334 |doi=10.1038/nclimate2979 |bibcode=2016NatCC...6..333S |issn=1758-6798}}</ref> Education, migration and ]s can reduce climate vulnerability.{{sfn|IPCC SR15 Ch4|2018|pp=336–337}} Planting mangroves or encouraging other coastal vegetation can buffer storms.<ref>{{Cite web |title=Mangroves against the storm |url=https://social.shorthand.com/IUCN_forests/nCec1jyqvn/mangroves-against-the-storm.html |access-date=20 January 2023 |website=Shorthand |language=en}}</ref><ref>{{Cite web |title=How marsh grass could help protect us from climate change |url=https://www.weforum.org/agenda/2021/10/how-marsh-grass-protects-shorelines/ |access-date=20 January 2023 |website=World Economic Forum |date=24 October 2021 |language=en}}</ref>
===Scientific===
*
* (GISS) &mdash; Global Temperature Trends.
*
* &mdash; ], ] &mdash; Global Warming FAQ
*
*
*
*
* Arctic Climate Impact Assessment (ACIA)
* Includes links to lots of useful Carbon Dioxide statistics.
* by ].
*
* a blog where scientists discuss the science of global warming
* UK chief scientific advisor explains history and science of global warming


Ecosystems adapt to climate change, a process that can be supported by human intervention. By increasing connectivity between ecosystems, species can migrate to more favourable climate conditions. Species can also be ]. Protection and restoration of natural and semi-natural areas helps build resilience, making it easier for ecosystems to adapt. Many of the actions that promote adaptation in ecosystems, also help humans adapt via ]. For instance, restoration of ] makes catastrophic fires less likely, and reduces human exposure. Giving rivers more space allows for more water storage in the natural system, reducing flood risk. Restored forest acts as a carbon sink, but planting trees in unsuitable regions can exacerbate climate impacts.<ref>{{Cite journal |last1=Morecroft |first1=Michael D. |last2=Duffield |first2=Simon |last3=Harley |first3=Mike |last4=Pearce-Higgins |first4=James W. |last5=Stevens |first5=Nicola |last6=Watts |first6=Olly |last7=Whitaker |first7=Jeanette |display-authors=4 |year=2019 |title=Measuring the success of climate change adaptation and mitigation in terrestrial ecosystems |journal=] |volume=366 |issue=6471 |page=eaaw9256 |doi=10.1126/science.aaw9256 |issn=0036-8075 |pmid=31831643 |s2cid=209339286 |doi-access=free}}</ref>
===Newspapers, magazines, and broadcasts===
* &mdash; Michael Leidig, LONDON SUNDAY TELEGRAPH
* &mdash; Broadcast ] ] on ]' '']'' (] format).
:*]: "Every credible scientific study in the world says human activity is creating global warming" (Grist Magazine, 2003).
* &mdash; US Election 2004 Web Monitor
* &mdash; MIT Technology Review
* &mdash; Space News
* &#8212; BBC (] ])
*
* &mdash; Real Climate
* by Robert Essenhigh.


There are ] but also trade-offs between adaptation and mitigation.<ref>{{Cite journal |last1=Berry |first1=Pam M. |last2=Brown |first2=Sally |last3=Chen |first3=Minpeng |last4=Kontogianni |first4=Areti |last5=Rowlands |first5=Olwen |last6=Simpson |first6=Gillian |last7=Skourtos |first7=Michalis |display-authors=4 |year=2015 |title=Cross-sectoral interactions of adaptation and mitigation measures |url=https://doi.org/10.1007/s10584-014-1214-0 |journal=] |volume=128 |issue=3 |pages=381–393 |bibcode=2015ClCh..128..381B |doi=10.1007/s10584-014-1214-0 |issn=1573-1480 |s2cid=153904466|hdl=10.1007/s10584-014-1214-0 |hdl-access=free }}</ref> An example for synergy is increased food productivity, which has large benefits for both adaptation and mitigation.<ref>{{Harvnb|IPCC AR5 SYR|2014|p=54}}.</ref> An example of a trade-off is that increased use of air conditioning allows people to better cope with heat, but increases energy demand. Another trade-off example is that more compact ] may reduce emissions from transport and construction, but may also increase the ] effect, exposing people to heat-related health risks.<ref>{{Cite journal |last=Sharifi |first=Ayyoob |year=2020 |title=Trade-offs and conflicts between urban climate change mitigation and adaptation measures: A literature review |journal=Journal of Cleaner Production |volume=276 |page=122813 |doi=10.1016/j.jclepro.2020.122813 |bibcode=2020JCPro.27622813S |s2cid=225638176 |issn=0959-6526 |url=http://www.sciencedirect.com/science/article/pii/S0959652620328584}}</ref>
===Educational===
* &mdash; Latest news, articles and FAQ on climate change from New Scientist magazine.
* &mdash; substantial article series by scientists, activists and others, and global debate about the politics of climate change.
* &mdash; An extensive introduction to the topic and the history of its discovery
* &mdash; , a guide to understanding the science behind climate change with a thorough .
*, summarising current arguments concerning global warming. They present various points of view and some of the basic problems in following the science.
*http://www.msc-smc.ec.gc.ca/cd/brochures/humidex_table_e.cfm
Humidex Table - Brochures - Meteorological Service of Canada - The Green Lane


{| class="center toccolours"
===]===
|+ '''Examples of adaptation methods'''
*http://www.ipcc.ch &mdash; the ] (IPCC), established by WMO and UNEP (below) in 1988
|<gallery mode="packed" heights="120" style="line-height:120%">
*http://www.wmo.ch &mdash; the ] (WMO)
File:FrontLines-EGAT 2011 Environment Photo Contest Top Entry (5842818280).jpg|] planting and other ] can reduce ].
*http://www.unep.org/ &mdash; the ]
File:Seawallventnor.jpg|]s to protect against ] worsened by ]
*http://unfccc.int/ &mdash; the ] (UNFCCC)
File:20080708 Chicago City Hall Green Roof Edit1.jpg|]s to provide cooling in cities
* (pdf file)
File:2013.02-402-294a_Pearl_millet,breeding,selfing_ICRISAT,Patancheru(Hyderabad,Andhra_Pradesh),IN_wed20feb2013.jpg|] for ]
* &mdash; Technical Summaries (pdf file)
</gallery>
|}


== Policies and politics ==
===Environmentalist===
{{See also|Politics of climate change|Climate change mitigation#Policies}}
] ranks countries by greenhouse gas emissions (40% of score), renewable energy (20%), energy use (20%), and climate policy (20%).
{| border="0" cellspacing="0" cellpadding="0" style="width:100%;"
|-
|valign="top"|
{{legend|#31a354|High}}
|valign="top"|
{{legend|#fee391|Medium}}
|valign="top"|
{{legend|#fe9929|Low}}
|valign="top"|
{{legend|#d7301f|Very low}}
|}]]
Countries that are most ] have typically been responsible for a small share of global emissions. This raises questions about justice and fairness.<ref>{{harvnb|IPCC AR5 SYR Summary for Policymakers|2014|loc=Section 3|p=17}}</ref> Limiting global warming makes it much easier to achieve the UN's ], such as eradicating poverty and reducing inequalities. The connection is recognized in ] which is to "take urgent action to combat climate change and its impacts".<ref>{{harvnb|IPCC SR15 Ch5|2018|p=447}}; United Nations (2017) Resolution adopted by the General Assembly on 6 July 2017, ] ()</ref> The goals on food, clean water and ecosystem protection have synergies with climate mitigation.{{sfn|IPCC SR15 Ch5|2018|p=477}}


The ] of climate change is complex. It has often been framed as a ], in which all countries benefit from mitigation done by other countries, but individual countries would lose from switching to a ] themselves. Sometimes mitigation also has localized benefits though. For instance, the benefits of a ] to public health and local environments exceed the costs in almost all regions.<ref name="Rauner 2020">{{harvnb|Rauner|Bauer|Dirnaichner|Van Dingenen|2020}}</ref> Furthermore, net importers of fossil fuels win economically from switching to clean energy, causing net exporters to face ]: fossil fuels they cannot sell.<ref>{{harvnb|Mercure|Pollitt|Viñuales|Edwards|2018}}</ref>
*http://www.greenpeace.org/ &mdash; ]
*http://www.panda.org/climate/ &mdash; the ] (WWF)
*http://www.worldwatch.org/about &mdash; ]
*http://www.greens.org/s-r/24/24-26.html John Hickman and Sarah Bartlett explain the "Global Tragedy of the Commons at COP 6" in the Green Party journal Synthesis/Regeneration.
* &mdash; ] (UCS)
* (NRDC)
*
*http://www.undoit.org Global Warming: Undo It (Environmental Defense)
* &mdash; Major feature from the BBC including , articles, Q&A, video, analysis, charts and quizes.
* &mdash; ] Includes maps of impact on birds and Senate voting records.


=== Policy options ===
===Global warming-skeptical organizations===
{{Further|Climate policy}}
*
A wide range of ], ]s, and laws are being used to reduce emissions. As of 2019, ] covers about 20% of global greenhouse gas emissions.<ref>{{harvnb|World Bank, June|2019|p=12|loc=Box 1}}</ref> Carbon can be priced with ]es and ].<ref>{{harvnb|Union of Concerned Scientists, 8 January|2017}}; {{harvnb|Hagmann|Ho|Loewenstein|2019}}.</ref> Direct global ] reached $319&nbsp;billion in 2017, and $5.2&nbsp;trillion when indirect costs such as air pollution are priced in.<ref>{{harvnb|Watts|Amann|Arnell|Ayeb-Karlsson|2019|p=1866}}</ref> Ending these can cause a 28% reduction in global carbon emissions and a 46% reduction in air pollution deaths.<ref>{{harvnb|UN Human Development Report|2020|p=10}}</ref> Money saved on fossil subsidies could be used to support the ] instead.<ref>{{harvnb|International Institute for Sustainable Development|2019|p=iv}}</ref> More direct methods to reduce greenhouse gases include vehicle efficiency standards, renewable fuel standards, and air pollution regulations on heavy industry.<ref>{{harvnb|ICCT|2019|p=iv}}; {{harvnb|Natural Resources Defense Council, 29 September|2017}}</ref> Several countries ].<ref>{{harvnb|National Conference of State Legislators, 17 April|2020}}; {{harvnb|European Parliament, February|2020}}</ref>
*http://www.sepp.org/ &mdash; the ] (])
*The ] (GMI)


===Industry-sponsored=== ==== Climate justice ====
Policy designed through the lens of ] tries to address ] issues and social inequality. According to proponents of climate justice, the costs of climate adaptation should be paid by those most responsible for climate change, while the beneficiaries of payments should be those suffering impacts. One way this can be addressed in practice is to have wealthy nations pay poorer countries to adapt.<ref>{{harvnb|Carbon Brief, 16 October|2021}}</ref>
* &mdash; Information on carbon capturing, storage, science and policy
*http://www.cei.org &mdash; the ]. Funded by petrol oil corporations (Source: )
*
*
* The ]
* sponsored by the ], a subgroup of the National Consumer Coalition.
*The ]


Oxfam found that in 2023 the wealthiest 10% of people were responsible for 50% of global emissions, while the bottom 50% were responsible for just 8%.<ref>{{Cite journal|title=Climate Equality: A planet for the 99% |last1=Khalfan|first1=Ashfaq|last2=Lewis|first2=Astrid Nilsson|last3=Aguilar|first3=Carlos|last4=Persson|first4=Jacqueline|last5=Lawson|first5=Max|last6=Dab|first6=Nafkote|last7=Jayoussi|first7=Safa|last8=Acharya|first8=Sunil|date=November 2023|website=Oxfam Digital Repository |publisher=Oxfam GB |doi=10.21201/2023.000001|url=https://oxfamilibrary.openrepository.com/bitstream/handle/10546/621551/cr-climate-equality-201123-en-summ.pdf|access-date=18 December 2023}}</ref> Production of emissions is another way to look at responsibility: under that approach, the top 21 fossil fuel companies would owe cumulative ] of $5.4&nbsp;trillion over the period 2025–2050.<ref name=OneEarth_20230519>{{cite journal |last1=Grasso |first1=Marco |last2=Heede |first2=Richard |title=Time to pay the piper: Fossil fuel companies' reparations for climate damages |journal=One Earth |date=19 May 2023 |volume=6 |issue=5 |pages=459–463 |doi=10.1016/j.oneear.2023.04.012 |bibcode=2023OEart...6..459G |bibcode-access=free |s2cid=258809532 |s2cid-access=free |doi-access=free |hdl=10281/416137 |hdl-access=free }}</ref> To achieve a ], people working in the fossil fuel sector would also need other jobs, and their communities would need investments.<ref>{{harvnb|Carbon Brief, 4 Jan|2017}}.</ref>
===Independent (or receives too little support to constitute "sponsorship")===
*&mdash; : Impacts and Solutions,on Climate Change.
* &mdash; Introduce interesting theories like "sequestering" or forcing carbon dioxide deep into the oceans
*&mdash; A faithful summary of the Third Assessment Report of the IPCC, a leading scientific consensus document on Climate Change and Global Warming produced in 2001 by a large international panel of scientists
*http://www.lomborg.com, personal site of ], author of '']''
*, analysis of industry efforts to discredit global warming science, by Bob Burton and Sheldon Rampton, published in the ''Earth Island Journal''.
*] ]] of ]
*] ]] of ]
*
* (])
* by Jean-Marc Jancovici
* by
* by
* &mdash; A skeptical blog; often addresses global warming, doubts of its existence by ]


=== International climate agreements ===
===Other===
{{Further|United Nations Framework Convention on Climate Change}}
]
]
Nearly all countries in the world are parties to the 1994 ] (UNFCCC).<ref>{{harvnb|UNFCCC, "What is the United Nations Framework Convention on Climate Change?"}}</ref> The goal of the UNFCCC is to prevent dangerous human interference with the climate system.<ref>{{harvnb|UNFCCC|1992|loc=Article 2}}.</ref> As stated in the convention, this requires that greenhouse gas concentrations are stabilized in the atmosphere at a level where ecosystems can adapt naturally to climate change, food production is not threatened, and ] can be sustained.<ref>{{Harvnb|IPCC AR4 WG3 Ch1|2007|p=97}}.</ref> The UNFCCC does not itself restrict emissions but rather provides a framework for protocols that do. Global emissions have risen since the UNFCCC was signed.<ref name="EPA-2019">{{harvnb|EPA|2019}}.</ref> ] are the stage of global negotiations.<ref>{{harvnb|UNFCCC, "What are United Nations Climate Change Conferences?"}}</ref>


The 1997 ] extended the UNFCCC and included legally binding commitments for most developed countries to limit their emissions.<ref>{{harvnb|Kyoto Protocol|1997}}; {{harvnb|Liverman|2009|p=290}}.</ref> During the negotiations, the ] (representing ]) pushed for a mandate requiring ] to " the lead" in reducing their emissions,<ref>{{harvnb|Dessai|2001|p=4}}; {{harvnb|Grubb|2003}}.</ref> since developed countries contributed most to the ] in the atmosphere. Per-capita emissions were also still relatively low in developing countries and developing countries would need to emit more to meet their development needs.<ref>{{harvnb|Liverman|2009|p=290}}.</ref>
* &mdash; A comprehensive FAQ.
*
*
* McKitrick reviews the criticisms of the Mann hockey stick for a general scientific audience.
* &mdash; Extensive commented list of Internet resources &mdash; Science and Technology Sources on the Internet.
*
*
*
* &mdash; Summary of arguments concerning global warming. They present various points of view and some of the basic problems in following the science.
* &mdash; Institute for Creation Research information about global warming.
* &mdash; includes a depiction of what the Earth would look like if all the icecaps melted.
* &mdash; How ExxonMobil funds scientists and media pundits to "de-bunk" the science of climate change
* a contrary link:
* by ], ''Technology Review'' , Oct. 2004; calls into question famous graph by ]
*
*


The 2009 ] has been widely portrayed as disappointing because of its low goals, and was rejected by poorer nations including the G77.<ref>{{harvnb|Müller|2010}}; {{harvnb|The New York Times, 25 May|2015}}; {{harvnb|UNFCCC: Copenhagen|2009}}; {{harvnb|EUobserver, 20 December|2009}}.</ref> Associated parties aimed to limit the global temperature rise to below 2&nbsp;°C.<ref>{{harvnb|UNFCCC: Copenhagen|2009}}.</ref> The Accord set the goal of sending $100&nbsp;billion per year to developing countries for mitigation and adaptation by 2020, and proposed the founding of the ].<ref>{{cite conference |date=7–18 December 2009 |title=Conference of the Parties to the Framework Convention on Climate Change |url=http://unfccc.int/meetings/cop_15/items/5257.php |location=Copenhagen |id=un document= FCCC/CP/2009/L.7 |archive-url=https://web.archive.org/web/20101018074452/http://unfccc.int/meetings/cop_15/items/5257.php |archive-date=18 October 2010 |access-date=24 October 2010 |url-status=live}}</ref> {{As of|2020|}}, only 83.3&nbsp;billion were delivered. Only in 2023 the target is expected to be achieved.<ref>{{cite news |last1=Bennett |first1=Paige |title=High-Income Nations Are on Track Now to Meet $100 Billion Climate Pledges, but They're Late |url=https://www.ecowatch.com/wealthy-countries-climate-change-reparations.html |access-date=10 May 2023 |agency=Ecowatch |date=2 May 2023}}</ref>
==See also==
<!-- This section is for links to other Misplaced Pages pages -->


In 2015 all UN countries negotiated the ], which aims to keep global warming well below 2.0&nbsp;°C and contains an aspirational goal of keeping warming under {{val|1.5|u=°C}}.{{sfn|Paris Agreement|2015}} The agreement replaced the Kyoto Protocol. Unlike Kyoto, no binding emission targets were set in the Paris Agreement. Instead, a set of procedures was made binding. Countries have to regularly set ever more ambitious goals and reevaluate these goals every five years.<ref>{{harvnb|Climate Focus|2015|p=3}}; {{harvnb|Carbon Brief, 8 October|2018}}.</ref> The Paris Agreement restated that developing countries must be financially supported.<ref>{{harvnb|Climate Focus|2015|p=5}}.</ref> {{As of|October 2021}}, 194 states and the ] have signed the treaty and 191 states and the EU have ] or acceded to the agreement.<ref>{{cite web |title=Status of Treaties, United Nations Framework Convention on Climate Change |url=https://treaties.un.org/Pages/ViewDetails.aspx?src=TREATY&mtdsg_no=XXVII-7-d&chapter=27&clang=_en |access-date=13 October 2021 |website=United Nations Treaty Collection}}; {{harvnb|Salon, 25 September|2019}}.</ref>
*] / ]
*]
*] &mdash; socio-political issues surrounding the theory of global warming.
*]
*]
*]
*]
*]
*]
*]
*]
*]


The 1987 ], an international agreement to phase out production of ozone-depleting gases, has had benefits for climate change mitigation.<ref>{{harvnb|Velders|Andersen|Daniel|Fahey|McFarland|2007}}; {{harvnb|Young|Harper|Huntingford|Paul|Morgenstern|Newman|Oman|Madronich|Garcia|2021}}</ref> Several ozone-depleting gases like ] are powerful greenhouse gases, so banning their production and usage may have avoided a temperature rise of 0.5&nbsp;°C–1.0&nbsp;°C,<ref>{{harvnb|WMO SAOD Executive Summary|2022|pp=20, 31}}</ref> as well as additional warming by preventing damage to vegetation from ] radiation.<ref>{{harvnb|WMO SAOD Executive Summary|2022|pp=20, 35}}; {{harvnb|Young|Harper|Huntingford|Paul|Morgenstern|Newman|Oman|Madronich|Garcia|2021}}</ref> It is estimated that the agreement has been more effective at curbing greenhouse gas emissions than the Kyoto Protocol specifically designed to do so.<ref>{{harvnb|Goyal|England|Sen Gupta|Jucker|2019}}; {{harvnb|Velders|Andersen|Daniel|Fahey|McFarland|2007}}</ref> The most recent amendment to the Montreal Protocol, the 2016 ], committed to reducing the emissions of ]s, which served as a replacement for banned ozone-depleting gases and are also potent greenhouse gases.<ref>{{harvnb|Carbon Brief, 21 November|2017}}</ref> Should countries comply with the amendment, a warming of 0.3&nbsp;°C–0.5&nbsp;°C is estimated to be avoided.<ref>{{harvnb|WMO SAOD Executive Summary|2022|p=15}}; {{harvnb|Velders|Daniel|Montzka|Vimont|Rigby|Krummel|Muhle|O'Doherty|Prinn,|Weiss|Young|2022}}</ref>
<!-- Categorization -->
]
]
]
]


=== National responses ===
<!-- Localization -->
]. This measures fossil fuel and industry emissions. ] is not included.<ref>{{cite web |url=https://ourworldindata.org/grapher/annual-co-emissions-by-region |title=Annual {{CO2}} emissions by world region |website=ourworldindata.org |publisher=] |format=chart|access-date=2024-09-18}}</ref>]]
]
In 2019, the ] became the first national government to declare a climate emergency.<ref>{{Harvnb|BBC, 1 May|2019}}; {{Harvnb|Vice, 2 May|2019}}.</ref> Other countries and ]s followed suit.<ref>{{harvnb|The Verge, 27 December|2019}}.</ref> That same year, the ] declared a "climate and environmental emergency".<ref>{{harvnb|The Guardian, 28 November|2019}}</ref> The ] presented its ] with the goal of making the EU carbon-neutral by 2050.<ref>{{harvnb|Politico, 11 December|2019}}.</ref> In 2021, the European Commission released its "]" legislation package, which contains guidelines for the ]; all new cars on the European market must be ] from 2035.<ref>{{cite news |title=European Green Deal: Commission proposes transformation of EU economy and society to meet climate ambitions |url=https://ec.europa.eu/commission/presscorner/detail/en/ip_21_3541 |work=] |date=14 July 2021}}</ref>
]

]
Major countries in Asia have made similar pledges: South Korea and Japan have committed to become carbon-neutral by 2050, and China by 2060.<ref>{{harvnb|The Guardian, 28 October|2020}}</ref> While India has strong incentives for renewables, it also plans a significant expansion of coal in the country.<ref>{{cite web |date=15 September 2021 |title=India |url=https://climateactiontracker.org/countries/india/ |access-date=3 October 2021 |website=Climate Action Tracker}}</ref> Vietnam is among very few coal-dependent, fast-developing countries that pledged to phase out unabated coal power by the 2040s or as soon as possible thereafter.<ref>{{cite journal |last1=Do |first1=Thang Nam |last2=Burke |first2=Paul J. |title=Phasing out coal power in a developing country context: Insights from Vietnam |journal=Energy Policy |year=2023 |volume=176 |issue=May 2023 113512 |page=113512 |doi=10.1016/j.enpol.2023.113512|bibcode=2023EnPol.17613512D |s2cid=257356936 |hdl=1885/286612 |hdl-access=free }}</ref>
]

]
As of 2021, based on information from 48 ], which represent 40% of the parties to the Paris Agreement, estimated total greenhouse gas emissions will be 0.5% lower compared to 2010 levels, below the 45% or 25% reduction goals to limit global warming to 1.5&nbsp;°C or 2&nbsp;°C, respectively.<ref>{{harvnb|UN NDC Synthesis Report|2021|pp=4–5}}; {{cite news |author=UNFCCC Press Office |date=26 February 2021 |title=Greater Climate Ambition Urged as Initial NDC Synthesis Report Is Published |url=https://unfccc.int/news/greater-climate-ambition-urged-as-initial-ndc-synthesis-report-is-published |access-date=21 April 2021}}</ref>
]

]
== Society ==
]
=== Denial and misinformation ===
]
{{Further|Climate change denial|Fossil fuels lobby}}
]
] from short periods to falsely assert that global temperatures are not rising. Blue trendlines show short periods that mask longer-term warming trends (red trendlines). Blue rectangle with blue dots shows the so-called ].{{sfn|Stover|2014}}]]
]
Public debate about climate change has been strongly affected by climate change denial and ], which originated in the United States and has since spread to other countries, particularly Canada and Australia. Climate change denial has originated from fossil fuel companies, industry groups, ] think tanks, and ] scientists.<ref>{{harvnb|Dunlap|McCright|2011|pp=144, }}; {{harvnb|Björnberg|Karlsson|Gilek|Hansson|2017}}</ref> ], the main strategy of these groups has been to manufacture doubt about climate-change related scientific data and results.<ref>{{harvnb|Oreskes|Conway|2010}}; {{harvnb|Björnberg|Karlsson|Gilek|Hansson|2017}}</ref> People who hold unwarranted doubt about climate change are called climate change "skeptics", although "contrarians" or "deniers" are more appropriate terms.<ref>{{harvnb|O'Neill|Boykoff|2010}}; {{harvnb|Björnberg|Karlsson|Gilek|Hansson|2017}}</ref>
]

