Scientific opinion on climate change

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National and international science academies and professional societies have assessed the current scientific opinion on climate change, in particular recent global warming. These assessments have largely followed or endorsed the IPCC postition that "An increasing body of observations gives a collective picture of a warming world and other changes in the climate system... There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities".[1]

This page documents scientific opinion as given by synthesis reports, bodies of national or international standing, and surveys of opinion among climate scientists. It does not document the views of individual scientists or self-selected lists of individuals such as petitions.

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[edit] Statements by organizations

[edit] Intergovernmental Panel on Climate Change (IPCC)

Main article: Intergovernmental Panel on Climate Change

In February 2007, the IPCC released a summary of the forthcoming Fourth Assessment Report. According to this summary, the Fourth Assessment Report finds that human actions are "very likely" the cause of global warming, meaning a 90% or greater probability.[2]

"The world's leading climate scientists said global warming has begun, is very likely caused by man, and will be unstoppable for centuries, ... . The phrase very likely translates to a more than 90 percent certainty that global warming is caused by man's burning of fossil fuels. That was the strongest conclusion to date, making it nearly impossible to say natural forces are to blame."[7]

"The report said that an increase in hurricane and tropical cyclone strength since 1970 more likely than not can be attributed to man-made global warming. The scientists said global warming's connection varies with storms in different parts of the world, but that the storms that strike the Americas are global warming-influenced."[8]

"On sea levels, the report projects rises of 7-23 inches by the end of the century. That could be augmented by an additional 4-8 inches if recent surprising polar ice sheet melt continues."[9]

[edit] Joint science academies’ statement 2005

In 2005 the national science academies of the G8 nations, plus Brazil, China and India, three of the largest emitters of greenhouse gases in the developing world, signed a statement on the global response to climate change. The statement stresses that the scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action [10], and explicitly endorsed the IPCC consensus.

[edit] Joint science academies’ statement 2001

In 2001, following the publication of the IPCC Third Assessment Report, sixteen national science academies issued a joint statement explicitely acknowledging the IPCC position as representing the scientific conensus on climate change science. Among the signatories are the science academies of Australia, Belgium, Brazil, Canada, the Carribean, China, France, Germany, India, Indonesia, Ireland, Italy, Malaysia, New Zealand, Sweden, and the United Kingdom.[11]

[edit] U.S. National Research Council, 2001

In 2001 the Committee on the Science of Climate Change of the National Research Council published Climate Change Science: An Analysis of Some Key Questions [12]. This report explicitly endorses the IPCC view of attribution of recent climate change as representing the view of the scientific community:

The changes observed over the last several decades are likely mostly due to human activities, but we cannot rule out that some significant part of these changes is also a reflection of natural variability. Human-induced warming and associated sea level rises are expected to continue through the 21st century... The IPCC's conclusion that most of the observed warming of the last 50 years is likely to have been due to the increase in greenhouse gas concentrations accurately reflects the current thinking of the scientific community on this issue. [13]

[edit] American Meteorological Society

The American Meteorological Society (AMS) statement adopted by their council in 2003 said:

There is now clear evidence that the mean annual temperature at the Earth's surface, averaged over the entire globe, has been increasing in the past 200 years. There is also clear evidence that the abundance of greenhouse gases in the atmosphere has increased over the same period. In the past decade, significant progress has been made toward a better understanding of the climate system and toward improved projections of long-term climate change... Human activities have become a major source of environmental change. Of great urgency are the climate consequences of the increasing atmospheric abundance of greenhouse gases... Because greenhouse gases continue to increase, we are, in effect, conducting a global climate experiment, neither planned nor controlled, the results of which may present unprecedented challenges to our wisdom and foresight as well as have significant impacts on our natural and societal systems. [14]

[edit] Federal Climate Change Science Program, 2006

On May 2, 2006, the Federal Climate Change Science Program commissioned by the Bush administration in 2002 released the first of 21 assessments that concluded that there is clear evidence of human influences on the climate system (due to changes in greenhouse gases, aerosols, and stratospheric ozone) [15]. The study said that observed patterns of change over the past 50 years cannot be explained by natural processes alone, though it did not state what percentage of climate change might be anthropogenic in nature.

