having an effect on

Scientific opinion on climate change

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 position 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."

This article documents scientific opinion as given by synthesis reports, scientific bodies of national or international standing, and surveys of opinion among climate scientists. It does not document the views of individual scientists, individual universities or laboratories, nor self-selected lists of individuals such as petitions.

Statements by concurring organizations

Intergovernmental Panel on Climate Change (IPCC) 2007

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. Global warming in this case is indicated by an increase of 0.75 degrees in average global temperatures over the last 100 years.

The New York Times reports on the report:

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.

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.

The Associated Press summarizes the position on sea level rise:

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.

InterAcademy Council

As the representative of the world’s scientific and engineering academies, the InterAcademy Council (IAC) issued a report in 2007 entitled Lighting the Way: Toward a Sustainable Energy Future.

Current patterns of energy resources and energy usage are proving detrimental to the long-term welfare of humanity. The integrity of essential natural systems is already at risk from climate change caused by the atmospheric emissions of greenhouse gases.

Concerted efforts should be mounted for improving energy efficiency and reducing the carbon intensity of the world economy.

Joint science academies' statement 2008

In preparation for the 34th G8 summit, the national science academies of the G8+5 nations issued a declaration reiterating the position of the 2005 joint science academies’ statement, and reaffirming “that climate change is happening and that anthropogenic warming is influencing many physical and biological systems.” Among other actions, the declaration urges all nations to “(t)ake appropriate economic and policy measures to accelerate transition to a low carbon society and to encourage and effect changes in individual and national behaviour.”

The thirteen signatories were the national science academies of Brazil, Canada, China, France, Germany, Italy, India, Japan, Mexico, Russia, South Africa, the United Kingdom, and the United States.

Joint science academies’ statement 2007

In preparation for the 2007 G8 summit, the national science academies of the G8+5 nations issued a declaration referencing the position of the 2005 joint science academies' statement, and acknowledging the confirmation of their previous conclusion by recent research. Following the IPCC Fourth Assessment Report, the declaration states:
It is unequivocal that the climate is changing, and it is very likely that this is predominantly caused by the increasing human interference with the atmosphere. These changes will transform the environmental conditions on Earth unless counter-measures are taken.
The thirteen signatories were the national science academies of Brazil, Canada, China, France, Germany, Italy, India, Japan, Mexico, Russia, South Africa, the United Kingdom, and the United States.

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, and explicitly endorsed the IPCC consensus. The eleven signatories were the science academies of Brazil, Canada, China, France, Germany, India, Italy, Japan, Russia, the United Kingdom, and the United States.

Joint science academies’ statement 2001

In 2001, following the publication of the IPCC Third Assessment Report, sixteen national science academies issued a joint statement explicitly acknowledging the IPCC position as representing the scientific consensus on climate change science. The sixteen science academies that issued the statement were those of Australia, Belgium, Brazil, Canada, the Caribbean, China, France, Germany, India, Indonesia, Ireland, Italy, Malaysia, New Zealand, Sweden, and the United Kingdom.

International Council of Academies of Engineering and Technological Sciences

In October 2007, the International Council of Academies of Engineering and Technological Sciences (CAETS) issued a Statement on Environment and Sustainable Growth

As reported by the Intergovernmental Panel on Climate Change (IPCC), most of the observed global warming since the mid-20th century is very likely due to human-produced emission of greenhouse gases and this warming will continue unabated if present anthropogenic emissions continue or, worse, expand without control.

CAETS, therefore, endorses the many recent calls to decrease and control greenhouse gas emissions to an acceptable level as quickly as possible.

