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IPCC directs here. For other uses see IPCC (disambiguation).

The Intergovernmental Panel on Climate Change (IPCC) was established in 1988 by two United Nations organizations, the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) to assess the "risk of human-induced climate change". The Panel is open to all members of the WMO and UNEP.

IPCC reports are widely cited in almost any debate related to climate change . The reports have been influential in forming national and international responses to climate change. A few of the scientists whose work is summarized in these reports have accused the IPCC of bias.

Aims

The principles of the IPCC operation are assigned by the relevant WMO Executive Council and UNEP Governing Council resolutions and decisions as well as on actions in support of the UN Framework Convention on Climate Change process.

"The role of the IPCC is to assess on a comprehensive, objective, open and transparent basis the scientific, technical and socio-economic information relevant to understanding the scientific basis of risk of human-induced climate change, its potential impacts and options for adaptation and mitigation. IPCC reports should be neutral with respect to policy, although they may need to deal objectively with scientific, technical and socio-economic factors relevant to the application of particular policies.

Review is an essential part of the IPCC process. Since the IPCC is an intergovernmental body, review of IPCC documents should involve both peer review by experts and review by governments" .

The stated aims of the IPCC are to assess scientific information relevant to:

1. human-induced climate change,
2. the impacts of human-induced climate change,
3. options for adaptation and mitigation.

The history of the IPCC is described here.

Operations

The current Chair of the IPCC is Rajendra K. Pachauri, elected in May 2002; previously Robert Watson headed the IPCC.

The IPCC Panel is composed of representatives appointed by governments and organizations. Participation of delegates with appropriate expertise is encouraged. Plenary sessions of the IPCC and IPCC Working Groups are held at the level of government representatives. Non Governmental and Intergovernmental Organisations may be allowed to attend as observers. Sessions of the IPCC Bureau, workshops, expert and lead authors meetings are by invitation only . Attendance at the 2003 meeting was 350 government officials and climate change experts. After the opening ceremonies, plenary sessions are closed meetings . The meeting report states there were 322 persons in attendance at Sessions and with about seven-eighths of participants being from governmental organizations .

The IPCC is led by government scientists, but also involves several hundred academic scientists and researchers. It synthesises the available information about climate change and global warming, has published four major reports reviewing the latest climate science, as well as more specialized reports.

The IPCC does not carry out research nor does it monitor climate related data or other relevant parameters. It bases its assessment mainly on peer reviewed and published scientific/technical literature .

There are several major groups:

• IPCC Panel: Meets in plenary session about once a year and controls the organization's structure and procedures. The Panel is the IPCC corporate entity.
• Chair: Elected by the Panel.
• Secretariat: Oversees and manages all activities. Supported by UNEP and WMO.
• Bureau: Elected by the Panel. Chaired by the Chair. 30 members include IPCC Vice-Chairs, Co-Chairs and Vice-Chairs of Working Groups and Task Force.
• Working Groups: Each has two Co-Chairs, one from the developed and one from developing world, and a technical support unit.
  • Working Group I: Assesses scientific aspects of the climate system and climate change.
  • Working Group II: Assesses vulnerability of socio-economic and natural systems to climate change, consequences, and adaptation options.
  • Working Group III: Assesses options for limiting greenhouse gas emissions and otherwise mitigating climate change.
• Task Force on National Greenhouse Gas Inventories

The IPCC receives funding from UNEP, WMO, and its own Trust Fund for which it solicits contributions from governments.

Activities

The IPCC concentrates its activities on the tasks allotted to it by the relevant WMO Executive Council and UNEP Governing Council resolutions and decisions as well as on actions in support of the UN Framework Convention on Climate Change process .

The IPCC is currently (May 2005) in the process of preparing the fourth assessment report or AR4 ; reports of the workshops held so far are available .