]
There are different variants of climate denial: some deny that warming takes place at all, some acknowledge warming but attribute it to natural influences, and some minimize the negative impacts of climate change.<ref name="Björnberg 2017">{{harvnb|Björnberg|Karlsson|Gilek|Hansson|2017}}</ref> Manufacturing uncertainty about the science later developed into a ]: creating the belief that there is significant uncertainty about climate change within the scientific community to delay policy changes.<ref>{{harvnb|Dunlap|McCright|2015|p=308}}.</ref> Strategies to promote these ideas include criticism of scientific institutions,<ref>{{harvnb|Dunlap|McCright|2011|p=146}}.</ref> and questioning the motives of individual scientists.<ref name="Björnberg 2017"/> An ] of climate-denying ] and media has further fomented misunderstanding of climate change.<ref>{{harvnb|Harvey|Van den Berg|Ellers|Kampen|2018}}</ref>
]

=== Public awareness and opinion ===
{{Further|Climate communication|Media coverage of climate change|Public opinion on climate change}}
] |volume=37 |issue=4 |pages=183–184 |doi=10.1177/0270467619886266 |s2cid=213454806}}</ref><ref name=Lynas_2021/><ref>{{cite journal |last1=Myers |first1=Krista F. |last2=Doran |first2=Peter T. |last3=Cook |first3=John |last4=Kotcher |first4=John E. |last5=Myers |first5=Teresa A. |title=Consensus revisited: quantifying scientific agreement on climate change and climate expertise among Earth scientists 10 years later |journal=] |date=20 October 2021 |volume=16 |issue=10 |page=104030 |doi=10.1088/1748-9326/ac2774 |bibcode=2021ERL....16j4030M |s2cid=239047650 |doi-access=free }}</ref> found scientific consensus to range from 98.7 to 100%.]]
Climate change came to international public attention in the late 1980s.<ref name="Weart">{{harvnb|Weart "The Public and Climate Change (since 1980)"}}</ref> Due to media coverage in the early 1990s, people often confused climate change with other environmental issues like ozone depletion.<ref name="Newell2006">{{harvnb|Newell|2006|p=80}}; {{harvnb|Yale Climate Connections, 2 November|2010}}</ref> ], the ] movie '']'' (2004) and the ] documentary '']'' (2006) focused on climate change.<ref name="Weart" />

Significant regional, gender, age and political differences exist in both public concern for, and understanding of, climate change. More highly educated people, and in some countries, women and younger people, were more likely to see climate change as a serious threat.<ref>{{harvnb|Pew|2015|p=10}}.</ref> College biology textbooks from the 2010s featured less content on climate change compared to those from the preceding decade, with decreasing emphasis on solutions.<ref name=":0">{{Cite web |last1=Preston |first1=Caroline |last2=Hechinger |date=1 October 2023 |title=In Some Textbooks, Climate Change Content Is Few and Far Between |url=https://undark.org/2023/01/10/in-some-textbooks-climate-change-content-is-few-and-far-between/ |website=undark.org/}}</ref> Partisan gaps also exist in many countries,<ref>{{harvnb|Pew|2020|}}.</ref> and countries with high ] tend to be less concerned.<ref>{{harvnb|Pew|2015|p=15}}.</ref> Views on causes of climate change vary widely between countries.<ref>{{harvnb|Yale|2021|p=7}}.</ref> Concern has increased over time,<ref>{{harvnb|Pew|2020|}}; {{harvnb|UNDP|2024|pp=22–26}}</ref> and a majority of citizens in many countries now express a high level of worry about climate change, or view it as a global emergency.<ref>{{harvnb|Yale|2021|p=9}}; {{harvnb|UNDP|2021|p=15}}.</ref> Higher levels of worry are associated with stronger public support for policies that address climate change.<ref>{{harvnb|Smith|Leiserowitz|2013|p=943}}.</ref>

==== Climate movement ====
{{Main|Climate movement|Climate change litigation}}
Climate protests demand that political leaders take action to prevent climate change. They can take the form of public demonstrations, ], lawsuits and other activities.<ref>{{harvnb|Gunningham|2018}}.</ref> Prominent demonstrations include the ]. In this initiative, young people across the globe have been protesting since 2018 by skipping school on Fridays, inspired by Swedish activist and then-teenager ].<ref>{{harvnb|The Guardian, 19 March|2019}}; {{harvnb|Boulianne|Lalancette|Ilkiw|2020}}.</ref> Mass ] actions by groups like ] have protested by disrupting roads and public transport.<ref>{{harvnb|Deutsche Welle, 22 June|2019}}.</ref>

] is increasingly used as a tool to strengthen climate action from public institutions and companies. Activists also initiate lawsuits which target governments and demand that they take ambitious action or enforce existing laws on climate change.<ref>{{cite news |last=Connolly |first=Kate |date=29 April 2021 |title='Historic' German ruling says climate goals not tough enough |url=http://www.theguardian.com/world/2021/apr/29/historic-german-ruling-says-climate-goals-not-tough-enough |access-date=1 May 2021 |work=]}}</ref> Lawsuits against fossil-fuel companies generally seek compensation for ].<ref>{{harvnb|Setzer|Byrnes|2019}}.</ref>

== History ==
{{Broader|History of climate change science}}

=== Early discoveries ===
], March 1912, p. 341.</ref>]]
Scientists in the 19th century such as ] began to foresee the effects of climate change.<ref name="Nord 2020 p. 51">{{cite book |last=Nord |first=D. C. |url=https://books.google.com/books?id=KmMGEAAAQBAJ&pg=PA51 |title=Nordic Perspectives on the Responsible Development of the Arctic: Pathways to Action |publisher=Springer International Publishing |year=2020 |isbn=978-3-030-52324-4 |series=Springer Polar Sciences |page=51 |access-date=11 March 2023}}</ref><ref name="Mukherjee Scanlon Aureli Langan 2020 p. 331">{{cite book |last1=Mukherjee |first1=A. |url=https://books.google.com/books?id=17vbDwAAQBAJ&pg=PA331 |title=Global Groundwater: Source, Scarcity, Sustainability, Security, and Solutions |last2=Scanlon |first2=B. R. |last3=Aureli |first3=A. |last4=Langan |first4=S. |last5=Guo |first5=H. |last6=McKenzie |first6=A. A. |publisher=Elsevier Science |year=2020 |isbn=978-0-12-818173-7 |page=331 |access-date=11 March 2023}}</ref><ref name="von Humboldt Wulf 2018 p. 10">{{cite book | last1=von Humboldt | first1=A. | last2=Wulf | first2=A. | title=Selected Writings of Alexander von Humboldt: Edited and Introduced by Andrea Wulf | publisher=Knopf Doubleday Publishing Group | series=Everyman's Library Classics Series | year=2018 | isbn=978-1-101-90807-5 | url=https://books.google.com/books?id=xal2DwAAQBAJ&pg=PR10 | access-date=11 March 2023 | page=10}}</ref><ref name="Erdkamp Manning Verboven 2021 p. 6">{{cite book |last1=Erdkamp |first1=Paul |url=https://books.google.com/books?id=ZbdMEAAAQBAJ&pg=PR6 |title=Climate Change and Ancient Societies in Europe and the Near East: Diversity in Collapse and Resilience |last2=Manning |first2=Joseph G. |author-link2=Joseph Manning (historian) |last3=Verboven |first3=Koenraad |publisher=Springer International Publishing |year=2021 |isbn=978-3-030-81103-7 |series=Palgrave Studies in Ancient Economies |page=6 |access-date=11 March 2023}}</ref> In the 1820s, ] proposed the greenhouse effect to explain why Earth's temperature was higher than the Sun's energy alone could explain. Earth's atmosphere is transparent to sunlight, so sunlight reaches the surface where it is converted to heat. However, the atmosphere is not transparent to heat radiating from the surface, and captures some of that heat, which in turn warms the planet.<ref>{{harvnb|Archer|Pierrehumbert|2013|pp=}}</ref>

In 1856 ] demonstrated that the warming effect of the Sun is greater for air with water vapour than for dry air, and that the effect is even greater with carbon dioxide ({{co2}}). She concluded that "An atmosphere of that gas would give to our earth a high temperature..."<ref>{{cite journal |url=https://books.google.com/books?id=6xhFAQAAMAAJ&pg=PA382 |last=Foote |first=Eunice |title=Circumstances affecting the Heat of the Sun's Rays |journal=The American Journal of Science and Arts |date=November 1856 |volume=22 |pages=382–383 |access-date=31 January 2016 |via=]}}</ref><ref>{{harvnb|Huddleston|2019}}</ref>

] measured how much various gases in a tube absorb and emit infrared radiation—which humans experience as heat.]]
Starting in 1859,<ref>{{harvnb|Tyndall|1861}}.</ref> ] established that nitrogen and oxygen—together totalling 99% of dry air—are transparent to radiated heat. However, water vapour and gases such as methane and carbon dioxide absorb radiated heat and re-radiate that heat into the atmosphere. Tyndall proposed that changes in the concentrations of these gases may have caused climatic changes in the past, including ]s.<ref>{{harvnb|Archer|Pierrehumbert|2013|pp=}}; {{harvnb|Fleming|2008|loc=}}</ref>

] noted that water vapour in air continuously varied, but the {{co2}} concentration in air was influenced by long-term geological processes. Warming from increased {{co2}} levels would increase the amount of water vapour, amplifying warming in a positive feedback loop. In 1896, he published the first ] of its kind, projecting that halving {{co2}} levels could have produced a drop in temperature initiating an ice age. Arrhenius calculated the temperature increase expected from doubling {{co2}} to be around 5–6&nbsp;°C.{{sfn|Lapenis|1998}} Other scientists were initially sceptical and believed that the greenhouse effect was saturated so that adding more {{co2}} would make no difference, and that the climate would be self-regulating.<ref name="Weart The Carbon Dioxide Greenhouse Effect">{{harvnb|Weart "The Carbon Dioxide Greenhouse Effect"}}; {{harvnb|Fleming|2008|loc=}}</ref> Beginning in 1938, ] published evidence that climate was warming and {{co2}} levels were rising,<ref>{{harvnb|Callendar|1938}}; {{harvnb|Fleming|2007}}.</ref> but his calculations met the same objections.<ref name="Weart The Carbon Dioxide Greenhouse Effect" />

=== Development of a scientific consensus ===
{{see also|Scientific consensus on climate change}}
] |volume=11 |issue=4 |page=048002 |bibcode= 2016ERL....11d8002C |doi= 10.1088/1748-9326/11/4/048002 |doi-access=free|hdl=1983/34949783-dac1-4ce7-ad95-5dc0798930a6 |hdl-access=free }}</ref> A 2019 study found scientific consensus to be at 100%,<ref name="Powell2019" /> and a 2021 study concluded that consensus exceeded 99%.<ref name="Lynas2021" /> Another 2021 study found that 98.7% of climate experts indicated that the Earth is getting warmer mostly because of human activity.<ref name="Myers2021">{{cite journal |last1=Myers |first1=Krista F. |last2= Doran |first2=Peter T. |last3=Cook |first3=John |last4=Kotcher |first4=John E. |last5=Myers |first5=Teresa A. |title=Consensus revisited: quantifying scientific agreement on climate change and climate expertise among Earth scientists 10 years later |journal= ] |date=20 October 2021 |volume=16 |issue=10 |page=104030 |doi= 10.1088/1748-9326/ac2774 |bibcode= 2021ERL....16j4030M |s2cid= 239047650 |doi-access=free}}</ref>]]
In the 1950s, ] created a detailed computer model that included different atmospheric layers and the infrared spectrum. This model predicted that increasing {{co2}} levels would cause warming. Around the same time, ] found evidence that {{co2}} levels had been rising, and ] showed that the oceans would not absorb the increase. The two scientists subsequently helped ] to begin a record of continued increase, which has been termed the "]".<ref name="Weart The Carbon Dioxide Greenhouse Effect" /> Scientists alerted the public,<ref>{{harvnb|Weart "Suspicions of a Human-Caused Greenhouse (1956–1969)"}}</ref> and the dangers were highlighted at James Hansen's 1988 Congressional testimony.<ref name="history.aip.org2"/> The ] (IPCC), set up in 1988 to provide formal advice to the world's governments, spurred ].<ref>{{harvnb|Weart|2013|p=3567}}.</ref> As part of the ], scientists assess the scientific discussion that takes place in ] ] articles.<ref>{{harvnb|Royal Society|2005}}.</ref>

There is a near-complete scientific consensus that the climate is warming and that this is caused by human activities. As of 2019, agreement in recent literature reached over 99%.<ref name="Powell2019">{{cite journal |last1=Powell |first1=James |date=20 November 2019 |title=Scientists Reach 100% Consensus on Anthropogenic Global Warming |url=https://journals.sagepub.com/doi/abs/10.1177/0270467619886266?journalCode=bsta |journal=] |volume=37 |issue=4 |pages=183–184 |doi=10.1177/0270467619886266 |access-date=15 November 2020 |s2cid=213454806}}</ref><ref name="Lynas2021">{{Cite journal |last1=Lynas |first1=Mark |last2=Houlton |first2=Benjamin Z |last3=Perry |first3=Simon |year=2021 |title=Greater than 99% consensus on human caused climate change in the peer-reviewed scientific literature |journal=] |volume=16 |issue=11 |pages=114005 |bibcode=2021ERL....16k4005L |doi=10.1088/1748-9326/ac2966 |issn=1748-9326 |s2cid=239032360|doi-access=free }}</ref> No scientific body of national or international standing ].<ref>{{harvnb|National Academies|2008|p=2}}; {{harvnb|Oreskes|2007|p=}}; {{Harvnb|Gleick, 7 January|2017}}</ref> Consensus has further developed that some form of action should be taken to protect people against the impacts of climate change. National science academies have called on world leaders to cut global emissions.<ref>Joint statement of the {{harvtxt|G8+5 Academies|2009}}; {{harvnb|Gleick, 7 January|2017}}.</ref> The 2021 IPCC Assessment Report stated that it is "unequivocal" that climate change is caused by humans.<ref name="Lynas2021"/>

== See also ==
<!-- Please note that the Manual of Style advices a minimum (or no) items in this sections for featured articles. -->
* {{portal-inline|Climate change}}
* ] – proposed geological time interval in which humans are having significant geological impact
* ]
* ]
{{clear right}}

== References ==
{{reflist|22em}}

=== Sources ===
{{Free-content attribution
| title = The status of women in agrifood systems – Overview
| author = FAO
| publisher = FAO
| page numbers =
| source =
| documentURL = https://doi.org/10.4060/cc5060en
| licence statement URL = https://commons.wikimedia.org/File:The_status_of_women_in_agrifood_systems_-_Overview.pdf
| license = CC BY-SA 3.0
}}

==== IPCC reports ====
{{refbegin}}

'''Fourth Assessment Report'''
<!-- Short-cite {{harvnb|IPCC AR4 WG1|2007}} links to this citation. -->
* {{cite book |ref={{harvid|IPCC AR4 WG1|2007}}
|author=IPCC |author-link=IPCC
|year =2007
|title=Climate Change 2007: The Physical Science Basis
|series=Contribution of Working Group I to the ] of the Intergovernmental Panel on Climate Change
|display-editors=4
|editor-first1=S. |editor-last1=Solomon
|editor-first2=D. |editor-last2=Qin
|editor-first3=M. |editor-last3=Manning
|editor-first4=Z. |editor-last4=Chen
|editor-first5=M. |editor-last5=Marquis
|editor-first6=K. B. |editor-last6=Averyt
|editor-first7=M. |editor-last7=Tignor
|editor-first8=H. L. |editor-last8=Miller
|publisher=]
|url=http://www.ipcc.ch/publications_and_data/ar4/wg1/en/contents.html
|isbn=978-0-521-88009-1
}}
<!-- # -->
** {{cite book |ref={{harvid|IPCC AR4 WG1 Ch1|2007}}
|chapter=Chapter 1: Historical Overview of Climate Change Science
|chapter-url=https://archive.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter1.pdf
|year=2007
|display-authors=4
|first1=H. |last1=Le Treut
|first2=R. |last2=Somerville
|first3=U. |last3=Cubasch
|first4=Y. |last4=Ding
|first5=C. |last5=Mauritzen
|first6=A. |last6=Mokssit
|first7=T. |last7=Peterson
|first8=M. |last8=Prather
|title={{Harvnb|IPCC AR4 WG1|2007}}
|pages=93–127
}}
** {{cite book |ref={{harvid|IPCC AR4 WG1 Ch8|2007}}
|chapter=Chapter 8: Climate Models and their Evaluation
|chapter-url=https://archive.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter8.pdf
|year=2007
|display-authors=4
|first1=D. A. |last1=Randall
|first2=R. A. |last2=Wood
|first3=S. |last3=Bony
|first4=R. |last4=Colman
|first5=T. |last5=Fichefet
|first6=J. |last6=Fyfe
|first7=V. |last7=Kattsov
|first8=A. |last8=Pitman
|first9=J. |last9=Shukla
|first10=J. |last10=Srinivasan
|first11=R. J. |last11=Stouffer
|first12=A. |last12=Sumi
|first13=K. E. |last13=Taylor
|title={{Harvnb|IPCC AR4 WG1|2007}}
|pages=589–662
}}
** {{cite book |ref={{harvid|IPCC AR4 WG1 Ch9|2007}}
|chapter=Chapter 9: Understanding and Attributing Climate Change
|chapter-url=https://archive.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter9.pdf
|year=2007
|display-authors=4
|first1=G. C. |last1=Hegerl
|first2=F. W. |last2=Zwiers
|first3=P. |last3=Braconnot |author-link3=Pascale Braconnot
|first4=N. P. |last4=Gillett
|first5=Y. |last5=Luo
|first6=J. A. |last6=Marengo Orsini
|first7=N. |last7=Nicholls
|first8=J. E. |last8=Penner
|first9=P. A. |last9=Stott
|title={{Harvnb|IPCC AR4 WG1|2007}}
|pages=663–745
}}

<!-- Short-cite {{harvnb|IPCC AR4 WG2|2007}} links to this citation. -->
* {{cite book |ref={{harvid|IPCC AR4 WG2|2007}}
|author=IPCC |author-link=IPCC
|year =2007
|title=Climate Change 2007: Impacts, Adaptation and Vulnerability
|series=Contribution of Working Group II to the ] of the Intergovernmental Panel on Climate Change
|display-editors=4
|editor-first1=M. L. |editor-last1=Parry
|editor-first2=O. F. |editor-last2=Canziani
|editor-first3=J. P. |editor-last3=Palutikof
|editor-first4=P. J. |editor-last4=van der Linden
|editor-first5=C. E. |editor-last5=Hanson
|publisher=]
|url=http://www.ipcc.ch/publications_and_data/ar4/wg2/en/contents.html
|isbn=978-0-521-88010-7
}}
<!-- ## -->
** {{cite book |ref={{harvid|IPCC AR4 WG2 Ch19|2007}}
|chapter=Chapter 19: Assessing key vulnerabilities and the risk from climate change
|chapter-url=https://archive.ipcc.ch/pdf/assessment-report/ar4/wg2/ar4-wg2-chapter19.pdf
|year=2007
|display-authors=4
|first1=S. H. |last1=Schneider
|first2=S. |last2=Semenov
|first3=A. |last3=Patwardhan
|first4=I. |last4=Burton
|first5=C. H. D. |last5=Magadza
|first6=M. |last6=Oppenheimer
|first7=A. B. |last7=Pittock
|first8=A. |last8=Rahman
|first9=J. B. |last9=Smith
|first10=A. |last10=Suarez
|first11=F. |last11=Yamin
|title={{Harvnb|IPCC AR4 WG2|2007}}
|pages=779–810
}}

<!-- Short-cite {{harvnb|IPCC AR4 WG3|2007}} links to this citation. -->
* {{cite book |ref={{harvid|IPCC AR4 WG3|2007}}
|author=IPCC |author-link=IPCC
|year =2007
|title=Climate Change 2007: Mitigation of Climate Change
|series=Contribution of Working Group III to the ] of the Intergovernmental Panel on Climate Change
|display-editors=4
|editor-first1=B. |editor-last1=Metz
|editor-first2=O. R. |editor-last2=Davidson
|editor-first3=P. R. |editor-last3=Bosch
|editor-first4=R. |editor-last4=Dave
|editor-first5=L. A. |editor-last5=Meyer
|publisher=]
|url=http://www.ipcc.ch/publications_and_data/ar4/wg3/en/contents.html
|isbn=978-0-521-88011-4
}}
** {{cite book |ref={{harvid|IPCC AR4 WG3 Ch1|2007}}
|chapter=Chapter 1: Introduction
|chapter-url=https://archive.ipcc.ch/pdf/assessment-report/ar4/wg3/ar4-wg3-chapter1.pdf
|year=2007
|display-authors=4
|first1=H.-H.|last1=Rogner
|first2=D. |last2=Zhou
|first3=R. |last3=Bradley
|first4=P. |last4=Crabbé
|first5=O. |last5=Edenhofer
|first6=B. |last6=Hare
|first7=L. |last7=Kuijpers
|first8=M. |last8=Yamaguchi
|title={{Harvnb|IPCC AR4 WG3|2007}}
|pages=95–116
}}