[edit] Other concurring organizations

Other scientific organizations that have issued concurring position statements on climate change include the following.

  • American Association for the Advancement of Science: "The scientific evidence is clear: global climate change caused by human activities is occurring now, and it is a growing threat to society." [16]
  • American Geophysical Union, also endorsed [17] by the American Institute of Physics: "Human activities are increasingly altering the Earth's climate. These effects add to natural influences that have been present over Earth's history. Scientific evidence strongly indicates that natural influences cannot explain the rapid increase in global near-surface temperatures observed during the second half of the 20th century." [18]
  • Stratigraphy Commission of the Geological Society of London: "We find that the evidence for human-induced climate change is now persuasive, and the need for direct action compelling." [19]
  • Geological Society of America: "The Geological Society of America (GSA) supports the scientific conclusions that Earth’s climate is changing; the climate changes are due in part to human activities; and the probable consequences of the climate changes will be significant and blind to geopolitical boundaries. Furthermore, the potential implications of global climate change and the time scale over which such changes will likely occur require active, effective, long-term planning." [20]
  • American Association of State Climatologists: This statement noted the difficulties with predicting impacts due to climate change, while acknowledging that human activities are having an effect on climate: "The AASC recognizes that human activities have an influence on the climate system. Such activities, however, are not limited to greenhouse gas forcing and include changing land use and sulfate emissions, which further complicates the issue of climate prediction... Whatever policies are promulgated with respect to energy, it is imperative that policy makers recognize that climate, its variability and change has a broad impact on society. The policy responses too should also be broad...Finally, ongoing political debate about global energy policy should not stand in the way of common sense action to reduce societal and environmental vulnerabilities to climate variability and change." [21]
  • Australian Medical Association: "Failure to commit to reducing greenhouse gas emissions has the potential to cause significant global public health problems... The AMA believes that an effective emissions control program could be instituted without having a negative impact on the Australian economy. This can best be achieved by combining energy conservation with new alternative technologies that would reduce dependency on fossil fuels... The AMA believes that the Federal Government should implement a National Greenhouse Policy that engages all Australians in ensuring that we meet the Kyoto target and start to dramatically cut our greenhouse pollution." [22]
  • American Chemical Society: "The overwhelming balance of evidence indicates that reducing greenhouse gas emissions is the prudent and responsible course of action at this time. Although vigorous climate research is certainly needed to reduce uncertainties and to identify potential adverse effects, it should not forestall prudent action now to address the issue. ACS believes that public and private efforts today are essential to protect the global climate system for the well-being of future generations." [23]
  • American Quaternary Association: "Few credible scientists now doubt that humans have influenced the documented rise in global temperatures since the Industrial Revolution. The first government-led U.S. Climate Change Science Program synthesis and assessment report supports the growing body of evidence that warming of the atmosphere, especially over the past 50 years, is directly impacted by human activity." [24]

[edit] Dissenting organizations

The only major scientific organization that rejects the finding of human influence on recent climate is the American Association of Petroleum Geologists (AAPG), according to a statement by the Council of the American Quaternary Association.[3] The undated AAPG Policy Statement on Climate Change Policy [25] states

"Current proposals (Kyoto Protocol signed by the executive branch of the U.S. government, but not ratified by Congress) would federally tax crude oil at the rate of about $43.50 per barrel. No reduction in existing levels of carbon dioxide in the atmosphere would result from this massive transfer of wealth from the private sector into the federal government...Scientific examination of the government case for such draconian taxation does not support the supposition of human-induced global climate change; in fact, the study resulted in recognition that the supposition is neither provable nor disprovable...Recently published research results do not support the supposition of an anthropogenic cause of global climate change...Detailed examination of current climate data strongly suggests that current observations do not correlate with the assumptions or supportable projections of human-induced greenhouse effects."

[edit] Recent surveys of scientists and scientific literature

Various surveys have been conducted to determine a scientific consensus on global warming. Few have been conducted within the last ten years.

