Board on Atmospheric Sciences and Climate (BASC) Reviews Draft Climate Science Special Report

By: April M. Melvin, Associate Program Officer, Polar Research Board, Board on Atmospheric Sciences and Climate

NASEM

In March 2017, the Board on Atmospheric Sciences and Climate (BASC) of the U.S. National Academies of Science, Engineering, and Medicine released the Review of the Draft Climate Science Special Report. This report was conducted at the request of the U.S. Global Change Research Program (USGCRP) and as the report name indicates, provides a review of the draft Climate Science Special Report (CSSR). The draft CSSR is a technical document intended to provide an updated, detailed analysis of how climate is changing across the U.S. and to serve as a technical input to the Fourth National Climate Assessment. The draft CSSR contains a chapter dedicated to "Arctic changes and their effects on Alaska and the rest of the United States." The review committee's task was to evaluate the accuracy and comprehensiveness of the included scientific literature, the treatment of data, analyses, and statistical approaches, and the effectiveness of the report in conveying information in a transparent and traceable way for the intended audience.

The review committee concluded that the draft CSSR is timely, accurate, and well-written, representing the breadth of available literature relating to the current state of climate science. The committee found the draft CSSR to also be new and significant in several ways, including particular focus on how the climate system affects the United States and discussion of significant recent advancements in the science of climate change, such as the rapid development of the field of extreme event attribution and new research on Antarctic ice sheet melt and projected sea level rise. Synthesis of recent manifestations of continued climate change observed since the publication of the last Intergovernmental Panel on Climate Change (IPCC) report in 2013, including continued decline in Arctic sea ice, among others, was also noted.

To strengthen the impact of the draft CSSR, the study committee recommended the CSSR authors increase the distinction between recent advancements in the science and long-understood aspects of the climate system, add quantitative statements to the key findings, and expand the discussion of specific topic areas to more fully reflect the literature. Standardization of the time periods used for the present and historical baseline, wherever possible, and inclusion of significance statements and/or ranges in values where appropriate, was also recommended. For the Arctic-focused chapter, the committee found that the draft CSSR provides a sound foundation. Specific recommendations included greater articulation of the science relating to carbon release from permafrost and expanded discussion of the linkages between Arctic change and mid-latitude weather that better reflects the breadth of current research on this topic, among other suggestions.

Overall, the committee found the draft CSSR, by building on previous solid work and incorporating recent advances, provides a valuable update. The CSSR is currently being revised by the author team and is expected to be released in final form later this year.