According to a July 11, 2019 Think Progress article, the following peer-reviewed papers found a scientific consensus of 93% to 100% on climate change: Anderegg 2010, Carlton 2015, Cook 2013, Doran 2009, Oreskes 2004, Stenhouse 2014, and Verheggen 2014. In the last two posts (here and here), I summarized each paper’s definition of the consensus position, their methods, and results. In brief:
Oreskes based her 100% consensus conclusion on an analysis of abstracts (typically one paragraph) identified in a keyword search using “climate change” as the keyword. The papers did not have to be about recent climate change or be authored by climate scientists. If the abstracts did not explicitly reject the idea that recent global warming is due mostly to human activities, she counted the paper in agreement with the consensus.
Doran et al conducted a survey in which 73.8% of the respondents believed global temps have risen and humans are a significant contributing factor in the change in global temperatures.
Anderegg et al reduced a dataset of 908 climate researchers who had published at least 20 climate-related papers to 50 - 200 scientists who had authored or coauthored the most papers. They found that 97-98% of this much smaller group of scientists agreed that most global warming since the mid-20th century was due to anthropogenic greenhouse gases. They did not reveal how many of the remaining 708 scientists supported or did not support the consensus.
Cook et al categorized 2142 papers that were self-rated by their authors. Of these, 62.7% were self-rated as endorsing the consensus, 35.5% had no opinion or were undecided, and 1.8% explicitly rejected the consensus. Cook et al came up with the 97% support for the consensus by ignoring the “no opinion/undecided” papers.
Verheggen et al sent out a survey, in which 66% of the respondents attributed at least 50% of recent global warming to human activities and 83% considered greenhouse gases a significant factor in recent warming.
Stenhouse et al categorized 1,821 survey responses and concluded that “majorities of experts view human activity as the primary cause of recent climate change: 78% of climate experts actively publishing on climate change, 73% of all people actively publishing on climate change, and 62% of active publishers who mostly do not publish on climate change.” They arrived at the consensus figure of 93% by considering only “actively publishing climate scientists” who are “convinced that humans have contributed to global warming.” I could not find information in this paper on the number of this subset of actively publishing climate scientists (which would have been fewer than 232 individuals - the total number of climate scientists that participated in the survey).
Carlton et al received 698 responses to a survey. Over 47% of the respondents were agricultural or biological scientists. Over 52% of the respondents endorsed the statement, “None of my research concerns climate change or the impacts of climate change.” Almost 92% of the respondents believed in anthropogenic climate change.
My take-away: except for Verheggen et al, the above papers are extremely flawed and agenda-driven, often including or excluding data to bolster the impression of overwhelming consensus. For example, scientists who indicated they are “undecided” about climate change are expressing opinions that should be incorporated into consensus calculations. Scientists who have authored at least 20 climate-related papers should be included in consensus calculations - there is no reason to believe that those who author the most papers are the most credible and the rest should just be ignored. The opinions of biologists and agricultural scientists with no climate-related research experience are irrelevant to the question of consensus on climate change. I say all this as someone who considers it plausible and probable that recent global warming is mainly due to human activities.
Verheggen et al gets the final word:
“Different surveys are not directly comparable, due to different groups of people being asked different questions…. Different surveys typically use slightly different criteria to determine their survey sample and to define the consensus position, hampering a direct comparison. It is possible that our definition of “agreement” sets a higher standard than, for example, Anderegg ’s definition…and Doran and Kendall-Zimmermann’s survey question about whether human activity is ‘a significant contributing factor’.”
Anderegg, W.R.L., Prall, J.W., Harold, J., and Schneider, S.H. 2010. Expert credibility in climate change. Proceedings of the National Academy of Sciences 107: 27. 12107–12109. https://doi.org/10.1073/pnas.1003187107
Carlton, JS, Perry-Hill, R, Huber, M, and Prokopy, LS. 2015. The climate change consensus extends beyond climate scientists. Environmental Research Letters https://doi.org/10.1088/1748-9326/10/9/094025
Cook, J. Nuccitelli, D., Green, S.A., Richardson, M., Winkler, B., Painting, R., Way, R. Jacobs, P., and Skuce, A. 2013. Quantifying the consensus on anthropogenic global warming in the scientific literature. Environmental Research Letters 8: 2. https://iopscience.iop.org/article/10.1088/1748-9326/8/2/024024;
Doran, P.T. and Zimmerman, M.K. 2009. Examining the scientific consensus on climate change. EOS 90: 3, 22–23. DOI: 10.1029/2009EO030002. https://doi.org/10.1029/2009EO030002
Oreskes, N. (2004). "The Scientific Consensus on Climate Change." Science 306(5702): 1686-1686. DOI: 0.1126/science.1103618 https://science.sciencemag.org/content/306/5702/1686.summary
Stenhouse, N., Maibach, E., Cobb, S., Ban, R., Bleistein, A., Croft, P., Bierly, E., Seitter, K., Rasmussen, G., and Leiserowitz, A. 2014: Meteorologists’ views about global warming: A survey of American Meteorological Society professional members. Bulletin of the American Meteorological Society 95: 1029–1040. https://doi.org/10.1175/BAMS-D-13-00091.1
Verheggen, B., Strengers, B., Cook, J. van Dorland, R., Vringer, K., Peters, J. Visser, H., and Meyer, L. 2014. Scientists’ views about attribution of global warming. Environmental Science & Technology 48: 16. 8963–8971, DOI: 10.1021/es501998e https://doi.org/10.1021/es501998e