European Academy of Sciences and Arts

In March 2007, the European Academy of Sciences and Arts issued a formal declaration in which they stated, “Human activity is most likely responsible for climate warming. Most of the climatic warming over the last 50 years is likely to have been caused by increased concentrations of greenhouse gases in the atmosphere. Documented long-term climate changes include changes in Arctic temperatures and ice, widespread changes in precipitation amounts, ocean salinity, wind patterns and extreme weather including droughts, heavy precipitation, heat waves and the intensity of tropical cyclones. The above development potentially has dramatic consequences for mankind’s future. “

Network of African Science Academies

In 2007, the Network of African Science Academies submitted a joint “statement on sustainability, energy efficiency, and climate change” to the leaders meeting at the G8 Summit in Heiligendamm, Germany.

“A consensus, based on current evidence, now exists within the global scientific community that human activities are the main source of climate change and that the burning of fossil fuels is largely responsible for driving this change.”

“The IPCC should be congratulated for the contribution it has made to public understanding of the nexus that exists between energy, climate and sustainability.”

The thirteen signatories were the science academies of Cameroon, Ghana, Kenya, Madagascar, Nigeria, Senegal, South Africa, Sudan, Tanzania, Uganda, Zambia, Zimbabwe, as well as the African Academy of Sciences.

National Research Council (US)

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. 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.

European Science Foundation

The European Science Foundation has issued a Position Paper on climate change in which they concur, "There is now convincing evidence that since the industrial revolution, human activities, resulting in increasing concentrations of greenhouse gases have become a major agent of climate change. These greenhouse gases affect the global climate by retaining heat in the troposphere, thus raising the average temperature of the planet and altering global atmospheric circulation and precipitation patterns." The paper concluded, "While on-going national and international actions to curtail and reduce greenhouse gas emissions are essential, the levels of greenhouse gases currently in the atmosphere, and their impact, are likely to persist for several decades. On-going and increased efforts to mitigate climate change through reduction in greenhouse gases are therefore crucial.

American Association for the Advancement of Science

In December 2006, the American Association for the Advancement of Science adopted an official statement on climate change in which they stated, "The scientific evidence is clear: global climate change caused by human activities is occurring now, and it is a growing threat to society....The pace of change and the evidence of harm have increased markedly over the last five years. The time to control greenhouse gas emissions is now."

Federation of American Scientists

In their Energy and Environment Overview, the Federation of American Scientists state, “There is no serious doubt that human activity is altering the earth's climate in potentially catastrophic ways. Even skeptics are forced to admit that the risk is real and that prudence demands action if only as an insurance policy, the only serious debate is about how best to respond."

World Meteorological Organization

In its Statement at the Twelfth Session of the Conference of the Parties to the U.N. Framework Convention on Climate Change, the World Meteorological Organization (WMO) confirms the need to “prevent dangerous anthropogenic interference with the climate system.” The WMO concurs that “scientific assessments have increasingly reaffirmed that human activities are indeed changing the composition of the atmosphere, in particular through the burning of fossil fuels for energy production and transportation.” The WMO concurs that “the present atmospheric concentration of CO2 was never exceeded over the past 420,000 years;” and that the IPCC “assessments provide the most authoritative, up-to-date scientific advice.”

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.

Royal Meteorological Society (UK)

In February 2007, after the release of the IPCC’s Fourth Assessment Report, the Royal Meteorological Society issued an endorsement of the report. In addition to referring to the IPCC as “world’s best climate scientists”, they stated that climate change is happening as “the result of emissions since industrialization and we have already set in motion the next 50 years of global warming – what we do from now on will determine how worse it will get.”

Australian Meteorological and Oceanographic Society

The Australian Meteorological and Oceanographic Society has issued a Statement on Climate Change, wherein they conclude, “Global climate change and global warming are real and observable…It is highly likely that those human activities that have increased the concentration of greenhouse gases in the atmosphere have been largely responsible for the observed warming since 1950. The warming associated with increases in greenhouse gases originating from human activity is called the enhanced greenhouse effect. The atmospheric concentration of carbon dioxide has increased by more than 30% since the start of the industrial age and is higher now than at any time in at least the past 650,000 years. This increase is a direct result of burning fossil fuels, broad-scale deforestation and other human activity.”

