The two methods
http://www.pnas.org/content/early/2010/06/04/1003187107Expert credibility in climate change
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.http://tigger.uic.edu/~pdoran/012009_Doran_final.pdf
2. Do you think human activity is a significant contributing factor in changing mean global temperatures?
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In our survey, the most specialized and knowledgeable respondents (with regard to climate
change) are those who listed climate science as their area of expertise and who also have published more than 50% of their recent peer-reviewed papers on the subject of climate change (79 individuals in total). Of these specialists, 96.2% (76 of 79) answered “risen” to question 1 and 97.4% (75 of 77) answered yes to question 2.