[edit] Oreskes, 2004

A 2004 article by geologist and historian of science Naomi Oreskes summarized a study of the scientific literature on climate change.[4] The essay concluded that there is a scientific consensus on the reality of anthropogenic climate change. The author analyzed 928 abstracts of papers from refereed scientific journals between 1993 and 2003, listed with the keywords "global climate change". Oreskes divided the abstracts into six categories: explicit endorsement of the consensus position, evaluation of impacts, mitigation proposals, methods, paleoclimate analysis, and rejection of the consensus position. 75% of the abstracts were placed in the first three categories, thus either explicitly or implicitly accepting the consensus view; 25% dealt with methods or paleoclimate, thus taking no position on current anthropogenic climate change; none of the abstracts disagreed with the consensus position, which the author found to be "remarkable". It was also pointed out, "authors evaluating impacts, developing methods, or studying paleoclimatic change might believe that current climate change is natural. However, none of these papers argued that point."

[edit] Bray and von Storch, 2003

A survey[5] was conducted in 2003 by Dennis Bray and Hans von Storch. Bray's submission to Science on December 22, 2004 was rejected [6] but the survey's results were reported through non-scientific venues[7] [8] [9]. The survey has been criticized on the grounds that it was performed on the web with no means to verify that the respondents were climate scientists or to prevent multiple submissions by the same individual. The survey required entry of a username and password, but this information was circulated to a climate skeptics mailing list and elsewhere on the internet.[10][11] The survey received 530 responses from 27 different countries. One of the questions asked was "To what extent do you agree or disagree that climate change is mostly the result of anthropogenic causes?", with a value of 1 indicating strongly agree and a value of 7 indicating strongly disagree. The results showed a mean of 3.62, with 50 responses (9.4%) indicating "strongly agree" and 54 responses (9.7%) indicating "strongly disagree". The same survey indicates a 72% to 20% endorsement of the IPCC reports as accurate, and a 15% to 80% rejection of the thesis that "there is enough uncertainty about the phenomenon of global warming that there is no need for immediate policy decisions".

[edit] Older surveys

[edit] Survey of U.S. state climatologists 1997

In 1997, the conservative advocacy group Citizens for a Sound Economy surveyed America's 48 official state climatologists on questions related to climate change [26]. Of the 36 respondents, 44% considered global warming to be a largely natural phenomenon, compared to 17% who considered warming to be largely manmade. The survey further found that 58% disagreed or somewhat disagreed with then-President Clinton's assertion that "the overwhelming balance of evidence and scientific opinion is that it is no longer a theory, but now fact, that global warming is for real". Eighty-nine percent agreed that "current science is unable to isolate and measure variations in global temperatures caused ONLY by man-made factors," and 61% said that historical data do not indicate "that fluctuations in global temperatures are attributable to human influences such as burning fossil fuels."

60% of the respondents said that reducing man-made CO2 emissions by 15% below 1990 levels would not prevent global temperatures from rising, and 86% said that reducing emissions to 1990 levels would not prevent rising temperatures. 39% agreed and 33% disagreed that "evidence exists to suggest that the earth is headed for another glacial period," [27] though the time scale for the next glacial period was not specified.

[edit] Bray and von Storch, 1996

In 1996, Dennis Bray and Hans von Storch undertook a survery of climate scientists on attitudes towards global warming and related matters. The results were subsequently published in the Bulletin of the American Meteorological Society. [28] The paper addressed the views of climate scientists, with a response rate of 40% from a mail survey questionnaire to 1000 scientists in Germany, the USA and Canada. Most of the scientists believed that global warming was occurring and appropriate policy action should be taken, but there was wide disagreement about the likely effects on society and almost all agreed that the predictive ability of currently existing models was limited.

The abstract says:

The international consensus was, however, apparent regarding the utility of the knowledge to date: climate science has provided enough knowledge so that the initiation of abatement measures is warranted. However, consensus also existed regarding the current inability to explicitly specify detrimental effects that might result from climate change. This incompatibility between the state of knowledge and the calls for action suggests that, to some degree at least, scientific advice is a product of both scientific knowledge and normative judgment, suggesting a socioscientific construction of the climate change issue.