Canadian Meteorological and Oceanographic Society

"CMOS endorses the process of periodic climate science assessment carried out by the Intergovernmental Panel on Climate Change and supports the conclusion, in its Third Assessment Report, which states that the balance of evidence suggests a discernible human influence on global climate.

Canadian Foundation for Climate and Atmospheric Sciences

In November 2005, the Canadian Foundation for Climate and Atmospheric Sciences (CFCAS) issued a letter to the Prime Minister of Canada stating that "We concur with the climate science assessment of the Intergovernmental Panel on Climate Change (IPCC) in 2001 ... We endorse the conclusions of the IPCC assessment that 'There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities'. ... There is increasingly unambiguous evidence of changing climate in Canada and around the world. There will be increasing impacts of climate change on Canada’s natural ecosystems and on our socio-economic activities. Advances in climate science since the 2001 IPCC Assessment have provided more evidence supporting the need for action and development of a strategy for adaptation to projected changes.

International Union for Quaternary Research

The statement on climate change issued by the International Union for Quaternary Research reiterates the conclusions of the IPCC, and urges all nations to take prompt action in line with the UNFCCC principles.

“Human activities are now causing atmospheric concentrations of greenhouse gasses - including carbon dioxide, methane, tropospheric ozone, and nitrous oxide - to rise well above pre-industrial levels….Increases in greenhouse gasses are causing temperatures to rise…The scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action….Minimizing the amount of this carbon dioxide reaching the atmosphere presents a huge challenge but must be a global priority.”

American Quaternary Association

The American Quaternary Association (AMQUA) has stated, “Few credible Scientists now doubt that humans have influenced the documented rise of global temperatures since the Industrial Revolution,” citing “the growing body of evidence that warming of the atmosphere, especially over the past 50 years, is directly impacted by human activity.”

Stratigraphy Commission of the Geological Society of London

The Stratigraphy Commission of the Geological Society of London stated, "We find that the evidence for human-induced climate change is now persuasive, and the need for direct action compelling.

International Union of Geodesy and Geophysics

In July 2007, the International Union of Geodesy and Geophysics (IUGG) adopted a resolution entitled “The Urgency of Addressing Climate Change”. In it, the IUGG concurs with the “comprehensive and widely accepted and endorsed scientific assessments carried out by the International Panel on Climate Change and regional and national bodies, which have firmly established, on the basis of scientific evidence, that human activities are the primary cause of recent climate change.” They state further that the “continuing reliance on combustion of fossil fuels as the world’s primary source of energy will lead to much higher atmospheric concentrations of greenhouse gasses, which will, in turn, cause significant increases in surface temperature, sea level, ocean acidification, and their related consequences to the environment and society.”

International Union of Geological Sciences

In their Climate Change prospectus for the International Year of Planet Earth project, the International Union of Geological Sciences (IUGS) stated, “The idea that there is a strong human imprint on recent climate change is now compelling, with forest clearing, building and man-made gas emissions all having a strong influence on Earth’s warming.”

We know that human activity has resulted in changes to atmospheric chemistry and land cover, and caused serious decline in biodiversity.

European Geosciences Union

In July 2005, the European Geosciences Union (EGU) issued a position statement in support of the joint science academies’ statement on global response to climate change. Additionally, the EGU concurred that the IPCC “represents the state-of-the-art of climate science supported by the major science academies around the world and by the vast majority of science researchers and investigators as documented by the peer-reviewed scientific literature.”

Canadian Federation of Earth Sciences

The Canadian Federation Of Earth Sciences has issued a position paper on global climate change in which they state, “ Canada's Earth scientists also recognize that humans are adding greenhouse gases (GHGs) to our atmosphere at an ever increasing rate. The level of CO2 in our atmosphere is now greater than at any time in the past 500,000 years; there will be consequences for our global climate and natural systems as a result….These could include: increased frequency and severity of drought, coastal erosion, sea level change, permafrost degradation, impact of reduced glacier cover on water resources, groundwater quality and quantity, and occurrence of climate-related natural hazards such as flooding, dust storms and landslides.”

