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Fifth National Climate Assessment - Read the Report

Fourth National Climate Assessment

Fourth National Climate Assessment Vol I + II

The Fourth National Climate Assessment (NCA4), completed in November 2018, is a comprehensive and authoritative report on climate change and its impacts in the United States. 

View the full report:

Cover of Climate Science Special Report

The Climate Science Special Report is Volume I of the Fourth National Climate Assessment.

Report development was overseen by the Subcommittee on Global Change Research (SGCR) through a Federal Science Steering Committee (SSC), made up of representatives from USGCRP agencies and appointed by the SGCR. NOAA serves as the administrative agency for CSSR (i.e., NOAA established the procedures for the report and released Federal Register Notices).

The SSC selected three Coordinating Lead Authors, all of whom were Federal employees during the development of this report. Following a public call (via Federal Register Notice) for technical contributor nominations in March 2016, the SSC endorsed writing team selections, consisting of scientists representing Federal agencies, national laboratories, universities, and the private sector. Contributing Authors were selected based on specific needs identified by the authors. Review Editors were chosen from the technical contributor pool and endorsed by SSC to ensure that authors adequately responded to all comments received during the public and National Academy of Sciences, Engineering, and Medicine review periods.

Planning for the report began in early 2015 with a prospectus developed in the summer of that year. That was followed by the development of process guidance and the naming of author teams.  Writing began in April 2016 and an initial draft was made available for public comment in December 2016. A series of technical expert reviews were conducted throughout the report’s development.  SGCR was responsible for its final clearance and, ultimately, its public release.

Table of Contents

  • Executive Summary
  • Our globally changing climate
  • Physical drivers of climate change
  • Detection and attribution of climate change
  • Climate models, scenarios, and projections 
  • Large-scale circulation and climate variability
  • Temperature changes in the United States
  • Precipitation changes in the United States
  • Droughts, floods, and wildfires
  • Extreme storms
  • Change in land cover and terrestrial biogeochemistry 
  • Arctic changes and their effects on Alaska and the rest of the United States
  • Sea level rise
  • Ocean acidification and other ocean changes
  • Perspectives on climate change mitigation
  • Potential surprises: Compound extremes and tipping elements
  • Plus several Appendices

Timeline

2015

  • Fall: SGCR approves report prospectus

2016

  • March: Federal Register Notice call for technical contributor nominations
  • Spring/Summer: First Order Draft development
  • Summer: SSC review, author revision and editorial cleanup (Second Order Draft)
  • Fall/Winter: SGCR review, author revision, editorial cleanup and SSC signoff (Third Order Draft)
  • Winter 2016/Spring 2017: Third Order Draft released for public comment and National Academy of Sciences, Engineering, and Medicine review

2017

  • Spring: Author revision and editorial cleanup (Fourth Order Draft)
  • Spring/Summer: SGCR review, author revision and editorial cleanup (Fifth Order Draft)
  • 21 July: Fifth Order Draft sent to SGCR agencies for clearance
  • 18 August: Deadline for SGCR agency clearance
  • Fall: Final production, layout and website development
  • November 2017: Public release
Cover of NCA4, Volume II

Volume II of the Fourth National Climate Assessment (NCA4), Impacts, Risks, and Adaptation in the United States, analyzes the impacts of global change, as described in Volume I (Climate Science Special Report), on topics and regions of the United States.

The development of NCA4 Vol. II was overseen by a Federal Steering Committee appointed by the SGCR and comprising representatives from USGCRP agencies. NOAA, as the administrative agency for NCA4, was responsible for establishing procedures for the report, releasing Federal Register Notices, and certifying the report met Information Quality Act standards. It has undergone an extensive, multi-phase process of internal and external review from Federal agency experts, the general public, and a panel of experts from the National Academies of Sciences, Engineering, and Medicine.  

