Fifth Oregon Climate Assessment Dudley Chelton Oregon Climate Change Research Institute 1 Acknowledgments This fifth Oregon Climate Assessment is consistent with the charge of the Oregon Climate Change Research Institute under Enrolled House Bill 3543 of the 74th Oregon Legislative Assembly. We are grateful to the many authors, other contributors, reviewers, and advisors to this Assessment, especially during a year that was extraordinarily difficult for so many. We welcome readers to contact us with ideas for ensuring that the sustained assessment process is relevant to their priorities. Thanks to John Abatzoglou, Rupa Basu, Hilary Boudet, Tim Brown, Maya Buchanan, Karin Bumbaco, Francis Chan, Tyler Creech, Steven Dundas, Alexander Gershunov, Ryan Haugo, Glen MacDonald, Deniss Martinez, Guillaume Mauger, Phil Mote, Michael Olsen, Andrew Plantinga, David Rupp, and Tim Sheehan for reviews of content in this Assessment. Published January 2021 at Oregon State University, Corvallis, Oregon. Recommended citation: Dalton, M., and E. Fleishman, editors. 2021. Fifth Oregon Climate Assessment. Oregon Climate Change Research Institute, Oregon State University, Corvallis, Oregon. https://blogs.oregonstate.edu/occri/oregon-climate-assessments/. The photographers and figure sources credited herein retain all rights to their images. All other elements of the document are published under a Creative Commons Attribution- NonCommercial-ShareAlike 4.0 International License (CC BY-NC-SA 4.0). 2 3 Authors Table of Contents Idowu Ajibade, Portland State University Acknowledgments 3 Coral Avery, Affiliated Tribes of Northwest Indians & Northwest Climate Adaptation Science Authors 4 Center Meghna Babbar-Sebens, Oregon State University Executive Summary 7 John A. Barth, Oregon State University Introduction 9 Caren Braby, Oregon Department of Fish and Wildlife State of Climate Science 11 Heejun Chang, Portland State University Samantha Chisholm Hatfield, Oregon State University Natural Hazards Meghan Dalton, Oregon State University Extreme Heat 31 Erica Fleishman, Oregon State University Drought 37 Benjamin Galindo, Doris Duke Conservation Scholars Program Wildfire 47 Kelly Gleason, Portland State University Floods 67 Jessica Halofsky, USDA Forest Service, Northwest Climate Hub and Western Wildland Coastal Hazards 75 Environmental Threat Assessment Center Marine and Coastal Change 81 Benjamin Hatchett, Desert Research Institute Adaptation Sectors Tia H. Ho, Finding Mindful Now & Portland State University Natural Systems 95 Andrés Holz, Portland State University Built Environment 113 Perry Hystad, Oregon State University Public Health 137 Lara Jacobs, Oregon State University Tribal Cultural Resources 157 Chas Jones, Affiliated Tribes of Northwest Indians & Northwest Climate Adaptation Science Center Social Systems 171 Paul Loikith, Portland State University Chris Lower, Portland State University Elizabeth Marino, Oregon State University–Cascades Philip Mote, Oregon State University William Nanavati, Portland State University Larry O’Neill, Oregon State University Laura Platt, Portland State University Laura Queen, Oregon State University Charlotte Regula Whitefield, Oregon Department of Fish and Wildlife Alexandra Rempel, University of Oregon Peter Ruggiero, Oregon State University David Rupp, Oregon State University Stephanie Salas, Doris Duke Conservation Scholars Program Emily York, Oregon Health Authority 4 5 Fifth Oregon Climate Assessment • January 2021 Executive Summary Established and emerging understanding of Oregon. During summer, relative increases in observed and projected climate change in Oregon, nighttime minimum temperatures have been greater and knowledge of the opportunities and risks that than those in daytime maximum temperatures. The climate change poses to natural and human systems, frequency, duration, and intensity of extreme heat may serve as a resource for actions including but not events is expected to increase throughout the state limited to planning for mitigation of climate-related during the twenty-first century. natural hazards and implementation of Oregon’s Drought. Over the past 20 years, the incidence, 2021 Climate Change Adaptation Framework. extent, and severity of drought in the Northwest State of Climate Science increased. These changes partially are attributable to human-caused climate change. As summers in Temperature. Oregon’s annual average temperature Oregon continue to become warmer and drier, and increased by about 2.2°F per century since 1895. If mountain snowpack decreases, the frequency of greenhouse gas emissions continue at current levels, droughts, particularly snow droughts such as those in temperature in Oregon is projected to increase on 2014 and 2015, is likely to increase. average by 