Scientific consensus on climate change


There is currently a strong scientific consensus that the Earth is warming and that this warming is mainly caused by human activities. This consensus is supported by various studies of scientists' opinions and by position statements of scientific organizations, many of which explicitly agree with the Intergovernmental Panel on Climate Change synthesis reports.
Nearly all actively publishing climate scientists support the consensus on anthropogenic climate change, and the remaining 3% of contrarian studies either cannot be replicated or contain errors. A November 2019 study showed that the consensus among research scientists had grown to 100%, based on a review of 11,602 peer-reviewed articles published in the first 7 months of 2019.

Consensus points

The current scientific consensus is that:
Several studies of the consensus have been undertaken. Among the most cited is a 2013 study of nearly 12,000 abstracts of peer-reviewed papers on climate science published since 1990, of which just over 4,000 papers expressed an opinion on the cause of recent global warming. Of these, 97% agree, explicitly or implicitly, that global warming is happening and is human-caused. It is "extremely likely" that this warming arises from "human activities, especially emissions of greenhouse gases" in the atmosphere. Natural change alone would have had a slight cooling effect rather than a warming effect.
This scientific opinion is expressed in synthesis reports, by scientific bodies of national or international standing, and by surveys of opinion among climate scientists. Individual scientists, universities, and laboratories contribute to the overall scientific opinion via their peer-reviewed publications, and the areas of collective agreement and relative certainty are summarised in these respected reports and surveys.
The IPCC's Fifth Assessment Report was completed in 2014. Its conclusions are summarized below:
National and international science academies and scientific societies have assessed current scientific opinion on global warming. These assessments are generally consistent with the conclusions of the Intergovernmental Panel on Climate Change.
Some scientific bodies have recommended specific policies to governments, and science can play a role in informing an effective response to climate change. Policy decisions, however, may require value judgements and so are not included in the scientific opinion.
No scientific body of national or international standing maintains a formal opinion dissenting from any of these main points. The last national or international scientific body to drop dissent was the American Association of Petroleum Geologists, which in 2007 updated its statement to its current non-committal position. Some other organizations, primarily those focusing on geology, also hold [|non-committal positions].

Synthesis reports

Synthesis reports are assessments of scientific literature that compile the results of a range of stand-alone studies in order to achieve a broad level of understanding, or to describe the state of knowledge of a given subject.

Intergovernmental Panel on Climate Change (IPCC) 2014

The IPCC Fifth Assessment Report followed the same general format as the Fourth Assessment Report, with three Working Group reports and a Synthesis report. The Working Group I report was published in September 2013. The report's Summary for Policymakers stated that warming of the climate system is 'unequivocal' with changes unprecedented over decades to millennia, including warming of the atmosphere and oceans, loss of snow and ice, and sea level rise. Greenhouse gas emissions, driven largely by economic and population growth, have led to greenhouse gas concentrations that are unprecedented in at least the last 800,000 years. These, together with other anthropogenic drivers, are "extremely likely" to have been the dominant cause of the observed global warming since the mid-20th century.
It said that
Reporting on the publication of the report, The Guardian said that
The New York Times reported that
It went on to say that Ban Ki-moon, the United Nations secretary general, had declared his intention to call a meeting of heads of state in 2014 to develop such a treaty. The last such meeting, in Copenhagen in 2009, the NY Times reported, had ended in disarray.

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 found that human actions are "very likely" the cause of global warming, meaning a 90% or greater probability. Global warming in this case was indicated by an increase of 0.75 degrees in average global temperatures over the last 100 years.
The IPCC Fourth Assessment Report stated that:
The New York Times reported that "the leading international network of climate scientists has concluded for the first time that global warming is 'unequivocal' and that human activity is the main driver, 'very likely' causing most of the rise in temperatures since 1950".
A retired journalist for The New York Times, William K. Stevens wrote: "The Intergovernmental Panel on Climate Change said the likelihood was 90 percent to 99 percent that emissions of heat-trapping greenhouse gases like carbon dioxide, spewed from tailpipes and smokestacks, were the dominant cause of the observed warming of the last 50 years. In the panel's parlance, this level of certainty is labeled 'very likely'. Only rarely does scientific odds-making provide a more definite answer than that, at least in this branch of science, and it describes the endpoint, so far, of a progression.".
The Associated Press summarized the position on sea level rise:

U.S. Global Change Research Program

Thirteen federal agencies, led by the National Oceanic and Atmospheric Administration, worked together under the auspices of the United States Global Change Research Program to prepare the country's Fourth National Climate Assessment, published in two volumes as described below.
The Climate Science Special Report: Fourth National Climate Assessment, Volume I provided the following summary:
This assessment concludes, based on extensive evidence, that it is extremely likely that human activities, especially emissions of greenhouse gases, are the dominant cause of the observed warming since the mid-20th century. For the warming over the last century, there is no convincing alternative explanation supported by the extent of the observational evidence.

Background

The U.S. Global Change Research Program reported in June 2009 that:
The 2009 report, which is about the effects that climate change is having in the United States, also said:

Arctic Climate Impact Assessment

In 2004, the intergovernmental Arctic Council and the non-governmental International Arctic Science Committee released the synthesis report of the Arctic Climate Impact Assessment:

Policy

There is an extensive discussion in the scientific literature on what policies might be effective in responding to climate change. Some scientific bodies have recommended specific policies to governments. The natural and social sciences can play a role in informing an effective response to climate change. However, policy decisions may require value judgements. For example, the US National Research Council has commented:
The question of whether there exists a "safe" level of concentration of greenhouse gases cannot be answered directly because it would require a value judgment of what constitutes an acceptable risk to human welfare and ecosystems in various parts of the world, as well as a more quantitative assessment of the risks and costs associated with the various impacts of global warming. In general, however, risk increases with increases in both the rate and the magnitude of climate change.

This article mostly focuses on the views of natural scientists. However, social scientists, medical experts, engineers and philosophers have also commented on climate change science and policies. Climate change policy is discussed in several articles: climate change mitigation, climate change adaptation, climate engineering, politics of global warming, climate ethics, and economics of global warming.

Statements by scientific organizations of national or international standing

This is a list of scientific bodies of national or international standing, that have issued formal statements of opinion, classifies those organizations according to whether they concur with the IPCC view, are non-committal, or dissent from it. The California Governor's Office website lists nearly 200 worldwide scientific organizations hold the position that climate change has been caused by human action.

Concurring

Academies of science (general science)

Since 2001, 34 national science academies, three regional academies, and both the international InterAcademy Council and International Council of Academies of Engineering and Technological Sciences have made formal declarations confirming human induced global warming and urging nations to reduce emissions of greenhouse gases. The 34 national science academy statements include 33 who have signed joint science academy statements and one individual declaration by the Polish Academy of Sciences in 2007.
Joint national science academy statements
In December 2007, the General Assembly of the Polish Academy of Sciences, which has not been a signatory to [|joint national science academy statements] issued a declaration endorsing the IPCC conclusions, and stating:
Additional national science academy and society statements
American Geophysical Union
The American Geophysical Union adopted a statement on Climate Change and Greenhouse Gases in 1998. A new statement, adopted by the society in 2003, revised in 2007, and revised and expanded in 2013, affirms that rising levels of greenhouse gases have caused and will continue to cause the global surface temperature to be warmer:
American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America
In May, 2011, the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America issued a joint position statement on climate change as it relates to agriculture:
European Federation of Geologists
In 2008, the European Federation of Geologists issued the position paper Carbon Capture and geological Storage :
European Geosciences Union
In 2005, the Divisions of Atmospheric and Climate Sciences of the European Geosciences Union issued a position statement in support of the joint science academies’ statement on global response to climate change. The statement refers to the Intergovernmental Panel on Climate Change, as "the main representative of the global scientific community", and asserts that the IPCC
Additionally, in 2008, the EGU issued a position statement on ocean acidification which states, "Ocean acidification is already occurring today and will continue to intensify, closely tracking atmospheric increase. Given the potential threat to marine ecosystems and its ensuing impact on human society and economy, especially as it acts in conjunction with anthropogenic global warming, there is an urgent need for immediate action." The statement then advocates for strategies "to limit future release of to the atmosphere and/or enhance removal of excess from the atmosphere". And, in 2018 the EGU issued a statement concurring with the findings of the Special Report on Global Warming of 1.5 °C, with Jonathan Bamber, president of the organisation, noting: “EGU concurs with, and supports, the findings of the SR15 that action to curb the most dangerous consequences of human-induced climate change is urgent, of the utmost importance and the window of opportunity extremely limited.”
Geological Society of America
In 2006, the Geological Society of America adopted a position statement on global climate change. It amended this position on April 20, 2010, with more explicit comments on need for reduction.
Geological Society of London
In November 2010, the Geological Society of London issued the position statement Climate change: evidence from the geological record:
International Union of Geodesy and Geophysics
In July 2007, the International Union of Geodesy and Geophysics adopted a resolution titled "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 Intergovernmental 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 gases, which will, in turn, cause significant increases in surface temperature, sea level, ocean acidification, and their related consequences to the environment and society".
National Association of Geoscience Teachers
In July 2009, the National Association of Geoscience Teachers adopted a position statement on climate change in which they assert that "Earth's climate is changing "that present warming trends are largely the result of human activities":

