Although the vast majority of climate scientists have reached consensus on global warming, arguments against the science of climate change have been on the increase, according to new research conducted by political scientists at Trinity College Dublin and University of Exeter.

The research, recently published in the journal of Global Environmental Change, analyzed more than 16,000 publications about climate change produced by 19 major conservative think tanks in the US over the 15 year period from 1998-2013 – the largest study of such material to date.

Using methodological approaches from the fields of computer science and artificial intelligence, the study sheds light on the climate change related material being produced by North American conservative think tanks. The data suggest that the "era of climate change denial" is not over.

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The research involved an examination of 8,300 articles, 3,000 reports, 100 interview transcripts, 680 press releases and open letters and 3,900 “scientific” reviews over a 15 year period. It focused on 47 themes ranging from arguments against climate science and scientific integrity to policy-related topics such as emissions reductions and international agreements. The overall level of material being produced by conservative think tanks about this topic has grown rapidly over the past decade and a half, reaching a peak during late 2009–early 2010.

The era of climate science denial is not over. Conservative think-tanks have not shifted from questioning the science of climate change to focusing on policy debates. Rather, the data reveals that challenges to the science of climate change have been on the rise in recent years.

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Beginning in 2002, the researchers observed a steady rise in an emphasis on topics related to science and an attendant decline in policy-oriented themes. Discussion of scientific integrity began to overtake that of energy policy during 2006 and 2007—which corresponds to a period dominated by Al Gore’s “An Inconvenient Truth” and his acceptance of the Nobel Peace Prize—and proceeded to become relatively more prevalent in the post-“climategate” era.

Dr Constantine Boussalis, Assistant Professor in Political Science, Trinity, commented: “Our data suggest that the era of climate change denial is not over. If anything, challenges to the science of climate change have been on the rise in recent years. While the level of uncertainty surrounding the causes and consequences of climate change has decreased, the emphasis on climate science skepticism by conservative think tanks has increased over time. This is a disturbing trend, as a general acceptance of human-caused global warming is a necessary condition for a comprehensive agreement on climate change mitigation.”

Dr Travis Coan, Lecturer in Quantitative Political Science, Exeter University, added: "The vast majority of climate scientists agree that the earth is warming and that observed changes in the global climate are predominantly attributable to human activity. Nevertheless, a significant segment of the American public and many lawmakers in the US Congress continue to deny this reality. With the support of industry groups, fossil fuel interests, and conservative foundations, conservative think tanks have played a crucial role in generating the narrative of climate change skepticism and, by extension, obstructing climate policy in the United States."

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