Definition of peer review from
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The U.S. Environmental Protection Agency (EPA) and the Department of Energy have recently proposed to use an alternative approach to standard peer review for evaluating climate change science, one that is patterned after the red team/blue team exercises developed in the military. In this approach, a red team attempts to penetrate a blue team’s defense. However, if the idea is to have the red team poke holes in the mainstream scientific community’s (the blue team) consensus on climate change, it discounts that such challenges have already been applied thousands of times while that consensus was gradually developed. A little history of climate science explains why.

We are old enough to remember when many, if not most, scientists were skeptical that the human impact on climate could be distinguished from natural climatic variation. The journey from the healthy skepticism that existed 40 to 50 years ago to today’s well-supported and widespread scientific consensus that humans are changing the climate is a remarkable story of the integrity of the scientific process.

The Long Journey from Skepticism to Consensus

Following theoretical predictions of the climatic effects of atmospheric carbon dioxide (CO2) made by Swedish chemist Svante Arrhenius in the 1890s, the first good observational record of increasing atmospheric CO2 began in the late 1950s as part of the International Geophysical Year. Modern climate science started in the 1960s, when general circulation models under development were modified to incorporate the effects of CO2 and water vapor to understand their impact on climate [Forster, 2017]. Not long thereafter, scientists systematically considered what else might explain the new warming trends that started in the 1970s and that continue today.

A number of hypotheses were evaluated from the 1970s through the 1990s. For example, solar scientists concluded that although solar variation (sunspot cycles) does modestly affect climate from one decade to the next, the effect is far too small and too cyclic to account for a multidecadal trend in warming. Similarly, other skeptical scientists hypothesized that expanding cities—with all their asphalt, concrete, and steel—were causing a heat island effect that could be influencing temperature measurements because weather observation stations that had at one time been outside cities had ended up being right in the middle of them. That hypothesis was also disproven, and surface temperature is now also measured on buoys in remote oceanic locations to minimize such an effect. Volcanoes were also studied both as warming agents from their CO2 emissions and as cooling agents from the particles they eject into the stratosphere. Scientific analysis showed that the former effect is very small relative to burning fossil fuels and that the latter effect persists only for a few years after the very largest subaerial volcanic eruptions.

Confidence in our understanding of the climatic effects of massive releases of CO2 from burning fossil fuels since the beginning of the industrial revolution converges from three independent lines of inquiry.

By the end of the 1990s, these alternate hypotheses and others to explain late 20th century warming were carefully ruled out one by one, and consistent with an anthropogenic cause, early 21st century warming continues unabated with fossil fuel burning.

At the same time, a multitude of climate change trends became clearer, including higher surface temperatures and heat waves, melting Arctic sea ice, receding glaciers, rising sea level, changing patterns of extreme weather events, bird migrations, freeze and thaw dates of lakes, and so on. Confidence in our understanding of the climatic effects of massive releases of CO2 from burning fossil fuels since the beginning of the industrial revolution now converges from three independent lines of inquiry:

  • theoretical calculations of the greenhouse effect based on well-known physics and chemistry
  • fingerprinting the detailed patterns of climate change caused by different human and natural influences, such as differences among regional patterns of land surface warming, ocean heat content, and sea ice extent that are consistent with an anthropogenic effect
  • growing confidence in globally distributed measurements of climate change and its impacts and greater skill in matching those observations to increasingly sophisticated computer models that include the various land, ocean, and atmospheric greenhouse gas sources, sinks, and feedbacks

The scientific community has gradually shifted, on the basis of evidence, from predominantly being skeptical in the 1970s that the human fingerprint on climate could be demonstrated to today being convinced that there are no other plausible explanations besides the cumulative effect of the last 150 years of burning fossil fuel for the recent extent of changing climate. Natural climatic variation is ongoing, but it cannot explain the current speed and amount of observed change. The science does not stand still; studies on how clouds may moderate the rate of climate change and how aerosols (particulate pollution) affect clouds and can offset some warming, for example, are still areas of active research in which hypotheses are being tested and challenged with characteristic scientific skepticism.

Healthy Skepticism Is in Scientists’ DNA

The scientific process is built on healthy skepticism.