The following groups contributed to NCA4 Vol. II:

  • A Federal Steering Committee (SC) was responsible for the development, production, and content of the report as well as high-level scoping to ensure coherence, relevance, and responsiveness to the Global Change Research Act and the USGCRP Strategic Plan. The SC selected Federal Coordinating Lead Authors, Regional Chapter Leads, and Review Editors based on a number of criteria, including scientific expertise and experience with scientific assessments.
  • Federal Coordinating Lead Authors (CLAs) oversaw development of a given chapter and liaised with non-Federal Regional Chapter Leads or Federal or non-Federal National Chapter Leads in their development of individual chapters. The Federal CLAs also worked across chapters to ensure consistency throughout the report.
  • Agency Chapter Leads oversaw the production of the National Topic and Response chapters and select National Chapter Leads. Effort was made to distribute the responsibility across USGCRP agencies.
  • National Chapter Leads were either Federal or non-Federal experts who, in consultation with Federal CLAs, organized, directed, and led authorship of individual National Topic or Response chapters. Chapter Author teams were established by the National Chapter Leads, with suggestions from the Federal CLAs and the SC. Chapters were submitted to the corresponding Federal CLA, and ultimately transmitted to the SC as the individual input of the National Chapter Leads.
  • Regional Chapter Leads were non-Federal experts selected by the SC from a pool of experts put forward through a public nominations process. In consultation with Federal CLAs, Regional Chapter Leads organized, directed, and led authorship of individual regional chapters. Chapter Author teams were established by the Regional Chapter Leads, with suggestions from the Federal CLAs and the SC. Chapters were submitted to the corresponding Federal CLA, and ultimately transmitted to the SC as the individual input of the Regional Chapter Leads.
  • Chapter Authors were selected by the Chapter Lead and responsible for developing chapter content. Chapter author teams worked with Regional or National Chapter Leads to develop and edit individual chapters in response to comments received during the multiple rounds of review.
  • Technical Contributors provided inputs into chapter development, but did not directly author sections of NCA4 Vol. II. They were selected on an as-needed basis, based on specific needs identified by the author team.
  • Review Editors were selected by the SC from a pool of experts put forward through a public nominations process. Their role was to ensure the authors adequately responded to all comments received during the public and National Academies review periods.

NCA4 Vol. II Table of Contents

  • Overview [Executive Summary]
  • Our Changing Climate [NCA4 Vol. I summary]

National Topics

  • Water
  • Energy Supply, Delivery, and Demand
  • Land Cover and Land-Use Change
  • Forests
  • Ecosystems, Ecosystem Services, and Biodiversity
  • Coastal Effects
  • Oceans and Marine Resources
  • Agriculture and Rural Communities
  • Built Environment, Urban Systems, and Cities
  • Transportation
  • Air Quality
  • Human Health
  • Tribes and Indigenous Peoples
  • Climate Effects on US International Interests
  • Sector Interactions, Multiple Stressors, and Complex Systems

Regional Analyses

  • Northeast
  • Southeast
  • U.S. Caribbean
  • Midwest
  • Northern Great Plains
  • Southern Great Plains
  • Northwest
  • Southwest
  • Alaska
  • Hawai`i and U.S.-Affiliated Pacific Islands

Response

  • Reducing Risks through Adaptation Actions
  • Reducing Risks through Emissions Mitigation

Appendices

  • Process
  • Information Quality Act
  • Data Tools & Scenario Products
  • Looking Abroad: How Other Nations Approach a National Climate Assessment
  • Frequently Asked Questions

Timeline

2016

Early 2016: Federal Steering Committee established

Summer: Public comment on draft Prospectus; Process guidance developed 

Summer/Fall: Public call for technical inputs and author nominations (specifically, Regional Chapter Leads); Regional background webinars

Fall: Agency Leads, Federal CLAs, and Chapter Leads selected

December: Preliminary chapter outlines reviewed by Steering Committee

Late 2016/Early 2017: Chapter Authors selected by Chapter Leads

2017

Jan: Interagency review of revised chapter outlines (Zero Order Draft) 