<!-- =========AR5================== -->
'''Fifth Assessment report'''
* {{cite book |ref={{harvid|IPCC AR5 WG1|2013}}<!-- ipcc:20200215 -->
|author=IPCC |author-link=IPCC
|year=2013
|title=Climate Change 2013: The Physical Science Basis
|series=Contribution of Working Group I to the ] of the Intergovernmental Panel on Climate Change
|display-editors=4
|editor1-first=T. F. |editor1-last=Stocker
|editor2-first=D. |editor2-last=Qin
|editor3-first=G.-K. |editor3-last=Plattner
|editor4-first=M. |editor4-last=Tignor
|editor5-first=S. K. |editor5-last=Allen
|editor6-first=J. |editor6-last=Boschung
|editor7-first=A. |editor7-last=Nauels
|editor8-first=Y. |editor8-last=Xia
|editor9-first=V. |editor9-last=Bex
|editor10-first=P. M. |editor10-last=Midgley
|publisher=]
|place=Cambridge, UK & New York
|isbn=978-1-107-05799-9 <!-- ISBN in printed source is incorrect. -->
|url=http://www.climatechange2013.org/images/report/WG1AR5_ALL_FINAL.pdf <!-- Same file, new url per IPCC. -->
}}.
** {{cite book |ref={{harvid|IPCC AR5 WG1 Summary for Policymakers|2013}}
|chapter=Summary for Policymakers
|chapter-url=https://ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_SPM_FINAL.pdf
|year=2013
|author=IPCC |author-link=IPCC
|title={{Harvnb|IPCC AR5 WG1|2013}}
}}
** {{cite book |ref={{harvid|IPCC AR5 WG1 Ch2|2013}}
|chapter=Chapter 2: Observations: Atmosphere and Surface
|chapter-url=https://www.ipcc.ch/site/assets/uploads/2017/09/WG1AR5_Chapter02_FINAL.pdf
|year=2013
|display-authors=4
|first1=D. L. |last1=Hartmann
|first2=A. M. G. |last2=Klein Tank
|first3=M. |last3=Rusticucci
|first4=L. V. |last4=Alexander
|first5=S. |last5=Brönnimann
|first6=Y. |last6=Charabi
|first7=F. J. |last7=Dentener
|first8=E. J. |last8=Dlugokencky
|first9=D. R. |last9=Easterling
|first10=A. |last10=Kaplan
|first11=B. J. |last11=Soden
|first12=P. W. |last12=Thorne
|first13=M. |last13=Wild
|first14=P. M. |last14=Zhai
|title={{Harvnb|IPCC AR5 WG1|2013}}
|pages=159–254
}}
** {{cite book |ref={{harvid|IPCC AR5 WG1 Ch3|2013}}
|chapter=Chapter 3: Observations: Ocean
|chapter-url=https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapter03_FINAL.pdf
|year=2013
|display-authors=4
|first1=M. |last1=Rhein
|first2=S. R. |last2=Rintoul
|first3=S. |last3=Aoki
|first4=E. |last4=Campos
|first5=D. |last5=Chambers
|first6=R. A. |last6=Feely
|first7=S. |last7=Gulev
|first8=G. C. |last8=Johnson
|first9=S. A. |last9=Josey
|first10=A. |last10=Kostianoy
|first11=C. |last11=Mauritzen
|first12=D. |last12=Roemmich
|first13=L. D. |last13=Talley
|first14=F. |last14=Wang
|title={{Harvnb|IPCC AR5 WG1|2013}}
|pages=255–315
}}
** {{cite book |ref= {{harvid|IPCC AR5 WG1 Ch5|2013}}
|chapter=Chapter 5: Information from Paleoclimate Archives
|chapter-url=https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapter05_FINAL.pdf
|year=2013
|display-authors=4
|first1=V. |last1=Masson-Delmotte
|first2=M. |last2=Schulz
|first3=A. |last3=Abe-Ouchi
|first4=J. |last4=Beer
|first5=A. |last5=Ganopolski
|first6=J. F. |last6=González Rouco
|first7=E. |last7=Jansen
|first8=K. |last8=Lambeck
|first9=J. |last9=Luterbacher
|first10=T. |last10=Naish
|first11=T. |last11=Osborn
|first12=B. |last12=Otto-Bliesner
|first13=T. |last13=Quinn
|first14=R. |last14=Ramesh
|first15=M. |last15=Rojas
|first16=X. |last16=Shao
|first17=A. |last17=Timmermann
|title={{Harvnb|IPCC AR5 WG1|2013}}
|pages=383–464
}}
** {{cite book |ref={{harvid|IPCC AR5 WG1 Ch10|2013}}
|chapter=Chapter 10: Detection and Attribution of Climate Change: from Global to Regional
|chapter-url=https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapter10_FINAL.pdf
|year=2013
|display-authors=4
|first1=N. L. |last1=Bindoff
|first2=P. A. |last2=Stott
|first3=K. M. |last3=AchutaRao
|first4=M. R. |last4=Allen
|first5=N. |last5=Gillett
|first6=D. |last6=Gutzler
|first7=K. |last7=Hansingo
|first8=G. |last8=Hegerl
|first9=Y. |last9=Hu
|first10=S. |last10=Jain
|first11=I. I. |last11=Mokhov
|first12=J. |last12=Overland
|first13=J. |last13=Perlwitz
|first14=R. |last14=Sebbari
|first15=X. |last15=Zhang
|title={{Harvnb|IPCC AR5 WG1|2013}}
|pages=867–952
}}
** {{cite book |ref={{harvid|IPCC AR5 WG1 Ch12|2013}}
|chapter=Chapter 12: Long-term Climate Change: Projections, Commitments and Irreversibility
|chapter-url=https://archive.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_Chapter12_FINAL.pdf
|year=2013
|display-authors=4
|first1=M. |last1=Collins
|first2=R. |last2=Knutti
|first3=J. M. |last3=Arblaster
|first4=J.-L. |last4=Dufresne
|first5=T. |last5=Fichefet
|first6=P. |last6=Friedlingstein
|first7=X. |last7=Gao
|first8=W. J. |last8=Gutowski
|first9=T. |last9=Johns
|first10=G. |last10=Krinner
|first11=M. |last11=Shongwe
|first12=C. |last12=Tebaldi
|first13=A. J. |last13=Weaver
|first14=M. |last14=Wehner
|pages=1029–1136
|title={{Harvnb|IPCC AR5 WG1|2013}}
}}

<!----------------AR5 Working Group II Report -->
{{anchor|{{harvid|IPCC AR5 WG2|2014}}}} <!-- For the entire AR5 WG2 report -->
* {{cite book |ref={{harvid|IPCC AR5 WG2 A|2014}}
|author=IPCC |author-link=IPCC
|year=2014
|title=Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part A: Global and Sectoral Aspects
|series=Contribution of Working Group II to the ] of the Intergovernmental Panel on Climate Change
|display-editors=4
|editor-first1=C. B. |editor-last1=Field
|editor-first2=V. R. |editor-last2=Barros
|editor-first3=D. J. |editor-last3=Dokken
|editor-first4=K. J. |editor-last4=Mach
|editor-first5=M. D. |editor-last5=Mastrandrea
|editor-first6=T. E. |editor-last6=Bilir
|editor-first7=M. |editor-last7=Chatterjee
|editor-first8=K. L. |editor-last8=Ebi
|editor-first9=Y. O. |editor-last9=Estrada
|editor-first10=R. C. |editor-last10=Genova
|editor-first11=B. |editor-last11=Girma
|editor-first12=E. S. |editor-last12=Kissel
|editor-first13=A. N. |editor-last13=Levy
|editor-first14=S. |editor-last14=MacCracken
|editor-first15=P. R. |editor-last15=Mastrandrea
|editor-first16=L. L. |editor-last16=White
|publisher=]
|isbn=978-1-107-05807-1
|url=<!-- ** I haven't added AR5 urls yet as I have not determined which is best. -JJ -->
}}. Chapters 1–20, SPM, and Technical Summary.
** {{cite book |ref={{harvid|IPCC AR5 WG2 Ch13|2014}}
|chapter=Chapter 13: Livelihoods and Poverty
|chapter-url=https://archive.ipcc.ch/pdf/assessment-report/ar5/wg2/WGIIAR5-Chap13_FINAL.pdf
|display-authors=4
|first1=L. |last1=Olsson
|first2=M. |last2=Opondo
|first3=P. |last3=Tschakert
|first4=A. |last4=Agrawal
|first5=S. H. |last5=Eriksen
|first6=S. |last6=Ma
|first7=L. N. |last7=Perch
|first8=S. A. |last8=Zakieldeen
|year=2014
|title={{Harvnb|IPCC AR5 WG2 A|2014}}
|pages=793–832
}}
** {{cite book |ref={{harvid|IPCC AR5 WG2 Ch18|2014}}
|chapter=Chapter 18: Detection and Attribution of Observed Impacts
|chapter-url=https://archive.ipcc.ch/pdf/assessment-report/ar5/wg2/WGIIAR5-Chap18_FINAL.pdf
|year=2014
|display-authors=4
|first1=W. |last1=Cramer
|first2=G. W. |last2=Yohe
|first3=M. |last3=Auffhammer
|first4=C. |last4=Huggel
|first5=U. |last5=Molau
|first6=M. A. F. |last6=da Silva Dias
|first7=A. |last7=Solow
|first8=D. A. |last8=Stone
|first9=L. |last9=Tibig
|title={{Harvnb|IPCC AR5 WG2 A|2014}}
|pages=979–1037
}}
** {{cite book |ref={{harvid|IPCC AR5 WG2 Ch19|2014}}
|chapter=Chapter 19: Emergent Risks and Key Vulnerabilities
|chapter-url=https://archive.ipcc.ch/pdf/assessment-report/ar5/wg2/WGIIAR5-Chap19_FINAL.pdf
|year=2014
|display-authors=4
|first1=M. |last1=Oppenheimer
|first2=M. |last2=Campos
|first3=R. |last3=Warren
|first4=J. |last4=Birkmann
|first5=G. |last5=Luber
|first6=B. |last6=O'Neill
|first7=K. |last7=Takahashi
|title={{Harvnb|IPCC AR5 WG2 A|2014}}
|pages=1039–1099
}}
* {{cite book |ref={{harvid|IPCC AR5 WG2 B|2014}}
|author=IPCC |author-link=IPCC
|year=2014
|title=Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part B: Regional Aspects
|series=Contribution of Working Group II to the ] of the Intergovernmental Panel on Climate Change
|display-editors=4
|editor-first1=V. R. |editor-last1=Barros
|editor-first2=C. B. |editor-last2=Field
|editor-first3=D. J. |editor-last3=Dokken
|editor-first4=K. J. |editor-last4=Mach
|editor-first5=M. D. |editor-last5=Mastrandrea
|editor-first6=T. E. |editor-last6=Bilir
|editor-first7=M. |editor-last7=Chatterjee
|editor-first8=K. L. |editor-last8=Ebi
|editor-first9=Y. O. |editor-last9=Estrada
|editor-first10=R. C. |editor-last10=Genova
|editor-first11=B. |editor-last11=Girma
|editor-first12=E. S. |editor-last12=Kissel
|editor-first13=A. N. |editor-last13=Levy
|editor-first14=S. |editor-last14=MacCracken
|editor-first15=P. R. |editor-last15=Mastrandrea
|editor-first16=L.L |editor-last16=White
|publisher=]
|place=Cambridge, UK & New York
|isbn=978-1-107-05816-3
|url=https://www.ipcc.ch/site/assets/uploads/2018/02/WGIIAR5-PartB_FINAL.pdf
}}. Chapters 21–30, Annexes, and Index.
** {{cite book |ref={{harvid|IPCC AR5 WG2 Ch28|2014}}
|chapter=Chapter 28: Polar Regions
|chapter-url=https://archive.ipcc.ch/pdf/assessment-report/ar5/wg2/WGIIAR5-Chap28_FINAL.pdf
|display-authors=4
|first1=J. N. |last1=Larsen
|first2=O. A. |last2=Anisimov
|first3=A. |last3=Constable
|first4=A. B. |last4=Hollowed
|first5=N. |last5=Maynard
|first6=P. |last6=Prestrud
|first7=T. D. |last7=Prowse
|first8=J. M. R.|last8=Stone
|year=2014
|title={{Harvnb|IPCC AR5 WG2 B|2014}}
|pages=1567–1612
}}

<!-- ------------------------------ -->
* {{cite book |ref={{harvid|IPCC AR5 WG3|2014}}
|author=IPCC |author-link=IPCC
|year=2014
|title=Climate Change 2014: Mitigation of Climate Change
|series=Contribution of Working Group III to the ] of the Intergovernmental Panel on Climate Change
|display-editors=4
|editor-first1=O. |editor-last1=Edenhofer
|editor-first2=R. |editor-last2=Pichs-Madruga
|editor-first3=Y. |editor-last3=Sokona
|editor-first4=E. |editor-last4=Farahani
|editor-first5=S. |editor-last5=Kadner
|editor-first6=K. |editor-last6=Seyboth
|editor-first7=A. |editor-last7=Adler
|editor-first8=I. |editor-last8=Baum
|editor-first9=S. |editor-last9=Brunner
|editor-first10=P. |editor-last10=Eickemeier
|editor-first11=B. |editor-last11=Kriemann
|editor-first12=J. |editor-last12=Savolainen
|editor-first13=S. |editor-last13=Schlömer
|editor-first14=C. |editor-last14=von Stechow
|editor-first15=T. |editor-last15=Zwickel
|editor-first16=J. C. |editor-last16=Minx
|publisher=]
|place=Cambridge, UK & New York, NY
|isbn= 978-1-107-05821-7
}}
<!-- ## -->
** {{cite book |ref={{harvid|IPCC AR5 WG3 Ch9|2014}}
|chapter=Chapter 9: Buildings
|chapter-url=https://archive.ipcc.ch/pdf/assessment-report/ar5/wg3/ipcc_wg3_ar5_chapter9.pdf
|year=2014
|display-authors=4
|first1=O. |last1=Lucon
|first2=D. |last2=Ürge-Vorsatz
|first3=A. |last3=Ahmed
|first4=H. |last4=Akbari
|first5=P. |last5=Bertoldi
|first6=L. |last6=Cabeza
|first7=N. |last7=Eyre
|first8=A. |last8=Gadgil
|first9=L. D. |last9=Harvey
|first10=Y. |last10=Jiang
|first11=E. |last11=Liphoto
|first12=S. |last12=Mirasgedis
|first13=S. |last13=Murakami
|first14=J. |last14=Parikh
|first15=C. |last15=Pyke
|first16=M. |last16=Vilariño
|title={{Harvnb|IPCC AR5 WG3|2014}}
}}
** {{cite book |ref={{harvid|IPCC AR5 WG3 Annex III|2014}}
|chapter=Annex III: Technology-specific Cost and Performance Parameters
|chapter-url=https://www.ipcc.ch/site/assets/uploads/2018/02/ipcc_wg3_ar5_annex-iii.pdf
|year=2014
|display-authors=4
|first1=O. |last1=Edenhofer
|first2=R. |last2=Pichs-Madruga
|first3=Y. |last3=Sokona
|first4=E. |last4=Farahani
|first5=S. |last5=Kadner
|first6=K. |last6=Seyboth
|first7=A. |last7=Adler
|first8=I. |last8=Baum
|first9=S. |last9=Brunner
|first10=P. |last10=Eickemeier
|first11=B. |last11=Kriemann
|first12=J. |last12=Savolainen
|first13=S. |last13=Schlömer
|first14=C. |last14=von Stechow
|first15=T. |last15=Zwickel
|first16=J.C. |last16=Minx
|publisher=Cambridge University Press
|location=Cambridge, United Kingdom and New York, NY, USA
|title={{Harvnb|IPCC AR5 WG3|2014}}
}}
* {{cite book
|author=IPCC AR5 SYR |author-link=IPCC
|year=2014
|title=Climate Change 2014: Synthesis Report
|series=Contribution of Working Groups I, II and III to the ] of the Intergovernmental Panel on Climate Change
|editor1=The Core Writing Team
|editor-first2=R. K. |editor-last2=Pachauri
|editor-first3=L. A. |editor-last3=Meyer
|publisher=IPCC
|place=Geneva, Switzerland
|isbn=<!-- no isbn -->
|url=https://www.ipcc.ch/report/ar5/syr/
}}
** {{cite book |ref={{harvid|IPCC AR5 SYR Summary for Policymakers|2014}}
|chapter=Summary for Policymakers
|chapter-url=https://archive.ipcc.ch/pdf/assessment-report/ar5/syr/AR5_SYR_FINAL_SPM.pdf
|year=2014
|author=IPCC |author-link=IPCC
|title={{Harvnb|IPCC AR5 SYR|2014}}
}}
** {{cite book |ref={{harvid|IPCC AR5 SYR Glossary|2014}}
|chapter=Annex II: Glossary
|chapter-url=https://archive.ipcc.ch/pdf/assessment-report/ar5/syr/AR5_SYR_FINAL_Annexes.pdf
|year=2014
|author=IPCC |author-link=IPCC
|title={{Harvnb|IPCC AR5 SYR|2014}}
}}

<!-- =========SR15================== -->
'''Special Report: Global Warming of 1.5&nbsp;°C'''
* {{cite book |ref={{harvid|IPCC SR15|2018}} <!-- ipcc:20200312 -->
|author=IPCC |author-link=IPCC
|year=2018
|title=Global Warming of 1.5&nbsp;°C. An IPCC Special Report on the impacts of global warming of 1.5&nbsp;°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty
|display-editors=4
|editor-first1=V. |editor-last1=Masson-Delmotte
|editor-first2=P. |editor-last2=Zhai
|editor-first3=H.-O. |editor-last3=Pörtner
|editor-first4=D. |editor-last4=Roberts
|editor-first5=J. |editor-last5=Skea
|editor-first6=P. R. |editor-last6=Shukla
|editor-first7=A. |editor-last7=Pirani
|editor-first8=W. |editor-last8=Moufouma-Okia
|editor-first9=C. |editor-last9=Péan
|editor-first10=R. |editor-last10=Pidcock
|editor-first11=S. |editor-last11=Connors
|editor-first12=J. B. R. |editor-last12=Matthews
|editor-first13=Y. |editor-last13=Chen
|editor-first14=X. |editor-last14=Zhou
|editor-first15=M. I. |editor-last15=Gomis
|editor-first16=E. |editor-last16=Lonnoy
|editor-first17=T. |editor-last17=Maycock
|editor-first18=M. |editor-last18=Tignor
|editor-first19=T. |editor-last19=Waterfeld
|publisher=]
|isbn=<!-- not issued? -->
|url=https://www.ipcc.ch/site/assets/uploads/sites/2/2019/06/SR15_Full_Report_High_Res.pdf
}} Global Warming of 1.5 °C –.
<!-- ## -->
** {{cite book |ref={{harvid|IPCC SR15 Summary for Policymakers|2018}} <!-- ipcc:20200312 -->
|author=IPCC |author-link=IPCC
|year=2018
|chapter=Summary for Policymakers
|chapter-url=https://www.ipcc.ch/site/assets/uploads/sites/2/2019/05/SR15_SPM_version_report_HR.pdf
|title={{Harvnb|IPCC SR15|2018}}
|pages=3–24
}}
<!-- ## -->
** {{cite book |ref={{harvid|IPCC SR15 Ch1|2018}} <!-- ipcc:20200312 -->
|year=2018
|chapter=Chapter 1: Framing and Context
|chapter-url=https://www.ipcc.ch/site/assets/uploads/sites/2/2019/05/SR15_Chapter1_High_Res.pdf
|display-authors=4
|first1=M. R. |last1=Allen
|first2=O. P. |last2=Dube
|first3=W. |last3=Solecki
|first4=F. |last4=Aragón-Durand
|first5=W. |last5=Cramer
|first6=S. |last6=Humphreys
|first7=M. |last7=Kainuma
|first8=J. |last8=Kala
|first9=N. |last9=Mahowald
|first10=Y. |last10=Mulugetta
|first11=R. |last11=Perez
|first12=M. |last12=Wairiu
|first13=K. |last13=Zickfeld
|title={{Harvnb|IPCC SR15|2018}}
|pages=49–91
}}
<!-- ## -->
** {{cite book |ref={{harvid|IPCC SR15 Ch2|2018}} <!-- ipcc:20200312 -->
|year=2018
|chapter=Chapter 2: Mitigation Pathways Compatible with 1.5&nbsp;°C in the Context of Sustainable Development
|chapter-url=https://www.ipcc.ch/site/assets/uploads/sites/2/2019/05/SR15_Chapter2_High_Res.pdf
|display-authors=4
|first1=J. |last1=Rogelj |author1-link=Joeri Rogelj
|first2=D. |last2=Shindell
|first3=K. |last3=Jiang
|first4=S. |last4=Fifta
|first5=P. |last5=Forster
|first6=V. |last6=Ginzburg
|first7=C. |last7=Handa
|first8=H. |last8=Kheshgi
|first9=S. |last9=Kobayashi
|first10=E. |last10=Kriegler
|first11=L. |last11=Mundaca
|first12=R. |last12=Séférian
|first13=M. V. |last13=Vilariño
|title={{Harvnb|IPCC SR15|2018}}
|pages=93–174
}}
<!-- ## -->
** {{cite book |ref={{harvid|IPCC SR15 Ch3|2018}} <!-- ipcc:20200312 -->
|year=2018
|chapter=Chapter 3: Impacts of 1.5&nbsp;°C Global Warming on Natural and Human Systems
|chapter-url=https://www.ipcc.ch/site/assets/uploads/sites/2/2019/05/SR15_Chapter3_High_Res.pdf
|display-authors=4
|first1=O. |last1=Hoegh-Guldberg
|first2=D. |last2=Jacob
|first3=M. |last3=Taylor
|first4=M. |last4=Bindi
|first5=S. |last5=Brown
|first6=I. |last6=Camilloni
|first7=A. |last7=Diedhiou
|first8=R. |last8=Djalante
|first9=K. L. |last9=Ebi
|first10=F. |last10=Engelbrecht
|first11=J. |last11=Guiot
|first12=Y. |last12=Hijioka
|first13=S. |last13=Mehrotra
|first14=A. |last14=Payne
|first15=S. I.|last15=Seneviratne
|first16=A. |last16=Thomas
|first17=R. |last17=Warren
|first18=G. |last18=Zhou
|title={{Harvnb|IPCC SR15|2018}}
|pages=175–311
}}
<!-- ## -->
** {{cite book |ref={{harvid|IPCC SR15 Ch4|2018}} <!-- ipcc:20200312 -->
|year=2018
|chapter=Chapter 4: Strengthening and Implementing the Global Response
|chapter-url=https://www.ipcc.ch/site/assets/uploads/sites/2/2019/05/SR15_Chapter4_High_Res.pdf
|display-authors=4
|first1=H. |last1=de Coninck
|first2=A. |last2=Revi
|first3=M. |last3=Babiker
|first4=P. |last4=Bertoldi
|first5=M. |last5=Buckeridge
|first6=A. |last6=Cartwright
|first7=W. |last7=Dong
|first8=J. |last8=Ford
|first9=S. |last9=Fuss
|first10=J.-C. |last10=Hourcade
|first11=D. |last11=Ley
|first12=R. |last12=Mechler
|first13=P. |last13=Newman
|first14=A. |last14=Revokatova
|first15=S. |last15=Schultz
|first16=L. |last16=Steg
|first17=T. |last17=Sugiyama
|title={{Harvnb|IPCC SR15|2018}}
|pages=313–443
}}
<!-- ## -->
** {{cite book |ref={{harvid|IPCC SR15 Ch5|2018}} <!-- ipcc:20200312 -->
|year=2018
|chapter=Chapter 5: Sustainable Development, Poverty Eradication and Reducing Inequalities
|chapter-url=https://www.ipcc.ch/site/assets/uploads/sites/2/2019/05/SR15_Chapter5_High_Res.pdf
|display-authors=4
|first1=J. |last1=Roy
|first2=P. |last2=Tschakert
|first3=H. |last3=Waisman
|first4=S. |last4=Abdul Halim
|first5=P. |last5=Antwi-Agyei
|first6=P. |last6=Dasgupta
|first7=B. |last7=Hayward
|first8=M. |last8=Kanninen
|first9=D. |last9=Liverman
|first10=C. |last10=Okereke
|first11=P. F. |last11=Pinho
|first12=K. |last12=Riahi
|first13=A. G. |last13=Suarez Rodriguez
|title={{Harvnb|IPCC SR15|2018}}
|pages=445–538
}}

<!-- =========SRCCL ============================ -->
'''Special Report: Climate change and Land'''
* {{cite book |ref={{harvid|IPCC SRCCL|2019}} <!-- ipcc:20200204 -->
|author=IPCC |author-link=IPCC
|display-editors=4
|editor-first1=P. R. |editor-last1=Shukla
|editor-first2=J. |editor-last2=Skea
|editor-first3=E. |editor-last3=Calvo Buendia
|editor-first4=V. |editor-last4=Masson-Delmotte
|editor-first5=H.-O. |editor-last5=Pörtner
|editor-first6=D. |editor-last6=C. Roberts
|editor-first7=P. |editor-last7=Zhai
|editor-first8=R. |editor-last8=Slade
|editor-first9=S. |editor-last9=Connors
|editor-first10=R. |editor-last10=van Diemen
|editor-first11=M. |editor-last11=Ferrat
|editor-first12=E. |editor-last12=Haughey
|editor-first13=S. |editor-last13=Luz
|editor-first14=S. |editor-last14=Neogi
|editor-first15=M. |editor-last15=Pathak
|editor-first16=J. |editor-last16=Petzold
|editor-first17=J. |editor-last17=Portugal Pereira
|editor-first18=P. |editor-last18=Vyas
|editor-first19=E. |editor-last19=Huntley
|editor-first20=K. |editor-last20=Kissick
|editor-first21=M. |editor-last21=Belkacemi
|editor-first22=J. |editor-last22=Malley
|year=2019
|title=IPCC Special Report on Climate Change, Desertification, Land Degradation, Sustainable Land Management, Food Security, and Greenhouse gas fluxes in Terrestrial Ecosystems
|url=https://www.ipcc.ch/site/assets/uploads/2019/11/SRCCL-Full-Report-Compiled-191128.pdf
|publisher=In press
}}
<!-- ## -->
** {{cite book |ref={{harvid|IPCC SRCCL Summary for Policymakers|2019}} <!-- ipcc:20200204 -->
|chapter=Summary for Policymakers
|chapter-url=https://www.ipcc.ch/site/assets/uploads/sites/4/2019/12/02_Summary-for-Policymakers_SPM.pdf
|author=IPCC |author-link=IPCC
|year=2019
|title={{Harvnb|IPCC SRCCL|2019}}
|pages=3–34
}}
<!-- ## -->
** {{cite book |ref={{harvid|IPCC SRCCL Ch2|2019}} <!-- ipcc:20200204 -->
|chapter=Chapter 2: Land-Climate Interactions
|chapter-url=https://www.ipcc.ch/site/assets/uploads/2019/11/05_Chapter-2.pdf
|display-authors=4
|first1=G. |last1=Jia
|first2=E. |last2=Shevliakova
|first3=P. E. |last3=Artaxo<!-- 'Artaxo-Netto'? -->
|first4=N. |last4=De Noblet-Ducoudré
|first5=R. |last5=Houghton
|first6=J. |last6=House
|first7=K. |last7=Kitajima
|first8=C. |last8=Lennard
|first9=A. |last9=Popp
|first10=A. |last10=Sirin
|first11=R. |last11=Sukumar
|first12=L. |last12=Verchot
|year=2019
|title={{Harvnb|IPCC SRCCL|2019}}
|pages=131–247
}}
<!-- ## -->
** {{cite book |ref={{harvid|IPCC SRCCL Ch5|2019}} <!-- ipcc:20200204 -->
|chapter=Chapter 5: Food Security
|chapter-url=https://www.ipcc.ch/site/assets/uploads/2019/11/08_Chapter-5.pdf
|display-authors=4
|first1=C. |last1=Mbow
|first2=C. |last2=Rosenzweig
|first3=L. G. |last3=Barioni
|first4=T. |last4=Benton
|first5=M. |last5=Herrero
|first6=M. V. |last6=Krishnapillai
|first7=E. |last7=Liwenga
|first8=P. |last8=Pradhan
|first9=M. G. |last9=Rivera-Ferre
|first10=T. |last10=Sapkota
|first11=F. N. |last11=Tubiello
|first12=Y. |last12=Xu
|year=2019
|title={{Harvnb|IPCC SRCCL|2019}}
|pages=437–550
}}