The scientific process is built on healthy skepticism. To publish a paper in a scientific journal—whether in human health, geoscience, astronomy, or other areas—the author must openly declare any real or perceived conflicts of interest and convince a group of anonymous expert reviewers that the paper’s conclusions are supported by the data. Expert reviewers are asked to evaluate the strength of the evidence presented, and they, too, must declare any possible conflicts of interest that could lead to a real or perceived lack of impartiality, such as a financial interest in the outcome or a familial or institutional affiliation with the author. These safeguards promote rigorous and objective review, and peer review remains the gold standard.

In addition to peer-reviewed journals, overview assessments are periodically conducted and published by scientific societies and academies. For example, the National Academies of Sciences, Engineering, and Medicine convene panels and review committees in response to requests from government agencies and others to summarize the existing state of scientific knowledge on topics of societal concern. The resulting peer-reviewed reports are usually not prescriptive but, rather, are intended to frame and inform considerations of policy options with current scientific evidence. Transparent protocols are followed to identify and avoid potential conflicts of interest of panelists, to confirm their credentials, and to include a diversity of experiences and perspectives.

The deliberative process generates a report of where consensus among experts was reached and where differences of opinion remained, including publishing minority views. An excellent recent example of how seriously the Academy takes peer review is its review [National Academies of Sciences, Engineering, and Medicine, 2017] of a draft report by the U.S. Global Change Research Program describing the current state of climate science. Another review on the impacts of climate change on the U.S. economy, environment, and human health is expected later this year.

Other nations have conducted similar deliberative processes through their respective academies of science, as has the Intergovernmental Panel on Climate Change (IPCC) through its series of five assessments since the 1990s [Trenberth, 2015]. The IPCC assessment reports are reviewed by science experts and by government representatives, following formal and transparent protocols that seek consensus.

Questions About a Red Team/Blue Team Approach

The state of climate science today includes the vast accumulation of 50+ years of published papers and reports, each subjected to reviewers’ skeptical eyes to ensure that published conclusions are supported by data.

The state of climate science today includes the vast accumulation of 50+ years of published papers and reports, each subjected to reviewers’ skeptical eyes to ensure that published conclusions are supported by data. This week, 16 scientific societies sent a letter to EPA Administrator Scott Pruitt to ask for clarification of what would be gained from a red team/blue team approach that peer reviewers didn’t already find in the vast body of climate science publications.

Beyond that overarching question, new procedural questions must be answered before applying the approach to science:

  • Will the team members be carefully and transparently screened by a neutral party for conflicts of interest, such as potential financial gain from influencing policies?
  • What scientific credentials and communication experience will be required of team members, and how will candidates be solicited and nominated?
  • Will the teams be encouraged to find scientific consensus where it occurs, and will there be a process for reconciling differences?
  • Is the proposed television venue for a red team/blue team debate, where TV personas could overshadow substance and time limitations can impede deep and thorough analysis, really appropriate for such important deliberation?
  • Will the team members be held to the highest standards of evidence in stating their positions, and if so, who will do the fact checking?
  • What sort of precedent will be established? Is this a one-off proposal targeting only climate science, or will it be applied to the scientific community’s research on vaccine safety, nuclear waste storage, or any of a number of important policies that should be informed by science?

Our peer review and Academy report processes are inclusive and tried and true and have helped build great institutions of science.

The United States should be proud of our long tradition of objectivity, rigor, and scholarship, going back to well before President Abraham Lincoln’s signing of legislation that established the National Academy of Sciences. Our peer review and Academy report processes are not flashy or entertaining, but they are inclusive and tried and true and have helped build great institutions of science. They provide the evidence-based analysis of climate science and all other scientific disciplines that are so important for informing the public policy decisions that we rely upon to protect our security, health, safety, environmental integrity, and economic prosperity.


Forster, P. (2017), Half a century of robust climate models, Nature, 545, 296–297,

National Academies of Sciences, Engineering, and Medicine (2017), Review of the Draft Climate Science Special Report, Natl. Acad. Press, Washington, D. C.,

Trenberth, K. E. (2015), Intergovernmental Panel on Climate Change, in Encyclopedia of Atmospheric Sciences, 2nd ed., pp. 90–94, Elsevier, Amsterdam,

—Eric Davidson (email:, President, American Geophysical Union; also at Appalachian Laboratory, University of Maryland Center for Environmental Science, Frostburg; and Marcia K. McNutt, President, National Academy of Sciences, Washington, D. C. (email:


Davidson, E.,McNutt, M. K. (2017), Red/blue and peer review, Eos, 98, Published on 02 August 2017.

Text © 2017. The authors. CC BY-NC-ND 3.0
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