Early Spring: Regional Engagement Workshops and Public Engagement Webinars

Spring: First Order Drafts developed by Chapter Author teams

July/Aug: NOAA Technical Support Unit (TSU) edits First Order Drafts; authors revise in light of comments, resulting in Second Order Draft

Aug: Interagency review of Second Order Draft

Sept/Oct: Authors and TSU revise chapters, resulting in Third Order Draft

Nov 3: Release of Third Order Draft for Public Comment & review by an expert panel of the National Academies of Sciences, Engineering, and Medicine (NASEM)

Winter: Third Order Draft out for public and NASEM review

2018

Early 2018: Authors work with Review Editors to revise chapters, resulting in Fourth Order Draft

Spring/Summer: Interagency review and final Federal clearance

Summer/Fall: Final production and layout of report

Nov 2018: Release of NCA4 Vol. II

To ensure that NCA4 Vol. II was informed by and useful to stakeholders, a number of engagement activities were planned for the spring of 2017. Regional Engagement Workshops were held in each of the 10 NCA4 regions, offering stakeholders an opportunity to provide input to the chapter author team on key message formulation, share relevant resources, and give individual feedback on issues of importance to their region. Organizers employed a ‘Hub and Satellite’ model for most NCA4 Regional Engagement Workshops. In addition, a number of national chapters planned activities to gather information from stakeholders. Dates, locations, and summaries of these activities are listed below.

NCA4 Regional Engagement Workshops

  • Alaska
    February 8
    Anchorage, AK | Summary

  • Northeast
    February 9
    Boston, MA
    Satellite Location(s): Huntington, WV; Ithaca, NY; New York City, NY; Portland, ME; State College, PA; Washington, DC | Summary

  • Southwest
    February 21
    Tucson, AZ
    Satellite Location(s): Albuquerque, NM; Boulder, CO; Davis, CA; Los Angeles, CA; Reno, NV; Salt Lake City, UT | Summary

  • Northern Great Plains
    February 22
    Rapid City, SD
    Satellite Location(s): Billings, MT; Fort Collins, CO; Lincoln, NE | Summary

  • Midwest
    March 1
    Chicago, IL
    Satellite Location(s): Ann Arbor, MI; Ames, IA; Cincinnati, OH; Columbus, OH; Duluth, MN; Houghton, MI; Madison, WI; St. Paul, MN; West Lafayette, IN | Summary

  • Southern Great Plains
    March 2
    Norman, OK
    Satellite Location(s): Austin, TX | Summary

  • Hawai'i and U.S.-Affiliated Pacific Islands
    March 6
    Honolulu, HI | Summary

  • U.S. Caribbean
    March 9 (Revised)
    San Juan, PR
    Satellite Location(s): Raleigh, NC; St. Thomas, VI; Washington, DC | Summary

  • Southeast
    March 16
    Raleigh, NC
    Satellite Location(s): Atlanta, GA; Biloxi, MS; Charleston, SC; Darien, GA; Fort Lauderdale, FL; Lafayette, LA; Washington, DC | Summary

  • Northwest
    March 21
    Portland, OR & Boise, ID | Summary

NCA4 National Overview Chapter Engagement

  • Transportation
    January 10
    Washington, DC
    Listening Session (Transportation Research Board Subcommittee for Aviation and Climate) | Summary

  • Coastal Effects
    February 28
    Webinar | Summary

  • Reducing Risks Through Emissions Mitigation
    March 6
    Webinar | Summary

  • Oceans and Marine Resources
    March 20
    Webinar | Summary

  • Human Health
    March 22
    Webinar | Summary

  • Built Environment, Urban Systems, and Cities 
    March 27
    Webinar | Summary

  • Climate Effects on U.S. International Interests 
    April 6
    Washington, DC
    Listening Session | Summary

  • Tribes and Indigenous Peoples 
    April 11
    Webinar | Summary

  • Air Quality
    May 8
    Webinar | Summary

  • Reducing Risks Through Adaptation Actions
    May 8
    Saint Paul, MN
    Listening Session (National Adaptation Forum) | Summary