<!-- =========SROCC ============================ -->
'''Special Report: The Ocean and Cryosphere in a Changing Climate'''
* {{cite book |ref={{harvid|IPCC SROCC|2019}} <!-- ipcc:20200202 -->
|author=IPCC |author-link=IPCC
|year=2019
|display-editors=4
|editor-first1=H.-O. |editor-last1=Pörtner
|editor-first2=D. C. |editor-last2=Roberts
|editor-first3=V. |editor-last3=Masson-Delmotte
|editor-first4=P. |editor-last4=Zhai
|editor-first5=M. |editor-last5=Tignor
|editor-first6=E. |editor-last6=Poloczanska
|editor-first7=K. |editor-last7=Mintenbeck
|editor-first8=A. |editor-last8=Alegría
|editor-first9=M. |editor-last9=Nicolai
|editor-first10=A. |editor-last10=Okem
|editor-first11=J. |editor-last11=Petzold
|editor-first12=B. |editor-last12=Rama
|editor-first13=N. |editor-last13=Weyer
|title=IPCC Special Report on the Ocean and Cryosphere in a Changing Climate
|publisher=In press
|isbn=<!-- Not yet assigned -->
|url=https://www.ipcc.ch/site/assets/uploads/sites/3/2019/12/SROCC_FullReport_FINAL.pdf
}}
<!-- ## -->
** {{cite book |ref={{harvid|IPCC SROCC Summary for Policymakers|2019}} <!-- ipcc:20200202 -->
|chapter=Summary for Policymakers
|chapter-url=https://www.ipcc.ch/site/assets/uploads/sites/3/2019/11/03_SROCC_SPM_FINAL.pdf
|author=IPCC |author-link=IPCC
|year=2019
|title={{Harvnb|IPCC SROCC|2019}}
|pages=3–35
}}
<!-- ## -->
** {{cite book |ref={{harvid|IPCC SROCC Ch4|2019}} <!-- ipcc:20200202 -->
|chapter=Chapter 4: Sea Level Rise and Implications for Low Lying Islands, Coasts and Communities
|chapter-url=https://www.ipcc.ch/site/assets/uploads/sites/3/2019/11/08_SROCC_Ch04_FINAL.pdf
|display-authors=4
|first1=M. |last1=Oppenheimer
|first2=B. |last2=Glavovic
|first3=J. |last3=Hinkel
|first4=R. |last4=van de Wal
|first5=A. K. |last5=Magnan
|first6=A. |last6=Abd-Elgawad
|first7=R. |last7=Cai
|first8=M. |last8=Cifuentes-Jara
|first9=R. M. |last9=Deconto
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|first13=B. |last13=Marzeion
|first14=B. |last14=Meyssignac
|first15=Z. |last15=Sebesvari
|year=2019
|title={{Harvnb|IPCC SROCC|2019}}
|pages=321–445
}}
<!-- ## -->
** {{cite book |ref={{harvid|IPCC SROCC Ch5|2019}} <!-- ipcc:20200202 -->
|chapter=Chapter 5: Changing Ocean, Marine Ecosystems, and Dependent Communities
|chapter-url=https://www.ipcc.ch/site/assets/uploads/sites/3/2019/11/09_SROCC_Ch05_FINAL.pdf
|display-authors=4
|first1=N. L. |last1=Bindoff
|first2=W. W. L. |last2=Cheung
|first3=J. G. |last3=Kairo
|first4=J. |last4=Arístegui
|first5=V. A. |last5=Guinder
|first6=R. |last6=Hallberg
|first7=N. J. M. |last7=Hilmi
|first8=N. |last8=Jiao
|first9=Md S. |last9=Karim
|first10=L. |last10=Levin
|first11=S. |last11=O'Donoghue
|first12=S. R. |last12=Purca Cuicapusa
|first13=B. |last13=Rinkevich
|first14=T. |last14=Suga
|first15=A. |last15=Tagliabue
|first16=P. |last16=Williamson
|year=2019
|title={{Harvnb|IPCC SROCC|2019}}
|pages=447–587
}}

'''Sixth Assessment Report'''
* {{Cite book |ref= {{harvid|IPCC AR6 WG1|2021}}
|author= IPCC |author-link= IPCC
|year= 2021
|title= Climate Change 2021: The Physical Science Basis
|series= Contribution of Working Group I to the ] of the Intergovernmental Panel on Climate Change
|display-editors= 4
|editor1-first=V. |editor1-last=Masson-Delmotte
|editor2-first=P. |editor2-last=Zhai
|editor3-first=A. |editor3-last=Pirani
|editor4-first=S. L. |editor4-last=Connors
|editor5-first=C. |editor5-last=Péan
|editor6-first=S. |editor6-last=Berger
|editor7-first=N. |editor7-last=Caud
|editor8-first=Y. |editor8-last=Chen
|editor9-first=L. |editor9-last=Goldfarb
|editor10-first=M. I. |editor10-last=Gomis
|publisher=] (In Press)
|place=Cambridge, United Kingdom and New York, NY, US
|url=https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_FullReport_small.pdf
}}
** {{Cite book |ref={{harvid|IPCC AR6 WG1 Summary for Policymakers|2021}}
|chapter=Summary for Policymakers
|chapter-url=https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_SPM_final.pdf
|author=IPCC |author-link= IPCC
|year=2021
|title={{Harvnb|IPCC AR6 WG1|2021}}
}}
** {{Cite book |ref={{harvid|IPCC AR6 WG1 Technical Summary|2021}}
|chapter=Technical Summary
|last1=Arias |first1=Paola A.
|last2=Bellouin |first2=Nicolas
|last3=Coppola |first3=Erika
|last4=Jones |first4=Richard G.
|last5=Krinner |first5=Gerhard
|display-authors=4
|chapter-url=https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_TS.pdf
|year=2021
|title={{Harvnb|IPCC AR6 WG1|2021}}
}}
** {{Cite book
|ref= {{harvid|IPCC AR6 WG1 Ch2|2021}}
|chapter=Chapter 2: Changing state of the climate system
|last1 = Gulev| first1 = Sergey K.| last2 = Thorne| first2 = Peter W.| last3 = Ahn| first3 = Jinho| last4 = Dentener| first4 = Frank J.| last5 = Domingues| first5 = Catia M.| last6 = Gerland| first6 = Sebastian| last7 = Gong| first7 = Daoyi| last8 = Kaufman| first8 = Darrell S.| last9 = Nnamchi| first9 = Hyacinth C.| last10 = Quaas| first10 = Johannes| last11 = Rivera| first11 = Juan Antonio| last12 = Sathyendranath| first12 = Shubha| last13 = Smith| first13 = Sharon L.| last14 = Trewin| first14 = Blair| last15 = von Shuckmann| first15 = Karina| last16 = Vose| first16 = Russell S.
|title = Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change
|chapter-url= https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter_02.pdf
|display-authors=4
|year=2021
}}
** {{Cite book
|ref= {{harvid|IPCC AR6 WG1 Ch11|2021}}
|chapter=Chapter 11: Weather and climate extreme events in a changing climate
|last1=Seneviratne |first1=Sonia I.
|last2=Zhang |first2=Xuebin
|last3=Adnan |first3=M.
|last4=Badi |first4=W.
|last5=Dereczynski |first5=Claudine
|last6=Di Luca |first6=Alejandro
|last7=Ghosh |first7=S.
|chapter-url=https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter_11.pdf
|display-authors=4
|title= {{Harvnb|IPCC AR6 WG1|2021}}
|year=2021
}}
* {{cite book
|author=IPCC
|ref={{harvid|IPCC AR6 WG2|2022}}
|editor-last1=Pörtner |editor-first1=H.-O.
|editor-last2=Roberts |editor-first2=D.C.
|editor-last3=Tignor |editor-first3=M.
|editor-last4=Poloczanska |editor-first4=E.S.
|editor-last5=Mintenbeck |editor-first5=K.
|editor-last6=Alegría |editor-first6=A.
|editor-last7=Craig |editor-first7=M.
|editor-last8=Langsdorf |editor-first8=S.
|editor-last9=Löschke |editor-first9=S.
|editor-last10=Möller |editor-first10=V.
|editor-last11=Okem |editor-first11=A.
|editor-last12=Rama |editor-first12=B.
|url=https://www.ipcc.ch/report/ar6/wg2/
|title=Climate Change 2022: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change
|publisher=]
|year=2022
|doi=10.1017/9781009325844|isbn=978-1-009-32584-4
}}
** {{Cite book
|ref={{harvid|IPCC AR6 WG2 SPM|2022}}
|author=IPCC
|chapter=Summary for Policymakers
|chapter-url=https://www.ipcc.ch/report/ar6/wg2/downloads/report/IPCC_AR6_WGII_SummaryForPolicymakers.pdf
|title= {{harvnb|IPCC AR6 WG2|2022}}
|year=2022
|pages=3–33
|doi=10.1017/9781009325844.001
|isbn=978-1-009-32584-4
}}
** {{Cite book
|ref={{harvid|IPCC AR6 WG2 Technical Summary|2022}}
|author=IPCC
|chapter=Technical Summary
|chapter-url=https://www.ipcc.ch/report/ar6/wg2/downloads/report/IPCC_AR6_WGII_TechnicalSummary.pdf
|title= {{harvnb|IPCC AR6 WG2|2022}}
|year=2022
|pages=37–118
|doi=10.1017/9781009325844.002
|isbn=978-1-009-32584-4
}}
** {{Cite book
|ref={{harvid|IPCC AR6 WG2 Ch5|2022}}
|chapter=Food, Fibre and Other Ecosystem Products
|chapter-url=https://www.ipcc.ch/report/ar6/wg2/downloads/report/IPCC_AR6_WGII_Chapter05.pdf
|last1=Bezner Kerr |first1=R.
|last2=Hasegawa |first2=T.
|last3=Lasco |first3=R.
|last4=Bhatt |first4=I.
|last5=Deryng |first5=D.
|last6=Farrell |first6=A.
|last7=Gurney-Smith |first7=H.
|last8=Ju |first8=H.
|last9=Lluch-Cota |first9=S.
|last10=Meza |first10=F.
|last11=Nelson |first11=G.
|last12=Neufeldt |first12=H.
|last13=Thornton |first13=P.
|title= {{harvnb|IPCC AR6 WG2|2022}}
|year=2022
|pages=713–906
|doi=10.1017/9781009325844.007
|isbn=978-1-009-32584-4
}}
** {{Cite book
|ref={{harvid|IPCC AR6 WG2 Ch6|2022}}
|chapter=Cities, Settlements and Key Infrastructure
|chapter-url=https://www.ipcc.ch/report/ar6/wg2/downloads/report/IPCC_AR6_WGII_Chapter06.pdf
|last1=Dodman |first1=D.
|last2=Hayward |first2=B.
|last3=Pelling |first3=M.
|last4=Castan Broto |first4=V.
|last5=Chow |first5=W.
|last6=Chu |first6=E.
|last7=Dawson |first7=R.
|last8=Khirfan |first8=L.
|last9=McPhearson |first9=T.
|last10=Prakash |first10=A.
|last11=Zheng |first11=Y.
|last12=Ziervogel |first12=G.
|title= {{harvnb|IPCC AR6 WG2|2022}}
|year=2022
|pages=907–1040
|doi=10.1017/9781009325844.008
|isbn=978-1-009-32584-4
}}
** {{Cite book
|ref={{harvid|IPCC AR6 WG2 Ch16|2022}}
|chapter=Key Risks across Sectors and Regions
|chapter-url=https://www.ipcc.ch/report/ar6/wg2/downloads/report/IPCC_AR6_WGII_Chapter16.pdf
|last1=O'Neill |first1=B.
|last2=van Aalst |first2=M.
|last3=Zaiton Ibrahim |first3=Z.
|last4=Berrang Ford |first4=L.
|last5=Bhadwal |first5=S.
|last6=Buhaug |first6=H.
|last7=Diaz |first7=D.
|last8=Frieler |first8=K.
|last9=Garschagen |first9=M.
|last10=Magnan |first10=A.
|last11=Midgley |first11=G.
|last12=Mirzabaev |first12=A.
|last13=Thomas |first13=A.
|last14=Warren |first14=R.
|title= {{harvnb|IPCC AR6 WG2|2022}}
|year=2022
|pages=2411–2538
|doi=10.1017/9781009325844.025
|isbn=978-1-009-32584-4
}}
* {{cite book
|author=IPCC
|ref={{harvid|IPCC AR6 WG3|2022}}
|editor-last1=Shukla |editor-first1=P.R.
|editor-last2=Skea |editor-first2=J.
|display-editors=etal
|url=https://www.ipcc.ch/report/ar6/wg3/
|title=Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change
|publisher=]
|year=2022
|location=Cambridge, UK and New York, NY, USA
|doi=10.1017/9781009157926|isbn=978-1-009-15792-6
}}
** {{Cite book |ref={{harvid|IPCC AR6 WG3 Summary for Policymakers|2022}}
|chapter=Summary for Policymakers
|chapter-url=https://www.ipcc.ch/report/ar6/wg3/downloads/report/IPCC_AR6_WGIII_SummaryForPolicymakers.pdf
|author=IPCC |author-link=IPCC
|year=2022
|title={{Harvnb|IPCC AR6 WG3|2022}}
}}
** {{Cite book
|ref={{harvid|IPCC AR6 WG3 Technical Summary|2022}}
|chapter=Technical Summary
|chapter-url=https://www.ipcc.ch/report/ar6/wg3/downloads/report/IPCC_AR6_WGIII_TechnicalSummary.pdf
|last1=Pathak |first1=M.
|last2=Slade |first2=R.
|last3=Shukla |first3=P.R.
|last4=Skea |first4=J.
|last5=Pichs-Madruga |first5=R.
|last6=Ürge-Vorsatz |first6=D.
|title= {{harvnb|IPCC AR6 WG3|2022}}
|year=2022
|pages=51–148
|doi=10.1017/9781009157926.002
|isbn=978-1-009-15792-6
}}
** {{Cite book
|ref={{harvid|IPCC AR6 WG3 Ch3|2022}}
|chapter=Mitigation Pathways Compatible with Long-term Goals
|chapter-url=https://www.ipcc.ch/report/ar6/wg3/downloads/report/IPCC_AR6_WGIII_Chapter03.pdf
|last1=Riahi |first1=K.
|last2=Schaeffer |first2=R.
|last3=Arango |first3=J.
|last4=Calvin |first4=K.
|last5=Guivarch |first5=C.
|last6=Hasegawa |first6=T.
|last7=Jiang |first7=K.
|last8=Kriegler |first8=E.
|last9=Matthews |first9=R.
|last10=Peters |first10=G.P.
|last11=Rao |first11=A.
|last12=Robertson |first12=S.
|last13=Sebbit |first13=A.M.
|last14=Steinberger |first14=J.
|last15=Tavoni |first15=M.
|last16=van Vuuren |first16=D.P.
|title= {{harvnb|IPCC AR6 WG3|2022}}
|year=2022
|pages=295–408
|doi=10.1017/9781009157926.005
|isbn=978-1-009-15792-6
}}
* {{cite book
|author=IPCC |title=Climate Change 2023: Synthesis Report. Contribution of Working Groups I, II and III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change
|author-link=IPCC
|ref={{harvid|IPCC AR6 SYR|2023}}
|url=https://www.ipcc.ch/report/ar6/syr/downloads/report/IPCC_AR6_SYR_FullVolume.pdf
|editor-last1=Core Writing Team |editor-last2=Lee |editor-first2=H.
|editor-last3=Romero |editor-first3=J.
|display-editors=etal
|publisher=IPCC
|year=2023
|location=Geneva, Switzerland
|isbn=978-92-9169-164-7
|doi=10.59327/IPCC/AR6-9789291691647
|hdl=1885/299630
|s2cid=260074696
}}
** {{Cite book
|ref={{harvid|IPCC AR6 SYR SPM|2023}}
|chapter=Summary for Policymakers
|chapter-url=https://report.ipcc.ch/ar6syr/pdf/IPCC_AR6_SYR_SPM.pdf
|author=IPCC |author-link=IPCC
|year=2023
|title={{Harvnb|IPCC AR6 SYR|2023}}
}}
{{refend}}

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* {{cite journal |last1=Williams |first1=Richard G |last2=Ceppi |first2=Paulo |last3=Katavouta |first3=Anna |title=Controls of the transient climate response to emissions by physical feedbacks, heat uptake and carbon cycling |year=2020 |journal=] |volume=15 |issue=9 |pages=0940c1 |doi=10.1088/1748-9326/ab97c9 |bibcode=2020ERL....15i40c1W |doi-access=free |hdl=10044/1/80154 |hdl-access=free}}
* {{cite journal |last1=Wolff |first1=Eric W. |last2=Shepherd |first2=John G. |last3=Shuckburgh |first3=Emily |last4=Watson |first4=Andrew J. |title=Feedbacks on climate in the Earth system: introduction |journal=Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences |pmid=26438277 |pmc=4608041 |doi=10.1098/rsta.2014.0428 |date=2015 |volume=373 |issue=2054 |page=20140428 |bibcode=2015RSPTA.37340428W}}
* {{cite journal |last1=Young |first1=Paul J. |last2=Harper |first2=Anna B. |last3=Huntingford |first3=Chris |last4=Paul |first4=Nigel D. |last5=Morgenstern |first5=Olaf |last6=Newman |first6=Paul A. |last7=Oman |first7=Luke D. |last8=Madronich |first8=Sasha |last9=Garcia |first9=Rolando R. |title=The Montreal Protocol protects the terrestrial carbon sink |date=2021 |display-authors=3 |journal=] |volume=596 |issue=7872 |pages=384–388 |doi=10.1038/s41586-021-03737-3 |doi-access=free |pmid=34408332 |bibcode=2021Natur.596..384Y}}
*
* {{cite journal |last1=Zeng |first1=Ning |last2=Yoon |first2=Jinho |s2cid=1708267 |title=Expansion of the world's deserts due to vegetation-albedo feedback under global warming |date=2009 |journal=] |volume=36 |issue=17 |page=L17401 |bibcode=2009GeoRL..3617401Z |doi=10.1029/2009GL039699 |issn=1944-8007 |doi-access=free}}
* {{cite journal |last1=Zhang |first1=Jinlun |last2=Lindsay |first2=Ron |last3=Steele |first3=Mike |last4=Schweiger |first4=Axel |s2cid=9387303 |date=2008 |title=What drove the dramatic arctic sea ice retreat during summer 2007? |journal=Geophysical Research Letters |volume=35 |issue=11 |pages=1–5 |doi=10.1029/2008gl034005 |bibcode=2008GeoRL..3511505Z |doi-access=free}}
{{refend}}

