Expert Commentary

Expert credibility in climate change

2010 study in PNAS analyzing the beliefs of more than 1,000 scientists about human-induced climate change.

Despite the fact that the U.N. Intergovernmental Panel on Climate Change has found “unequivocal” evidence of anthropogenic (human-induced) climate change, the levels of public belief in this phenomenon continue to lag the scientific consensus. The explanations for this gap are myriad, and research has investigated everything from cognitive mechanisms to polarization among political elites. In any case, a small minority of scientists do express some degree of doubt about this consensus, and they have often been given prominence in the public debate. This has prompted media researchers in this area to note a trend of “false balance” in some reporting.

A 2010 study published in the Proceedings of the National Academy of Sciences, “Expert Credibility in Climate Change,” analyzed the research patterns and scholarly citations of 1,372 climate scientists who publish in this field. Of these, 908 scientists had published 20 or more climate-related papers. The study’s authors, from Stanford University, the University of Toronto and the William and Flora Hewlett Foundation, examined public statements from groups of scientists that indicated they were either convinced or unconvinced by evidence of climate change, and matched these to the sample of scientists. (The study notes that researchers who are unconvinced of the evidence are “often referred to as climate change skeptics, contrarians, or deniers.”) Though the sample of scientists is not comprehensive, the study’s authors note, the criteria used likely yield the “strongest and most credentialed researchers” in both the unconvinced and unconvinced camps.

The study’s findings include:

  • About 97% of the group with the most expertise — the 908 climate scientists with 20 or more papers published — are convinced by the evidence of human-induced climate change.
  • Those who are unconvinced by the evidence make up “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.”
  • Overall, researchers with fewer than 20 climate publications comprise 80% the group that is unconvinced, as opposed to less than 10% of the group that is convinced by the evidence: “This indicates that the bulk of [unconvinced] researchers on the most prominent multi-signatory statements about climate change have not published extensively in the peer-reviewed climate literature.”

“Despite media tendencies to present both sides in [human-induced climate change] debates,” the authors conclude, “which can contribute to continued public misunderstanding … not all climate researchers are equal in scientific credibility and expertise in the climate system. This extensive analysis of the mainstream versus skeptical/contrarian researchers suggests a strong role for considering expert credibility in the relative weight of and attention to these groups of researchers in future discussions in media, policy, and public forums regarding anthropogenic climate change.”

In related research, a 2011 study from George Mason University also found that, among a more diverse pool of researchers across government, industry and academia, 97% agreed that global temperatures are rising and 84% agreed that “human-induced greenhouse warming” is now occurring.

Tags: global warming, science, climate politics

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