A new study of the scientific literature confirms that there is a robust consensus that humans are causing global warming. The paper — John Cook, Dana Nuccitelli, Sarah A. Green, Mark Richardson, Bärbel Winkler, Rob Painting, Robert Way, Peter Jacobs, and Andrew Skuce's "Quantifying the consensus on anthropogenic global warming in the scientific literature," Environmental Research Letters 2013; 8(2):024024 — is freely available on-line.
The study examined almost twelve thousand abstracts of scientific articles published between 1991 and 2011 on the topics "global climate change" or "global warming," and found that "66.4% of abstracts expressed no position on AGW, 32.6% endorsed AGW, 0.7% rejected AGW and 0.3% were uncertain about the cause of global warming. Among abstracts expressing a position on AGW, 97.1% endorsed the consensus position that humans are causing global warming."
The study confirmed, as well as refined and extended, previous work by Naomi Oreskes and James Lawrence Powell investigating the consensus in the scientific literature; it is also consistent with surveys of climate scientists, such as William R. L. Anderegg, James W. Prall, Jacob Harold, and Stephen H. Schneider's paper (in Proceedings of the National Academy of Sciences 2011), that show a similar percentage accepting the consensus position.
In contrast, polling suggests that the American public is largely unaware, or unwilling to acknowledge, that there is a scientific consensus about human responsibility for global climate change. In 2012, for example, a Pew Research Center poll asked (PDF, p. 3), "Do scientists agree earth is getting warmer because of human activity?" A slight plurality of the respondents, 45%, answered yes, while 43% answered no and 12% said that they didn't know.
The study's lead author John Cook commented, in a May 15, 2013, press release, "Our findings prove that there is a strong scientific agreement about the cause of climate change, despite public perceptions to the contrary. ... It's staggering given the evidence for consensus that less than half of the general public think scientists agree that humans are causing global warming." The Consensus Project website contains a wealth of further information about the study.
The study was widely applauded. Naomi Oreskes told the Guardian (May 15, 2013), "It is a nice, independent confirmation, using a somewhat different methodology than I used, that comes to the same result. It also refutes the claim, sometimes made by contrarians, that the consensus has broken down, much less 'shattered'." And as the Sydney Morning Herald (May 17, 2013) noted, President Obama drew it to the attention of his 31-million-plus audience on Twitter.