==== Books, reports and legal documents ====
{{refbegin|30em}}
* {{cite web |ref={{harvid|G8+5 Academies|2009}}
|title=G8+5 Academies' joint statement: Climate change and the transformation of energy technologies for a low carbon future
|date=May 2009
|publisher=The National Academies of Sciences, Engineering, and Medicine
|author1=Academia Brasileira de Ciéncias (Brazil)
|author2=Royal Society of Canada
|author3=Chinese Academy of Sciences
|author4=Académie des Sciences (France)
|author5=Deutsche Akademie der Naturforscher Leopoldina (Germany)
|author6=Indian National Science Academy
|author7=Accademia Nazionale dei Lincei (Italy)
|author8=Science Council of Japan, Academia Mexicana de Ciencias
|author9=Academia Mexicana de Ciencias (Mexico)
|author10=Russian Academy of Sciences
|author11=Academy of Science of South Africa
|author12=Royal Society (United Kingdom)
|author13=National Academy of Sciences (United States of America)
|url=http://www.nationalacademies.org/includes/G8+5energy-climate09.pdf
|archive-url=https://web.archive.org/web/20100215171429/http://www.nationalacademies.org/includes/G8+5energy-climate09.pdf
|archive-date=15 February 2010
|url-status=dead
|access-date=5 May 2010
}}
* {{cite book
|first1=David |last1=Archer
|author-link=David Archer (scientist)
|first2=Raymond |last2=Pierrehumbert
|author-link2=Raymond Pierrehumbert
|title=The Warming Papers: The Scientific Foundation for the Climate Change Forecast
|url=https://books.google.com/books?id=sPY9HOfnuS0C&pg=PT10|year=2013|publisher=John Wiley & Sons|isbn=978-1-118-68733-8
}}
* {{cite report |ref={{harvid|International Institute for Sustainable Development|2019}}
|url=https://www.iisd.org/sites/default/files/publications/fossil-fuel-clean-energy-subsidy-swap.pdf
|title=Fossil Fuel to Clean Energy Subsidy Swaps
|last1=Bridle |first1=Richard
|last2=Sharma |first2=Shruti
|last3=Mostafa |first3=Mostafa
|last4=Geddes |first4=Anna
|date=June 2019
}}
* {{cite web
|title=The Paris Agreement: Summary. Climate Focus Client Brief on the Paris Agreement III
|author=Climate Focus
|date=December 2015
|access-date=12 April 2019
|url=https://climatefocus.com/sites/default/files/20151228%20COP%2021%20briefing%20FIN.pdf
|archive-url=https://web.archive.org/web/20181005005832/https://climatefocus.com/sites/default/files/20151228%20COP%2021%20briefing%20FIN.pdf
|archive-date=5 October 2018
|url-status=live
}}
* {{cite report |ref={{harvid|UN Human Development Report|2020}}
|author =Conceição
|display-authors=etal
| year =2020
| title =Human Development Report 2020 The Next Frontier: Human Development and the Anthropocene
| url =http://hdr.undp.org/sites/default/files/hdr2020.pdf
| publisher =]
| access-date =9 January 2021
}}
* {{cite report
|last1=DeFries |first1=Ruth
|author-link1=Ruth DeFries
|last2=Edenhofer |first2=Ottmar
|last3=Halliday |first3=Alex
|last4=Heal |first4=Geoffrey
|display-authors=etal
|date=September 2019
|title=The missing economic risks in assessments of climate change impacts
|publisher=Grantham Research Institute on Climate Change and the Environment, London School of Economics and Political Science
|url=https://www.lse.ac.uk/granthaminstitute/wp-content/uploads/2019/09/The-missing-economic-risks-in-assessments-of-climate-change-impacts-2.pdf
}}
* Dessler, Andrew E. and Edward A. Parson, eds. ''The science and politics of global climate change: A guide to the debate'' (Cambridge University Press, 2019).
* {{cite web
|title=The climate regime from The Hague to Marrakech: Saving or sinking the Kyoto Protocol?
|last=Dessai |first=Suraje
|date=2001
|work=Tyndall Centre Working Paper 12
|publisher=Tyndall Centre
|archive-url=https://web.archive.org/web/20120610013556/http://www.tyndall.ac.uk/sites/default/files/wp12.pdf
|archive-date=10 June 2012
|url-status=dead
|url=http://www.tyndall.ac.uk/sites/default/files/wp12.pdf
|access-date=5 May 2010
}}
* {{cite book
|last1=Dunlap |first1=Riley E.
|last2=McCright |first2=Aaron M.
|editor-last1=Dryzek |editor-first1=John S.
|editor-first2=Richard B. |editor-last2=Norgaard
|editor-first3=David |editor-last3=Schlosberg
|title=The Oxford Handbook of Climate Change and Society
|publisher=Oxford University Press
|date=2011
|pages=144–160
|chapter=Chapter 10: Organized climate change denial
|isbn=978-0-19-956660-0}}
* {{cite book
|last1=Dunlap |first1=Riley E.
|last2=McCright |first2=Aaron M.
|editor-last1=Dunlap |editor-first1=Riley E.
|editor-first2=Robert J. |editor-last2=Brulle
|title=Climate Change and Society: Sociological Perspectives
|publisher=Oxford University Press
|date=2015
|pages=300–332
|chapter=Chapter 10: Challenging Climate Change: The Denial Countermovement
|isbn=978-0-19-935611-9}}
*{{cite report |ref={{harvid|Ebi et al.|2018}} | last1=Ebi | first1=Kristie L. | last2=Balbus | first2=John | last3=Luber | first3=George | last4=Bole | first4=Aparna | last5=Crimmins | first5=Allison R. | last6=Glass | first6=Gregory E. | last7=Saha | first7=Shubhayu | last8=Shimamoto | first8=Mark M. | last9=Trtanj | first9=Juli M. | last10=White-Newsome | first10=Jalonne L. | title=Chapter 14 : Human Health. Impacts, Risks, and Adaptation in the United States: The Fourth National Climate Assessment, Volume II | date=2018 | doi=10.7930/nca4.2018.ch14}}
* {{cite report
| last=Flavell | first=Alex
| title=IOM outlook on migration, environment and climate change
| publisher=] (IOM) | publication-place=Geneva, Switzerland | year=2014
| url = https://publications.iom.int/system/files/pdf/mecc_outlook.pdf
| isbn=978-92-9068-703-0 | oclc=913058074}}
* {{cite book
|title=The Callendar Effect: the life and work of Guy Stewart Callendar (1898–1964)
|year=2007
|last=Fleming |first=James Rodger
|publisher=American Meteorological Society
|location=Boston
|isbn=978-1-878220-76-9
}}
* {{cite report |ref={{harvid|UNDP|2021}}
|title= Peoples' Climate Vote
|last1 = Flynn |first1=C.
|last2 = Yamasumi |first2=E.
|last3 = Fisher |first3=S.
|last4 = Snow |first4=D.
|last5 = Grant |first5=Z.
|last6 = Kirby |first6=M.
|last7 = Browning |first7=P.
|last8 = Rommerskirchen |first8=M.
|last9 = Russell |first9=I.
|display-authors= 4
|publisher= UNDP and University of Oxford
|date= January 2021
|url= https://www.undp.org/sites/g/files/zskgke326/files/publications/UNDP-Oxford-Peoples-Climate-Vote-Results.pdf
| access-date=5 August 2021
}}
* {{cite report |ref={{harvid|UNDP|2024}}
|title= Peoples' Climate Vote 2024 Results
|last1 = Flynn |first1=C.
|last2 = Jardon |first2=S. T.
|last3 = Fisher |first3=S.
|last4 = Blayney |first4=M.
|last5 = Ward |first5=A.
|last6 = Smith |first6=H.
|last7 = Struthoff |first7=P.
|last8 = Fillingham |first8=Z.
|display-authors= 2
|publisher= UNDP and University of Oxford
|date= June 2024
|url= https://peoplesclimate.vote/document/Peoples_Climate_Vote_Report_2024.pdf
| access-date=1 November 2024
}}
* {{cite report
|author=Global Methane Initiative
|title=Global Methane Emissions and Mitigation Opportunities
|url=https://www.globalmethane.org/documents/gmi-mitigation-factsheet.pdf
|date=2020
|publisher=Global Methane Initiative
}}
* {{cite book
|title=Shock Waves : Managing the Impacts of Climate Change on Poverty. Climate Change and Development
|date=2016
|isbn=978-1-4648-0674-2
|doi=10.1596/978-1-4648-0673-5
|last1=Hallegatte |first1=Stephane
|last2=Bangalore |first2=Mook
|last3=Bonzanigo |first3=Laura
|last4=Fay |first4=Marianne
|last5=Kane |first5=Tamaro
|last6=Narloch |first6=Ulf
|last7=Rozenberg |first7=Julie
|last8=Treguer |first8=David
|last9=Vogt-Schilb |first9=Adrien
|display-authors=4
|location=Washington, D.C.
|publisher=World Bank
|hdl=10986/22787
|url=https://openknowledge.worldbank.org/bitstream/handle/10986/22787/9781464806735.pdf?sequence=13&isAllowed=y
}}
* {{cite book
|title=Climate Change: Observed Impacts on Planet Earth
|last=Haywood |first=Jim
|year=2016
|publisher=Elsevier
|isbn=978-0-444-63524-2
|editor-last=Letcher |editor-first=Trevor M.
|chapter=Chapter 27 – Atmospheric Aerosols and Their Role in Climate Change
}}
* {{Cite report |ref={{harvid|IEA|2020b}}
| author= IEA
| date= December 2020
| title= Energy Efficiency 2020
|chapter=COVID-19 and energy efficiency
|chapter-url= https://www.iea.org/reports/energy-efficiency-2020/covid-19-and-energy-efficiency#abstract
| location= Paris, France
| access-date=6 April 2021
}}
* {{Cite report
| author= IEA
| date= October 2021
| title= Net Zero By 2050: A Roadmap for the Global Energy Sector
| url= https://iea.blob.core.windows.net/assets/deebef5d-0c34-4539-9d0c-10b13d840027/NetZeroby2050-ARoadmapfortheGlobalEnergySector_CORR.pdf
| location= Paris, France
| access-date=4 April 2022
}}
* {{Cite report | ref={{harvid|IEA World Energy Outlook 2023}}
| author= IEA
| date= October 2023
| title=World Energy Outlook 2023
| url= https://iea.blob.core.windows.net/assets/26ca51d0-4a42-4649-a7c0-552d75ddf9b2/WorldEnergyOutlook2023.pdf
| location= Paris, France
| access-date=25 October 2021
}}
* {{cite book
|title=Macroeconomic and Financial Policies for Climate Change Mitigation: A Review of the Literature
|url=https://www.elibrary.imf.org/doc/IMF001/28337-9781513511955/28337-9781513511955/Other_formats/Source_PDF/28337-9781513512938.pdf
|isbn=978-1-5135-1195-5
|last1=Krogstrup |first1=Signe
|last2=Oman |first2=William
|series=IMF working papers
|date=4 September 2019
|volume=19
|issue=185
|doi=10.5089/9781513511955.001
|s2cid=203245445
|issn=1018-5941
}}
* {{cite report |ref={{harvid|Yale|2021}}
|title= International Public Opinion on Climate Change
|last1 = Leiserowitz |first1=A.
|last2 = Carman |first2=J.
|last3 = Buttermore |first3=N.
|last4 = Wang |first4=X.
|last5 = Rosenthal |first5=S.
|last6 = Marlon |first6=J.
|last7 = Mulcahy |first7=K.
|display-authors= 4
|publisher= Yale Program on Climate Change Communication and Facebook Data for Good
|year= 2021
|location= New Haven, CT
|url= https://climatecommunication.yale.edu/wp-content/uploads/2021/06/international-climate-opinion-february-2021d.pdf
| access-date=5 August 2021
}}
* {{Cite book|title=Future Energy: Improved, Sustainable and Clean Options for our Planet |edition=Third |publisher=] |year=2020|isbn=978-0-08-102886-5 |editor-last=Letcher|editor-first=Trevor M.}}
* {{cite book
|last1=Meinshausen |first1=Malte
|chapter=Implications of the Developed Scenarios for Climate Change
|date=2019
|title=Achieving the Paris Climate Agreement Goals: Global and Regional 100% Renewable Energy Scenarios with Non-energy GHG Pathways for +1.5&nbsp;°C and +2&nbsp;°C
|pages=459–469
|editor-last=Teske |editor-first=Sven
|publisher=Springer International Publishing
|doi=10.1007/978-3-030-05843-2_12 |doi-access=free
|isbn=978-3-030-05843-2
|s2cid=133868222
|url=https://apo.org.au/node/235336
}}
* {{cite report|ref={{harvid|ICCT|2019}}
|first1=J. |last1=Miller
|first2=L. |last2=Du
|first3=D. |last3=Kodjak
|title=Impacts of World-Class Vehicle Efficiency and Emissions Regulations in Select G20 Countries
|url=https://theicct.org/sites/default/files/publications/ICCT_G20-briefing-paper_Jan2017_vF.pdf
|publisher=The International Council on Clean Transportation
|location=Washington, D.C.
|year=2017
}}
* {{cite book
|title=Copenhagen 2009: Failure or final wake-up call for our leaders? EV 49
|last=Müller |first=Benito
|date=February 2010
|publisher=]
|isbn=978-1-907555-04-6
|page=i
|url=https://www.oxfordenergy.org/wpcms/wp-content/uploads/2011/03/EV49-Copenhagen2009Failureorfinalwake-upcallforourleaders-BenitoMuller-2010.pdf
|access-date=18 May 2010
|archive-url=https://web.archive.org/web/20170710081944/https://www.oxfordenergy.org/wpcms/wp-content/uploads/2011/03/EV49-Copenhagen2009Failureorfinalwake-upcallforourleaders-BenitoMuller-2010.pdf
|archive-date=10 July 2017|url-status=live
}}
* {{cite report
|title=Understanding and responding to climate change: Highlights of National Academies Reports, 2008 edition
|author=National Academies
|year=2008
|publisher=National Academy of Sciences
|url=http://dels.nas.edu/resources/static-assets/materials-based-on-reports/booklets/climate_change_2008_final.pdf
|access-date=9 November 2010
|url-status=dead
|archive-url=https://web.archive.org/web/20171011182257/http://dels.nas.edu/resources/static-assets/materials-based-on-reports/booklets/climate_change_2008_final.pdf
|archive-date=11 October 2017
}}
* {{cite report
|author=National Research Council
|year=2012
|title=Climate Change: Evidence, Impacts, and Choices
|publisher=National Academy of Sciences
|location=Washington, D.C.
|url=https://nap.nationalacademies.org/download/14673
|access-date=21 November 2023
}}
* {{cite book
|last1=Newell |first1=Peter
|title=Climate for Change: Non-State Actors and the Global Politics of the Greenhouse
|date=14 December 2006
|access-date=30 July 2018
|publisher=Cambridge University Press
|url=https://books.google.com/books?id=ing21MGmh5UC
|isbn=978-0-521-02123-4
}}
* {{cite web |ref={{harvid|NOAA|2017}}
|author=NOAA
|url=https://tidesandcurrents.noaa.gov/publications/techrpt83_Global_and_Regional_SLR_Scenarios_for_the_US_final.pdf
|title=January 2017 analysis from NOAA: Global and Regional Sea Level Rise Scenarios for the United States
|access-date=7 February 2019
|archive-url=https://web.archive.org/web/20171218140625/https://tidesandcurrents.noaa.gov/publications/techrpt83_Global_and_Regional_SLR_Scenarios_for_the_US_final.pdf
|archive-date=18 December 2017 |url-status=live }}
* {{cite book
|last1=Olivier |first1=J. G. J.
|last2=Peters |first2=J. A. H. W.
|year=2019
|title=Trends in global CO2 and total greenhouse gas emissions
|publisher=PBL Netherlands Environmental Assessment Agency
|url=https://www.pbl.nl/sites/default/files/downloads/pbl-2020-trends-in-global-co2-and-total-greenhouse-gas-emissions-2019-report_4068.pdf
|place=The Hague
}}
* {{cite book
|chapter=The scientific consensus on climate change: How do we know we're not wrong?
|last1=Oreskes |first1=Naomi
|author1-link=Naomi Oreskes
|title=Climate Change: What It Means for Us, Our Children, and Our Grandchildren
|editor-last1=DiMento |editor-first1=Joseph F. C.
|editor-last2=Doughman |editor-first2=Pamela M.
|publisher=The MIT Press
|year=2007
|isbn=978-0-262-54193-0
}}
* {{cite book
|title=Merchants of Doubt: How a Handful of Scientists Obscured the Truth on Issues from Tobacco Smoke to Global Warming
|date=2010
|last1=Oreskes |first1=Naomi
|first2=Erik |last2=Conway
|publisher=Bloomsbury Press
|edition=first
|isbn=978-1-59691-610-4
}}
* {{Cite report | ref= {{harvid|Pew|2015}}
| author= Pew Research Center
| date=November 2015
| title= Global Concern about Climate Change, Broad Support for Limiting Emissions
| url= https://www.pewresearch.org/global/wp-content/uploads/sites/2/2015/11/Pew-Research-Center-Climate-Change-Report-FINAL-November-5-2015.pdf
| access-date=5 August 2021
}}
* {{cite book
|author=REN21
|year=2020
|title=Renewables 2020 Global Status Report
|url=https://www.ren21.net/wp-content/uploads/2019/05/gsr_2020_full_report_en.pdf
|location=Paris |publisher=REN21 Secretariat
|isbn=978-3-948393-00-7
}}
* {{cite book
|date=13 April 2005
|author=Royal Society
|title=Economic Affairs – Written Evidence
|series=The Economics of Climate Change, the Second Report of the 2005–2006 session, produced by the UK Parliament House of Lords Economics Affairs Select Committee
|url=https://publications.parliament.uk/pa/ld200506/ldselect/ldeconaf/12/12we24.htm
|publisher=UK Parliament
|access-date=9 July 2011
|archive-url=https://web.archive.org/web/20111113084025/http://www.publications.parliament.uk/pa/ld200506/ldselect/ldeconaf/12/12we24.htm
|archive-date=13 November 2011
|url-status=live
}}
* {{cite book
|title=Global trends in climate change litigation: 2019 snapshot
|last1=Setzer |first1=Joana
|last2=Byrnes |first2=Rebecca
|date=July 2019
|publisher=the Grantham Research Institute on Climate Change and the Environment and the Centre for Climate Change Economics and Policy
|url=http://www.lse.ac.uk/GranthamInstitute/wp-content/uploads/2019/07/GRI_Global-trends-in-climate-change-litigation-2019-snapshot.pdf
|location=London
}}
* {{cite report |ref={{harvid|NREL|2017}}
|last1 = Steinberg |first1=D.
|last2 = Bielen |first2=D.
|last3 = Eichman |first3=J.
|last4 = Eurek |first4=K.
|last5 = Logan |first5=J.
|last6 = Mai |first6=T.
|last7 = McMillan |first7=C.
|last8 = Parker |first8=A.
|display-authors= 2
|title= Electrification & Decarbonization: Exploring U.S. Energy Use and Greenhouse Gas Emissions in Scenarios with Widespread Electrification and Power Sector Decarbonization
|publisher= National Renewable Energy Laboratory
|date= July 2017
|location=Golden, Colorado
|url= https://www.nrel.gov/docs/fy17osti/68214.pdf
}}
* {{cite book |ref={{harvid|Teske, ed.|2019}}
|chapter=Executive Summary
|date=2019
|title=Achieving the Paris Climate Agreement Goals: Global and Regional 100% Renewable Energy Scenarios with Non-energy GHG Pathways for +1.5&nbsp;°C and +2&nbsp;°C
|pages=xiii–xxxv
|editor-last=Teske |editor-first=Sven
|publisher=Springer International Publishing
|doi=10.1007/978-3-030-05843-2 |doi-access=free
|isbn=978-3-030-05843-2
|s2cid=198078901
|chapter-url=https://link.springer.com/content/pdf/bfm%3A978-3-030-05843-2%2F1.pdf
|url=https://apo.org.au/node/235336
}}
* {{cite book
|last1=Teske |first1=Sven
|last2=Pregger |first2=Thomas
|last3=Naegler|first3=Tobias
|last4=Simon |first4=Sonja
|last5=Pagenkopf |first5=Johannes
|last6=Vvan den Adel |first6=Bent
|last7=Deniz |first7= Özcan
|display-authors= 4
|chapter= Energy Scenario Results
|date=2019
|title=Achieving the Paris Climate Agreement Goals: Global and Regional 100% Renewable Energy Scenarios with Non-energy GHG Pathways for +1.5&nbsp;°C and +2&nbsp;°C
|pages=175–402
|editor-last=Teske |editor-first=Sven
|publisher=Springer International Publishing
|doi=10.1007/978-3-030-05843-2_8 |doi-access=free
|isbn=978-3-030-05843-2
|s2cid=
|url=https://apo.org.au/node/235336
}}
* {{cite book
|last1=Teske |first1=Sven
|chapter= Trajectories for a Just Transition of the Fossil Fuel Industry
|date=2019
|title=Achieving the Paris Climate Agreement Goals: Global and Regional 100% Renewable Energy Scenarios with Non-energy GHG Pathways for +1.5&nbsp;°C and +2&nbsp;°C
|pages=403–411
|editor-last=Teske |editor-first=Sven
|publisher=Springer International Publishing
|doi=10.1007/978-3-030-05843-2_9 |doi-access=free
|isbn=978-3-030-05843-2
|s2cid=133961910
|url=https://apo.org.au/node/235336
}}
* {{cite report
|author=UN FAO
|year=2016
|title=Global Forest Resources Assessment 2015. How are the world's forests changing?
|url=http://www.fao.org/3/a-i4793e.pdf#page=11
|publisher=Food and Agriculture Organization of the United Nations
|isbn=978-92-5-109283-5
|access-date=1 December 2019
}}
* {{cite book |ref={{harvid|United Nations Environment Programme|2019}}
|publisher=United Nations Environment Programme
|year=2019
|title=Emissions Gap Report 2019
|url=https://wedocs.unep.org/bitstream/handle/20.500.11822/30797/EGR2019.pdf?sequence=1&isAllowed=y
|location=Nairobi
|isbn=978-92-807-3766-0
}}
* {{cite book |ref={{harvid|United Nations Environment Programme|2024}}
|publisher=United Nations Environment Programme
|year=2024
|title=Emissions Gap Report 2024
|url=https://www.unep.org/resources/emissions-gap-report-2024
|location=Nairobi
|isbn=978-92-807-4185-8
}}
* {{cite book|author = UNEP |year= 2018|title=The Adaptation Gap Report 2018|location=Nairobi, Kenya|url =https://www.unenvironment.org/resources/adaptation-gap-report|isbn=978-92-807-3728-8|publisher = United Nations Environment Programme (UNEP)}}
* {{cite conference
|year =1992
|author=UNFCCC |author-link=UNFCCC
|title=United Nations Framework Convention on Climate Change
|url=https://unfccc.int/files/essential_background/background_publications_htmlpdf/application/pdf/conveng.pdf
}}
<!-- ## -->
* {{cite web |ref={{harvid|Kyoto Protocol|1997}}
|date =1997
|author=UNFCCC
|title=Kyoto Protocol to the United Nations Framework Convention on Climate Change
|publisher=United Nations
|url=https://unfccc.int/resource/docs/convkp/kpeng.html
}}
<!-- ## -->
<!-- Example: Decision 2/CP.15 in {{harvnb|UNFCCC: Copenhagen|2009|loc=}} -->
<!-- Cite by paragraph, as page numbering is variable. -->
* {{cite conference |ref={{harvid|UNFCCC: Copenhagen|2009}}
|date =30 March 2010
|author=UNFCCC
|chapter=Decision 2/CP.15: Copenhagen Accord
|title=Report of the Conference of the Parties on its fifteenth session, held in Copenhagen from 7 to 19&nbsp;December&nbsp;2009
|id =FCCC/CP/2009/11/Add.1
|publisher=United Nations Framework Convention on Climate Change
|chapter-url=http://unfccc.int/documentation/documents/advanced_search/items/3594.php?rec=j&priref=600005735#beg
|access-date=17 May 2010
|archive-url=https://web.archive.org/web/20100430005322/https://unfccc.int/documentation/documents/advanced_search/items/3594.php?rec=j&priref=600005735#beg
|archive-date=30 April 2010
|url-status=live
}}
<!-- ## -->
* {{cite web |ref={{harvid|Paris Agreement|2015}}
|date =2015
|author=UNFCCC
|title=Paris Agreement
|publisher=United Nations Framework Convention on Climate Change
|url=https://unfccc.int/files/essential_background/convention/application/pdf/english_paris_agreement.pdf
}}
<!-- ## -->
* {{cite report |ref={{harvid|UN NDC Synthesis Report|2021}}
| author = UNFCCC
| date = 26 February 2021
| title = Nationally determined contributions under the Paris Agreement Synthesis report by the secretariat
| url = https://unfccc.int/sites/default/files/resource/cma2021_02E.pdf
| publisher = ]
}}
<!-- ## -->
* {{cite web |ref={{harvid|UNHCR|2011}}
|title=Climate Change and the Risk of Statelessness: The Situation of Low-lying Island States
|last=Park |first=Susin
|date=May 2011
|publisher=United Nations High Commissioner for Refugees
|url=http://www.unhcr.org/4df9cb0c9.pdf
|archive-url=https://web.archive.org/web/20130502223251/http://www.unhcr.org/4df9cb0c9.pdf
|archive-date=2 May 2013|url-status=live|access-date=13 April 2012
}}
* {{cite report
|author=United States Environmental Protection Agency
|year=2016
|title=Methane and Black Carbon Impacts on the Arctic: Communicating the Science
|url=https://19january2017snapshot.epa.gov/climate-change-science/methane-and-black-carbon-impacts-arctic-communicating-science_.html
|access-date=27 February 2019
|archive-url=https://web.archive.org/web/20170906225344/https://19january2017snapshot.epa.gov/climate-change-science/methane-and-black-carbon-impacts-arctic-communicating-science_.html
|archive-date=6 September 2017 |url-status=live
}}
* {{cite journal
|last1=Van Oldenborgh |first1=Geert-Jan
|last2=Philip |first2=Sjoukje
|last3=Kew |first3=Sarah
|last4=Vautard |first4=Robert
|display-authors=etal
|date=2019
|website=Semantic Scholar
|s2cid=199454488 |title=Human contribution to the record-breaking June 2019 heat wave in France
}}
* {{cite book
|ref=none
|last=Weart
|first=Spencer
|date=October 2008
|title=The Discovery of Global Warming
|edition=2nd
|location=Cambridge, MA
|publisher=Harvard University Press
|isbn=978-0-674-03189-0
|url=http://history.aip.org/climate/reviews.htm
|access-date=16 June 2020
|url-status=live
|archive-url=https://web.archive.org/web/20161118000413/http://history.aip.org/climate/reviews.htm
|archive-date=18 November 2016}}
* {{cite book
|ref=none
|last=Weart
|first=Spencer
|date=February 2019
|title=The Discovery of Global Warming
|edition=online
|url=http://history.aip.org/climate/index.htm
|access-date=19 June 2020
|url-status=live
|archive-url=https://web.archive.org/web/20200618075616/http://history.aip.org/climate/index.htm
|archive-date=18 June 2020
|author-link=Spencer R. Weart}}
** {{citation|ref={{harvid|Weart "The Carbon Dioxide Greenhouse Effect"}} |mode=cs1 <!-- Because {cite web} doesn't do chapters. -->
|last =Weart |first=Spencer
|date =January 2020<!-- "The Discovery of Global Warming" is an evolving website, date is not useful for SFNs. -->
|title=The Discovery of Global Warming
|chapter=The Carbon Dioxide Greenhouse Effect
|chapter-url=http://history.aip.org/climate/co2.htm
|access-date=19 June 2020
|publisher=American Institute of Physics
|archive-url=https://web.archive.org/web/20161111191800/http://history.aip.org/climate/co2.htm
|archive-date=11 November 2016
|url-status=live
}}
** {{citation|ref=none |mode=cs1 <!-- Because {cite web} doesn't do chapters. -->
|last =Weart |first=Spencer
|date =January 2020<!-- "The Discovery of Global Warming" is an evolving website, date is not useful for SFNs. -->
|title=The Discovery of Global Warming
|chapter=The Public and Climate Change
|chapter-url=http://history.aip.org/climate/public.htm
|access-date=19 June 2020
|publisher =American Institute of Physics
|archive-url=https://web.archive.org/web/20161111191711/http://history.aip.org/climate/public.htm
|archive-date=11 November 2016
|url-status=live
}}
*** {{citation|ref={{harvid|Weart "Suspicions of a Human-Caused Greenhouse (1956–1969)"}} |mode=cs1 <!-- Because {cite web} doesn't do chapters. -->
|last =Weart |first=Spencer
|date =January 2020<!-- "The Discovery of Global Warming" is an evolving website, date is not useful for SFNs. -->
|title=The Discovery of Global Warming
|chapter=The Public and Climate Change: Suspicions of a Human-Caused Greenhouse (1956–1969)
|chapter-url=http://history.aip.org/climate/public.htm#S2
|access-date=19 June 2020
|publisher =American Institute of Physics
|archive-url=https://web.archive.org/web/20161111191711/http://history.aip.org/climate/public.htm#S2
|archive-date=11 November 2016
|url-status=live
}}
** {{citation|ref={{harvid|Weart "The Public and Climate Change (since 1980)"}} |mode=cs1 <!-- Because {cite web} doesn't do chapters. -->
|last1=Weart |first1=Spencer
|date =January 2020<!-- "The Discovery of Global Warming" is an evolving website, date is not useful for SFNs. -->
|title=The Discovery of Global warming
|chapter=The Public and Climate Change (cont.&nbsp;– since 1980)
|chapter-url=https://history.aip.org/climate/public2.htm
|access-date=19 June 2020
|publisher =American Institute of Physics
|archive-url=https://web.archive.org/web/20161111191659/http://history.aip.org/climate/public2.htm
|archive-date=11 November 2016
|url-status=live
}}
*** {{citation|ref={{harvid|Weart "The Public and Climate Change: The Summer of 1988"}} |mode=cs1 <!-- Because {cite web} doesn't do chapters. -->
|first=Spencer |last=Weart
|date =January 2020<!-- "The Discovery of Global Warming" is an evolving website, date is not useful for SFNs. -->
|title=The Discovery of Global Warming
|chapter=The Public and Climate Change: The Summer of 1988
|chapter-url=http://history.aip.org/climate/public2.htm#S1988
|access-date=19 June 2020
|publisher=American Institute of Physics
|archive-url=https://web.archive.org/web/20161111191659/http://history.aip.org/climate/public2.htm#S1988
|archive-date=11 November 2016
|url-status=live
}}
* {{cite report|ref={{harvid|World Bank, June|2019}}
|title=State and Trends of Carbon Pricing 2019
|url=http://documents.worldbank.org/curated/en/191801559846379845/pdf/State-and-Trends-of-Carbon-Pricing-2019.pdf
|date=June 2019
|publisher=World Bank
|location=Washington, D.C.
|doi=10.1596/978-1-4648-1435-8
|hdl=10986/29687
|isbn=978-1-4648-1435-8
|hdl-access=free
}}
*{{cite report |ref={{harvid|World Economic Forum|2024}} |author=World Economic Forum |title=Quantifying the Impact of Climate Change on Human Health |year=2024 |url=https://www3.weforum.org/docs/WEF_Quantifying_the_Impact_of_Climate_Change_on_Human_Health_2024.pdf}}
* {{Cite report |ref={{harvid|WHO|2016}}
| author= World Health Organization
| year= 2016
| title=Ambient air pollution: a global assessment of exposure and burden of disease
| location= Geneva, Switzerland
| isbn = 978-92-4-151135-3
| url= https://apps.who.int/iris/rest/bitstreams/1061179/retrieve
}}
* {{cite book |ref={{harvid|WHO|2018}}
|publisher=World Health Organization
|title=COP24 Special Report Health and Climate Change
|url=https://apps.who.int/iris/bitstream/handle/10665/276405/9789241514972-eng.pdf?ua=1
|year=2018
|location=Geneva
|isbn=978-92-4-151497-2
}}
* {{cite report |ref={{harvid|WMO SAOD|2022}} <!-- ipcc:20200204 -->
|author=]
|publisher=]
|title=Scientific Assessment of Ozone Depletion|url=https://csl.noaa.gov/assessments/ozone/2022/downloads/2022OzoneAssessment.pdf
|series=GAW Report No. 278
|isbn=978-9914-733-99-0
|year=2022
|location=Geneva
}}
** {{cite book |ref={{harvid|WMO SAOD Executive Summary|2022}}
|author=]
|title={{Harvnb|WMO SAOD|2022}}
|chapter-url=https://csl.noaa.gov/assessments/ozone/2022/downloads/executivesummary.pdf
|year=2022
|chapter=Executive Summary
}}
* {{cite book |ref={{harvid|WMO|2024a}}
|publisher=]
|title=WMO Statement on the State of the Global Climate in 2023
|url=https://library.wmo.int/viewer/68835/download?file=1347_Global-statement-2023_en.pdf&type=pdf&navigator=1
|year=2024
|location=Geneva
|series=WMO-No. 1347
|isbn=978-92-63-11347-4
}}
* {{cite report |ref={{harvid|WMO|2024b}}
|publisher=]
|title=WMO Global Annual to Decadal Climate Update: 2024-2028
|url=https://library.wmo.int/viewer/68910/download?file=WMO_GADCU_2024-2028_en.pdf&type=pdf&navigator=1
|year=2024
|location=Geneva
}}
* {{cite book |ref={{harvid|World Resources Institute, December|2019}}
|publisher=World Resources Institute
|date=December 2019
|title=Creating a Sustainable Food Future: A Menu of Solutions to Feed Nearly 10 Billion People by 2050
|location=Washington, D.C.
|url=https://files.wri.org/d8/s3fs-public/wrr-food-full-report.pdf
|isbn=978-1-56973-953-2
}}
{{refend}}

