4th U.S. National Climate Assessment: What Is It?

The U.S. National Climate Assessment (NCA) is a regular science report mandated by Congress to inform the nation and our government about climate change. NOAA has led the work on Volume 1 of the 4th Assessment report expected to be published this Friday, November 3, 2017.

Volume 1, entitled “Climate Science Special Report” (CSSR), addresses the causes of climate change, the impacts on temperature, extreme weather, and wildfires, the anticipated trends for the future, and the broad requirements to meet current policy goals. A copy the final clearance draft was leaked to the New York Times in August amid fears the Trump administration would suppress the report.

The report has gone through 5 rounds of peer review by NOAA and NASA, as well as review by the National Academy of Sciences.  In addition, the report has gone through open public comment and response. NCA authors have responded to each public comment and to each comment by the National Academy of Sciences, in a process overseen by review editors to ensure robust responses. All of these comments and responses will be published upon release of the report as an appendix, ensuring response to public comment and providing complete transparency. All of the 13 participating federal agencies have approved the final content of the report.

The NCA is also currently on track to publish a draft of volume 2 in the 4th Assessment cycle, which will be released for public review and comment as well as peer review by the U.S. National Academy of Sciences.[1]

In its review report on the 3rd order draft of Volume 1/CSSR, the National Academy of Sciences stated: The Committee commends the CSSR authors for producing an impressive, timely, and generally well-written draft report and was impressed with the breadth, accuracy, and rigor of the draft CSSR.  The Academy also stated: The draft CSSR, by building on previous solid work and incorporating recent advances, provides a valuable update. In this document, the Committee also provides recommendations for how the draft CSSR could be strengthened. The final draft of the Volume 1/CSSR that secured inter-agency approval of content responded to those Academy suggestions for improvement.

NCA reports have several important distinctions:

  • NCA assessments are conducted by leading U.S. scientists, many of whom are based in the nation’s premier universities and research institutions. Most of the federal scientists participating in these reports are based in NOAA, NASA, and USGS, agencies with strong science reputations.
  • The NCA report is produced under the explicit mandate of Congressional legislation – Section 106 of the Global Change Research Act (GCRA) of 1990 – that calls for a national report every four years.
  • NCA reports undergo formal review by the National Academy of Sciences and formal response by the report’s authors (already completed for Volume 1 of the 4th NCA), greatly enhancing their rigor and credibility.
  • Finally, these reports go through formal public comment and author response (also completed for the Volume 1) providing public input and complete transparency.

[1] Note: Another important federal climate science report, State of the Carbon Cycle Report 2 (SOCCR2), is scheduled for release in November.  While not part of the National Climate Assessment cycle per se, it is also produced under the auspices of the U.S. Global Change Research Program.  The lead agency for this report is the USDA. The White House recently announced the nomination of a noted climate-science denier to be Chief Scientist at the USDA. The focus of SOCCR-2 is on the scientific understanding of U.S. and North American carbon cycle stocks and fluxes, in the context of and interactions with global scale budgets and climate change impacts in managed and unmanaged systems. Included in this assessment report will be relevant carbon management science perspectives and support tools for supporting decisions, as addressed in and related to the US Carbon Cycle Science Plan (2011) and U.S. National Climate Assessment, USGCRP 2012-2021 Strategic Plan and Global Change Research Act (GCRA) of 1990.  

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