A fairly convoluted (but interesting none the less) paper just got published in PNAS by Anderegg et al (2010) looking at climate change and scientific credibility (more coverage by the Guardian here). Why don’t we trust climate scientists? To answer this question, the authors conducted a literature search of 1,372 climate researchers whose work “constitutes expertise or credibility in technical and policy-relevant scientific research”, and conclude what we’ve been blogging here for some time: “Despite media tendencies to present both sides in debates, which can contribute to continued public misunderstanding,not all climate researchers are equal in scientific credibility and expertise in the climate system”
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.
Here’s the nuts and bolts of the paper (CE = convinced by the evidence, UE = unconvinced by the evidence):
So: not only is there a pretty considerable difference between the number of expert researchers between CE and UE groups, the mean expertise of the UE group was around half (60 publications) that of the CE group (119 publications). Here’s the real interesting statistic: researchers with fewer than 20 climate publications comprise ≈80% the UE group, as opposed to less than 10% of the CE group. To quote the authors: “This indicates that the bulk of UE researchers on the most prominent multisignatory statements about climate change have not published extensively in the peer-reviewed climate literature.”
From a subsample of the 50 most-published researchers from each group, there was a considerable difference in relative expertise between the CE and UE groups:
Of these top 50 researchers, the CE group have an average of 408 climate publications, whilst the UE researchers averaged only 89 publications. Again, to quote the authors. “this suggests that not all experts are equal, and top CE researchers have much stronger expertise in climate science than those in the top UE group“.
So who’s citing who? Anderegg et al use citation metrics to determine “…the quality and impact of a researcher’s contribution—a critical component to overall scientific credibility—as opposed to measuring a researcher’s involvement in a field, or expertise“. In examining the top four most-cited papers for each CE and UE researcher with 20 or more climate publications, the disparity in citation metrics between the CE and UE groups is astonishing:
(i) 97–98% of the climate researchers most actively publishing in the field support the tenets of Anthropogenic Climate Change (ACC) outlined by the Intergovernmental Panel on Climate Change
(ii) the relative climate expertise and scientific prominence of the researchers unconvinced of ACC are substantially below that of the convinced researchers.
As Phil M commented on a post the other day, the UE group:
1) Also happen to have close ties to fossil fuel & mining industries.
2) Have ties to right wing lobby groups.
3) Have only a handful of scientists who back the denier side, of whom few have published or conducted research in any relevant climate science field, much less publish any papers in reputable journals debunking AGW.
4) Have not a single scientific instituion backing them.
Anderegg W.R.L., Prall J.W., Harold J. & Schneider S.H. (2010 Online Early) Expert credibility in climate change. Proceedings of the National Academy of Sciences 21 June 2010, doi: 10.1073/pnas.1003187107