This study, published in 2010, aims to evaluate the extent of agreement among climate change scientists with the view of the Intergovernmental Panel on Climate Change (IPCC) that “anthropogenic [caused by humans] greenhouse gases have been responsible for most of the unequivocal warming of the Earth’s average temperature over the second half of the 20th century”.
Anderegg, William R. L., Prall, James W., Harold, Jacob; Schneider, Stephen H., 2010. Expert credibility in climate change. Proceedings of the National Academy of Sciences. Available at: http://www.pnas.org/content/early/2010/06/04/1003187107.full.pdf+html
The authors seek to identify “credible” experts in the field of climate change science based on the number of papers they have authored and the number of times their papers have been cited by other scientific researchers. They find that 97-98% of the most active scientists agree with the IPCC. They also find that the group of scientists categorised as agreeing with the IPCC typically have more published papers and are cited more often than the scientists that have not publicly supported the IPCC’s view. The authors conclude from this that the scientists in agreement have greater expertise and are more prominent among the scientific community than those that could be termed “climate change skeptics”.
Anderegg et al compiled a database of over 1300 climate change scientists drawing on authors of research papers on this topic, membership of working groups, and signatories to public statements of agreement or disagreement with the IPCC’s conclusions on climate change. They categorised each individual as either “convinced”, or “unconvinced” by the IPCC’s evidence based on their support of public statements either in support of or dissenting from the views of the IPCC. Over 900 researchers were deemed to be climate “experts”, by virtue of having published over 20 research papers on the topic, and the number of citations of each author’s four most cited papers counted using the online resource Google Scholar. The 900 scientists were then ranked by expertise (total number of climaterelated publications) and prominence (number of citations).
Of the fifty most prolific researchers on climate change, 98% were in the “convinced” category. Of the 200 most prolific researchers, 97% were convinced. Anderegg et al believe that this broadly agrees with other qualitative polls of scientific opinion. They also found that the mean expertise of the convinced group was almost double that of the unconvinced group (119 publications compared with 60 publications), and that the convinced group was considerably more prominent than the unconvinced group in terms of the number of citations of their research.
The authors conclude that their assessment supports the view that the credibility of climate scientists that are in agreement with the IPCC is superior to the credibility of the “skeptics”. They acknowledge that their measures of expertise and prominence are subjective and there are risks of bias and data collection error, but believe they provide a “reasonable estimate” of the most expert scientists in this field. They offer the opinion that while decision-making must include the views of many different stakeholders, the relative credibility of experts on each side of the debate should be considered when determining how much attention to give their views. For example, of researchers that were excluded from the expert group of 900, 80% were in the unconvinced category suggesting, in the authors’ view, that many of the scientists publicly aligned with views opposing the IPCC have not extensively published research on the topic themselves.
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RI Quarterly Vol. 4: Focus on climate
RI Quarterly Vol. 4: Focus on climate
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Expert credibility in climate change