• Working Group I :
  • Report is due to be finalised during the first quarter of 2007.
  • As of May 2005, there have been 3 AR4 meetings, with only public information being meeting locations, an author list, one invitation, one agenda, and one list of presentation titles.
• Working Group II :
  • Report is due to be finalised in mid-2007.
  • As of May 2005, there have been 2 AR4 meetings, with no public information released.
  • One shared meeting with WG III has taken place, with a published summary.
• Working Group III :
  • Report is due to be finalized in mid-2007.
  • As of May 2005, there has been 1 AR4 meeting, with no public information released.

If it is decided to prepare one the AR4 Synthesis Report (SYR) would be finalised during the last quarter of 2007. Documentation on the scoping meetings for the AR4 are available as are the outlines for the WG I report and a provisional author list .

While the preparation of the assessment reports is a major IPCC function, it also supports other activities, such as the Data Distribution Centre and the National Greenhouse Gas Inventories Programme , required under the UNFCCC. This involves publishing default emission factors, which are factors used to derive emissions estimates based on the levels of fuel consumption, industrial production and so on.

The IPCC also often answers inquiries from the UNFCCC Subsidiary Body for Scientific and Technological Advice (SBSTA).

Publications

The IPCC reports are a compendium of peer reviewed and published science. Each subsequent IPCC report notes areas where the science has improved since the previous report and also notes areas where further research is required.

Authors for the IPCC reports are chosen from a list of researchers prepared by governments, and participating organisations and the Working Group/Task Force Bureaux, and other experts as appropriate, known through their publications and works (, 4.2.1,2). The composition of the group of Coordinating Lead Authors and Lead Authors for a section or chapter of a Report is intended to reflect the need to aim for a range of views, expertise and geographical representation (ensuring appropriate representation of experts from developing and developed countries and countries with economies in transition).

There are generally three stages in the review process :

• Expert review (6-8 weeks)
• Government/expert review
• Government review of:
  • Summaries for Policymakers
  • Overview Chapters
  • Synthesis Report

Review comments are in an open archive for at least five years.

There are several types of endorsement which documents receive :

• approval: Material has been subjected to detailed, line by line discussion and agreement.
  • Working Group Summaries for Policymakers are approved by their Working Groups.
  • Synthesis Report Summary for Policymakers is approved by Panel.
• adoption: Endorsed section by section (and not line by line).
  • Panel adopts Overview Chapters of Methodology Reports.
  • Panel adopts IPCC Synthesis Report.
• acceptance: Not been subject to line by line discussion and agreement, but presents a comprehensive, objective, and balanced view of the subject matter.
  • Working Groups accepts their reports.
  • Task Force Reports are accepted by the Panel.
  • Working Group Summaries for Policymakers are accepted by the Panel after group approval.

The Panel is responsible for the IPCC and its endorsement of Reports allows it to ensure they meet IPCC standards. The Panel's approval process has been criticized for changing the product of the experts who create the Reports. On the other hand, not requiring Panel re-endorsement of Reports has also been criticized, after changes required by the approval process were made to Reports.

IPCC Reports

The IPCC published a first assessment report in 1990, a supplementary report in 1992, a second assessment report (SAR) in 1995, and a third assessment report (TAR) in 2001. Each of the assessment reports is in three volumes from the working groups I, II and III. Unqualified, "the IPCC report" is often used to mean the WG I report.

Consensus in reports

IPCC Reports attempt to present a scientific consensus view. The general approach of identifying consensus among a group of climate scientists means that areas where there remains considerable uncertainty tend to be automatically deemphasized or simply omitted . Another means of handling consensus problems was used in the SRES scenarios, where due to a lack of consensus there were many variations included with no indication of which are more probable doi:10.1038/35075167.

"Firstly, the Panel as a whole must always respect and consider the specific perspectives of each member. But, more importantly, each member must respect and consider the perspectives of the entire Panel. Consensus is not something that happens by itself. It is an outcome that has to be shaped, and the only basis for shaping it is to follow the two cardinal rules that I have just mentioned" — Dr Rajendra K. Pachauri, Chairman of the IPCC.

IPCC Fourth Assessment Report: AR4

Work on the fourth assessment report (AR4) is well underway . Author lists and a chapter outline of the WGI report is available .