==== Non-technical sources ====
{{refbegin|30em}}
* '']''
** {{cite web |ref={{harvid|Associated Press, 22 September|2015}} |url=https://www.apstylebook.com/blog_posts/4 |title=An addition to AP Stylebook entry on global warming |last=Colford |first=Paul |date=22 September 2015 |website=AP Style Blog |access-date=6 November 2019}}
* '']''
** {{cite news |ref={{harvid|BBC, 1 May|2019}} |date=1 May 2019 |title=UK Parliament declares climate change emergency |publisher=BBC |url=https://www.bbc.com/news/uk-politics-48126677 |access-date=30 June 2019}}
** {{cite web |ref={{harvid|BBC Science Focus Magazine, 3 February|2020}} |last=Rigby |first=Sara |date=3 February 2020 |title=Climate change: should we change the terminology? |website=BBC Science Focus Magazine |url=https://www.sciencefocus.com/news/climate-change-should-we-change-the-terminology/ |access-date=24 March 2020}}
* '']''
** {{cite news |last1=Stover |first1=Dawn |title=The global warming 'hiatus' |url=https://thebulletin.org/2014/09/the-global-warming-hiatus/ |work=Bulletin of the Atomic Scientists |date=23 September 2014 |archive-url=https://web.archive.org/web/20200711032006/https://thebulletin.org/2014/09/the-global-warming-hiatus/ |archive-date=11 July 2020 |url-status=live}}
* '']''
** {{cite web |ref={{harvid|Carbon Brief, 4 Jan|2017}} |date=4 January 2017 |last=Yeo |first=Sophie |title=Clean energy: The challenge of achieving a 'just transition' for workers |website=Carbon Brief |url=https://www.carbonbrief.org/clean-energy-the-challenge-of-achieving-a-just-transition-for-workers |access-date=18 May 2020}}
** {{cite web |ref={{harvid|Carbon Brief, 19 June|2017}} |url=https://www.carbonbrief.org/billions-face-deadly-threshold-heat-extremes-2100-study/ |title=Billions to face 'deadly threshold' of heat extremes by 2100, finds study |last=McSweeney |first=Robert M. |date=19 June 2017 |website=Carbon Brief}}
** {{cite web |ref={{harvid|Carbon Brief, 21 November|2017}} |last=Yeo |first=Sophie |date=21 November 2017 |title=Explainer: Why a UN climate deal on HFCs matters |url=https://www.carbonbrief.org/explainer-why-a-un-climate-deal-on-hfcs-matters |access-date=10 January 2021 |url-status=live |website=Carbon Brief |archive-date=May 1, 2024 |archive-url=https://web.archive.org/web/20240501225407/https://www.carbonbrief.org/explainer-why-a-un-climate-deal-on-hfcs-matters/}}
** {{cite web |ref={{harvid|Carbon Brief, 15 January|2018}} |date=15 January 2018 |last1=McSweeney |first1=Robert M. |last2=Hausfather |first2=Zeke |title=Q&A: How do climate models work? |website=Carbon Brief |url=https://www.carbonbrief.org/qa-how-do-climate-models-work |access-date=2 March 2019 |archive-url=https://web.archive.org/web/20190305004530/https://www.carbonbrief.org/qa-how-do-climate-models-work |archive-date=5 March 2019 |url-status=live}}
** {{cite web |ref={{harvid|Carbon Brief, 19 April|2018}} |date=19 April 2018 |last1=Hausfather |first1=Zeke |title=Explainer: How 'Shared Socioeconomic Pathways' explore future climate change |website=Carbon Brief |url=https://www.carbonbrief.org/explainer-how-shared-socioeconomic-pathways-explore-future-climate-change |access-date=20 July 2019}}
** {{cite web |ref={{harvid|Carbon Brief, 8 October|2018}} |date=8 October 2018 |last1=Hausfather |first1=Zeke |title=Analysis: Why the IPCC 1.5C report expanded the carbon budget |url=https://www.carbonbrief.org/analysis-why-the-ipcc-1-5c-report-expanded-the-carbon-budget |access-date=28 July 2020 |website=Carbon Brief}}
** {{cite web |ref={{harvid|Carbon Brief, 7 January|2020}} |url=https://www.carbonbrief.org/media-reaction-australias-bushfires-and-climate-change |title=Media reaction: Australia's bushfires and climate change |last1=Dunne |first1=Daisy |last2=Gabbatiss |first2=Josh |last3=McSweeney |first3=Robert |date=7 January 2020 |website=Carbon Brief |access-date=11 January 2020}}
** {{cite web |ref={{Harvid|Carbon Brief, 10 February|2020}} |last=McSweeney |first=Robert |title=Nine Tipping Points That Could Be Triggered by Climate Change |url=https://www.carbonbrief.org/explainer-nine-tipping-points-that-could-be-triggered-by-climate-change/ |website=Carbon Brief | date=10 February 2020 |access-date=27 May 2022 |archive-date=October 7, 2024 |archive-url=https://web.archive.org/web/20241007002119/https://www.carbonbrief.org/explainer-nine-tipping-points-that-could-be-triggered-by-climate-change/ |url-status=live}}
** {{Cite web |ref={{harvid|Carbon Brief, 16 October|2021}} |last1=Gabbatiss|first1=Josh|last2=Tandon|first2=Ayesha|date=4 October 2021|title=In-depth Q&A: What is 'climate justice'?|url=https://www.carbonbrief.org/in-depth-qa-what-is-climate-justice|access-date=16 October 2021|website=Carbon Brief|language=en}}
** {{cite web |ref={{harvid|Carbon Brief, 3 July|2023}} |url=https://www.carbonbrief.org/analysis-how-low-sulphur-shipping-rules-are-affecting-global-warming/ |title=Analysis: How low-sulphur shipping rules are affecting global warming |last1=Hausfather |first1=Zeke |last2=Forster |first2=Piers |author-link2=Piers Forster |date=3 July 2023 |website=Carbon Brief |access-date=2 November 2024}}
* '']''
** {{Cite web |ref={{harvid|Climate.gov, 23 June|2022}} |last=Lindsey |first=Rebecca |title=Climate Change: Atmospheric Carbon Dioxide |website=Climate.gov |url=https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide |date=23 June 2022 |access-date=7 May 2023}}
* '']''
** {{cite news |ref={{harvid|Deutsche Welle, 22 June|2019}} |last1=Ruiz |first1=Irene Banos |title=Climate Action: Can We Change the Climate From the Grassroots Up? |url=https://www.ecowatch.com/climate-action-grassroots-2638915946.html |access-date=23 June 2019 |publisher=Deutsche Welle |date=22 June 2019 |archive-url=https://web.archive.org/web/20190623124154/https://www.ecowatch.com/climate-action-grassroots-2638915946.html |archive-date=23 June 2019 |url-status=live}}
* '']''
** {{cite web |ref={{harvid|EPA|2016}} |title=Myths vs. Facts: Denial of Petitions for Reconsideration of the Endangerment and Cause or Contribute Findings for Greenhouse Gases under Section 202(a) of the Clean Air Act |publisher=U.S. Environmental Protection Agency |date=10 September 2020 |url=https://www.epa.gov/ghgemissions/myths-vs-facts-denial-petitions-reconsideration-endangerment-and-cause-or-contribute |access-date=7 August 2017 |archive-url=https://web.archive.org/web/20210523211147/https://www.epa.gov/ghgemissions/myths-vs-facts-denial-petitions-reconsideration-endangerment-and-cause-or-contribute |archive-date=23 May 2021}}
** {{cite web |ref={{harvid|EPA|2019}} |url=https://www.epa.gov/ghgemissions/global-greenhouse-gas-emissions-data |title=Global Greenhouse Gas Emissions Data |publisher=U.S. Environmental Protection Agency |date=10 September 2024 |access-date=8 August 2020 |archive-url=https://web.archive.org/web/20200218125157/https://www.epa.gov/ghgemissions/global-greenhouse-gas-emissions-data |archive-date=18 February 2020 |url-status=live}}
** {{cite web |ref={{harvid|EPA|2020}} |url=https://www.epa.gov/ghgemissions/overview-greenhouse-gases |title=Overview of Greenhouse Gases |publisher=U.S. Environmental Protection Agency |date=11 April 2024 |access-date=15 September 2020 |archive-date=October 9, 2024 |archive-url=https://web.archive.org/web/20241009203854/https://www.epa.gov/ghgemissions/overview-greenhouse-gases}}
* '']''
** {{cite web |ref={{harvid|EUobserver, 20 December|2009}} |date=20 December 2009 |title=Copenhagen failure 'disappointing', 'shameful' |website=EUobserver |access-date=12 April 2019 |url=https://euobserver.com/environment/29181 |archive-url=https://web.archive.org/web/20190412092312/https://euobserver.com/environment/29181 |archive-date=12 April 2019 |url-status=live}}
* '']''
** {{cite web |ref={{harvid|European Parliament, February|2020}} |date=February 2020 |first=M. |last=Ciucci |title=Renewable Energy |website=European Parliament |url=https://www.europarl.europa.eu/factsheets/en/sheet/70/renewable-energy |access-date=3 June 2020}}
* '']''<!--
|issn=0261-3077 - not needed, nor location.
The parameters for harvid should match the first two parameters
used in harvnb for the short-cite in the text. -->
** {{cite news |ref={{harvid|The Guardian, 19 March|2019}} |last=Carrington |first=Damian |date=19 March 2019 |title=School climate strikes: 1.4 million people took part, say campaigners |newspaper=The Guardian |url=https://www.theguardian.com/environment/2019/mar/19/school-climate-strikes-more-than-1-million-took-part-say-campaigners-greta-thunberg |access-date=12 April 2019 |archive-url=https://web.archive.org/web/20190320122303/https://www.theguardian.com/environment/2019/mar/19/school-climate-strikes-more-than-1-million-took-part-say-campaigners-greta-thunberg |archive-date=20 March 2019 |url-status=live}}
** {{cite news |ref={{harvid|The Guardian, 28 November|2019}} |url=https://www.theguardian.com/world/2019/nov/28/eu-parliament-declares-climate-emergency |title='Our house is on fire': EU parliament declares climate emergency |last=Rankin |first=Jennifer |date=28 November 2019 |work=The Guardian |access-date=28 November 2019 |issn=0261-3077}}
** {{cite news |ref={{harvid|The Guardian, 19 February|2020}} |last=Watts |first=Jonathan |date=19 February 2020 |title=Oil and gas firms 'have had far worse climate impact than thought' |url=https://www.theguardian.com/environment/2020/feb/19/oil-gas-industry-far-worse-climate-impact-than-thought-fossil-fuels-methane |newspaper=The Guardian}}
** {{cite web |ref={{harvid|The Guardian, 28 October|2020}} |date=28 October 2020 |last=McCurry |first=Justin |title=South Korea vows to go carbon neutral by 2050 to fight climate emergency |url=http://www.theguardian.com/world/2020/oct/28/south-korea-vows-to-go-carbon-neutral-by-2050-to-fight-climate-emergency |access-date=6 December 2020 |work=The Guardian}}
* '']''
** {{cite web |ref={{harvid|IEA – Projected Costs of Generating Electricity 2020}} |title=Projected Costs of Generating Electricity 2020 |website=IEA |date=9 December 2020 |url=https://www.iea.org/reports/projected-costs-of-generating-electricity-2020 |access-date=4 April 2022}}
* '']''
** {{cite news |ref={{harvid|NASA, 28 May|2013}} |year=2013 |title=Arctic amplification |publisher=NASA |url=https://climate.nasa.gov/news/927/arctic-amplification |archive-url=https://web.archive.org/web/20180731054007/https://climate.nasa.gov/news/927/arctic-amplification/ |archive-date=31 July 2018 |url-status=live}}
** {{cite web |ref={{harvid|NASA, 5 December|2008}} |date=5 December 2008 |last=Conway |first=Erik M. |author-link=Erik M. Conway |title=What's in a Name? Global Warming vs. Climate Change |publisher=NASA |url=http://www.nasa.gov/topics/earth/features/climate_by_any_other_name.html |archive-url=https://web.archive.org/web/20100809221926/http://www.nasa.gov/topics/earth/features/climate_by_any_other_name.html |archive-date=9 August 2010}}
** {{cite web |date=January 2016 |last1=Shaftel |first1=Holly |title=What's in a name? Weather, global warming and climate change |website=NASA Climate Change: Vital Signs of the Planet |url=https://climate.nasa.gov/resources/global-warming |access-date=12 October 2018 |archive-url=https://web.archive.org/web/20180928145703/https://climate.nasa.gov/resources/global-warming/ |archive-date=28 September 2018 |url-status=dead}}
** {{cite web |ref={{harvid|NASA, 7 July|2020}} |date=7 July 2020 |editor-last=Shaftel |editor-first=Holly |editor2-last=Jackson |editor2-first=Randal |editor3-last=Callery |editor3-first=Susan |editor4-last=Bailey |editor4-first=Daniel |title=Overview: Weather, Global Warming and Climate Change |url=https://climate.nasa.gov/resources/global-warming-vs-climate-change |access-date=14 July 2020 |website=Climate Change: Vital Signs of the Planet}}
* '']''
** {{cite web |ref={{harvid|National Conference of State Legislators, 17 April|2020}} |date=17 April 2020 |title=State Renewable Portfolio Standards and Goals |website=National Conference of State Legislators |url=https://www.ncsl.org/research/energy/renewable-portfolio-standards.aspx |access-date=3 June 2020}}
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** {{cite journal |ref={{harvid|World Resources Institute, 8 August|2019}} |date=8 August 2019 |last1=Levin |first1=Kelly |title=How Effective Is Land At Removing Carbon Pollution? The IPCC Weighs In |website=World Resources institute |url=https://www.wri.org/blog/2019/08/how-effective-land-removing-carbon-pollution-ipcc-weighs |access-date=15 May 2020}}
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** {{cite web |ref={{harvid|Yale Climate Connections, 2 November|2010}} |title=Yale Researcher Anthony Leiserowitz on Studying, Communicating with American Public |date=2 November 2010 |last=Peach |first=Sara |publisher=Yale Climate Connections |access-date=30 July 2018 |url=https://www.yaleclimateconnections.org/2010/11/communicating-with-american-public |archive-url=https://web.archive.org/web/20190207130823/https://www.yaleclimateconnections.org/2010/11/communicating-with-american-public/ |archive-date=7 February 2019 |url-status=live}}
{{refend}}

== External links ==
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Latest revision as of 17:32, 22 December 2024

Human-caused changes to climate on Earth This article is about the present-day human-induced rise in global temperatures. For natural historical climate trends, see Climate variability and change. "Global warming" redirects here. For other uses, see Climate change (disambiguation) and Global warming (disambiguation).

The global map shows sea temperature rises of 0.5 to 1 degree Celsius; land temperature rises of 1 to 2 degrees Celsius; and Arctic temperature rises of up to 4 degrees Celsius.
Changes in surface air temperature over the past 50 years. The Arctic has warmed the most, and temperatures on land have generally increased more than sea surface temperatures.
Earth's average surface air temperature has increased almost 1.5 °C (about 2.5 °F) since the Industrial Revolution. Natural forces cause some variability, but the 20-year average shows the progressive influence of human activity.

Present-day climate change includes both global warming—the ongoing increase in global average temperature—and its wider effects on Earth's climate. Climate change in a broader sense also includes previous long-term changes to Earth's climate. The current rise in global temperatures is driven by human activities, especially fossil fuel burning since the Industrial Revolution. Fossil fuel use, deforestation, and some agricultural and industrial practices release greenhouse gases. These gases absorb some of the heat that the Earth radiates after it warms from sunlight, warming the lower atmosphere. Carbon dioxide, the primary greenhouse gas driving global warming, has grown by about 50% and is at levels not seen for millions of years.

Climate change has an increasingly large impact on the environment. Deserts are expanding, while heat waves and wildfires are becoming more common. Amplified warming in the Arctic has contributed to thawing permafrost, retreat of glaciers and sea ice decline. Higher temperatures are also causing more intense storms, droughts, and other weather extremes. Rapid environmental change in mountains, coral reefs, and the Arctic is forcing many species to relocate or become extinct. Even if efforts to minimize future warming are successful, some effects will continue for centuries. These include ocean heating, ocean acidification and sea level rise.

Climate change threatens people with increased flooding, extreme heat, increased food and water scarcity, more disease, and economic loss. Human migration and conflict can also be a result. The World Health Organization calls climate change one of the biggest threats to global health in the 21st century. Societies and ecosystems will experience more severe risks without action to limit warming. Adapting to climate change through efforts like flood control measures or drought-resistant crops partially reduces climate change risks, although some limits to adaptation have already been reached. Poorer communities are responsible for a small share of global emissions, yet have the least ability to adapt and are most vulnerable to climate change.

Bobcat Fire in Monrovia, CA, September 10, 2020Bleached colony of Acropora coralA dry lakebed in California, which is experiencing its worst megadrought in 1,200 years.Examples of some effects of climate change: Wildfire intensified by heat and drought, bleaching of corals occurring more often due to marine heatwaves, and worsening droughts compromising water supplies.

Many climate change impacts have been observed in the first decades of the 21st century, with 2023 the warmest on record at +1.48 °C (2.66 °F) since regular tracking began in 1850. Additional warming will increase these impacts and can trigger tipping points, such as melting all of the Greenland ice sheet. Under the 2015 Paris Agreement, nations collectively agreed to keep warming "well under 2 °C". However, with pledges made under the Agreement, global warming would still reach about 2.8 °C (5.0 °F) by the end of the century. Limiting warming to 1.5 °C would require halving emissions by 2030 and achieving net-zero emissions by 2050.

Fossil fuel use can be phased out by conserving energy and switching to energy sources that do not produce significant carbon pollution. These energy sources include wind, solar, hydro, and nuclear power. Cleanly generated electricity can replace fossil fuels for powering transportation, heating buildings, and running industrial processes. Carbon can also be removed from the atmosphere, for instance by increasing forest cover and farming with methods that capture carbon in soil.

Terminology

Before the 1980s it was unclear whether the warming effect of increased greenhouse gases was stronger than the cooling effect of airborne particulates in air pollution. Scientists used the term inadvertent climate modification to refer to human impacts on the climate at this time. In the 1980s, the terms global warming and climate change became more common, often being used interchangeably. Scientifically, global warming refers only to increased surface warming, while climate change describes both global warming and its effects on Earth's climate system, such as precipitation changes.

Climate change can also be used more broadly to include changes to the climate that have happened throughout Earth's history. Global warming—used as early as 1975—became the more popular term after NASA climate scientist James Hansen used it in his 1988 testimony in the U.S. Senate. Since the 2000s, climate change has increased usage. Various scientists, politicians and media may use the terms climate crisis or climate emergency to talk about climate change, and may use the term global heating instead of global warming.

