The myth of the 97% climate change consensus
By Joseph Bast and Roy Spencer
Recently Secretary of State John Kerry warned graduating Boston College students that climate change would have "crippling consequences." Indeed, he added, "Ninety-seven percent of the world's scientists tell us this is urgent."
Where did Mr. Kerry get his 97% figure? Perhaps from his boss, President Obama, who tweeted on May 16 that "Ninety-seven percent of scientists agree: #climate change is real, man-made and dangerous." Or maybe from NASA, which posted (in more measured language) on its website, "Ninety-seven percent of climate scientists agree that climate-warming trends over the past century are very likely due to human activities."
In reality, the assertion that 97% of scientists believe that climate change is a man-made, urgent problem is science fiction. The so-called consensus comes from a handful of surveys and exercises in counting abstracts from scientific papers – all of which have been contradicted by more reliable research.
One frequently cited source for the consensus is a 2004 opinion essay published in Science magazine by Naomi Oreskes, a science historian now at Harvard. She claimed to have examined abstracts of 928 articles published in scientific journals between 1993 and 2003, and to have found that 75% supported the view that human activities are responsible for most of the observed warming over the previous 50 years, while none directly dissented.
Ms. Oreskes's definition of consensus covered "man-made" influences but left out "dangerous" – and excluded scores of articles by prominent scientists such as Richard Lindzen, John Christy, Sherwood Idso and Patrick Michaels, who question the consensus. Her methodology is also flawed. A study published earlier this year in the journal Naturenoted that abstracts of academic papers often contain claims that aren't substantiated in the papers – but she failed to acknowledge or address this.
Another widely cited source for the consensus view is a 2009 article in Eos: Transactions of the American Geophysical Union, by Maggie Kendall Zimmerman, a student at the University of Illinois, and her master's thesis adviser Peter Doran. It reported the results of a two-question online survey of selected scientists. Mr. Doran and Ms. Zimmerman claimed "97 percent of climate scientists agree" that global temperatures have risen, and that humans are a significant contributing factor.
The survey's questions don't reveal much of interest. Most scientists who are skeptical of man-made catastrophic global warming would nevertheless answer "yes" to both questions. However, the survey was silent on whether the human impact – or the rise in temperature – is large enough to constitute a problem. It also failed to include solar scientists, space scientists, cosmologists, physicists, meteorologists or astronomers, who are the scientists most likely to be aware of natural causes of climate change.
The "97 percent" figure in the Zimmerman/Doran survey represents the views of only 79 respondents who listed climate science as an area of expertise and said they published more than half of their recent peer-reviewed papers on climate change. Seventy-nine scientists out of the 3,146 who responded to the survey – or out of the 10,257 scientists who received it – does not a consensus make.
In 2010, William R. Love Anderegg, then a student at Stanford University, used Google Scholar to identify the views of the most prolific writers on climate change. His findings were published in Proceedings of the National Academies of Sciences. Mr. Love Anderegg found that 97% to 98% of the 200 most prolific writers on climate change believe "anthropogenic greenhouse gases have been responsible for ‘most' of the ‘unequivocal' warming." There was no mention of how dangerous this climate change might be; and, of course, 200 researchers out of the thousands who have contributed to the climate science debate is not evidence of consensus.
In 2013, John Cook, an Australia-based blogger, and some of his friends reviewed abstracts of peer-reviewed papers published from 1991 to 2011. Mr. Cook reported that 97% of those who stated a position explicitly or implicitly suggest that human activity is responsible for some warming. [emphasis added] His findings were published in Environmental Research Letters.
Mr. Cook's work was quickly debunked. In the August 2013 Science and Education, for example, David R. Legates (a professor of geography at the University of Delaware and former director of its Center for Climatic Research) and three coauthors reviewed the same papers as Mr. Cook did. They found that "only 41 papers – 0.3% of all 11,944 abstracts or 1.0% of the 4,014 expressing an opinion, and not 97.1% – had been found to endorse" the claim that human activity is causing most of the current warming.
Elsewhere, Craig Idso, Nicola Scafetta, Nir J. Shaviv and Nils-Axel Morner and other climate scientists protested that Mr. Cook ignored or misrepresented their work. In each case, their research questions or contradicts the alleged consensus.
Rigorous international surveys conducted by German scientists Dennis Bray and Hans von Storch – most recently published in Environmental Science & Policy in 2010 – have found that most climate scientists disagree with the alleged consensus on various key issues, such as the reliability of climate data and computer models. They also do not believe climate processes like cloud formation and precipitation are sufficiently understood to enable accurate predictions of future climate change.
Surveys of meteorologists repeatedly find a majority oppose or disagree with the alleged consensus. Only 39.5% of 1,854 American Meteorological Society members who responded to a survey in 2012 said man-made global warming is dangerous.
Finally, the UN's Intergovernmental Panel on Climate Change – which claims to speak for more than 2,500 scientists – is probably the most frequently cited source for the asserted consensus. Its latest report claims that "human interference with the climate system is occurring, and climate change poses risks for human and natural systems." Yet relatively few have either written about or reviewed research having to do with the key questions: How much of the temperature increase and other climate changes observed in the twentieth century were caused by man-made greenhouse-gas emissions – and how serious are the risks? The IPCC lists only 41 authors and editors of the relevant chapter of the Fifth Assessment Report addressing "anthropogenic and natural radiative forcing." What about the views of other experts?
Of the various petitions on global warming circulated for signatures by scientists, the one by the Petition Project, a group of physicists and physical chemists based in La Jolla, California, has by far the most signatures: more than 31,000 (more than 9,000 of whom have PhDs). It was most recently published in 2009, and most signers were added or reaffirmed since 2007. The petition states that "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."
We could go on, but the larger point is plain. There is no basis for the claim that 97% of scientists believe that man-made climate change is a dangerous problem.
Mr. Bast is president of the Heartland Institute. Dr. Spencer is a principal research scientist for the University of Alabama in Huntsville and the U.S. Science Team Leader for the Advanced Microwave Scanning Radiometer on NASA's Aqua satellite.A version of this article appeared in the Wall Street Journal on May 26, 2014. It is based on a longer Research and Commentary article: http://heartland.org/policy-documents/research-commentary-myth-global-warming-consensus