National Climate Assessment Regional Technical Input Report Series Assessment of Climate Change in the Southwest United States A Report Prepared for the National Climate Assessment Edited by: Gregg Garfin Angela Jardine Robert Merideth Mary Black Sarah LeRoy Assessment of Climate Change in the Southwest United States A Report Prepared for the National Climate Assessment © 2013 Institute of the Environment All rights reserved under International and Pan-American Copyright Conventions. Reproduction of this report by electronic means for personal and noncommercial purposes is permitted as long as proper acknowledgement is included. Users are restricted from photocopying or mechanical reproduction as well as creating derivative works for commercial purposes without the prior written permission of the publisher. ISLAND PRESS is a trademark of the Center for Resource Economics. Printed on recycled, acid-free paper Manufactured in the United States of America Citation: Garfin, G., A. Jardine, R. Merideth, M. Black, and S. LeRoy, eds. 2013.Assessment of Climate Change in the Southwest United States: A Report Prepared for the National Climate Assessment. A report by the Southwest Climate Alliance. Washington, DC: Island Press. Keywords: Adaptation, agriculture, air quality, assessment, atmospheric river, biodiversity, climate change, climate impacts, climate modeling, climate variability, coastal, Colorado River, decision making, drought, electric power generation, extreme events, flooding, forest mortality, Great Basin, heat related illness, heat wave, land-use change, mitigation, Native American tribes, natural resource management, ocean acidification, phenology, public health, ranching, Rio Grande, Sacramento-San Joaquin, sea-level rise, social vulnerability, Southwest, stationarity, uncertainty, urban metabolism, U.S.Mexico border, vector-borne disease, water resources, wildfire This technical input document in its current form does not represent a Federal document of any kind and should not be interpreted as the position or policy of any Federal, State, Local, or Tribal Government or Non-governmental entity. Front Cover Images: Eagle Dancers courtesy of the New Mexico Tourism Department. All other images courtesy of iStock. About This Series This report is published as one of a series of technical inputs to the National Climate Assessment (NCA) 2013 report. The NCA is being conducted under the auspices of the Global Change Research Act of 1990, which requires a report to the President and Con- gress every four years on the status of climate change science and impacts. The NCA in- forms the nation about already observed changes, the current status of the climate, and anticipated trends for the future. The NCA report process integrates scientific informa- tion from multiple sources and sectors to highlight key findings and significant gaps in our knowledge. Findings from the NCA provide input to federal science priorities and are used by U.S. citizens, communities and businesses as they create more sustainable and environmentally sound plans for the nation’s future. In fall of 2011, the NCA requested technical input from a broad range of experts in academia, private industry, state and local governments, non-governmental organiza- tions, professional societies, and impacted communities, with the intent of producing a better informed and more useful report in 2013. In particular, the eight NCA regions, as well as the Coastal and the Ocean biogeographical regions, were asked to contribute technical input reports highlighting past climate trends, projected climate change, and impacts to specific sectors in their regions. Each region established its own process for developing this technical input. The lead authors for related chapters in the 2013 NCA report, which will include a much shorter synthesis of climate change for each region, are using these technical input reports as important source material. By publishing this series of regional technical input reports, Island Press hopes to make this rich collection of information more widely available. This series includes the following reports: Climate Change and Pacific Islands: Indicators and Impacts Coastal Impacts, Adaptation, and Vulnerabilities Great Plains Regional Technical Input Report Climate Change in the Midwest: A Synthesis Report for the National Climate Assessment Climate Change in the Northeast: A Sourcebook Climate Change in the Northwest: Implications for Our Landscapes, Waters, and Communities Oceans and Marine Resources in a Changing Climate Climate of the Southeast United States: Variability, Change, Impacts, and Vulnerability Assessment of Climate Change in the Southwest United States Electronic copies of all reports can be accessed on the Climate