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Global warming skepticism

The global warming controversy is a long-running dispute about human effects - past, present and future - on climate. The starting point is whether there has been significant global warming caused by industrial emissions of carbon dioxide. But this alone would be a scientific argument confined to the scientific press. The point that leads to major controversy - because it could have significant economic impacts - is whether action (usually, restrictions on the use of fossil fuels to reduce CO2 emmissions) should be taken now or in the near future.

The science of global warming is spread over several articles:

• The basic science is covered in greenhouse effect
• Recent climate trends include: global warming, global cooling
• Past climate behavior, being studied in determining normal variation as well as recent climate: historical temperature record, temperature record of the past 1000 years, satellite temperature record
• Causes of recent climate trends: attribution of recent climate change

Supporters' position

Supporters of the global warming theory assert that:

• the IPCC reports correctly summarise the state of climate science
• the historical temperature record shows a rise of 0.4-0.8 °C over the last 100 years
• this rise is unprecedented in the temperature record of the past 1000 years
• climate models can reproduce this trend, but only when using greenhouse gas forcing
• attribution of recent climate change shows that the rise can be attributed to human emissions of greenhouse gases
• climate models predict more warming, and other climate effects (sea level rise, etc) in the future
• there is a scientific consensus behind all of the above
• humankind is performing a great geophysical experiment and if it turns out badly - however that is defined - we cannot undo it.

Proponents of global warming tend to support the IPCC position and thus represent a broadly unified viewpoint, though with considerable differences over what action should be taken. Optionally, supporters may go on to point out that there is a good chance that the future changes may be undesirable, and that planning to avoid or mitigate them would be a good idea.

Participation in the IPCC process does not imply endorsement of it. However, only 2 of the 120 contributing authors to the IPCC TAR are known to have voiced any complaint.

Opponents' position

There are many reasons for opposition to the global warming theory and these major positions are independent of each other. Some items in this list may contradict others:

• IPCC draw firm conclusions unjustified by the science, especially given the acknowledged weakness of cloud physics in the climate models.
• Using "consensus" as evidence is an appeal to the majority argument rather than scientific discussion.
• Earth's climate has been both colder and warmer than today, and these changes are adequately explained by mechanisms that do not involve human greenhouse gas emissions.
• There is no significant global warming relative to the expected natural trends.
• Climate science can not make definitive predictions yet, since the computer models used to make these predictions are still evolving and do not yet take into account recently discovered feedback mechanisms.
• Global warming studies have errors or have not been reproduced.

Members of this faction give more weight to data such as paleoclimatic studies, temperature measurements made from weather balloons, and satellites which they claim show less warming than surface land and sea records.

Opponents tend to define themselves in terms of opposition to the IPCC position. They generally believe that climate science is not yet able to provide us with solid answers to all the major questions about the global climate.

Opponents frequently characterise supporters claims as alarmist and premature, so as to emphasise what they perceive as the lack of scientific evidence supporting global warming scenarios.

Opponents also say that if global warning is real and man-made, no action need be taken now because:

• Future scientific advances or engineering projects will remedy the problem before it becomes serious.
• A small amount of global warming would be benign or even beneficial.
• There is a distinct correlation between GDP growth and greenhouse gas emissions. A cutback in emissions would lead to a decrease in the rate of GDP growth.

See-also: global warming skepticism.

Scope of the controversy

The controversy occurs almost entirely within the press and political arenas. In the scientific press and amongst climate researchers, there is little "controversy" about global warming, only a desire to investigate a scientific problem and determine its consequences. As Kevin E. Trenberth writes:

In 1995 the IPCC assessment concluded that "the balance of evidence suggests that there is a discernible human influence on global climate". Since then the evidence has become much stronger ... Thus the headline in IPCC (2001) is "There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities"... While some changes arising from global warming are benign or even beneficial, the economic effects of the weather extremes are substantial and clearly warrant attention in policy debates... Consequently, there is a strong case for slowing down the projected rates of climate change from human influences.

