Policy Documents

Research & Commentary: The Myth of a Global Warming Consensus

May 14, 2014

Many legislators are told they must enact climate change legislation because an alleged “scientific consensus” holds that man-made climate change requires urgent action. They are repeatedly told “97 percent of climate scientists agree” that human activities are causing dangerous climate change, and that the only way to prevent this disaster from occurring is to adopt government policies that raise the price of fossil fuels and subsidize or mandate the use of alternatives such as wind and solar energy. But what evidence is there for such unanimity? What do scientists really say?

The United Nations’ Intergovernmental Panel on Climate Change (IPCC) claims to represent more than 2,500 scientists who agree that man-made global warming is a serious problem. But this is misleading. While a total of 2,500 (or some similar number) scientists participate in some way in the writing or review of its reports, the IPCC’s working group responsible for assessing the causes of climate change and its future trajectory consists of only about 600 scientists, and many of those are activists working for environmental interest groups. For the Fourth Assessment Report, only 62 were responsible for reviewing the chapter that attributed climate change to man-made greenhouse gas emissions, with 55 of those being known advocates of the theory of man-made global warming. Of the seven impartial reviewers, two disagreed with the statement, leaving only five credible scientific reviewers who unequivocally endorse the IPCC’s conclusion, a far cry from 2,500.

In 2004, science historian Naomi Oreskes wrote an essay for the journal Science that examined abstracts from 928 papers reported by the Institute for Scientific Information database published in scientific journals from 1993 and 2003, using the key words “global climate change.” She concluded 75 percent of the abstracts either implicitly or explicitly supported the IPCC’s view that human activities are responsible for most of the observed warming over the previous 50 years while none directly dissented. Oreskes’ essay, which was not peer-reviewed, became the basis of a book (Merchants of Doubt)and an academic career built on claiming that global warming “skeptics” were a tiny minority within the scientific community. Her claim appeared in former Vice President Al Gore’s movie, An Inconvenient Truth.

Oreskes’ definition of consensus is silent on whether man-made climate change is dangerous or benign and her literature review inexplicably overlooked scores of articles by prominent global warming skeptics including John Christy, Sherwood Idso, Richard Lindzen, and Patrick Michaels. More than 1,300 such articles are now identified in an online bibliography at populartechnology.net.

Anthropologist Benny Peiser attempted to replicate Oreskes’ findings and found only one-third of the papers endorsed the alarmist view and only 1 percent did so explicitly. In 2008, medical researcher Klaus-Martin Schulte used the same database and search terms as Oreskes to examine papers published from 2004 to February 2007 and found fewer than half endorsed the “consensus” and only 7 percent did so explicitly. Schulte counted 31 papers (6 percent of the sample) that explicitly or implicitly rejected the “consensus.” Finally, Oreskes’ methodology assumes the abstracts of papers accurately reflect their findings, an assumption proven false by In-Uck Park et al. in research published in Nature in 2014.

In 2009, a paper by Doran and Zimmerman published in EOS claimed “97 percent of climate scientists agree” that mean global temperatures have risen since before the 1800s and that humans are a significant contributing factor. This study, too, has been debunked. The survey asked the wrong questions. Most scientists who are skeptical of catastrophic global warming also support those statements. The survey was silent on whether or not the human impact was large enough to constitute a problem or would cause a problem in the future. Moreover, the “97 percent” figure represents the views of only 79 of the 3,146 respondents who listed climate science as an area of expertise and said they published more than 50 percent of their recent peer-reviewed papers on climate change. This is not evidence of consensus.

In 2010, a paper by William Anderegg et al. published in Proceedings of the National Academies of Sciences claimed “97–98 percent of climate researchers most actively publishing in the field support the tenets of ACC [anthropogenic climate change] outlined by the Intergovernmental Panel on Climate Change.” Actually, the authors found that 97 to 98 percent of the most prolific 200 climate researchers (not necessarily scientists) say they believe “anthropogenic greenhouse gases have been responsible for ‘most’ of the ‘unequivocal’ warming of the Earth’s average global temperature over the second half of the 20th century.”

The views of 200 researchers out of the thousands of earth scientists who have contributed to the climate science debate is not evidence of consensus, and may instead be evidence of editorial bias in favor of a small clique of writers who have come to dominate the peer-review processes of science journals. Once again, the authors did not ask if authors believe global warming is a serious problem or if science is sufficiently established to be the basis for public policy. Anyone who cites this study as evidence of scientific support for such views is misrepresenting the paper.

In 2013, a paper by Cook et al. published in Environmental Research Letters claimed their review of the abstracts of peer-reviewed papers from 1991 to 2011 found 97 percent of those that stated a position explicitly or implicitly suggesting that human activity is responsible for some warming. This exercise in abstract counting doesn’t support the alarmist claim that climate change is both man-made and dangerous, and doesn’t even support the IPCC’s claim that a majority of global warming in the 20th century was man-made.

