3.04.2019

Disabusing the 97% claim




Fact Checking The Claim Of 97% Consensus On Anthropogenic Climate Change

Excerpt:

The 97% figure has been disputed and vigorously defended, with emotional arguments and counterarguments published in a number of papers. Although the degree of consensus is only one of several arguments for anthropogenic climate change – the statements of professional societies and evidence presented in reports from the Intergovernmental Panel on Climate Change are others – there is data to suggest that support is lower. In this post, I attempt to determine whether the 97% consensus is fact or fiction.

The 97% number was popularized by two articles, the first by Naomi Oreskes, now Professor of Science History and Affiliated Professor of Earth and Planetary Sciences at Harvard University, and the second by a group of authors led by John Cook, the Climate Communication Fellow for the Global Change Institute at The University of Queensland. Both papers were based on analyses of earlier publications. Other analyses and surveys arrive at different, often lower, numbers depending in part on how support for the concept was defined and on the population surveyed.

This public discussion was started by Oreskes’ brief 2004 article, which included an analysis of 928 papers containing the keywords “global climate change.” The article says “none of the papers disagreed with the consensus position” of anthropogenic global warming. Although this article makes no claim to a specific number, it is routinely described as indicating 100% agreement and used as support for the 97% figure.

In a 2007 book chapter, Oreskes infers that the lack of expressed dissent “demonstrates that any remaining professional dissent is now exceedingly minor.” The chapter revealed that there were about 235 papers in the 2004 article, or 25%, that endorsed the position. An additional 50% were interpreted to have implicitly endorsed, primarily on the basis that they discussed evaluation of impacts. Authors addressing impacts might believe that the Earth is warming without believing it is anthropogenic. In the article, Oreskes said some authors she counted "might believe that current climate change is natural." It is impossible to tell from this analysis how many actually believed it. On that basis, I find that this study does not support the 97% number.

The most influential and most debated article was the 2013 paper by Cook, et al., which popularized the 97% figure. The authors used methodology similar to Oreskes but based their analysis on abstracts rather than full content. I do not intend to reopen the debate over this paper. Instead, let’s consider it along with some of the numerous other surveys available.

Reviews of published surveys were published in 2016 by Cook and his collaborators and by Richard S. J. Tol, Professor of Economics at the University of Sussex. The 2016 Cook paper, which reviews 14 published analyses and includes among its authors Oreskes and several authors of the papers shown in the chart below, concludes that the scientific consensus “is robust, with a range of 90%–100% depending on the exact question, timing and sampling methodology.” The chart shows the post-2000 opinions summarized in Table 1 of the paper. Dates given are those of the survey, not the publication date. I’ve added a 2016 survey of meteorologists from George Mason University and omitted the Oreskes article.

... Despite the difficulty in defining a precise number and the opinion that the exact number is not important, 97% continues to be widely publicized and defended. One might ask why 97% is important. Perhaps it’s because 97% has marketing value. It sounds precise and says that only 3% disagree. By implication, that small number who disagree must be out of the mainstream: cranks, chronic naysayers, or shills of the fossil fuel industry. They are frequently described as a “tiny minority.” It’s not as easy to discount dissenters if the number is 10 or 15 percent.

Comment: It's repeated so much ...

From 1989:



1 comment:

  1. My take is that a century ago, probably 97% of scientists believed in the luminiferous aether, and took Mickelson seriously when he, at the opening of the U. of Chicago's Ryerson Physics laboratory, said that future discoveries would be in the fifth decimal place. A little bit earlier, similar majorities believed in caloric as the mechanism of heat, and a few centuries earlier, all the smart people save Newton believed in Aristotelian physics.

    Really, it's just an appeal to authority fallacy that proves nothing but that those making it are unwilling, or unable, to make a real argument. Now that's a nice little confession on their part.

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