About the Assessment

About the Assessment

California’s Fourth Climate Change Assessment (Fourth Assessment) advances actionable science that serves the growing needs of state and local-level decision-makers from a variety of sectors.

The Fourth Assessment presents information in a variety of ways, all accessible through this site. Regional reports summarize climate impacts and adaptation needs around the state, at a resolution useful for local decision makers. Statewide impacts are summarized in the Statewide Summary Report, as well as reports on Tribal and Indigenous Communities, Climate Justice, and California’s Ocean and Coast. The Technical Reports are the foundation of the Fourth Assessment, and include climate projections and analyses of expected impacts in various sectors across the state.

History of California’s Climate Assessment

California is a global leader in using, investing in, and advancing research to set proactive climate change policy, and its Climate Change Assessments contribute to the scientific foundation for understanding climate-related vulnerability at the local scale and informing resilience actions.

Since 2006, the State has undertaken four comprehensive climate change assessments, designed to assess the impacts and risks from climate change and to identify potential solutions to inform policy actions. The Climate Change Assessments directly inform State policies, plans, programs, and guidance to promote effective and integrated action to safeguard California from climate change. Information on previous assessments is available here.

California’s climate change assessments are a regionally focused example of a regular series of broader assessments, including the U.S. National Climate Assessment (NCA) and global assessments from the Intergovernmental Panel on Climate Change (IPCC). These assessments estimate climate change impacts under different future emission scenarios using a set of global climate models (GCMs). While the IPCC assessments analyze impacts at a global scale, the NCA and California assessments share approaches to downscale climate model outputs to produce projections relevant on a regional scale. The California Climate Change Assessment goes further by including a set of state-funded research reports that examine how climate change will affect specific sectors, potential responses to climate change, and other policy-driven questions. Each of these reports presents original research findings for specific questions relevant to California’s climate change policy.

First California Climate Assessment Second California Climate Assessment Third California Climate Assessment Fourth California Climate Assessment
Year 2006 2009 2012 2018
Description Understanding climate impacts in California. Developed to provide support for undertaking greenhouse gas emission reductions. Understanding how climate change will affect specific sectors. Made the case that adaptation could reduce costs. Increased understanding of vulnerability in natural and human systems, and generated two pilot regional assessments. Technical and regional reports designed to support adaptation actions at the state, regional, and local level.
Driver Executive Order S-3-05 Policymakers’ desire to know if adaptation was needed 2009 Climate Adaptation Strategy 2015 Climate Change Research Plan
Outcome Assembly Bill (AB) 32 2009 Climate Adaptation Strategy Supported passage of new climate adaptation laws Informing the implementation of AB 2800, which requires a report on how engineering standards should be changed to consider climate change. Other outcomes to be determined.


Multiple sources of funding, dozens of state agencies, and hundreds of researchers from public universities, federal agencies, and the private sector – not to mention a wide range of stakeholders – made California’s Fourth Climate Change Assessment possible. We are not able to list every person who contributed to the Fourth Assessment.

Thank you to everyone who contributed to the Fourth Assessment!

State Agency Management Team

Agency Leadership

Secretary John Laird (California Natural Resources Agency), Chair Robert Weisenmiller (California Energy Commission), Director Ken Alex (California Governor’s Office of Planning and Research)

Executive Management

Louise Bedsworth (California Strategic Growth Council/Governor’s Office of Planning and Research), Keali’i Bright (California Natural Resources Agency), Drew Bohan (California Energy Commission)

Management Staff

Jamie Anderson (California Department of Water Resources), Pamela Doughman (California Energy Commission), Leah Fisher (California Governor’s Office of Planning and Research), Guido Franco (California Energy Commission), Nuin-Tara Key (California Governor’s Office of Planning and Research), Susan Wilhelm (California Energy Commission), Joseph Wraithwall (California Natural Resources Agency)

Editorial Board for the Fourth Assessment

Dan Cayan (University of California, San Diego), Editor-in-Chief

Susan Wilhelm (California Energy Commission), Deputy Editor-in-Chief

Associate Editors

Alan Sanstad (Lawrence Berkeley National Laboratory), Fred Lipschultz (USGCRP), Glynis Lough (Union of Concerned Scientists), Guido Franco (California Energy Commission), Jamie Anderson (California Department of Water Resources), James H. Thorne (University of California, Davis), John Andrew (California Department of Water Resources), John Battles (University of California, Berkeley), Klaus Scott (California Air Resources Board), Michael Mastrandrea (Stanford University), Nuin-Tara Key (California Governor’s Office of Planning and Research), Pamela Doughman (California Energy Commission), Rupa Basu (California Office of Environmental Health Hazard Assessment). Tamara Wall (United States Geological Survey), Terry Surles (California Institute for Energy and Environment), Duane Waliser (Lawrence Berkeley National Laboratory), Julie Maldonado (University of California, Santa Barbara), Louise Bedsworth (California Strategic Growth Council)

Peer Review Committee for Statewide Summary Report

Robert Lempert, Chair (RAND Corporation), Phil Duffy (Woods Hole Research Center), Chris Field (Stanford University), Juliette Finzi Hart (U.S. Geological Survey), David Graves (Saintsbury Winery), Lara Kueppers (University of California, Berkeley), Robert Leiter, Peter Moyle (University of California, Davis), Jonathan Parfrey (Climate Resolve), Stephanie Pincetl (University of California, Los Angeles), Margaret Torn (Lawrence Berkeley National Laboratory), Sarah White (California Workforce Development Board)