Global temperature rise

Further information: Global surface temperature

Temperatures prior to present-day global warming

Main articles: Climate variability and change; Temperature record of the last 2,000 years; and Paleoclimatology
Global surface temperature reconstruction over the last 2000 years using proxy data from tree rings, corals, and ice cores in blue. Directly observed data is in red.

Over the last few million years the climate cycled through ice ages. One of the hotter periods was the Last Interglacial, around 125,000 years ago, where temperatures were between 0.5 °C and 1.5 °C warmer than before the start of global warming. This period saw sea levels 5 to 10 metres higher than today. The most recent glacial maximum 20,000 years ago was some 5–7 °C colder. This period has sea levels that were over 125 metres (410 ft) lower than today.

Temperatures stabilized in the current interglacial period beginning 11,700 years ago. This period also saw the start of agriculture. Historical patterns of warming and cooling, like the Medieval Warm Period and the Little Ice Age, did not occur at the same time across different regions. Temperatures may have reached as high as those of the late 20th century in a limited set of regions. Climate information for that period comes from climate proxies, such as trees and ice cores.

Warming since the Industrial Revolution

In recent decades, new high temperature records have substantially outpaced new low temperature records on a growing portion of Earth's surface.
There has been an increase in ocean heat content during recent decades as the oceans absorb over 90% of the heat from global warming.

Around 1850 thermometer records began to provide global coverage. Between the 18th century and 1970 there was little net warming, as the warming impact of greenhouse gas emissions was offset by cooling from sulfur dioxide emissions. Sulfur dioxide causes acid rain, but it also produces sulfate aerosols in the atmosphere, which reflect sunlight and cause global dimming. After 1970, the increasing accumulation of greenhouse gases and controls on sulfur pollution led to a marked increase in temperature.

NASA animation portraying global surface temperature changes from 1880 to 2023. The colour blue denotes cooler temperatures and red denotes warmer temperatures.

Ongoing changes in climate have had no precedent for several thousand years. Multiple independent datasets all show worldwide increases in surface temperature, at a rate of around 0.2 °C per decade. The 2014–2023 decade warmed to an average 1.19 °C compared to the pre-industrial baseline (1850–1900). Not every single year was warmer than the last: internal climate variability processes can make any year 0.2 °C warmer or colder than the average. From 1998 to 2013, negative phases of two such processes, Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO) caused a short slower period of warming called the "global warming hiatus". After the "hiatus", the opposite occurred, with years like 2023 exhibiting temperatures well above even the recent average. This is why the temperature change is defined in terms of a 20-year average, which reduces the noise of hot and cold years and decadal climate patterns, and detects the long-term signal.

A wide range of other observations reinforce the evidence of warming. The upper atmosphere is cooling, because greenhouse gases are trapping heat near the Earth's surface, and so less heat is radiating into space. Warming reduces average snow cover and forces the retreat of glaciers. At the same time, warming also causes greater evaporation from the oceans, leading to more atmospheric humidity, more and heavier precipitation. Plants are flowering earlier in spring, and thousands of animal species have been permanently moving to cooler areas.

Differences by region

Different regions of the world warm at different rates. The pattern is independent of where greenhouse gases are emitted, because the gases persist long enough to diffuse across the planet. Since the pre-industrial period, the average surface temperature over land regions has increased almost twice as fast as the global average surface temperature. This is because oceans lose more heat by evaporation and oceans can store a lot of heat. The thermal energy in the global climate system has grown with only brief pauses since at least 1970, and over 90% of this extra energy has been stored in the ocean. The rest has heated the atmosphere, melted ice, and warmed the continents.

The Northern Hemisphere and the North Pole have warmed much faster than the South Pole and Southern Hemisphere. The Northern Hemisphere not only has much more land, but also more seasonal snow cover and sea ice. As these surfaces flip from reflecting a lot of light to being dark after the ice has melted, they start absorbing more heat. Local black carbon deposits on snow and ice also contribute to Arctic warming. Arctic surface temperatures are increasing between three and four times faster than in the rest of the world. Melting of ice sheets near the poles weakens both the Atlantic and the Antarctic limb of thermohaline circulation, which further changes the distribution of heat and precipitation around the globe.

Future global temperatures

CMIP6 multi-model projections of global surface temperature changes for the year 2090 relative to the 1850–1900 average. The current trajectory for warming by the end of the century is roughly halfway between these two extremes.

The World Meteorological Organization estimates there is an 80% chance that global temperatures will exceed 1.5 °C warming for at least one year between 2024 and 2028. The chance of the 5-year average being above 1.5 °C is almost half.

The IPCC expects the 20-year average global temperature to exceed +1.5 °C in the early 2030s. The IPCC Sixth Assessment Report (2021) included projections that by 2100 global warming is very likely to reach 1.0–1.8 °C under a scenario with very low emissions of greenhouse gases, 2.1–3.5 °C under an intermediate emissions scenario, or 3.3–5.7 °C under a very high emissions scenario. The warming will continue past 2100 in the intermediate and high emission scenarios, with future projections of global surface temperatures by year 2300 being similar to millions of years ago.

The remaining carbon budget for staying beneath certain temperature increases is determined by modelling the carbon cycle and climate sensitivity to greenhouse gases. According to UNEP, global warming can be kept below 1.5 °C with a 50% chance if emissions after 2023 do not exceed 200 gigatonnes of CO2. This corresponds to around 4 years of current emissions. To stay under 2.0 °C, the carbon budget is 900 gigatonnes of CO2, or 16 years of current emissions.

Causes of recent global temperature rise

Main article: Causes of climate change
Physical drivers of global warming that has happened so far. Future global warming potential for long lived drivers like carbon dioxide emissions is not represented. Whiskers on each bar show the possible error range.

The climate system experiences various cycles on its own which can last for years, decades or even centuries. For example, El Niño events cause short-term spikes in surface temperature while La Niña events cause short term cooling. Their relative frequency can affect global temperature trends on a decadal timescale. Other changes are caused by an imbalance of energy from external forcings. Examples of these include changes in the concentrations of greenhouse gases, solar luminosity, volcanic eruptions, and variations in the Earth's orbit around the Sun.

To determine the human contribution to climate change, unique "fingerprints" for all potential causes are developed and compared with both observed patterns and known internal climate variability. For example, solar forcing—whose fingerprint involves warming the entire atmosphere—is ruled out because only the lower atmosphere has warmed. Atmospheric aerosols produce a smaller, cooling effect. Other drivers, such as changes in albedo, are less impactful.

Greenhouse gases

Main articles: Greenhouse gas, Greenhouse gas emissions, Greenhouse effect, and Carbon dioxide in Earth's atmosphere
CO2 concentrations over the last 800,000 years as measured from ice cores (blue/green) and directly (black)

Greenhouse gases are transparent to sunlight, and thus allow it to pass through the atmosphere to heat the Earth's surface. The Earth radiates it as heat, and greenhouse gases absorb a portion of it. This absorption slows the rate at which heat escapes into space, trapping heat near the Earth's surface and warming it over time.

While water vapour (≈50%) and clouds (≈25%) are the biggest contributors to the greenhouse effect, they primarily change as a function of temperature and are therefore mostly considered to be feedbacks that change climate sensitivity. On the other hand, concentrations of gases such as CO2 (≈20%), tropospheric ozone, CFCs and nitrous oxide are added or removed independently from temperature, and are therefore considered to be external forcings that change global temperatures.

Before the Industrial Revolution, naturally-occurring amounts of greenhouse gases caused the air near the surface to be about 33 °C warmer than it would have been in their absence. Human activity since the Industrial Revolution, mainly extracting and burning fossil fuels (coal, oil, and natural gas), has increased the amount of greenhouse gases in the atmosphere. In 2022, the concentrations of CO2 and methane had increased by about 50% and 164%, respectively, since 1750. These CO2 levels are higher than they have been at any time during the last 14 million years. Concentrations of methane are far higher than they were over the last 800,000 years.

The Global Carbon Project shows how additions to CO2 since 1880 have been caused by different sources ramping up one after another.

Global human-caused greenhouse gas emissions in 2019 were equivalent to 59 billion tonnes of CO2. Of these emissions, 75% was CO2, 18% was methane, 4% was nitrous oxide, and 2% was fluorinated gases. CO2 emissions primarily come from burning fossil fuels to provide energy for transport, manufacturing, heating, and electricity. Additional CO2 emissions come from deforestation and industrial processes, which include the CO2 released by the chemical reactions for making cement, steel, aluminum, and fertilizer. Methane emissions come from livestock, manure, rice cultivation, landfills, wastewater, and coal mining, as well as oil and gas extraction. Nitrous oxide emissions largely come from the microbial decomposition of fertilizer.

While methane only lasts in the atmosphere for an average of 12 years, CO2 lasts much longer. The Earth's surface absorbs CO2 as part of the carbon cycle. While plants on land and in the ocean absorb most excess emissions of CO2 every year, that CO2 is returned to the atmosphere when biological matter is digested, burns, or decays. Land-surface carbon sink processes, such as carbon fixation in the soil and photosynthesis, remove about 29% of annual global CO2 emissions. The ocean has absorbed 20 to 30% of emitted CO2 over the last two decades. CO2 is only removed from the atmosphere for the long term when it is stored in the Earth's crust, which is a process that can take millions of years to complete.

Land surface changes

The rate of global tree cover loss has approximately doubled since 2001, to an annual loss approaching an area the size of Italy.

Around 30% of Earth's land area is largely unusable for humans (glaciers, deserts, etc.), 26% is forests, 10% is shrubland and 34% is agricultural land. Deforestation is the main land use change contributor to global warming, as the destroyed trees release CO2, and are not replaced by new trees, removing that carbon sink. Between 2001 and 2018, 27% of deforestation was from permanent clearing to enable agricultural expansion for crops and livestock. Another 24% has been lost to temporary clearing under the shifting cultivation agricultural systems. 26% was due to logging for wood and derived products, and wildfires have accounted for the remaining 23%. Some forests have not been fully cleared, but were already degraded by these impacts. Restoring these forests also recovers their potential as a carbon sink.

Local vegetation cover impacts how much of the sunlight gets reflected back into space (albedo), and how much heat is lost by evaporation. For instance, the change from a dark forest to grassland makes the surface lighter, causing it to reflect more sunlight. Deforestation can also modify the release of chemical compounds that influence clouds, and by changing wind patterns. In tropic and temperate areas the net effect is to produce significant warming, and forest restoration can make local temperatures cooler. At latitudes closer to the poles, there is a cooling effect as forest is replaced by snow-covered (and more reflective) plains. Globally, these increases in surface albedo have been the dominant direct influence on temperature from land use change. Thus, land use change to date is estimated to have a slight cooling effect.

Other factors

Aerosols and clouds

Air pollution, in the form of aerosols, affects the climate on a large scale. Aerosols scatter and absorb solar radiation. From 1961 to 1990, a gradual reduction in the amount of sunlight reaching the Earth's surface was observed. This phenomenon is popularly known as global dimming, and is primarily attributed to sulfate aerosols produced by the combustion of fossil fuels with heavy sulfur concentrations like coal and bunker fuel. Smaller contributions come from black carbon (from combustion of fossil fuels and biomass), and from dust. Globally, aerosols have been declining since 1990 due to pollution controls, meaning that they no longer mask greenhouse gas warming as much.

Aerosols also have indirect effects on the Earth's energy budget. Sulfate aerosols act as cloud condensation nuclei and lead to clouds that have more and smaller cloud droplets. These clouds reflect solar radiation more efficiently than clouds with fewer and larger droplets. They also reduce the growth of raindrops, which makes clouds more reflective to incoming sunlight. Indirect effects of aerosols are the largest uncertainty in radiative forcing.

While aerosols typically limit global warming by reflecting sunlight, black carbon in soot that falls on snow or ice can contribute to global warming. Not only does this increase the absorption of sunlight, it also increases melting and sea-level rise. Limiting new black carbon deposits in the Arctic could reduce global warming by 0.2 °C by 2050. The effect of decreasing sulfur content of fuel oil for ships since 2020 is estimated to cause an additional 0.05 °C increase in global mean temperature by 2050.

Solar and volcanic activity

Further information: Solar activity and climate
The Fourth National Climate Assessment ("NCA4", USGCRP, 2017) includes charts illustrating that neither solar nor volcanic activity can explain the observed warming.

As the Sun is the Earth's primary energy source, changes in incoming sunlight directly affect the climate system. Solar irradiance has been measured directly by satellites, and indirect measurements are available from the early 1600s onwards. Since 1880, there has been no upward trend in the amount of the Sun's energy reaching the Earth, in contrast to the warming of the lower atmosphere (the troposphere). The upper atmosphere (the stratosphere) would also be warming if the Sun was sending more energy to Earth, but instead, it has been cooling. This is consistent with greenhouse gases preventing heat from leaving the Earth's atmosphere.

Explosive volcanic eruptions can release gases, dust and ash that partially block sunlight and reduce temperatures, or they can send water vapour into the atmosphere, which adds to greenhouse gases and increases temperatures. These impacts on temperature only last for several years, because both water vapour and volcanic material have low persistence in the atmosphere. volcanic CO2 emissions are more persistent, but they are equivalent to less than 1% of current human-caused CO2 emissions. Volcanic activity still represents the single largest natural impact (forcing) on temperature in the industrial era. Yet, like the other natural forcings, it has had negligible impacts on global temperature trends since the Industrial Revolution.

Climate change feedbacks

Main articles: Climate change feedbacks and Climate sensitivity
Sea ice reflects 50% to 70% of incoming sunlight, while the ocean, being darker, reflects only 6%. As an area of sea ice melts and exposes more ocean, more heat is absorbed by the ocean, raising temperatures that melt still more ice. This is a positive feedback process.

The climate system's response to an initial forcing is shaped by feedbacks, which either amplify or dampen the change. Self-reinforcing or positive feedbacks increase the response, while balancing or negative feedbacks reduce it. The main reinforcing feedbacks are the water-vapour feedback, the ice–albedo feedback, and the net effect of clouds. The primary balancing mechanism is radiative cooling, as Earth's surface gives off more heat to space in response to rising temperature. In addition to temperature feedbacks, there are feedbacks in the carbon cycle, such as the fertilizing effect of CO2 on plant growth. Feedbacks are expected to trend in a positive direction as greenhouse gas emissions continue, raising climate sensitivity.

These feedback processes alter the pace of global warming. For instance, warmer air can hold more moisture in the form of water vapour, which is itself a potent greenhouse gas. Warmer air can also make clouds higher and thinner, and therefore more insulating, increasing climate warming. The reduction of snow cover and sea ice in the Arctic is another major feedback, this reduces the reflectivity of the Earth's surface in the region and accelerates Arctic warming. This additional warming also contributes to permafrost thawing, which releases methane and CO2 into the atmosphere.

Around half of human-caused CO2 emissions have been absorbed by land plants and by the oceans. This fraction is not static and if future CO2 emissions decrease, the Earth will be able to absorb up to around 70%. If they increase substantially, it'll still absorb more carbon than now, but the overall fraction will decrease to below 40%. This is because climate change increases droughts and heat waves that eventually inhibit plant growth on land, and soils will release more carbon from dead plants when they are warmer. The rate at which oceans absorb atmospheric carbon will be lowered as they become more acidic and experience changes in thermohaline circulation and phytoplankton distribution. Uncertainty over feedbacks, particularly cloud cover, is the major reason why different climate models project different magnitudes of warming for a given amount of emissions.

Modelling

Further information: Climate model and Climate change scenario
Energy flows between space, the atmosphere, and Earth's surface. Most sunlight passes through the atmosphere to heat the Earth's surface, then greenhouse gases absorb most of the heat the Earth radiates in response. Adding to greenhouse gases increases this insulating effect, causing an energy imbalance that heats the planet up.

A climate model is a representation of the physical, chemical and biological processes that affect the climate system. Models include natural processes like changes in the Earth's orbit, historical changes in the Sun's activity, and volcanic forcing. Models are used to estimate the degree of warming future emissions will cause when accounting for the strength of climate feedbacks. Models also predict the circulation of the oceans, the annual cycle of the seasons, and the flows of carbon between the land surface and the atmosphere.

The physical realism of models is tested by examining their ability to simulate current or past climates. Past models have underestimated the rate of Arctic shrinkage and underestimated the rate of precipitation increase. Sea level rise since 1990 was underestimated in older models, but more recent models agree well with observations. The 2017 United States-published National Climate Assessment notes that "climate models may still be underestimating or missing relevant feedback processes". Additionally, climate models may be unable to adequately predict short-term regional climatic shifts.

A subset of climate models add societal factors to a physical climate model. These models simulate how population, economic growth, and energy use affect—and interact with—the physical climate. With this information, these models can produce scenarios of future greenhouse gas emissions. This is then used as input for physical climate models and carbon cycle models to predict how atmospheric concentrations of greenhouse gases might change. Depending on the socioeconomic scenario and the mitigation scenario, models produce atmospheric CO2 concentrations that range widely between 380 and 1400 ppm.

Impacts

Main article: Effects of climate change
The sixth IPCC Assessment Report projects changes in average soil moisture at 2.0 °C of warming, as measured in standard deviations from the 1850 to 1900 baseline.

Environmental effects

Further information: Effects of climate change on oceans and Effects of climate change on the water cycle

The environmental effects of climate change are broad and far-reaching, affecting oceans, ice, and weather. Changes may occur gradually or rapidly. Evidence for these effects comes from studying climate change in the past, from modelling, and from modern observations. Since the 1950s, droughts and heat waves have appeared simultaneously with increasing frequency. Extremely wet or dry events within the monsoon period have increased in India and East Asia. Monsoonal precipitation over the Northern Hemisphere has increased since 1980. The rainfall rate and intensity of hurricanes and typhoons is likely increasing, and the geographic range likely expanding poleward in response to climate warming. Frequency of tropical cyclones has not increased as a result of climate change.

Historical sea level reconstruction and projections up to 2100 published in 2017 by the U.S. Global Change Research Program

Global sea level is rising as a consequence of thermal expansion and the melting of glaciers and ice sheets. Sea level rise has increased over time, reaching 4.8 cm per decade between 2014 and 2023. Over the 21st century, the IPCC projects 32–62 cm of sea level rise under a low emission scenario, 44–76 cm under an intermediate one and 65–101 cm under a very high emission scenario. Marine ice sheet instability processes in Antarctica may add substantially to these values, including the possibility of a 2-meter sea level rise by 2100 under high emissions.

Climate change has led to decades of shrinking and thinning of the Arctic sea ice. While ice-free summers are expected to be rare at 1.5 °C degrees of warming, they are set to occur once every three to ten years at a warming level of 2 °C. Higher atmospheric CO2 concentrations cause more CO2 to dissolve in the oceans, which is making them more acidic. Because oxygen is less soluble in warmer water, its concentrations in the ocean are decreasing, and dead zones are expanding.

Tipping points and long-term impacts

Different levels of global warming may cause different parts of Earth's climate system to reach tipping points that cause transitions to different states.
Main article: Tipping points in the climate system

Greater degrees of global warming increase the risk of passing through 'tipping points'—thresholds beyond which certain major impacts can no longer be avoided even if temperatures return to their previous state. For instance, the Greenland ice sheet is already melting, but if global warming reaches levels between 1.7 °C and 2.3 °C, its melting will continue until it fully disappears. If the warming is later reduced to 1.5 °C or less, it will still lose a lot more ice than if the warming was never allowed to reach the threshold in the first place. While the ice sheets would melt over millennia, other tipping points would occur faster and give societies less time to respond. The collapse of major ocean currents like the Atlantic meridional overturning circulation (AMOC), and irreversible damage to key ecosystems like the Amazon rainforest and coral reefs can unfold in a matter of decades.

The long-term effects of climate change on oceans include further ice melt, ocean warming, sea level rise, ocean acidification and ocean deoxygenation. The timescale of long-term impacts are centuries to millennia due to CO2's long atmospheric lifetime. The result is an estimated total sea level rise of 2.3 metres per degree Celsius (4.2 ft/°F) after 2000 years. Oceanic CO2 uptake is slow enough that ocean acidification will also continue for hundreds to thousands of years. Deep oceans (below 2,000 metres (6,600 ft)) are also already committed to losing over 10% of their dissolved oxygen by the warming which occurred to date. Further, the West Antarctic ice sheet appears committed to practically irreversible melting, which would increase the sea levels by at least 3.3 m (10 ft 10 in) over approximately 2000 years.

Nature and wildlife

Further information: Effects of climate change on oceans and Effects of climate change on biomes

Recent warming has driven many terrestrial and freshwater species poleward and towards higher altitudes. For instance, the range of hundreds of North American birds has shifted northward at an average rate of 1.5 km/year over the past 55 years. Higher atmospheric CO2 levels and an extended growing season have resulted in global greening. However, heatwaves and drought have reduced ecosystem productivity in some regions. The future balance of these opposing effects is unclear. A related phenomenon driven by climate change is woody plant encroachment, affecting up to 500 million hectares globally. Climate change has contributed to the expansion of drier climate zones, such as the expansion of deserts in the subtropics. The size and speed of global warming is making abrupt changes in ecosystems more likely. Overall, it is expected that climate change will result in the extinction of many species.

The oceans have heated more slowly than the land, but plants and animals in the ocean have migrated towards the colder poles faster than species on land. Just as on land, heat waves in the ocean occur more frequently due to climate change, harming a wide range of organisms such as corals, kelp, and seabirds. Ocean acidification makes it harder for marine calcifying organisms such as mussels, barnacles and corals to produce shells and skeletons; and heatwaves have bleached coral reefs. Harmful algal blooms enhanced by climate change and eutrophication lower oxygen levels, disrupt food webs and cause great loss of marine life. Coastal ecosystems are under particular stress. Almost half of global wetlands have disappeared due to climate change and other human impacts. Plants have come under increased stress from damage by insects.

Climate change impacts on the environment

Humans

Main article: Effects of climate change
Extreme weather will be progressively more common as the Earth warms.

The effects of climate change are impacting humans everywhere in the world. Impacts can be observed on all continents and ocean regions, with low-latitude, less developed areas facing the greatest risk. Continued warming has potentially "severe, pervasive and irreversible impacts" for people and ecosystems. The risks are unevenly distributed, but are generally greater for disadvantaged people in developing and developed countries.

Health and food

Main articles: Effects of climate change on agriculture § Global food security and undernutrition, and Effects of climate change on human health

The World Health Organization calls climate change one of the biggest threats to global health in the 21st century. Scientists have warned about the irreversible harms it poses. Extreme weather events affect public health, and food and water security. Temperature extremes lead to increased illness and death. Climate change increases the intensity and frequency of extreme weather events. It can affect transmission of infectious diseases, such as dengue fever and malaria. According to the World Economic Forum, 14.5 million more deaths are expected due to climate change by 2050. 30% of the global population currently live in areas where extreme heat and humidity are already associated with excess deaths. By 2100, 50% to 75% of the global population would live in such areas.

While total crop yields have been increasing in the past 50 years due to agricultural improvements, climate change has already decreased the rate of yield growth. Fisheries have been negatively affected in multiple regions. While agricultural productivity has been positively affected in some high latitude areas, mid- and low-latitude areas have been negatively affected. According to the World Economic Forum, an increase in drought in certain regions could cause 3.2 million deaths from malnutrition by 2050 and stunting in children. With 2 °C warming, global livestock headcounts could decline by 7–10% by 2050, as less animal feed will be available. If the emissions continue to increase for the rest of century, then over 9 million climate-related deaths would occur annually by 2100.

Livelihoods and inequality

Further information: Economic analysis of climate change and Climate security

Economic damages due to climate change may be severe and there is a chance of disastrous consequences. Severe impacts are expected in South-East Asia and sub-Saharan Africa, where most of the local inhabitants are dependent upon natural and agricultural resources. Heat stress can prevent outdoor labourers from working. If warming reaches 4 °C then labour capacity in those regions could be reduced by 30 to 50%. The World Bank estimates that between 2016 and 2030, climate change could drive over 120 million people into extreme poverty without adaptation.

Inequalities based on wealth and social status have worsened due to climate change. Major difficulties in mitigating, adapting to, and recovering from climate shocks are faced by marginalized people who have less control over resources. Indigenous people, who are subsistent on their land and ecosystems, will face endangerment to their wellness and lifestyles due to climate change. An expert elicitation concluded that the role of climate change in armed conflict has been small compared to factors such as socio-economic inequality and state capabilities.