Meteorology and oceanography

American Meteorological Society
The American Meteorological Society statement adopted by their council in 2012 concluded:
A 2016 survey found that two-thirds of AMS members think that all or most of climate change is caused by human activity.
Australian Meteorological and Oceanographic Society
The Australian Meteorological and Oceanographic Society has issued a Statement on Climate Change, wherein they conclude:
Canadian Foundation for Climate and Atmospheric Sciences
In November 2005, the Canadian Foundation for Climate and Atmospheric Sciences issued a letter to the Prime Minister of Canada stating that
Canadian Meteorological and Oceanographic Society
In November 2009, a letter to the Canadian Parliament by The Canadian Meteorological and Oceanographic Society states:
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."
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 presented on November 15, 2006, the World Meteorological Organization 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 was never exceeded over the past 420,000 years"; and that the IPCC "assessments provide the most authoritative, up-to-date scientific advice".
American Quaternary Association
The American Quaternary Association has stated
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.

Biology and life sciences

Life science organizations have outlined the dangers climate change pose to wildlife.
A number of health organizations have warned about the numerous negative health effects of global warming
A group of scientists launched a project named the "Bulletin of the Atomic Scientists" that contains the "Doomsday Clock" after the bombardment of Hiroshima and Nagasaky. The biggest is the danger to humanity the clock moves closer to midnight and vice versa. The target is to show the extent of danger to humanity, create awareness in public that will lead to solutions. In the beginning the organization focused on the danger of nuclear war, but in the 21th century, it has begun to deal with other issues like climate change and disinformation on the internet.
On 23 January 2020 the organization moved the doomsday clock to 100 seconds before midnight, closer than ever. It explained that it did it because of 3 factors:
The organization, praised the climate movement of young people and called to citizens and governments to act for solving the problems.

Miscellaneous

A number of other national scientific societies have also endorsed the opinion of the IPCC:

American Association of Petroleum Geologists

As of June 2007, the American Association of Petroleum Geologists Position Statement on climate change stated:
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:
AAPG President John Lorenz announced the "sunsetting" of AAPG's Global Climate Change Committee in January 2010. The AAPG Executive Committee determined:

American Institute of Professional Geologists (AIPG)

The official position statement from AIPG on the Environment states that "combustion of fossil fuel include and the generation of GHGs including carbon dioxide and methane. Emissions of GHGs are perceived by some to be one of the largest, global environmental concerns related to energy production due to potential effects on the global energy system and possibly global climate. Fossil fuel use is the primary source of the increased atmospheric concentration of GHGs since industrialization".
In March 2010, AIPG's Executive Director issued a statement regarding polarization of opinions on climate change within the membership and announced that the AIPG Executive had made a decision to cease publication of articles and opinion pieces concerning climate change in AIPG's news journal, The Professional Geologist.

Opposing

Since 2007, when the American Association of Petroleum Geologists released a revised statement, no national or international scientific body any longer rejects the findings of human-induced effects on climate change.