This study was quickly debunked by a paper by Legates et al. published in Science & Education. Legates et al. found “just 0.03 percent endorsement of the standard definition of consensus: that most warming since 1950 is anthropogenic.” They found “only 41 papers – 0.3 percent of all 11,944 abstracts or 1.0 percent of the 4,014 expressing an opinion, and not 97.1 percent – had been found to endorse the standard or quantitative hypothesis.” Scientists whose work questions the consensus, including Craig Idso, Nils-Axel Morner, Nicola Scafetta, and Nir J. Shaviv, protested that Cook misrepresented their work. Richard Tol, a lead author of the United Nations’ IPCC reports, said of the Cook report, “the sample of papers does not represent the literature. That is, the main finding of the paper is incorrect, invalid and unrepresentative.”

In striking contrast to these studies, which try but fail to find a consensus in support of the claim that global warming is man-made and dangerous, many authors and surveys have found disagreement and even a majority of scientists oppose the alleged consensus. Surveys by German scientists Dennis Bray and Hans von Storch have found that most scientists disagree with the consensus on key issues such as the reliability of climate data and computer models and do not believe key climate processes such as cloud formation and precipitation are adequately understood to predict future climate changes.

Surveys of meteorologists, including one by the American Meteorological Society of its members conducted in 2012, find a majority oppose the alleged consensus. Of the various petitions circulated for signatures by scientists on the global warming issue, the one that has garnered by far the most signatures – more than 31,000 names – says “there is no convincing scientific evidence that human release of carbon dioxide, methane, or other greenhouse gases is causing or will, in the foreseeable future, cause catastrophic heating of the Earth’s atmosphere and disruption of the Earth’s climate.”

Even prominent “alarmists” in the climate change debate admit there is no consensus. Phil Jones, director of the Climatic Research Unit at the University of East Anglia, when asked if the debate on climate change is over, told the BBC, “I don’t believe the vast majority of climate scientists think this. This is not my view.” Mike Hulme, also a professor at the University of East Anglia and a contributor to IPCC reports, wrote in 2009: “What is causing climate change? By how much is warming likely to accelerate? What level of warming is dangerous? - represent just three of a number of contested or uncertain areas of knowledge about climate change.”

As this summary makes apparent, there is no survey or study that supports the claim of a scientific consensus that global warming is both man-made and a problem, and ample evidence to the contrary. There is no scientific consensus on global warming.

The following documents provide additional information about the so-called global warming consensus. 

The UN Climate Change Numbers Hoax
In this 2007 article, climate researcher John McLean and International Climate Science Coalition Executive Director Tom Harris systematically take apart the claim that “2,500 scientist reviewers” support the IPCC’s claim that man-made global warming is a serious problem.

1350+ Peer-Reviewed Papers Supporting Skeptic Arguments Against ACC/AGW Alarm
PopularTechnology.net presents a bibliography of more than 1,350 peer-reviewed papers that support arguments skeptical of alarmism over anthropogenic climate change (ACC) or anthropogenic global warming. 

Scientific Consensus on Climate Change?
Medical researcher Klaus-Martin Schulte used the same database and search terms as Oreskes to examine papers published from 2004 to February 2007 and found fewer than half endorsed the “consensus” and only 7 percent did so explicitly. Schulte counted 31 papers (6 percent of the sample) that explicitly or implicitly rejected the “consensus.” His findings were published in the peer-reviewed journal Energy & Environment, 19 (2) (2008).

Modelling the Effects of Subjective and Objective Decision Making in Scientific Peer Review
A 2014 paper published in Nature explains how scientists converge on false conclusions, summarizing research on publication bias, careerism, data fabrication, and fraud. The authors also find “a mismatch between the claims made in the abstracts, and the strength of evidence for those claims based on a neutral analysis of the data, consistent with the occurrence of herding.”

The Myth of the 98 Percent
Heartland Institute President Joseph Bast critiques articles by Doran and Zimmerman (2009) and Anderegg et al. (2010) and explains why global warming alarmists publish more than skeptics, rendering abstract-counting exercises unreliable and misleading. 

“Consensus?” What “Consensus”? Among Scientists, the Debate is Not Over
This 2007 report published by the Science and Public Policy Institute rebuts Naomi Orestes and the IPCC as reliable sources of the alleged “consensus” of scientists.

AMS Survey Shows No Consensus on Global Warming
In this September 2013 Heartland Institute Policy Brief, Heartland Institute President Joseph Bast examines an American Meteorological Survey of its members that revealed only 39.5 percent of those who responded said they believed manmade global warming is dangerous.

You Call This Consensus?
Heartland Institute President Joseph Bast, in a 2011 paper, examines the claim of a scientific “consensus” that humans are the primary cause of catastrophic climate change. Bast traces the origins of such claims and finds they are often conflicted, disingenuous, and patently false. 

Consensus? What Consensus?
This 2013 report by Andrew Montford, published by the Global Warming Policy Foundation, examines the paper by Cook et al. and concludes “the consensus referred to is trivial” since the paper “said nothing about global warming being dangerous” and that “the project was not a scientific investigation to determine the extent of agreement on global warming, but a public relations exercise.” 

97 Percent Consensus? No! Global Warming Math Myths & Social Proofs
This 2014 paper from Friends of Science, a Canadian public policy group, closely examines five  studies that seek to establish a scientific consensus on the causes and consequences of climate change and finds mathematical errors and in some cases, manipulation. “The deconstruction of the surveys that follow shows the claim of a 97 percent consensus is pure spin and ‘statisticulation’ – mathematical manipulation.” 

97% Study Falsely Classifies Scientists' Papers, according to the scientists that published them
The author contacted a sample of scientists whose papers were used in the report by Cook et al. (2013) and asked them if their papers were accurately represented. Craig Idso, Nils-Axel Morner, Nicola Scafetta, and Nir J. Shaviv protested that their work had been misrepresented.

IPCC Lead Author Reports Flaws in Asserted 97-Percent Consensus
Richard Tol, a lead author of the United Nations’ IPCC reports, says the study by Cook et al. claiming 97 percent of peer-reviewed studies on climate agree “humans are causing global warming” is riddled with procedural errors. 

Analysis: New International Survey of Climate Scientists
In a September 2010 Heartland Institute Policy Brief, Heartland Institute President Joseph Bast examines the latest international survey of climate scientists conducted by German scientists Dennis Bray and Hans von Storch, and finds scientific opinion to be deeply divided on some two-thirds of the questions asked about the underlying science. Approximately half of scientists dissent from the assumptions and predictions presented in the reports of the United Nations’ IPCC. 

Scientific Consensus on Global Warming
Heartland Institute senior fellow James Taylor and President Joseph Bast calculated and reported the average responses to every question in international surveys of climate scientists conducted by Bray and von Storch in 1996 and 2003 and then singled out 18 questions from the 2003 survey and presented the answers here in a simplified and less academic style. The results reveal a lack of consensus on the most important questions in the climate change debate.

31,072 American Scientists Say There Is No Climate Crisis
The Petition Project, an independent initiative to identify the amount of support for or opposition to claims that man-made global warming is a serious problem, has collected more than 31,000 signatures by American scientists on a petition stating, “there is no convincing scientific evidence that human release of carbon dioxide, methane, or other greenhouse gases is causing or will, in the foreseeable future, cause catastrophic heating of the Earth’s atmosphere and disruption of the Earth’s climate.” This 2009 document presents background on the Petition Project and a directory of the signers. 

Q&A: Prof. Phil Jones
In the wake of the Climategate scandal in February, 2010, the BBC's environment analyst Roger Harrabin put a series of questions to Professor Phil Jones, director of the Climatic Research Unit (CRU) at the University of East Anglia (UEA). Jones confessed “for the two periods 1910-40 and 1975-1998 the warming rates are not statistically significantly different,” that “from 1995 to the present there has been no statistically-significant global warming,” and when asked, “When scientists say "the debate on climate change is over", what exactly do they mean - and what don't they mean?” he replied, “I don’t believe the vast majority of climate scientists think this. This is not my view. There is still much that needs to be undertaken to reduce uncertainties, not just for the future, but for the instrumental (and especially the palaeoclimatic) past as well.”

A Truly Disturbing Look at Why Global Warming Alarmists Lie about the Science
This 2009 review of Why We Disagree About Climate Change: Understanding Controversy, Inaction and Opportunity (Cambridge University Press, 2009) highlights some of the astonishing admissions made by one of the leading spokespersons for global warming alarmism. For example, he writes, "Uncertainty pervades scientific predictions about the future performance of global and regional climates. And uncertainties multiply when considering all the consequences that might follow from such changes in climate." (p. 83) On the subject of the IPCC's credibility, he admits “the Panel was not to be a self-governing body of independent scientists." (p. 95)

Nothing in this Research & Commentary is intended to influence the passage of legislation, and it does not necessarily represent the views of The Heartland Institute. For further information on this and other topics, visit the Environment & Climate News Web site at http://news.heartland.org/energy-and-environment, The Heartland Institute’s Web site at http://www.heartland.org, and PolicyBot, Heartland’s free online research database, at www.policybot.org.

If you have any questions about this issue or The Heartland Institute, contact Heartland Institute Policy Analyst Taylor Smith at tsmith@heartland.org or 312/377-4000.