Trenberth also provides evidence for the controversy that occurs when science meets the political arene:

The SPM was approved line by line by governments... The argument here is that the scientists determine what can said, but the governments determine how it can best be said. Negotiations occur over wording to ensure accuracy, balance, clarity of message, and relevance to understanding and policy. The IPCC process is dependent on the good will of the participants in producing a balanced assessment. However, in Shanghai, it appeared that there were attempts to blunt, and perhaps obfuscate, the messages in the report, most notably by Saudi Arabia. This led to very protracted debates over wording on even bland and what should be uncontroversial text... The most contentious paragraph in the IPCC (2001) SPM was the concluding one on attribution. After much debate the following was carefully crafted: "In the light of new evidence, and taking into account the remaining uncertainties, most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations."

Counting experts

The proportion of scientists who support or oppose any of the global warming theories is a matter of controversy in its own right (see scientific opinion of global warming). Environmentalists and their allies claim virtually unanimous support for the global warming theory from the scientific community. Opponents maintain that it is the other way around, claiming that the overwhelming majority of scientists either dismiss global warming altogether or merely consider it "unproven" (see global warming skepticism).

Arguments around the world

The arguments over global warming are viewed differently in different parts of the world. In Europe for example the environmentalist argument over Global warming has gained wider acceptance than in other parts of the world, most notably North America.

Beneficial or detrimental

There is also disagreement on whether the effects of global warming will be beneficial or detrimental. Many researchers predict disastrous consequences for a warming of 1.5 to 7 degrees Celsius. The UN's Intergovernmental Panel on Climate Change (IPCC) predicts such a warming is likely within the 21st century, unless severe measures are taken (see Kyoto Protocol).

Other researchers feel that up to 1.5 degrees Celsius of warming would increase crop yields and stabilize weather. Many of these doubt a larger warming is likely. In response, some advocates of strong early measures (well beyond Kyoto) note that the belief in beneficial effects and the doubt that a large warming is possible should be independent if these conclusions were in fact neutrally derived from scientific research.

Wait and see

Others suggest that a "wait and see" strategy disadvantages 3.5 billion people in favor of narrow advantage for a few growing regions and developed nations. However, those others have not provided details for their claims nor the advantages given to the other 3 billion people.

An unstable world

New findings have suggested that the earth's climate system is inherently unstable, and that global warming could thus precipitate non-linear sudden climate shifts, as have been discovered to have occurred within the earth's past. Ocean circulation, believed to be the key to such climate shifts, has been observed to be slowing, causing alarm among oceanographers. Some scientists fear that the Gulf Stream, which conveys warm water from the Caribbean Sea across the Atlantic Ocean and is partly responsible for the relative mildness of northern Europe's climate (though other factors also predominate: ), could be reduced or stopped altogether by the decreased salt content of sea water resulting from global warming. This could cause temperatures in northern Europe to drop.

The US National Academy of Sciences issued a report on this phenomenon in 2002, titled Abrupt Climate Change - Inevitable Surprises. "It is important not to be fatalistic about the threats posed by abrupt climate change," it stated. "Societies have faced both gradual and abrupt climate changes for millennia and have learned to adapt through various mechanisms, such as moving indoors, developing irrigation for crops, and migrating away from inhospitable regions. Nevertheless, because climate change will likely continue in the coming decades, denying the likelihood or downplaying the relevance of past abrupt events could be costly."

Recent reports

However, the US National Academy of Sciences, both in its 2002 report to President George W. Bush, and in its latest publications, has strongly endorsed evidence of an average global temperature increase in the 20th century and stated that human activity is heavily implicated in causing this increase. The American Meteorological Society (AMS statement), the American Geophysical Union (AGU statement), and other scientific societies have issued similar declarations. John Christy, who is usually placed in the skeptics camp, has signed the AGU statement on climate change.

Advocates of the global warming hypothesis who predict adverse consequences from as little as 1.5 degrees Celsius of warming nearly all support the Kyoto Protocol as a countermeasure. Details of the agreement are in the article about the Kyoto Protocol, including both the pollution and fiscal requirements.

• Climate change