This is a guest post by James Lawrence Powell.*



Polls show that many members of the public believe that scientists substantially disagree about human-caused global warming. The gold standard of science is the peer-reviewed literature. If there is disagreement among scientists, based not on opinion but on hard evidence, it will be found in the peer-reviewed literature.

I searched the Web of Science for peer-reviewed scientific articles published between 1 January 1991 and 9 November 2012 that have the keyword phrases “global warming” or “global climate change.” The search produced 13,950 articles. See methodology.





I read whatever combination of titles, abstracts, and entire articles was necessary to identify articles that “reject” human-caused global warming. To be classified as rejecting, an article had to clearly and explicitly state that the theory of global warming is false or, as happened in a few cases, that some other process better explains the observed warming. Articles that merely claimed to have found some discrepancy, some minor flaw, some reason for doubt, I did not classify as rejecting global warming. Articles about methods, paleoclimatology, mitigation, adaptation, and effects at least implicitly accept human-caused global warming and were usually obvious from the title alone. John Cook and Dana Nuccitelli also reviewed and assigned some of these articles; John provided invaluable technical expertise.

This work follows that of Oreskes (Science, 2005) who searched for articles published between 1993 and 2003 with the keyword phrase “global climate change.” She found 928, read the abstracts of each and classified them. None rejected human-caused global warming. Using her criteria and time-span, I get the same result. Deniers attacked Oreskes and her findings, but they have held up.

Some articles on global warming may use other keywords, for example, “climate change” without the “global” prefix. But there is no reason to think that the proportion rejecting global warming would be any higher.

By my definition, 24 of the 13,950 articles, 0.17% or 1 in 581, clearly reject global warming or endorse a cause other than CO2 emissions for observed warming. The list of articles that reject global warming is here. The 24 articles have been cited a total of 113 times over the nearly 21-year period, for an average of close to 5 citations each. That compares to an average of about 19 citations for articles answering to “global warming,” for example. Four of the rejecting articles have never been cited; four have citations in the double-digits. The most-cited has 17.

Of one thing we can be certain: had any of these articles presented the magic bullet that falsifies human-caused global warming, that article would be on its way to becoming one of the most-cited in the history of science.

The articles have a total of 33,690 individual authors. The top ten countries represented, in order, are USA, England, China, Germany, Japan, Canada, Australia, France, Spain, and Netherlands. (The chart shows results through 9 November 2012.)

Global warming deniers often claim that bias prevents them from publishing in peer-reviewed journals. But 24 articles in 18 different journals, collectively making several different arguments against global warming, expose that claim as false. Articles rejecting global warming can be published, but those that have been have earned little support or notice, even from other deniers.

A few deniers have become well known from newspaper interviews, Congressional hearings, conferences of climate change critics, books, lectures, websites and the like. Their names are conspicuously rare among the authors of the rejecting articles. Like those authors, the prominent deniers must have no evidence that falsifies global warming.

Anyone can repeat this search and post their findings. Another reviewer would likely have slightly different standards than mine and get a different number of rejecting articles. But no one will be able to reach a different conclusion, for only one conclusion is possible: Within science, global warming denial has virtually no influence. Its influence is instead on a misguided media, politicians all-too-willing to deny science for their own gain, and a gullible public.

Scientists do not disagree about human-caused global warming. It is the ruling paradigm of climate science, in the same way that plate tectonics is the ruling paradigm of geology. We know that continents move. We know that the earth is warming and that human emissions of greenhouse gases are the primary cause. These are known facts about which virtually all publishing scientists agree.

Jim Powell is a science author. He has been a college and museum president and was a member of the National Science Board for 12 years, appointed first by President Reagan and then by President George H. W. Bush.

* The original version has been updated to note one additional paper.