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.

American Geophysical Union

The American Geophysical Union (AGU) statement adopted by the society in 2003 and revised in 2007 affirms that rising levels of greenhouse gases have caused and will continue to cause the global surface temperature to be warmer:

The Earth's climate is now clearly out of balance and is warming. Many components of the climate system—including the temperatures of the atmosphere, land and ocean, the extent of sea ice and mountain glaciers, the sea level, the distribution of precipitation, and the length of seasons—are now changing at rates and in patterns that are not natural and are best explained by the increased atmospheric abundances of greenhouse gases and aerosols generated by human activity during the 20th century. Global average surface temperatures increased on average by about 0.6°C over the period 1956–2006. As of 2006, eleven of the previous twelve years were warmer than any others since 1850. The observed rapid retreat of Arctic sea ice is expected to continue and lead to the disappearance of summertime ice within this century. Evidence from most oceans and all continents except Antarctica shows warming attributable to human activities. Recent changes in many physical and biological systems are linked with this regional climate change. A sustained research effort, involving many AGU members and summarized in the 2007 assessments of the Intergovernmental Panel on Climate Change, continues to improve our scientific understanding of the climate.

American Astronomical Society

The American Astronomical Society has endorsed the AGU statement:

In endorsing the "Human Impacts on Climate" statement [issued by the American Geophysical Union], the AAS recognizes the collective expertise of the AGU in scientific subfields central to assessing and understanding global change, and acknowledges the strength of agreement among our AGU colleagues that the global climate is changing and human activities are contributing to that change.

American Institute of Physics

The Governing Board of the American Institute of Physics endorsed the AGU statement on human-induced climate change:

The Governing Board of the American Institute of Physics has endorsed a position statement on climate change adopted by the American Geophysical Union (AGU) Council in December 2003.

American Physical Society

In November 2007, the American Physical Society (APS) adopted an official statement on climate change: "Emissions of greenhouse gases from human activities are changing the atmosphere in ways that affect the Earth's climate. Greenhouse gases include carbon dioxide as well as methane, nitrous oxide and other gases. They are emitted from fossil fuel combustion and a range of industrial and agricultural processes.

"The evidence is incontrovertible: Global warming is occurring. If no mitigating actions are taken, significant disruptions in the Earth’s physical and ecological systems, social systems, security and human health are likely to occur. We must reduce emissions of greenhouse gases beginning now.

American Chemical Society

The American Chemical Society stated:
Careful and comprehensive scientific assessments have clearly demonstrated that the Earth’s climate system is changing rapidly in response to growing atmospheric burdens of greenhouse gases and absorbing aerosol particles (IPCC, 2007). There is very little room for doubt that observed climate trends are due to human activities. The threats are serious and action is urgently needed to mitigate the risks of climate change.
The reality of global warming, its current serious and potentially disastrous impacts on Earth system properties, and the key role emissions from human activities play in driving these phenomena have been recognized by earlier versions of this ACS policy statement (ACS, 2004), by other major scientific societies, including the American Geophysical Union (AGU, 2003), the American Meteorological Society (AMS, 2007) and the American Association for the Advancement of Science (AAAS, 2007), and by the U. S. National Academies and ten other leading national academies of science (NA, 2005). This statement reviews key global climate change impacts and recommends actions required to mitigate or adapt to currently anticipated consequences.

Engineers Australia (The Institution of Engineers Australia)

"Engineers Australia believes that Australia must act swiftly and proactively in line with global expectations to address climate change as an economic, social and environmental risk... We believe that addressing the costs of atmospheric emissions will lead to increasing our competitive advantage by minimising risks and creating new economic opportunities. Engineers Australia believes the Australian Government should ratify the Kyoto Protocol.