While women are not inherently more at risk from climate change and shocks, limits on women's resources and discriminatory gender norms constrain their adaptive capacity and resilience. For example, women's work burdens, including hours worked in agriculture, tend to decline less than men's during climate shocks such as heat stress.

Climate migration

Main article: Climate migration

Low-lying islands and coastal communities are threatened by sea level rise, which makes urban flooding more common. Sometimes, land is permanently lost to the sea. This could lead to statelessness for people in island nations, such as the Maldives and Tuvalu. In some regions, the rise in temperature and humidity may be too severe for humans to adapt to. With worst-case climate change, models project that almost one-third of humanity might live in Sahara-like uninhabitable and extremely hot climates.

These factors can drive climate or environmental migration, within and between countries. More people are expected to be displaced because of sea level rise, extreme weather and conflict from increased competition over natural resources. Climate change may also increase vulnerability, leading to "trapped populations" who are not able to move due to a lack of resources.

Climate change impacts on people

Reducing and recapturing emissions

Further information: Climate change mitigation
Global greenhouse gas emission scenarios, based on policies and pledges as of November 2021

Climate change can be mitigated by reducing the rate at which greenhouse gases are emitted into the atmosphere, and by increasing the rate at which carbon dioxide is removed from the atmosphere. To limit global warming to less than 1.5 °C global greenhouse gas emissions needs to be net-zero by 2050, or by 2070 with a 2 °C target. This requires far-reaching, systemic changes on an unprecedented scale in energy, land, cities, transport, buildings, and industry.

The United Nations Environment Programme estimates that countries need to triple their pledges under the Paris Agreement within the next decade to limit global warming to 2 °C. An even greater level of reduction is required to meet the 1.5 °C goal. With pledges made under the Paris Agreement as of 2024, there would be a 66% chance that global warming is kept under 2.8 °C by the end of the century (range: 1.9–3.7 °C, depending on exact implementation and technological progress). When only considering current policies, this raises to 3.1 °C. Globally, limiting warming to 2 °C may result in higher economic benefits than economic costs.

Although there is no single pathway to limit global warming to 1.5 or 2 °C, most scenarios and strategies see a major increase in the use of renewable energy in combination with increased energy efficiency measures to generate the needed greenhouse gas reductions. To reduce pressures on ecosystems and enhance their carbon sequestration capabilities, changes would also be necessary in agriculture and forestry, such as preventing deforestation and restoring natural ecosystems by reforestation.

Other approaches to mitigating climate change have a higher level of risk. Scenarios that limit global warming to 1.5 °C typically project the large-scale use of carbon dioxide removal methods over the 21st century. There are concerns, though, about over-reliance on these technologies, and environmental impacts. Solar radiation modification (SRM) is under discussion as a possible supplement to reductions in emissions. However, SRM raises significant ethical and global governance concerns, and its risks are not well understood.

Clean energy

Main articles: Sustainable energy and Sustainable transport
Coal, oil, and natural gas remain the primary global energy sources even as renewables have begun rapidly increasing.
Wind and solar power, Germany

Renewable energy is key to limiting climate change. For decades, fossil fuels have accounted for roughly 80% of the world's energy use. The remaining share has been split between nuclear power and renewables (including hydropower, bioenergy, wind and solar power and geothermal energy). Fossil fuel use is expected to peak in absolute terms prior to 2030 and then to decline, with coal use experiencing the sharpest reductions. Renewables represented 86% of all new electricity generation installed in 2023. Other forms of clean energy, such as nuclear and hydropower, currently have a larger share of the energy supply. However, their future growth forecasts appear limited in comparison.

While solar panels and onshore wind are now among the cheapest forms of adding new power generation capacity in many locations, green energy policies are needed to achieve a rapid transition from fossil fuels to renewables. To achieve carbon neutrality by 2050, renewable energy would become the dominant form of electricity generation, rising to 85% or more by 2050 in some scenarios. Investment in coal would be eliminated and coal use nearly phased out by 2050.

Electricity generated from renewable sources would also need to become the main energy source for heating and transport. Transport can switch away from internal combustion engine vehicles and towards electric vehicles, public transit, and active transport (cycling and walking). For shipping and flying, low-carbon fuels would reduce emissions. Heating could be increasingly decarbonized with technologies like heat pumps.

There are obstacles to the continued rapid growth of clean energy, including renewables. Wind and solar produce energy intermittently and with seasonal variability. Traditionally, hydro dams with reservoirs and fossil fuel power plants have been used when variable energy production is low. Going forward, battery storage can be expanded, energy demand and supply can be matched, and long-distance transmission can smooth variability of renewable outputs. Bioenergy is often not carbon-neutral and may have negative consequences for food security. The growth of nuclear power is constrained by controversy around radioactive waste, nuclear weapon proliferation, and accidents. Hydropower growth is limited by the fact that the best sites have been developed, and new projects are confronting increased social and environmental concerns.

Low-carbon energy improves human health by minimizing climate change as well as reducing air pollution deaths, which were estimated at 7 million annually in 2016. Meeting the Paris Agreement goals that limit warming to a 2 °C increase could save about a million of those lives per year by 2050, whereas limiting global warming to 1.5 °C could save millions and simultaneously increase energy security and reduce poverty. Improving air quality also has economic benefits which may be larger than mitigation costs.

Energy conservation

Main articles: Efficient energy use and Energy conservation

Reducing energy demand is another major aspect of reducing emissions. If less energy is needed, there is more flexibility for clean energy development. It also makes it easier to manage the electricity grid, and minimizes carbon-intensive infrastructure development. Major increases in energy efficiency investment will be required to achieve climate goals, comparable to the level of investment in renewable energy. Several COVID-19 related changes in energy use patterns, energy efficiency investments, and funding have made forecasts for this decade more difficult and uncertain.

Strategies to reduce energy demand vary by sector. In the transport sector, passengers and freight can switch to more efficient travel modes, such as buses and trains, or use electric vehicles. Industrial strategies to reduce energy demand include improving heating systems and motors, designing less energy-intensive products, and increasing product lifetimes. In the building sector the focus is on better design of new buildings, and higher levels of energy efficiency in retrofitting. The use of technologies like heat pumps can also increase building energy efficiency.

Agriculture and industry

See also: Sustainable agriculture and Green industrial policy
Taking into account direct and indirect emissions, industry is the sector with the highest share of global emissions. Data as of 2019 from the IPCC.

Agriculture and forestry face a triple challenge of limiting greenhouse gas emissions, preventing the further conversion of forests to agricultural land, and meeting increases in world food demand. A set of actions could reduce agriculture and forestry-based emissions by two-thirds from 2010 levels. These include reducing growth in demand for food and other agricultural products, increasing land productivity, protecting and restoring forests, and reducing greenhouse gas emissions from agricultural production.

On the demand side, a key component of reducing emissions is shifting people towards plant-based diets. Eliminating the production of livestock for meat and dairy would eliminate about 3/4ths of all emissions from agriculture and other land use. Livestock also occupy 37% of ice-free land area on Earth and consume feed from the 12% of land area used for crops, driving deforestation and land degradation.

Steel and cement production are responsible for about 13% of industrial CO2 emissions. In these industries, carbon-intensive materials such as coke and lime play an integral role in the production, so that reducing CO2 emissions requires research into alternative chemistries. Where energy production or CO2-intensive heavy industries continue to produce waste CO2, technology can sometimes be used to capture and store most of the gas instead of releasing it to the atmosphere. This technology, carbon capture and storage (CCS), could have a critical but limited role in reducing emissions. It is relatively expensive and has been deployed only to an extent that removes around 0.1% of annual greenhouse gas emissions.

Carbon dioxide removal

Main articles: Carbon dioxide removal and Carbon sequestration
Most CO2 emissions have been absorbed by carbon sinks, including plant growth, soil uptake, and ocean uptake (2020 Global Carbon Budget).

Natural carbon sinks can be enhanced to sequester significantly larger amounts of CO2 beyond naturally occurring levels. Reforestation and afforestation (planting forests where there were none before) are among the most mature sequestration techniques, although the latter raises food security concerns. Farmers can promote sequestration of carbon in soils through practices such as use of winter cover crops, reducing the intensity and frequency of tillage, and using compost and manure as soil amendments. Forest and landscape restoration yields many benefits for the climate, including greenhouse gas emissions sequestration and reduction. Restoration/recreation of coastal wetlands, prairie plots and seagrass meadows increases the uptake of carbon into organic matter. When carbon is sequestered in soils and in organic matter such as trees, there is a risk of the carbon being re-released into the atmosphere later through changes in land use, fire, or other changes in ecosystems.

The use of bioenergy in conjunction with carbon capture and storage (BECCS) can result in net negative emissions as CO2 is drawn from the atmosphere. It remains highly uncertain whether carbon dioxide removal techniques will be able to play a large role in limiting warming to 1.5 °C. Policy decisions that rely on carbon dioxide removal increase the risk of global warming rising beyond international goals.

Adaptation

Main article: Climate change adaptation

Adaptation is "the process of adjustment to current or expected changes in climate and its effects". Without additional mitigation, adaptation cannot avert the risk of "severe, widespread and irreversible" impacts. More severe climate change requires more transformative adaptation, which can be prohibitively expensive. The capacity and potential for humans to adapt is unevenly distributed across different regions and populations, and developing countries generally have less. The first two decades of the 21st century saw an increase in adaptive capacity in most low- and middle-income countries with improved access to basic sanitation and electricity, but progress is slow. Many countries have implemented adaptation policies. However, there is a considerable gap between necessary and available finance.

Adaptation to sea level rise consists of avoiding at-risk areas, learning to live with increased flooding, and building flood controls. If that fails, managed retreat may be needed. There are economic barriers for tackling dangerous heat impact. Avoiding strenuous work or having air conditioning is not possible for everybody. In agriculture, adaptation options include a switch to more sustainable diets, diversification, erosion control, and genetic improvements for increased tolerance to a changing climate. Insurance allows for risk-sharing, but is often difficult to get for people on lower incomes. Education, migration and early warning systems can reduce climate vulnerability. Planting mangroves or encouraging other coastal vegetation can buffer storms.

Ecosystems adapt to climate change, a process that can be supported by human intervention. By increasing connectivity between ecosystems, species can migrate to more favourable climate conditions. Species can also be introduced to areas acquiring a favourable climate. Protection and restoration of natural and semi-natural areas helps build resilience, making it easier for ecosystems to adapt. Many of the actions that promote adaptation in ecosystems, also help humans adapt via ecosystem-based adaptation. For instance, restoration of natural fire regimes makes catastrophic fires less likely, and reduces human exposure. Giving rivers more space allows for more water storage in the natural system, reducing flood risk. Restored forest acts as a carbon sink, but planting trees in unsuitable regions can exacerbate climate impacts.

There are synergies but also trade-offs between adaptation and mitigation. An example for synergy is increased food productivity, which has large benefits for both adaptation and mitigation. An example of a trade-off is that increased use of air conditioning allows people to better cope with heat, but increases energy demand. Another trade-off example is that more compact urban development may reduce emissions from transport and construction, but may also increase the urban heat island effect, exposing people to heat-related health risks.

Examples of adaptation methods

Policies and politics

See also: Politics of climate change and Climate change mitigation § Policies
The Climate Change Performance Index ranks countries by greenhouse gas emissions (40% of score), renewable energy (20%), energy use (20%), and climate policy (20%).
  High   Medium   Low   Very low

Countries that are most vulnerable to climate change have typically been responsible for a small share of global emissions. This raises questions about justice and fairness. Limiting global warming makes it much easier to achieve the UN's Sustainable Development Goals, such as eradicating poverty and reducing inequalities. The connection is recognized in Sustainable Development Goal 13 which is to "take urgent action to combat climate change and its impacts". The goals on food, clean water and ecosystem protection have synergies with climate mitigation.

The geopolitics of climate change is complex. It has often been framed as a free-rider problem, in which all countries benefit from mitigation done by other countries, but individual countries would lose from switching to a low-carbon economy themselves. Sometimes mitigation also has localized benefits though. For instance, the benefits of a coal phase-out to public health and local environments exceed the costs in almost all regions. Furthermore, net importers of fossil fuels win economically from switching to clean energy, causing net exporters to face stranded assets: fossil fuels they cannot sell.

Policy options

Further information: Climate policy

A wide range of policies, regulations, and laws are being used to reduce emissions. As of 2019, carbon pricing covers about 20% of global greenhouse gas emissions. Carbon can be priced with carbon taxes and emissions trading systems. Direct global fossil fuel subsidies reached $319 billion in 2017, and $5.2 trillion when indirect costs such as air pollution are priced in. Ending these can cause a 28% reduction in global carbon emissions and a 46% reduction in air pollution deaths. Money saved on fossil subsidies could be used to support the transition to clean energy instead. More direct methods to reduce greenhouse gases include vehicle efficiency standards, renewable fuel standards, and air pollution regulations on heavy industry. Several countries require utilities to increase the share of renewables in power production.

Climate justice

Policy designed through the lens of climate justice tries to address human rights issues and social inequality. According to proponents of climate justice, the costs of climate adaptation should be paid by those most responsible for climate change, while the beneficiaries of payments should be those suffering impacts. One way this can be addressed in practice is to have wealthy nations pay poorer countries to adapt.

Oxfam found that in 2023 the wealthiest 10% of people were responsible for 50% of global emissions, while the bottom 50% were responsible for just 8%. Production of emissions is another way to look at responsibility: under that approach, the top 21 fossil fuel companies would owe cumulative climate reparations of $5.4 trillion over the period 2025–2050. To achieve a just transition, people working in the fossil fuel sector would also need other jobs, and their communities would need investments.

International climate agreements

Further information: United Nations Framework Convention on Climate Change
Since 2000, rising CO2 emissions in China and the rest of world have surpassed the output of the United States and Europe.
Per person, the United States generates CO2 at a far faster rate than other primary regions.

Nearly all countries in the world are parties to the 1994 United Nations Framework Convention on Climate Change (UNFCCC). The goal of the UNFCCC is to prevent dangerous human interference with the climate system. As stated in the convention, this requires that greenhouse gas concentrations are stabilized in the atmosphere at a level where ecosystems can adapt naturally to climate change, food production is not threatened, and economic development can be sustained. The UNFCCC does not itself restrict emissions but rather provides a framework for protocols that do. Global emissions have risen since the UNFCCC was signed. Its yearly conferences are the stage of global negotiations.

The 1997 Kyoto Protocol extended the UNFCCC and included legally binding commitments for most developed countries to limit their emissions. During the negotiations, the G77 (representing developing countries) pushed for a mandate requiring developed countries to " the lead" in reducing their emissions, since developed countries contributed most to the accumulation of greenhouse gases in the atmosphere. Per-capita emissions were also still relatively low in developing countries and developing countries would need to emit more to meet their development needs.

The 2009 Copenhagen Accord has been widely portrayed as disappointing because of its low goals, and was rejected by poorer nations including the G77. Associated parties aimed to limit the global temperature rise to below 2 °C. The Accord set the goal of sending $100 billion per year to developing countries for mitigation and adaptation by 2020, and proposed the founding of the Green Climate Fund. As of 2020, only 83.3 billion were delivered. Only in 2023 the target is expected to be achieved.

In 2015 all UN countries negotiated the Paris Agreement, which aims to keep global warming well below 2.0 °C and contains an aspirational goal of keeping warming under 1.5 °C. The agreement replaced the Kyoto Protocol. Unlike Kyoto, no binding emission targets were set in the Paris Agreement. Instead, a set of procedures was made binding. Countries have to regularly set ever more ambitious goals and reevaluate these goals every five years. The Paris Agreement restated that developing countries must be financially supported. As of October 2021, 194 states and the European Union have signed the treaty and 191 states and the EU have ratified or acceded to the agreement.

The 1987 Montreal Protocol, an international agreement to phase out production of ozone-depleting gases, has had benefits for climate change mitigation. Several ozone-depleting gases like chlorofluorocarbons are powerful greenhouse gases, so banning their production and usage may have avoided a temperature rise of 0.5 °C–1.0 °C, as well as additional warming by preventing damage to vegetation from ultraviolet radiation. It is estimated that the agreement has been more effective at curbing greenhouse gas emissions than the Kyoto Protocol specifically designed to do so. The most recent amendment to the Montreal Protocol, the 2016 Kigali Amendment, committed to reducing the emissions of hydrofluorocarbons, which served as a replacement for banned ozone-depleting gases and are also potent greenhouse gases. Should countries comply with the amendment, a warming of 0.3 °C–0.5 °C is estimated to be avoided.

National responses

Annual CO2 emissions by region. This measures fossil fuel and industry emissions. Land use change is not included.

In 2019, the United Kingdom parliament became the first national government to declare a climate emergency. Other countries and jurisdictions followed suit. That same year, the European Parliament declared a "climate and environmental emergency". The European Commission presented its European Green Deal with the goal of making the EU carbon-neutral by 2050. In 2021, the European Commission released its "Fit for 55" legislation package, which contains guidelines for the car industry; all new cars on the European market must be zero-emission vehicles from 2035.

Major countries in Asia have made similar pledges: South Korea and Japan have committed to become carbon-neutral by 2050, and China by 2060. While India has strong incentives for renewables, it also plans a significant expansion of coal in the country. Vietnam is among very few coal-dependent, fast-developing countries that pledged to phase out unabated coal power by the 2040s or as soon as possible thereafter.

As of 2021, based on information from 48 national climate plans, which represent 40% of the parties to the Paris Agreement, estimated total greenhouse gas emissions will be 0.5% lower compared to 2010 levels, below the 45% or 25% reduction goals to limit global warming to 1.5 °C or 2 °C, respectively.

Society

Denial and misinformation

Further information: Climate change denial and Fossil fuels lobby
Data has been cherry picked from short periods to falsely assert that global temperatures are not rising. Blue trendlines show short periods that mask longer-term warming trends (red trendlines). Blue rectangle with blue dots shows the so-called global warming hiatus.

Public debate about climate change has been strongly affected by climate change denial and misinformation, which originated in the United States and has since spread to other countries, particularly Canada and Australia. Climate change denial has originated from fossil fuel companies, industry groups, conservative think tanks, and contrarian scientists. Like the tobacco industry, the main strategy of these groups has been to manufacture doubt about climate-change related scientific data and results. People who hold unwarranted doubt about climate change are called climate change "skeptics", although "contrarians" or "deniers" are more appropriate terms.

There are different variants of climate denial: some deny that warming takes place at all, some acknowledge warming but attribute it to natural influences, and some minimize the negative impacts of climate change. Manufacturing uncertainty about the science later developed into a manufactured controversy: creating the belief that there is significant uncertainty about climate change within the scientific community to delay policy changes. Strategies to promote these ideas include criticism of scientific institutions, and questioning the motives of individual scientists. An echo chamber of climate-denying blogs and media has further fomented misunderstanding of climate change.

Public awareness and opinion

Further information: Climate communication, Media coverage of climate change, and Public opinion on climate change
The public substantially underestimates the degree of scientific consensus that humans are causing climate change. Studies from 2019 to 2021 found scientific consensus to range from 98.7 to 100%.

Climate change came to international public attention in the late 1980s. Due to media coverage in the early 1990s, people often confused climate change with other environmental issues like ozone depletion. In popular culture, the climate fiction movie The Day After Tomorrow (2004) and the Al Gore documentary An Inconvenient Truth (2006) focused on climate change.

Significant regional, gender, age and political differences exist in both public concern for, and understanding of, climate change. More highly educated people, and in some countries, women and younger people, were more likely to see climate change as a serious threat. College biology textbooks from the 2010s featured less content on climate change compared to those from the preceding decade, with decreasing emphasis on solutions. Partisan gaps also exist in many countries, and countries with high CO2 emissions tend to be less concerned. Views on causes of climate change vary widely between countries. Concern has increased over time, and a majority of citizens in many countries now express a high level of worry about climate change, or view it as a global emergency. Higher levels of worry are associated with stronger public support for policies that address climate change.

Climate movement

Main articles: Climate movement and Climate change litigation

Climate protests demand that political leaders take action to prevent climate change. They can take the form of public demonstrations, fossil fuel divestment, lawsuits and other activities. Prominent demonstrations include the School Strike for Climate. In this initiative, young people across the globe have been protesting since 2018 by skipping school on Fridays, inspired by Swedish activist and then-teenager Greta Thunberg. Mass civil disobedience actions by groups like Extinction Rebellion have protested by disrupting roads and public transport.

Litigation is increasingly used as a tool to strengthen climate action from public institutions and companies. Activists also initiate lawsuits which target governments and demand that they take ambitious action or enforce existing laws on climate change. Lawsuits against fossil-fuel companies generally seek compensation for loss and damage.

History

For broader coverage of this topic, see History of climate change science.

Early discoveries

This 1912 article succinctly describes the greenhouse effect, how burning coal creates carbon dioxide to cause global warming and climate change.

Scientists in the 19th century such as Alexander von Humboldt began to foresee the effects of climate change. In the 1820s, Joseph Fourier proposed the greenhouse effect to explain why Earth's temperature was higher than the Sun's energy alone could explain. Earth's atmosphere is transparent to sunlight, so sunlight reaches the surface where it is converted to heat. However, the atmosphere is not transparent to heat radiating from the surface, and captures some of that heat, which in turn warms the planet.

In 1856 Eunice Newton Foote demonstrated that the warming effect of the Sun is greater for air with water vapour than for dry air, and that the effect is even greater with carbon dioxide (CO2). She concluded that "An atmosphere of that gas would give to our earth a high temperature..."

Studying what would become known as the greenhouse effect, Tyndall's pre-1861 ratio spectrophotometer measured how much various gases in a tube absorb and emit infrared radiation—which humans experience as heat.

Starting in 1859, John Tyndall established that nitrogen and oxygen—together totalling 99% of dry air—are transparent to radiated heat. However, water vapour and gases such as methane and carbon dioxide absorb radiated heat and re-radiate that heat into the atmosphere. Tyndall proposed that changes in the concentrations of these gases may have caused climatic changes in the past, including ice ages.

Svante Arrhenius noted that water vapour in air continuously varied, but the CO2 concentration in air was influenced by long-term geological processes. Warming from increased CO2 levels would increase the amount of water vapour, amplifying warming in a positive feedback loop. In 1896, he published the first climate model of its kind, projecting that halving CO2 levels could have produced a drop in temperature initiating an ice age. Arrhenius calculated the temperature increase expected from doubling CO2 to be around 5–6 °C. Other scientists were initially sceptical and believed that the greenhouse effect was saturated so that adding more CO2 would make no difference, and that the climate would be self-regulating. Beginning in 1938, Guy Stewart Callendar published evidence that climate was warming and CO2 levels were rising, but his calculations met the same objections.

Development of a scientific consensus

See also: Scientific consensus on climate change
Scientific consensus on causation: Academic studies of scientific agreement on human-caused global warming among climate experts (2010–2015) reflect that the level of consensus correlates with expertise in climate science. A 2019 study found scientific consensus to be at 100%, and a 2021 study concluded that consensus exceeded 99%. Another 2021 study found that 98.7% of climate experts indicated that the Earth is getting warmer mostly because of human activity.

In the 1950s, Gilbert Plass created a detailed computer model that included different atmospheric layers and the infrared spectrum. This model predicted that increasing CO2 levels would cause warming. Around the same time, Hans Suess found evidence that CO2 levels had been rising, and Roger Revelle showed that the oceans would not absorb the increase. The two scientists subsequently helped Charles Keeling to begin a record of continued increase, which has been termed the "Keeling Curve". Scientists alerted the public, and the dangers were highlighted at James Hansen's 1988 Congressional testimony. The Intergovernmental Panel on Climate Change (IPCC), set up in 1988 to provide formal advice to the world's governments, spurred interdisciplinary research. As part of the IPCC reports, scientists assess the scientific discussion that takes place in peer-reviewed journal articles.

There is a near-complete scientific consensus that the climate is warming and that this is caused by human activities. As of 2019, agreement in recent literature reached over 99%. No scientific body of national or international standing disagrees with this view. Consensus has further developed that some form of action should be taken to protect people against the impacts of climate change. National science academies have called on world leaders to cut global emissions. The 2021 IPCC Assessment Report stated that it is "unequivocal" that climate change is caused by humans.

See also

References

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