USGCRP completed the Fourth National Climate Assessment (NCA4) in November 2018 with the release of NCA4 Volume II (Impacts, Risks, and Adaptation in the United States). Building on an assessment of observed and projected changes in the physical climate system released as Volume I of NCA4 (Climate Science Special Report) in 2017, Volume II focuses on climate-related risks to systems that support our well-being and economy. 

 

A number of ongoing assessment products and efforts undertaken by USGCRP’s member agencies and interagency groups provided valuable inputs to NCA4 Volume II. USGCRP led the development of two major sustained assessment products that served as inputs to the report: The Impacts of Climate Change on Human Health in the United States: A Scientific Assessment and the Second State of the Carbon Cycle Report. A number of USGCRP agency-led products also improved the thoroughness of the assessment, including the USDA-led assessment Climate Change, Global Food Security, and the U.S. Food System conducted on behalf of USGCRP, and Effects of Drought on Forests and Rangelands in the United States: A Comprehensive Science Synthesis; NOAA’s Climate Resilience Toolkit, Climate Explorer, and State Climate Summaries; and EPA’s updated economic impacts of climate change report. In addition, a variety of USGCRP indicators and scenario products supported the evaluation of climate-related risks throughout the report’s regional and sectoral chapters, and the report’s Overview chapter featured an interactive graphic on climate-relevant indicators based on data collected around the United States. 

 

Both volumes of NCA4 are supported by the Global Change Information System (GCIS), a freely accessible database linking together all the information used in USGCRP assessments. The GCIS acts as an advanced, multifaceted bibliography for the more than 6,000 unique references cited across the 29 chapters of Volume II, maintaining easy-to-find records of the sources of all scientific information in the report and providing access to the original data and research. This includes analysis and visualization processes for figures, enabling reproducibility and transparency of results. GCIS also supports other USGCRP sustained assessment products. 

 

NCA4 Volume II was authored by more than 300 federal and non-federal experts, including individuals from federal, state, and local governments; tribes and indigenous communities; national laboratories; universities; and the private sector. The entire process was informed by engagement with hundreds of external stakeholders, including a series of regional workshops that reached more than 1,000 individuals in over 40 cities. Listening sessions, webinars, and public comment periods also provided valuable input to the authors. The report underwent an extensive, multi-phase process of review⎯involving the submission of and response to nearly 10,000 review comments⎯received from USGCRP federal agency experts, the general public, and a panel of experts from the National Academies of Sciences, Engineering, and Medicine. NCA4 Volume II is available at nca2018.globalchange.gov.