Federal Climate Change Science Program (US)

On May 2, 2006, the Federal Climate Change Science Program commissioned by the Bush administration in 2002 released the first of 21 assessments. Though it did not state what percentage of climate change might be anthropogenic, the assessment concluded:
Studies ... show clear evidence of human influences on the climate system (due to changes in greenhouse gases, aerosols, and stratospheric ozone). ... The observed patterns of change over the past 50 years cannot be explained by natural processes alone, nor by the effects of short-lived atmospheric constituents (such as aerosols and tropospheric ozone) alone.
In a May 29, 2008 assessment, they stated:
It is well established through formal attribution studies that the global warming of the past 50 years is due primarily to human-induced increases in heat-trapping gases.

American Statistical Association

On November 30, 2007, the American Statistical Association Board of Directors adopted a statement on climate change:
The ASA endorses the IPCC conclusions. ... Over the course of four assessment reports, a small number of statisticians have served as authors or reviewers. Although this involvement is encouraging, it does not represent the full range of statistical expertise available. ASA recommends that more statisticians should become part of the IPCC process. Such participation would be mutually beneficial to the assessment of climate change and its impacts and also to the statistical community.

Noncommittal statements

American Association of State Climatologists

The 2001 statement from the American Association of State Climatologists noted the difficulties with predicting impacts due to climate change, while acknowledging that human activities are having an effect on climate:
Climate prediction is difficult because it involves complex, nonlinear interactions among all components of the earth’s environmental system. (...) 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. Furthermore, climate predictions have not demonstrated skill in projecting future variability and changes in such important climate conditions as growing season, drought, flood-producing rainfall, heat waves, tropical cyclones and winter storms. These are the type of events that have a more significant impact on society than annual average global temperature trends. Policy responses to climate variability and change should be flexible and sensible – The difficulty of prediction and the impossibility of verification of predictions decades into the future are important factors that allow for competing views of the long-term climate future. Therefore, the AASC recommends that policies related to long-term climate not be based on particular predictions, but instead should focus on policy alternatives that make sense for a wide range of plausible climatic conditions regardless of future climate... 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. Considerable potential exists to improve policies related to climate.

American Association of Petroleum Geologists

The American Association of Petroleum Geologists (AAPG) Position Statement on climate change states that "the AAPG membership is divided on the degree of influence that anthropogenic CO2 has on recent and potential global temperature increases ... Certain climate simulation models predict that the warming trend will continue, as reported through NAS, AGU, AAAS and AMS. AAPG respects these scientific opinions but wants to add that the current climate warming projections could fall within well-documented natural variations in past climate and observed temperature data. These data do not necessarily support the maximum case scenarios forecast in some models.

Prior to the adoption of this statement, the AAPG was the only major scientific organization that rejected the finding of significant human influence on recent climate, according to a statement by the Council of the American Quaternary Association. Explaining the plan for a revision, AAPG president Lee Billingsly wrote in March 2007 that "Members have threatened to not renew their memberships ... if AAPG does not alter its position on global climate change ... . And I have been told of members who already have resigned in previous years because of our current global climate change position. ... The current policy statement is not supported by a significant number of our members and prospective members.

Statements by dissenting organizations

With the July 2007 release of the revised statement by the American Association of Petroleum Geologists, no remaining scientific body of national or international standing is known to reject the basic findings of human influence on recent climate.