Surveys of scientists and scientific literature

Various surveys have been conducted to evaluate scientific opinion on global warming. They have concluded that the majority of scientists support the idea of anthropogenic climate change.
In 2004, the geologist and historian of science Naomi Oreskes summarized a study of the scientific literature on climate change. She analyzed 928 abstracts of papers from refereed scientific journals between 1993 and 2003 and concluded that there is a scientific consensus on the reality of anthropogenic 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. Seventy-five per cent of the abstracts were placed in the first three categories ; 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."
In 2007, Harris Interactive surveyed 489 randomly selected members of either the American Meteorological Society or the American Geophysical Union for the Statistical Assessment Service at George Mason University. 97% of the scientists surveyed agreed that global temperatures had increased during the past 100 years; 84% said they personally believed human-induced warming was occurring, and 74% agreed that "currently available scientific evidence" substantiated its occurrence. Catastrophic effects in 50–100 years would likely be observed according to 41%, while 44% thought the effects would be moderate and about 13 percent saw relatively little danger. 5% said they thought human activity did not contribute to greenhouse warming.
Dennis Bray and Hans von Storch conducted a survey in August 2008 of 2058 climate scientists from 34 different countries. A web link with a unique identifier was given to each respondent to eliminate multiple responses. A total of 373 responses were received giving an overall response rate of 18.2%. No paper on climate change consensus based on this survey has been published yet, but one on another subject has been published based on the survey.
The survey was made up of 76 questions split into a number of sections.
There were sections on the demographics of the respondents, their assessment of the state of climate science, how good the science is, climate change impacts, adaptation and mitigation, their opinion of the IPCC, and how well climate science was being communicated to the public.
Most of the answers were on a scale from 1 to 7 from "not at all" to "very much".
To the question "How convinced are you that climate change, whether natural or anthropogenic, is occurring now?", 67.1% said they very much agreed, 26.7% agreed to some large extent, 6.2% said to they agreed to some small extent, none said they did not agree at all. To the question "How convinced are you that most of recent or near future climate change is, or will
be, a result of anthropogenic causes?" the responses were 34.6% very much agree, 48.9% agreeing to a large extent, 15.1% to a small extent, and 1.35% not agreeing at all.
A poll performed by Peter Doran and Maggie Kendall Zimmerman at University of Illinois at Chicago received replies from 3,146 of the 10,257 polled Earth scientists. Results were analyzed globally and by specialization. 76 out of 79 climatologists who "listed climate science as their area of expertise and who also have published more than 50% of their recent peer-reviewed papers on the subject of climate change" believed that mean global temperatures had risen compared to pre-1800s levels. Seventy-five of 77 believed that human activity is a significant factor in changing mean global temperatures. Among all respondents, 90% agreed that temperatures have risen compared to pre-1800 levels, and 82% agreed that humans significantly influence the global temperature. Economic geologists and meteorologists were among the biggest doubters, with only 47 percent and 64 percent, respectively, believing in significant human involvement. The authors summarised the findings:
A 2010 paper in the Proceedings of the National Academy of Sciences of the United States reviewed publication and citation data for 1,372 climate researchers and drew the following two conclusions:
97–98% of the climate researchers most actively publishing in the field support the tenets of ACC outlined by the Intergovernmental Panel on Climate Change, and the relative climate expertise and scientific prominence of the researchers unconvinced of ACC are substantially below that of the convinced researchers.

A 2013 paper in Environmental Research Letters reviewed 11,944 abstracts of scientific papers matching "global warming" or "global climate change". They found 4,014 which discussed the cause of recent global warming, and of these "97.1% endorsed the consensus position that humans are causing global warming". This study was criticised in 2016 by Richard Tol, but strongly defended by a companion paper in the same volume.
A 2012 analysis of published research on global warming and climate change between 1991 and 2012 found that of the 13,950 articles in peer-reviewed journals, only 24 rejected anthropogenic global warming. A follow-up analysis looking at 2,258 peer-reviewed climate articles with 9,136 authors published between November 2012 and December 2013 revealed that only one of the 9,136 authors rejected anthropogenic global warming. His 2015 paper on the topic, covering 24,210 articles published by 69,406 authors during 2013 and 2014 found only five articles by four authors rejecting anthropogenic global warming. Over 99.99% of climate scientists did not reject AGW in their peer-reviewed research.
James Lawrence Powell reported in 2017 that using rejection as the criterion of consensus, five surveys of the peer-reviewed literature from 1991 to 2015, including several of those above, combine to 54,195 articles with an average consensus of 99.94%.
In November 2019, his survey of over 11,600 peer-reviewed articles published in the first seven months of 2019 showed that the consensus had reached 100%.

Existence of a scientific consensus

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