Contracting and Peer Review Support

Carl Blumstein and Eric Lee (Berkeley Energy and Climate Institute)

Publication Team

Marketing by Design and Della Gilleran

Chief Technical Editor

Grayson Hough

Stakeholder Advisor

Bruce Riordan

Brochure Author

Jim Thorne


While space limitations do not allow us to list the names of hundreds of contributors to the 57 reports published in the Fourth Assessment, the efforts of each and every researcher are gratefully acknowledged. Below we list the principal investigators for the 44 technical reports and the coordinating lead authors for the 13 summary reports:

Principal Investigators

David Ackerly (University of California, Berkeley)

Amir AghaKouchak (University of California, Irvine)

Maximilian Auffhammer (University of California, Berkeley)

Patrick Barnard (United States Geological Survey)

John Battles (University of California, Berkeley)

Benjamin Brooks (United States Geological Survey)

Judsen Bruzgul (ICF)

Dan Cayan (University of California, San Diego)

Larry Dale (Lawrence Berkeley National Laboratory)

Lloyd Dixon (RAND Corporation)

Holly Doremus (University of California, Berkeley)

Julia Ekstrom (University of California, Davis)

Robert Kay (ICF)

Lorraine Flint (United States Geological Survey)

Guido Franco (California Energy Commission)

Brian Gaylord (University of California, Davis)

Steven Glaser (University of California, Berkeley)

Minxue He (California Department of Water Resources)

Jonathan Herman (University of California, Davis)

Megan Jennings (San Diego State University)

Ruth Langridge (University of California, Santa Cruz)

Andrew Lauland (RAND Corporation)

Ronnen Levinson (Lawrence Berkeley National Laboratory)

Romain Maendly (California Department of Water Resources)

Emilie Mazzacurati (427 Climate Solutions)

Adina Merenlender (University of California, Berkeley)

Mithra Moezzi (QQForward)

Susanne Moser (Susanne Moser Research and Consulting)

Sarah Newkirk (The Nature Conservancy)

David Saah (Spatial Informatics Group)

Andrew Schwarz (California Department of Water Resources)

Whendee Silver (University of California, Berkeley)

Daniel Sumner (University of California, Davis)

Nancy Thomas (University of California, Berkeley)

Jianzhong Wang (California Department of Water Resources)

LeRoy Westerling (University of California, Merced)

Coordinating Lead Authors

David Ackerly (University of California, Berkeley)

Louise Bedsworth (California Strategic Growth Council)

Dan Cayan (University of California, San Diego)

Julie Kalansky (University of California, San Diego)

Alex Hall (University of California, Los Angeles)

Francesca Hopkins (University of California, Riverside)

Ben Houlton (University of California, Davis)

Guido Franco (California Energy Commission)

Ron Goode (North Fork Mono Tribe)

Ted Grantham (University of California, Berkeley)

Ruth Langridge (University of California, Santa Cruz)

Jay Lund (University of California, Davis)

Josue Medellin (University of California, Merced)

Jenn Phillips (Ocean Protection Council)

Michelle Roos (E4 Consulting)

Leila Sievanen (Ocean Science Trust)

Joshua Viers (University of California, Merced)

LeRoy Westerling (University of California, Merced)

State Technical Managers and Support for Research Projects

Jamie Anderson (California Department of Water Resources), Whitney Albright (California Department of Fish and Wildlife), Louise Bedsworth (California Strategic Growth Council/Governor’s Office of Planning and Research), Crystal Reul-Chen (California Department of Resources Recycling and Recovery), Dorette English (California Department of Public Health), Lesley Ewing (California Coastal Commission), Guido Franco (California Energy Commission), Les Grober (State Water Resources Control Board), Bruce Gwynne (California Department of Conservation), You Hou (California Energy Commission), Geetika Joshi (California Department of Food and Agriculture), Nuin-Tara Key (Governor’s Office of Planning and Research), Victoria LaMar-Haas (California Office of Emergency Services), Bradley Leong (California Public Utility Commission), Geoff Margolis (California Department of Insurance), Michael McCormick (Governor’s Office of Planning and Research), Meredith Milet (California Department of Public Health), Jenn Phillips (Ocean Protection Council), Dave Sapsis (CALFIRE), Klaus Scott (California Air Resources Board), Katharina Snyder (California Energy Commission), David Stoms (California Energy Commission), Tara Ursell (California Department of Parks and Recreation), Susan Wilhelm (California Energy Commission), Sonya Ziaja (California Energy Commission)

Volunteer Technical Editors

Peter Benoliel (University of California, Davis), Dylan Chapple (California Council on Science and Technology), Nico De Golia (Middlebury Institute of International Studies), Tiffany Kinh Lam (Climate Resolve), Erin Lannon (Middlebury Institute of International Studies), Cole Mellino (Middlebury Institute of International Studies), Erica Orcutt (University of California, Davis), Stuart Ross, Christina Sloop (California Department of Fish and Wildfire), Erin Satterthwaite (University of California, Davis), Prescott Williams, Aaron Young