Adaptation Knowledge Exchange (CAKE) website at www.cakex.org/NCAreports. Printed copies are available for sale on the Island Press website at www.islandpress.org/NCAreports. Assessment of Climate Change in the Southwest United States A Report Prepared for the National Climate Assessment EXECUTIVE EDITOR Gregg Garfin (University of Arizona) ASSOCIATE EDITOR Angela Jardine (University of Arizona) CONTRIBUTING EDITORS Robert Merideth (University of Arizona) Mary Black (University of Arizona) Sarah LeRoy (University of Arizona) Washington | Covelo | London Acknowledgements The authors thank the members of the Southwest Climate Alliance Executive Commit- tee, who developed the original Expression of Interest for this technical report. Mem- bers included: David Busch (USGS), Dan Cayan (Scripps Institution of Oceanography/ UCSD), Michael Dettinger (USGS), Erica Fleishman (University of California, Davis), Gregg Garfin (University of Arizona), Alexander Sasha Gershunov (Scripps Institution of Oceanography/UCSD), Glen MacDonald (UCLA), Jonathan Overpeck (University of Arizona), Kelly Redmond (Desert Research Institute), Mark Schwartz (University of California, Davis), William Travis (University of Colorado), and Brad Udall (Uni- versity of Colorado). We acknowledge the contributions of the three NOAA Regional Integrated Sciences and Assessments (RISA) projects in the region, and their program managers, through the generous donation of staff time and assessment advice: California- Nevada Applications Program (CNAP; Dan Cayan), Climate Assessment for the South- west (CLIMAS; Dan Ferguson), and Western Water Assessment (WWA; Brad Udall). We also acknowledge the contributions of the Southwest Climate Science Center (SWCSC). The NOAA Climate Program Office and the USGS provided funding and development support. For guidance and input in writing this report, we thank the National Climate Assess- ment staff: Emily Cloyd, Katharine Jacobs, Fred Lipschultz, Sheila O’Brien, and Anne Waple. We thank the National Climate Assessment Development and Advisory Com- mittee for guidance and input in writing this report. This includes the following people: Jim Buizer (University of Arizona), Guido Franco (California Energy Commission), Nan- cy Grimm (Arizona State University), Diana Liverman (University of Arizona), Susanne Moser (Susanne Moser Research and Consulting, Stanford University), Richard Moss (Pacific Northwest National Laboratory), and Gary Yohe (Wesleyan University). The authors are grateful to Jaimie Galayda (University of Arizona) for exceptional assistance in organizing the August 2011 prospective authors’ workshop. Eric Gordon (University of Colorado), Sarah Guthrie (CIRES), William Travis (University of Colo- rado), and Suzanne van Drunick (CIRES) hosted the 2011 workshop, providing rooms, technical support, and hospitality. Mary Floyd (Zantech IT Services) assisted with travel arrangements for some of the workshop participants. Tamara Wall (Desert Research In- stitute) also provided assistance. Jennifer Paolini (Scripps Institution of Oceanography) provided exceptional logistical support and hospitality for our August workshop and our January 2012 Coordinating Lead Authors’ workshop. Lesa Langan DuBerry (Uni- versity of Arizona) and Anh Le (University of Arizona) provided logistical support for both workshops. The Assessment of Climate Change in the Southwest United States was developed with the benefit of a scientifically rigorous first draft expert review and we thank the review editors and expert reviewers. We also thank everyone who contributed in the public review, as well as the decision makers, resource managers, citizens, and experts who provided feedback on the content of the report, in addition to valuable insights about the form of the report and ancillary materials. ix x ASSESSMENT OF CLIMATE CHANGE IN THE SOUTHWEST UNITED STATES We acknowledge the modeling groups, the Program for Climate Model Diagnosis and Intercomparison (PCMDI) and the World Climate Research Programme (WCRP) Working Group on Coupled Modeling (WGCM) for their roles in making available the WCRP CMIP3 multi-model dataset. Support of this dataset is provided by the Office of Science, U.S. Department of Energy. The GCM projections from the CMIP3 dataset are part of the World Climate Research Programme’s (WCRP’s) Coupled Model Intercom- parison Project phase 3 (CMIP3) multi-model dataset. Bias Corrected and Downscaled (BCSD) and VIC hydrological model projections were obtained from the http://gdo-dcp. ucllnl.org/downscaled_cmip3_projections/ archive provided by the U.S. Bureau of Rec- lamation and partners (see Reclamation, 2011, “West-Wide Climate Risk Assessments: Bias-Corrected and Spatially Downscaled Surface Water Projections,” Technical Memo-