5°F by the 2050s and 8.2°F by the 2080s, with the greatest seasonal increases in summer. Wildfire. Wildfire dynamics are affected by climate change, past and contemporary land management Precipitation. Precipitation is projected to increase and human activity, and expansion of non-native during winter and decrease during summer. The invasive grasses. From 1984 through 2018, annual number and intensity of heavy precipitation area burned in Oregon increased considerably. events, particularly in winter, is projected to Over the next 50 to 100 years, area burned and fire increase throughout the twenty-first century. frequency are projected to increase substantially, Furthermore, as temperatures warm, the proportion initially east of the crest of the Cascade Range of precipitation falling as rain rather than snow in and then in the western Cascade Range. Over the Oregon is projected to increase, especially at lower to long term, depending on how vegetation and fire intermediate elevations in the Cascade Range. weather shift with climatic changes and fuel and fire Snowpack and runoff. Snowpack throughout management, fire severity also may increase. Oregon, especially on the west slope of the Cascade Floods. Flood magnitudes in Oregon are likely to Range, is accumulating more slowly, reaching lower increase. Heavy precipitation events are expected to peak values, and melting earlier. These trends are become more intense because a warmer atmosphere likely to continue, and may accelerate, as temperature can carry more moisture. Also, in a warmer climate, increases. Concomitantly, runoff is expected to begin the relatively contribution to floods of rainfall will and peak earlier in the year, decline in summer, and be greater than that of snowmelt. The consequence increase in winter, but will vary geographically. is larger flood peaks because, for a given amount of Science advances. In addition to simulations of precipitation, the peaks of rainfall-driven floods tend future climate from the newest generation of global to be larger than those of snowmelt-driven floods. climate models, advances in climate science have Projected increases in wet-season precipitation improved the accuracy of climate forecasts one week also are likely to increase winter flood magnitude. to one month into the future. Also, it is becoming Increases in regulated flows from the main stem of more feasible to estimate the extent to which human- the Columbia River during winter appear likely to caused climate change affects the likelihood of some increase flood risk throughout the Columbia River types of extreme weather events. reservoir system. Coastal hazards. Sea-level rise, storminess, sediment Climate-Related Natural Hazards supply, and human adaptation measures influence Extreme heat. The frequency and magnitude of whether a given stretch of Oregon’s coastline has days that are warmer than 90°F is increasing across eroded or built up in recent decades. Therefore, 6 7 predicting future shoreline change is challenging. As and risks of heat stress. Opportunities for mitigation Introduction sea level rises, coastal storms and high tides are likely and adaptation include wind and solar power, grid to increase the frequency and severity of flooding integration of electric transportation, and green Consistent with its charge under Oregon House Bill 3543, the Oregon Climate Change Research along Oregon’s coastline. By the year 2050, relative infrastructure for resilience to flooding. Data- Institute (OCCRI) conducts a biennial assessment of the state of climate change science, including sea level at Newport is very likely to rise between driven, science-based capital planning that engages biological, physical, and social science, as it relates to Oregon and the likely effects of climate change 0.6 and 1.8 feet, and at least one flood is likely to stakeholders can help to realize these adaptations. exceed four feet above mean high tide. Accounting on Oregon. This fifth Oregon Climate Assessment builds on previous assessments (Dello and Mote Public health. Racial and economic injustices for plausible, yet uncertain, estimates of Antarctic 2010; Dalton et al. 2013, 2017; Mote et al. 2019) by continuing to evaluate past and projected future have created disparities in health outcomes among ice sheet melt suggests that sea level could rise 2.9 changes in Oregon’s climate and hydrology. This Assessment is structured with the goal of serving populations in Oregon. Black, Indigenous, and feet by the year 2050, with regular nuisance flooding as a resource for the state’s mitigation planning for natural hazards and implementation of the 2021 People of Color; underinvested rural, Tribal, and occurring earlier. Oregon Climate Change Adaptation Framework. low-income