Tuesday, February 18, 2014

PNAS, Proceedings of the National Academy of Sciences, ACC, Anthropogenic Climate Change, Global Warming, Survey, 97%

2010 PNAS Survey

Abstract:
Although preliminary estimates from published literature and expert surveys suggest striking agreement among climate scientists on the tenets of anthropogenic climate change (ACC), the American public expresses substantial doubt about both the anthropogenic cause and the level of scientific agreement underpinning ACC. A broad analysis of the climate scientist community itself, the distribution of credibility of dissenting researchers relative to agreeing researchers, and the level of agreement among top climate experts has not been conducted and would inform future ACC discussions. Here, we use an extensive dataset of 1,372 climate researchers and their publication and citation data to show that (i) 97–98% of the climate researchers most actively publishing in the field support the tenets of ACC outlined by the Intergovernmental Panel on Climate Change, and (ii) the relative climate expertise and scientific prominence of the researchers unconvinced of ACC are substantially below that of the convinced researchers.

Authors:
William R. L. Anderegg --- Department of Biology, Stanford University
James W. Prall --- Electrical and Computer Engineering, University of Toronto
Jacob Harold --- William and Flora Hewlett Foundation in Palo Alto, CA
Stephen H. Schneider --- Department of Biology & Woods Institute for the Environment, Stanford University


Excerpts from the survey:

"We compiled a database of 1,372 climate researchers based on authorship of scientific assessment reports and membership on multisignatory statements about ACC...

Between December 2008 and July 2009, we collected the number of climate-relevant publications for all 1,372 researchers from Google Scholar (search terms: "author:fi-lastname climate")...


We compiled a database of 1,372 climate researchers and classified each researcher into two categories: convinced by the evidence (CE) for anthropogenic climate change (ACC) or unconvinced by the evidence (UE) for ACC. We defined CE researchers as those who signed statements broadly agreeing with or directly endorsing the primary tenets of the IPCC Fourth Assessment Report that it is "very likely" that anthropogenic greenhouse gases have been responsible for most of the unequivocal warming of the Earth's average global temperature in the second half of the 20th century...

We then imposed an a priori criterion that a researcher must have authored a minimum of 20 climate publications to be considered a climate researcher, thus reducing the database to 908 researchers...

We ranked researchers based on the total number of climate publications authored. Though our compiled researcher list is not comprehensive nor designed to be representative of the entire climate science community, we have drawn researchers from the most high-profile reports and public statements about ACC...

The UE [those unconvinced by the ACC evidence] group comprises only 2% of the top 50 climate researchers as ranked by expertise (number of climate publications), 3% of researchers of the top 100, and 2.5% of the top 200, excluding researchers present in both groups...

Regarding the influence of citation patterns, we acknowledge that it is difficult to quantify potential biases of self-citation or clique citation in the analysis presented here...

Ultimately, of course, scientific confidence is earned by the winnowing process of peer review and replication of studies over time. In the meanwhile, climate science, we must seek estimates while confidence builds. Based on the arguments presented here, we believe our findings capture the differential climate science credentials of the two groups."