The survey was extensive, and asked numerous questions on many aspects of climate science, model formulation, and utility, and science/public/policy interactions. To pick out some of the more vital topics, from the body of the paper:

The resulting questionnaire, consisting of 74 questions, was pre-tested in a German institution and after revisions, distributed to a total of 1,000 scientists in North America and Germany... The number of completed returns was as follows: USA 149, Canada 35, and Germany 228, a response rate of approximately 40%...
...With a value of 1 indicating the highest level of belief that predictions are possible and a value of 7 expressing the least faith in the predictive capabilities of the current state of climate science knowledge, the mean of the entire sample of 4.6 for the ability to make reasonable predictions of inter-annual variability tends to indicate that scientists feel that reasonable prediction is not yet a possibility... mean of 4.8 for reasonable predictions of 10 years... mean of 5.2 for periods of 100 years...
...a response of a value of 1 indicates a strong level of agreement with the statement of certainty that global warming is already underway or will occur without modification to human behavior... the mean response for the entire sample was 3.3 indicating a slight tendency towards the position that global warming has indeed been detected and is underway.... Regarding global warming as being a possible future event, there is a higher expression of confidence as indicated by the mean of 2.6.

[edit] Other older surveys of scientists

It should be noted that these surveys are over 15 years old and the state of climate science has changed radically since their time; current beliefs of the scientific community are different as shown in the reviews cited above.

  • Global Environmental Change Report, 1990: GECR climate survey shows strong agreement on action, less so on warming. Global Environmental Change Report 2, No. 9, pp. 1-3
  • Stewart, T.R., Mumpower, J.L., and Reagan-Cirincione, P. (1992). Scientists' opinions about global climate change: Summary of the results of a survey. NAEP (National Association of Environmental Professionals) Newsletter, 17(2), 6-7.
  • A 1991 Gallup poll of 400 members of the American Geophysical Union and the American Meteorological Society[citation needed]
    • Fairness and Accuracy in Reporting states that the report said that 66 % of the scientists said that human-induced global warming was occurring, with 10 % disagreeing and the rest undecided. In a correction Gallup stated: "Most scientists involved in research in this area believe that human-induced global warming is occurring now."
    • George Will reported "53 percent do not believe warming has occurred, and another 30 percent are uncertain." (Washington Post, September 3, 1992)
    • A 1993 publication by the politically conservative[29] Heartland Institute states: "A Gallup poll conducted on February 13, 1992 of members of the American Geophysical Union and the American Meteorological Society - the two professional societies whose members are most likely to be involved in climate research - found that 18 percent thought some global warming had occurred, 33 percent said insufficient information existed to tell, and 49 percent believed no warming had taken place."[30]


[edit] See also

[edit] References

  1. ^ Working Group 1, IPCC.
  2. ^ "Warming 'very likely' human-made", BBC News, BBC, 2007-02-01. Retrieved on February 1, 2007.
  3. ^ "The AAPG stands alone among scientific societies in its denial of human-induced effects on global warming." [1]
  4. ^ Naomi Oreskes (December 3, 2004). "Beyond the Ivory Tower: The Scientific Consensus on Climate Change". Science 306 (5702): 1686. DOI:10.1126/science.1103618.  (see also for an exchange of letters to Science)
  5. ^ [2]
  6. ^ [3]
  7. ^ [4]
  8. ^ [5]
  9. ^ [6]
  10. ^ Useless on-line survey of climate scientists
  11. ^ DIALOG and DISCCRS News

[edit] External links

Part of a series on Global Warming
Subtopics
Scientific opinion • Attribution of causes • Effects • Mitigation • Adaptation • Controversy • Politics • Economics
Related articles
Climate change • Deforestation • Global climate modelling • Global cooling • Global dimming • Greenhouse effect • Greenhouse gases
Intergovernmental Panel on Climate Change • Kyoto Protocol • Peak Oil • Renewable energy • Temperature data
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