New study finds striking level of agreement among climate experts on anthropogenic climate change


“Expert Credibility in Climate Change,” a new study in Proceedings of the National Academy of Sciences, finds that 97-98% of climate researchers examined who are most actively publishing in the field support the IPCC conclusions, i.e., are convinced by the evidence for human-caused climate change, and that the relative climate expertise and scientific prominence of researchers questioning the findings is significantly below that of convinced researchers. The authors of this first-of-its-kind study used metrics of climate-specific expertise and overall scientific prominence to examine expert credibility among scientists who agree with or question the primary conclusions of the IPCC.

Climate change deniers have claimed that there are thousands of credible scientists who question the basic science of global warming. These claims have contributed to media fervor over the “Climategate” e-mail hack and IPCC errors, and have fostered the public perception that the leading experts within the climate science community are deeply divided.  Lazy and irresponsible news stories (see here, here, and here) implying major disagreements among mainstream scientists working in the field have furthered public confusion about the risks of anthropogenic climate change.

A new paper from William R.L. Anderegg (Stanford University), James W. Prall (Univ. of Toronto), Jacob Harold (Hewlett Foundation), and Stephen H. Schneider (Stanford) provides a clear answer on the overwhelming level of agreement among climate scientists on anthropogenic global warming, and demonstrates that the “relative climate expertise and prominence of the researchers unconvinced of anthropogenic climate change is substantially below that of convinced researchers.”  The paper will be posted online sometime after 3:00 p.m. EDT June 21 in the journal Proceedings of the National Academy of Sciences.

The author team used a dataset of 1,372 climate researchers and their publication and citation data to reach the following conclusions:

1) 97-98% of the climate researchers most actively publishing peer-reviewed studies in the field support the tenets of anthropogenic climate change outlined in the Intergovernmental Panel on Climate Change assessment reports;

2) the relative climate expertise and overall scientific prominence of the researchers unconvinced of anthropogenic climate change is substantially below that of convinced researchers.

The authors write:

“A vocal minority of researchers and other critics contest the conclusions of the mainstream scientific assessment, frequently citing large numbers of scientists whom they believe support their claims…This group, often termed climate change skeptics, contrarians, or deniers, has received large amounts of media attention and wields significant influence in the societal debate about climate change impacts and policy.

“Despite media tendencies to present ‘both sides’ in ACC debates [anthropogenic climate change], which can contribute to continued public misunderstanding regarding ACC, 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.”

Global climatic disruption presents a profound challenge for government policy, societal decisionmaking, media coverage, and public opinion. The formulation of an adequate response strategy must build on a bedrock foundation of scientific understanding developed within specialized fields of scientific expertise. In such a case, policymakers and the public should pay attention to the assessments and communications of those who are regarded within the science community as the leading and most credible experts in the field.

The communication between the climate science community and the wider society is too important to be distorted and manipulated by people who find the mainstream science politically inconvenient. That is what denialists and contrarians in the political arena, whether elected officials or nongovernmental operatives (those who would like to be called “skeptics” as though they were custodians of intellectual integrity) have been doing with specious claims that a large proportion of credible climate science experts reject the evidence for anthropogenic climate change.

In particular, recent activity by the global warming denial machine is aimed at undermining support for the comprehensive IPCC climate change assessment reports, by attacking the overall integrity and credibility of the IPCC and its hundreds of participating scientist-authors. There are legitimate procedural questions to be considered and dealt with appropriately in developing the next set of IPCC reports. But those who propagate the phony argument that there are two “sides” – an IPCC side and a “skeptic” side – with comparable overall climate science expertise and credibility and deserving of comparable consideration – are doing a public disservice and should be called out on it.

In getting this point across, the climate science community should speak out effectively on its own behalf. In addition, allies of the science community and advocates for government accountability would do well to lend their support. 

While a single study cannot be conclusive, this solid empirically based analysis by Anderegg et al. and similar efforts in the future can hopefully encourage greater clarity in news coverage and public conversation about the level of scientific understanding of climate change and the relative credibility/expertise of scientists who question its basic tenets.

The article, “Expert Credibility in Climate Change,” is available online without a paid subscription to the journal.


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