Climate Change Consensus Tracked


A 2012 poll found that 43 percent of Americans believe scientists disagree on whether climate change is caused by human activities. A new study emphasizes just how wrong they were. Not only is there scientific consensus on the causes of greenhouse warming, there’s near-unanimity.

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The study – written by a team led by John Cook of the University of Queensland Climate Change Institute and founder of the website Skeptical Science - began with a keyword search of scientific journal papers published between 1991 and 2011 for the terms ‘global warming’ and ‘global climate change.’ That search returned 12,465 papers. Eliminating papers that weren’t peer-reviewed, not climate-related, or without an abstract reduced that figure to 11,944. A team of 24 volunteers then analyzed the abstracts of each of those 11,944 papers, with each abstract being reviewed independently by two analysts.

Almost 8,000 of those abstracts expressed no opinion on human-caused global warming. Of the rest, 40 (0.3%) expressed uncertainty on the cause of climate change; 78 (0.7%) rejected a human cause for global warming; and fully 3,896 (97.1%) endorsed the theory that climate change is the result of human activities such as burning fossil fuels.

The team then contacted 8,500 of the authors of those papers, asking them to rate their own papers; the responses closely matched the independent analysis, with 97.2 percent of the papers that took a position on the subject being rated by their own authors as supporting the notion of human-caused global warming.

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These figures very closely track the findings of similar previous studies, although this latest research, published in the open-access online journal Environmental Research Letters, used a far larger sample set than earlier papers. In the interests of transparency and spreading the word, the full analysis is being made available on a website,, complete with supporting and explanatory graphics.

The study may even understate the level of consensus. As Cook and co-author Dana Nuccitelli note in a blog post on Skeptical Science, the fact that 8,000 or so abstracts were excluded from the analysis because they didn’t express an opinion on the human factor in climate change doesn’t mean that two-thirds of climate science papers are ambivalent on the subject. “Frankly, every scientist doing climate research knows humans are causing global warming,” they write. “There’s no longer a need to state something so obvious. For example, would you expect every geological paper to note in its abstract that the Earth is a spherical body that orbits the sun?”

IMAGE: Mantoloking, N.J., devastated by Superstorm Sandy, remains a disaster zone sixth months after the storm. The process of removing totaled homes started recently and will pick up this month as more permits for demolition are issued. (Julie Dermansky/Corbis)

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