Last two post were about the consensus and how it was “quantified” by Oreskes in 2004 and Doran/Zimmerman in 2009. This post is about another attempt: Expert credibility in climate change from William R. L. Anderegg, James W. Prall, Jacob Harold, and Stephen H. Schneider.
This is the statement that was being assessed:
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.
How they accessed this is a lot less clear. According to their Materials and Methods they compiled a database of 1,372 climate researchers and classified them either as convinced by the evidence (CE) for anthropogenic climate change or unconvinced by the evidence (UE). Apparently according to where they publish or if they found their name as contributors in for example open letters or protest letters. In that way they came to 903 convinced and 472 unconvinced. 3 scientists were classified in both groups.
After this classification the credentials of these researchers was tallied by counting the number of climate relevant publications that are authored or coauthored by the researcher via name and key word “climate” (expertise) and the number of citations for each of the researchers four highest-cited papers (prominence) via Google Scholar. They came to this result:
The UE 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 (Materials and Methods). This result closely agrees with expert surveys, indicating that ≈97% of self-identified actively publishing climate scientists agree with the tenets of ACC [Anthropogenic Climate Change].
It is not really clear if Anderegg et al read the publications and accessed if they were according to conclusions of the IPCC fourth report. Probably they just assumed that when someone is/was an author of the IPCC report that they adhere the position of the IPCC. And when signing a dissident letter they assumed the author didn’t adhere the IPCC report and was classified in the not-convinced group.
This aside, what the survey basically says is that the alarmist scientists publish more than their skeptics counterparts. But that is no secret and it has to do with other things than with the validity of their assessment.
In the end, also here nowhere is said that those scientists agree that this warming is dangerous or necessitates action. The public and the politicians don’t only want to know that our world is warming, but if this warming is bad or not. There is obvious a consensus that there is a warming and that this could be partly because of human influences. But there is no consensus about the consequences of this warming. Even if there would be such a consensus, it is certainly not found in this survey and also not in the Oreskes as in the Doran & Zimmerman survey.