Scientific consensus

A question which frequently arises in popular discussion of climate change is whether there is a scientific consensus. Several scientific organizations have explicitly used the term "consensus" in their statements:

  • American Association for the Advancement of Science: "The conclusions in this statement reflect the scientific consensus represented by, for example, the Intergovernmental Panel on Climate Change, and the Joint National Academies' statement."
  • US National Academy of Science: "In the judgment of most climate scientists, Earth’s warming in recent decades has been caused primarily by human activities that have increased the amount of greenhouse gases in the atmosphere. ... On climate change, [the National Academies’ reports] have assessed consensus findings on the science...
  • Joint Science Academies' statement, 2005: "We recognise the international scientific consensus of the Intergovernmental Panel on Climate Change (IPCC).
  • Joint Science Academies' statement, 2001: "The work of the Intergovernmental Panel on Climate Change (IPCC) represents the consensus of the international scientific community on climate change science. We recognise IPCC as the world’s most reliable source of information on climate change and its causes, and we endorse its method of achieving this consensus.
  • American Meteorological Society: "The nature of science is such that there is rarely total agreement among scientists. Individual scientific statements and papers—the validity of some of which has yet to be assessed adequately—can be exploited in the policy debate and can leave the impression that the scientific community is sharply divided on issues where there is, in reality, a strong scientific consensus. ...IPCC assessment reports are prepared at approximately five-year intervals by a large international group of experts who represent the broad range of expertise and perspectives relevant to the issues. The reports strive to reflect a consensus evaluation of the results of the full body of peer-reviewed research. ... They provide an analysis of what is known and not known, the degree of consensus, and some indication of the degree of confidence that can be placed on the various statements and conclusions.
  • Network of African Science Academies: “A consensus, based on current evidence, now exists within the global scientific community that human activities are the main source of climate change and that the burning of fossil fuels is largely responsible for driving this change.”

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.

Oreskes, 2004

A 2004 article by geologist and historian of science Naomi Oreskes summarized a study of the scientific literature on climate change. 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". According to the report, "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."

Bray and von Storch, 2003

A survey was conducted in 2003 by Dennis Bray and Hans von Storch Bray's submission to Science on December 22, 2004 was rejected, but the survey's results were reported through non-scientific venues. 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."

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. The survey required entry of a username and password, but the username and password were circulated to a climate skeptics mailing list and elsewhere on the internet. Bray and von Storch defended their results and accused climate change skeptics of interpreting the results with bias.

Bray and von Storch distributed an updated version of their survey in August 2008, sent to 1842 selected scientists drawn from authors in ISI listed climate related journals for the past 10 years, as well as lists used in previously published analyses. This survey contains a web link with a unique identifier for each respondent. Results of this survey are not yet available.

Survey of U.S. state climatologists 1997

In 1997, the conservative think tank Citizens for a Sound Economy surveyed America's 48 state climatologists on questions related to climate change. Of the 36 respondents, 44% considered global warming to be a largely natural phenomenon, compared to 17% who considered warming to be largely man-made. 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."

Sixty percent 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. Thirty nine percent agreed and 33% disagreed that "evidence exists to suggest that the earth is headed for another glacial period, though the time scale for the next glacial period was not specified.

Bray and von Storch, 1996

In 1996, Dennis Bray and Hans von Storch undertook a survey of climate scientists on attitudes towards global warming and related matters. The results were subsequently published in the Bulletin of the American Meteorological Society. 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.

Other older surveys of scientists

Note that the following surveys are over 15 years old. The state of climate science and the beliefs of climate scientists have changed radically since their time, as demonstrated by 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.
  • In 1991, the Center for Science, Technology, and Media commissioned a Gallup poll of 400 members of the American Geophysical Union and the American Meteorological Society along with an analysis of reporting on global warming by the Center for Media and Public Affairs, a report on which was issued in 1992. Accounts of the results of that survey differ in their interpretation and even in the basic statistical percentages:
    • Fairness and Accuracy in Reporting states that the report said that 67% of the scientists said that human-induced global warming was occurring, with 11% disagreeing and the rest undecided.
    • George Will reported "53 percent do not believe warming has occurred, and another 30 percent are uncertain." (Washington Post, September 3, 1992). In a correction Gallup stated: "Most scientists involved in research in this area believe that human-induced global warming is occurring now.
    • A 1993 publication by the Heartland Institute reports: "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.

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