  • Land Cover and Land-Use Change
    May 9
    Webinar | Summary

  • Forests
    May 11
    Webinar | Summary

 

Public engagement was critical to the entire NCA4 process. Learn more about past opportunities to participate:

Review and Comment on the Public Draft of NCA4 Vol. II

A critical component of NCA4 success is a robust, inclusive, and transparent pub­lic review process. NCA4 Vol. II was made available for public review and comment from 03 November 2017 until 31 January 2018. View the Federal Register Notice

Technical Inputs

The call for technical inputs for NCA4 Vol. II closed on January 15, 2017. If you wish to share additional information or technical inputs (literature, case studies, etc.) with the chapter author teams, please consider submitting comment on the report during the public comment period. Note that inputs received early in the process (such as those received during the open call) are more likely to shape chapter development.

Regional Workshops

Regional Engagement Workshops were held in each of our 10 NCA4 regions from February-March 2017. More information on these workshops can be found here.

General

The U.S. Global Change Research Program (USGCRP) was established by Presidential initiative in 1989 and mandated by Congress in the Global Change Research Act (GCRA) of 1990. Its mandate is to develop and coordinate “a comprehensive and integrated United States research program which will assist the Nation and the world to understand, assess, predict, and respond to human-induced and natural processes of global change.” USGCRP comprises 13 Federal agencies that conduct or use research on global change and its impacts on society.

Through the GCRA, USGCRP is mandated to produce a quadrennial assessment, which has become known as the National Climate Assessment (NCA). The NCA is required to a) integrate, evaluate, and interpret the findings of the Program and discuss the scientific uncertainties associated with such findings; b) analyze the effects of global change on the natural environment, agriculture, energy production and use, land and water resources, transportation, human health and welfare, human social systems, and biological diversity, and c) analyze current trends in global change, both human-induced and natural, and project major trends for the subsequent 25 to 100 years.

To date, three NCAs have been released. The first NCA was published in 2000, and the second was published in 2009. More information on these reports can be accessed here. The third NCA, Climate Change Impacts in the United States was published in 2014 and released in printable format and as an interactive website. The Fourth NCA (NCA4) builds on the work of these previous assessments.

For the Third NCA (released in 2014), authors developed a large physical science appendix. In the early planning stages for NCA4, it was decided that to best inform the impacts assessment, the physical science assessment should be completed in advance. As a result, NCA4 is being developed in two sequential volumes.

Volume I, the Climate Science Special Report, or CSSR, was released in November 2017. The CSSR assesses the science of climate change, with a focus on the United States. It is intended to serve as the foundation for efforts to assess climate-related risks and inform decision-making about responses. The findings in CSSR are based on a large body of scientific, peer-reviewed research, as well as a number of other publicly available sources, including well-established and carefully evaluated observational and modeling datasets.

NCA4 Volume II, Impacts, Risks and Adaptation in the United States, is a technical, scientific assessment of climate change-related impacts, risks, and adaptation. It assesses a range of potential impacts, helping decision makers better identify risks that could be avoided or reduced. Like the CSSR, the findings in Volume II are based on a large body of scientific, peer-reviewed research, as well as a number of other publicly available sources, including well-established and carefully evaluated observational and modeling datasets.

Consistent with common practice for USGCRP assessment products, both Volume I and Volume II of NCA4 are technical scientific assessments. Neither makes policy recommendations or evaluates existing or proposed policies.

CSSR Process

CSSR is the responsibility of the Subcommittee on Global Change Research (SGCR), which directs the activities of USGCRP. The SGCR established a Federal Science Steering Committee (SSC) to direct the CSSR project. A team of three Coordinating Lead Authors, selected by the SSC, led the report’s development. CSSR was written by a team of 32 Lead Authors, including scientists from Federal agencies, academia, and the private sector. These authors were nominated through a public process and selected by the SSC for their expertise. Contributing authors were invited to provide input on specific topics, as needed.