IPCC Third Assessment Report: Climate Change 2001

The most recent IPCC report is Climate Change 2001, the Third Assessment Report (TAR).

The TAR consists of four reports, three of them from the Working Groups:

• Working Group I: The Scientific Basis
• Working Group II: Impacts, Adaptation and Vulnerability
• Working Group III: Mitigation
• Synthesis Report

The "headlines" from the summary for policymakers in The Scientific Basis were:

1. An increasing body of observations gives a collective picture of a warming world and other changes in the climate system (The global average surface temperature has increased over the 20th century by about 0.6°C; Temperatures have risen during the past four decades in the lowest 8 kilometres of the atmosphere; Snow cover and ice extent have decreased)
2. Emissions of greenhouse gases and aerosols due to human activities continue to alter the atmosphere in ways that are expected to affect the climate (Anthropogenic aerosols are short-lived and mostly produce negative radiative forcing; Natural factors have made small contributions to radiative forcing over the past century)
3. Confidence in the ability of models to project future climate has increased (Complex physically-based climate models are required to provide detailed estimates of feedbacks and of regional features. Such models cannot yet simulate all aspects of climate (e.g., they still cannot account fully for the observed trend in the surface-troposphere temperature difference since 1979) and there are particular uncertainties associated with clouds and their interaction with radiation and aerosols. Nevertheless, confidence in the ability of these models to provide useful projections of future climate has improved due to their demonstrated performance on a range of space and time-scales .)
4. There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities
5. Human influences will continue to change atmospheric composition throughout the 21st century
6. Global average temperature and sea level are projected to rise under all IPCC SRES scenarios

The TAR estimate for the climate sensitivity is 1.5 to 4.5 oC; and the average surface temperature is projected to increase by 1.4 to 5.8 Celsius degrees over the period 1990 to 2100, and the sea level is projected to rise by 0.1 to 0.9 metres over the same period. The wide range in predictions is based upon several different scenarios that assume different levels of future CO₂ emissions. Each scenario then has a range of possible outcomes associated with it. The most optimistic outcome assumes an aggressive campaign to reduce CO₂ emissions, while the most pessimistic is a "business as usual" scenario. The more realistic scenarios fall in between.

IPCC predictions are based on the same models used to establish the importance of the different factors in global warming. These models need data about anthropogenic emissions of greenhouse gases and aerosols. These data are predicted from economic models based on 35 different scenarios. Scenarios go from pessimistic to optimistic, and predictions of global warming depend on the kind of scenario considered.

IPCC uses the best available predictions and their reports are under strong scientific scrutiny. The IPCC concedes that there is a need for better models and better scientific understanding of some climate phenomena, as well as the uncertainties involved. Critics assert that the available data is not sufficient to determine the real importance of greenhouse gases in climate change. Sensitivity of climate to greenhouse gases may be overestimated or underestimated because of some flaws in the models and because the importance of some external factors may be misestimated. The predictions are based on scenarios, and the IPCC did not assign any probability to the 35 scenarios used.

Debate over Climate Change 2001

Economic growth estimates

Castles and Henderson asserted that the IPCC has been using inflated economic growth rates, which result in increased emission estimates . This was incorrect because IPCC growth and emissions rates were based upon several factors and not only GDP, as rebutted by Nebojsa Nakicenovic et al.

Physical modeling

A few participants in IPCC Working Group I (Science) do not agree with the IPCC reports (of the 120 lead authors, 2 have complained ).

A particularly active critic, MIT physicist Richard Lindzen, expressed his unhappiness about those portions in the Executive Summary based on his contributions in May 2001 before the U.S. Senate Committee on Commerce, Science and Transportation:

"The summary does not reflect the full document... For example, I worked on Chapter 7, Physical Processes. This chapter dealt with the nature of the basic processes which determine the response of climate, and found numerous problems with model treatments – including those of clouds and water vapor. The chapter was summarized with the following sentence: 'Understanding of climate processes and their incorporation in climate models have improved, including water vapour, sea-ice dynamics, and ocean heat transport.'"

The "Summary for Policymakers" of the WG1 reports does include caveats on model treatments: Such models cannot yet simulate all aspects of climate (e.g., they still cannot account fully for the observed trend in the surface-troposphere temperature difference since 1979) and there are particular uncertainties associated with clouds and their interaction with radiation and aerosols. Nevertheless, confidence in the ability of these models to provide useful projections of future climate has improved due to their demonstrated performance on a range of space and time-scales. .

These statements are in turn supported by the executive summary of chapter 8 of the report, which includes:

• Coupled models can provide credible simulations of both the present annual mean climate and the climatological seasonal cycle over broad continental scales for most variables of interest for climate change. Clouds and humidity remain sources of significant uncertainty but there have been incremental improvements in simulations of these quantities.

• Confidence in the ability of models to project future climates is increased by the ability of several models to reproduce the warming trend in 20th century surface air temperature when driven by radiative forcing due to increasing greenhouse gases and sulphate aerosols. However, only idealised scenarios of only sulphate aerosols have been used.

IPCC Second Assessment Report: Climate Change 1995

Climate Change 1995, the IPCC Second Assessment Report (SAR) was finished in 1996. It is split into four parts:

• A synthesis to help interpret UNFCCC article 2.
• The Science of Climate Change (WG I)
• Impacts, Adaptations and Mitigation of Climate Change (WG II)
• Economic and Social Dimensions of Climate Change (WG III)

Each of the last three parts was completed by a separate working group, and each has a Summary for Policymakers (SfP) that represents a consensus of national representatives. The SfP of the WG I report contains headings:

1. Greenhouse gas concentrations have continued to increase
2. Anthropogenic aerosols tend to produce negative radiative forcings
3. Climate has changed over the past century (air temperature has increased by between 0.3 and 0.6 °C since the late 19th century; this estimate has not significantly changed since the 1990 report).
4. The balance of evidence suggests a discernible human influence on global climate (considerable progress since the 1990 report in distinguishing between natural and anthropogenic influences on climate, because of: including aerosols; coupled models; pattern-based studies)
5. Climate is expected to continue to change in the future (increasing realism of simulations increases confidence; important uncertainties remain but are taken into account in the range of model projections)
6. There are still many uncertainties (estimates of future emissions and biogeochemical cycling; models; instrument data for model testing, assessment of variability, and detection studies)

Debate over Climate Change 1995

Most scientists involved in climate research believe that the IPCC reports accurately summarise the state of knowledge. Few scientists have objected and made public comments to that effect.

The report formed the basis of negotiations over the Kyoto Protocol.

A December 20, 1995, Reuters report quoted British scientist Keith Shine, one of IPCC's lead authors, discussing the Policymakers' Summary. He said: "We produce a draft, and then the policymakers go through it line by line and change the way it is presented.... It's peculiar that they have the final say in what goes into a scientists' report". It is not clear, in this case, whether Shine was complaining that the report had been changed to be more skeptical, or less, or something else entirely.

Dr. Frederick Seitz, president emeritus of Rockefeller University and past president of the National Academy of Sciences, has publicly denounced the IPCC report, writing "I have never witnessed a more disturbing corruption of the peer-review process than the events that led to this IPCC report". He opposed it in the Leipzig Declaration of his Science and Environmental Policy Project.

In turn, Seitz's comments were vigourously opposed by the presidents of the American Meteorological Society and University Corporation for Atmospheric Research, who wrote about a systematic effort by some individuals to undermine and discredit the scientific process that has led many scientists working on understanding climate to conclude that there is a very real possibility that humans are modifying Earth's climate on a global scale. Rather than carrying out a legitimate scientific debate... they are waging in the public media a vocal campaign against scientific results with which they disagree .

S. Fred Singer disseminated a letter about what he learned about changes to Chapter 8, interpretations of the IPCC Summary's key conclusion, and some policy implications :

1. Chapter 8 was altered substantially in order to make it conform to the Summary;
2. Three key clauses-- expressing the consensus of authors, contributors, and reviewers-- should have been placed into the Summary instead of being deleted from the approved draft chapter;
3. The ambiguous phrase "the balance of evidence suggests a discernible human influence on global climate" has been (mis)interpreted by policymakers to mean that a major global warming catastrophe will soon be upon us;
4. The IPCC report and its authors are being (mis)used by politicians and others to push an ideologically based agenda.

Dr. Benjamin D. Santer, Convening Lead Author of Chapter 8 of 1995 IPCC Working Group I Report, replied :

1. All revisions were made with the sole purpose of producing the best-possible and most clearly-explained assessment of the science, and were under the full scientific control of the Convening Lead Author of Chapter 8.
   • Changes were made in direct response to:
     • Written comments made by governments and non-governmental organizations (NGOs) during October and November 1995.
     • Comments made by governments and NGOs during the plenary sessions of the IPCC meeting that was held in Madrid from November 27-29th, 1995.
   • Post-Madrid changes to Chapter 8 were made solely in response to review comments and/or in order to clarify scientific points.
2. After receiving much criticism of the redundancy of a concluding summary (Section 8.7) in October and November 1995, the Convening Lead Author of Chapter 8 decided to remove it. About half of the information in the concluding summary was integrated with material in Section 8.6.
3. The bottom-line assessment of the science in the October 9th draft of Chapter 8 was "Taken together, these results point towards a human influence on climate".
   • The final assessment in the now-published Summary for Policymakers is that "the balance of evidence suggests that there is a discernible human influence on global climate".
     • The latter sentence, which is entirely consistent with the earlier Oct. 9th sentence, was unanimously approved at the Madrid meeting by delegates from nearly 100 countries.
4. None of the changes were politically motivated.

IPCC supplementary report, 1992

The 1992 supplementary report was an update, requested in the context of the negotiations on the Framework Convention on Climate Change at the Earth Summit (United Nations Conference on Environment and Development) in Rio de Janeiro in 1992.

The major conclusion was that research since 1990 did "not affect our fundamental understanding of the science of the greenhouse effect and either confirm or do not justify alteration of the major conclusions of the first IPCC scientific assessment". It noted that transient (time-dependent) simulations, which had been very preliminary in the FAR, were now improved, but did not include aerosol or ozone changes.

IPCC First Assessment Report: 1990

The IPCC first assessment report was completed in 1990, and served as the basis of the United Nations Framework Convention on Climate Change (UNFCCC).

The executive summary of the policymakers summary of the WG I report includes:

• We are certain of the following: there is a natural greenhouse effect...; emissions resulting from human activities are substantially increasing the atmospheric concentrations of the greenhouse gases: CO₂, methane, CFCs and nitrous oxide. These increases will enhance the greenhouse effect, resulting on average in an additional warming of the Earth's surface. The main greenhouse gas, water vapour, will increase in response to global warming and further enhance it.

• We calculate with confidence that: ...CO₂ has been responsible for over half the enhanced greenhouse effect; long-lived gases would require immeadiate reductions in emissions from human activities of over 60% to stabilise their concentrations at today's levels...

• Based on current models, we predict: under increase of global mean temperature during the century of about 0.3 C per decade (with an uncertainty range of 0.2 to 0.5 C per decade); this is greater than that seen over the past 10,000 years; under other ... scenarios which assume progressively increasing levels of controls, rates of increase in global mean temperature of about 0.2 C about 0.1 C per decade.

• There are many uncertainties in our predictions particularly with regard to the timing, magnitude and regional patterns of climate change, due to our incomplete understanding of: sources and sinks of GHGs; clouds; oceans; polar ice sheets.

• Our judgement is that: global mean surface air temperature has increased by 0.3 to 0.6 C over the last 100 years...; The size of this warming is broadly consistent with predicion of climate models, but it is also of the same magnitude as natural climate variability. Thus the observed increase could be largely due to this natural variability; alternatively this variability and other human factors could have offset a still larger human-induced greenhouse warming. The unequivocal detection of the enhanced greenhouse effect is not likely for a decade or more.

Debate over IPCC First Assessment Report: 1990

In 1991, the SEPP (The Science & Environmental Policy Project) surveyed IPCC contributors and researchers, along with a comparison group of global warming skeptics who had not contributed . The responses showed that 40% of the IPCC group did not agree with the IPCC FAR summary, and felt that it might convey a misleading message to the public with its emphasis on the certainty about the natural greenhouse effect. The responses also showed that the majority of respondents thought that models had not been adequately validated with observational data, and that attribution of observed warming to an enhanced greenhouse effect had not been shown using only observational data. 60% of respondents also thought that the climate models used did not accurately represent the physical atmosphere-ocean system.

Criticism of IPCC

Landsea

In January of 2005 Christopher Landsea resigned from work on the IPCC AR4, saying:

"I personally cannot in good faith continue to contribute to a process that I view as both being motivated by pre-conceived agendas and being scientifically unsound. As the IPCC leadership has seen no wrong in Dr. Trenberth's actions and have retained him as a Lead Author for the AR4, I have decided to no longer participate in the IPCC AR4" .

Stott

Emeritus professor of biogeography Philip Stott claimed in an interview that the computer models are still inadequate to make predictions about the change of climate. He criticises the IPCC for not having a risk assessment, meaning that there is allegedly no assessment about the likelihood of a scenario taking place.

"Stott does not appear to have had a single paper published in a scientific journal in the fields in which he most frequently applies this 'expertise', e.g. climate change or tropical ecology" .

Mörner on sea level

Nils-Axel Mörner has been critical of the IPCC TAR sea level chapter .

Mörner, at the time president of the INQUA Commission on Sea Level Changes and Coastal Evolution "reviewed" the IPCC TAR in 2000. Morner disagrees with the IPCC estimate of 0.09 to 0.88 metres between 1990 and 2100 and prefers his own figure of 10 cm ±10 cm". Morner believes that "All handling by IPCC of the Sea Level questions have been done in a way that cannot be accepted and that certainly not concur with modern knowledge of the mode and mechanism of sea level changes".

IPCC processes

• "It is strange that the climate reconstruction of Mann has passed both peer review rounds of the IPCC without anyone ever really having checked it. I think this issue will be on the agenda of the next IPCC meeting in Peking in May" (Rob van Dorland, Royal Netherlands Meteorological Institute, 27 January 2005).

• "The IPCC is monolithic and complacent, and it is conceivable that they are exaggerating the speed of change" (John Maddox, a former editor of the journal Nature, quoted by David Adam in The Guardian, 28 January 2005).

• UK House of Lords Science and Economic Analysis and Report on IPCC for the G-8 Summit, July 2005: "We have some concerns about the objectivity of the IPCC process, with some of

its emissions scenarios and summary documentation apparently influenced by political considerations. There are significant doubts about some aspects of the IPCC’s emissions scenario exercise, in particular, the high emissions scenarios. The Government should press the IPCC to change their approach. There are some positive aspects to global warming and these appear to have been played down in the IPCC reports; the Government should press the IPCC to reflect in a more balanced way the costs and benefits of climate change. The Government should press the IPCC for better estimates of the monetary costs of global warming damage and for explicit monetary comparisons between the costs of measures to control warming and their benefits. Since warming will continue, regardless of action now, due to the lengthy time lags."

See also

• Global warming

External links

• The IPCC web site
  • IPCC organisation
  • IPCC Principles
  • Second Assessment Synthesis Report (pdf)
  • Second Assessment Summary for Policymakers from the Working Group 1 (Science) Report.
  • Third Assessment Report
• The IPCC Controversy - from the SEPP
• climate change - What is the IPCC by Jean-Marc Jancovici

• International environmental organizations
• Climate change
• NGO reports
• United Nations specialized agencies
• Climate change organizations