CSSR was subjected to a rigorous, six-step review process. The Zero Order Draft was reviewed by the author team. The First and Second Order Drafts were reviewed by the SSC and SGCR, respectively. The Third Order Draft of CSSR was released for public comment and simultaneous review by an expert panel of the National Academies of Sciences, Engineering, and Medicine in December 2016. This review resulted in a Fourth Order Draft that underwent an additional round of interagency review in May 2017. Authors responded to those comments and produced a Fifth Order Draft, which was subject to Final Federal Clearance.

CSSR has been in production since early 2015.

Yes. Unless otherwise stated, all information and figures in this report are in the public domain. We just ask that you use the appropriate citation when using this document.

NCA4 Vol. II Process

NCA4 Vol. II is the responsibility of the Subcommittee on Global Change Research (SGCR), which directs the activities of USGCRP. The SGCR established a Federal Steering Committee to oversee the NCA4 process. NCA4 Volume II was written by more than 300 Federal and non-Federal authors representing a range of expertise, a number of whom were selected through a public call for author nominations. Technical contributors were invited to provide input on specific topics, as needed.

NCA4 Vol. II underwent a rigorous, 8-step review process both internal and external to the U.S. Government: (1) Initial chapter outlines were reviewed in December 2016 by the Federal Steering Committee, and (2) a Zero Order Draft (consisting of annotated outlines) was then reviewed by the SGCR. A full First Order Draft underwent (3) a technical and editorial review by the NOAA Technical Support Unit (TSU), which resulted in a Second Order Draft that was (4) reviewed by the SGCR. The Third Order Draft of NCA4 Vol. II was released for (5) public comment and (6) simultaneous review by an expert panel of the National Academies of Sciences, Engineering, and Medicine in November 2017. This review resulted in a Fourth Order Draft for (7) final agency review and clearance in May 2018. The Federal Steering Committee ensured all final agency review comments were adequately addressed and (8) a final round of technical and editorial review was provided during summer 2018 on the Fifth Order Draft by NCA leadership and the NOAA TSU. NCA and TSU staff, as well as the authors themselves, performed a final showstopper review of chapter proofs in Autumn 2018. 

Planning for Volume II of NCA4 began shortly after the release of the Third NCA in 2014. A draft prospectus was released for public comment in the summer of 2016.

Content (General)

Most fundamentally, the majority of the report’s focus has shifted from national-level chapters to regional chapters, in response to public demand for more localized information on climate impacts. As a result, not only do the regional chapters provide more detail, but the Great Plains chapter has been split into separate Northern and Southern Great Plains chapters, and a new chapter focusing exclusively on the U.S. Caribbean has been added. Volume II also reflects a number of advances in the science of climate change impacts and adaptation with the inclusion of new national-level chapters on Air Quality; Climate Effects on U.S. International Interests; and a chapter on Sector Interactions, Multiple Stressors and Complex Systems. Finally, and again in response to public feedback and input, the report reflects three cross-cutting contextual advances: (1) more of an international context, (2) enhanced coverage of the economic impacts, and (3) greater focus on risk-based framing.

Yes. Unless otherwise stated, all information and figures in this report are in the public domain. We just ask that you use the appropriate citation when using this document.

USGCRP is implementing a sustained National Climate Assessment process that will ultimately facilitate continuous and transparent participation of scientists and stakeholders across regions and sectors, enabling new information and insights to be synthesized as they emerge. Current sustained assessment activities are listed below; more information will be added as it becomes available. 

Interim Assessments and Technical Reports inform the larger quadrennial process of National Climate Assessments

Scenarios

  • The Climate Scenarios Task Force (CSTF) and the Scenarios and Interpretive Science Coordinating Group (SISCG) work on the underlying scenarios for the sustained assessment and the upcoming NCA4.

Global Change Information System (GCIS)

  • GCIS is a tool that underpins many parts of the sustained assessment process

Indicators

A network of climate change indicators supports the sustained assessment process: