Washington State Climate Change Impacts Assessment: HB 1303 Key Findings JISAO/CSES Climate Impacts Group University of Washington Washington State University Pacific Northwest National Laboratory Climate science in the public interest UW Climate Impacts Group

Assessment Overview: Study Region

Scientific progress, assessment limitations Progress: –Vertical integration of climate change projections –Wide range of research areas –Narrowing of uncertainty with many climate models –Quantified impacts and ranges for decision making Limitations: –Modeling climate variability (interannual, decadal) –Interactions between impacts –Uncertainty in climate and projections –There may be thresholds we have yet to understand

Scenarios changes in future temperature and precipitation for the PNW and assessment of sub-regional climate change using regional climate models

Projected Increases in Annual Temperature 2020s 2040s 2080s °F°F°C°C 5.9°F 3.5°F 2.2°F * Compared with average

Projected Changes in Annual Precipitation * Compared with average Changes in annual precipitation averaged over all models are small but some models show large seasonal changes, especially toward wetter autumns and winters and drier summers.

Regional climate model projections High-resolution models provide some key projections that are similar across models, namely increases in extreme precipitation in western WA and reductions in Cascade snowpack. Regional climate models provide detail about local differences in the seasonal temperature and precipitation changes compared to the state-wide mean obtained from global models.

Regional climate model projections

Hydrology and Water Resources changes in the hydrology (streamflow, snowpack, soil moisture) and the water resources (water storage, irrigated agriculture) of Washington

Hydrology and water resources April 1 snowpack is projected to decrease by an average of 28% to 29% across the state by the 2020s, 38% to 46% by the 2040s and 56% to 70% by the 2080s Seasonal streamflow timing will shift significantly in sensitive watersheds. Due to changing seasonal streamflow, the Yakima basin reservoir system will be less able to supply water to all users, especially those with junior water rights. Historically, the Yakima basin has been significantly water short 14% of the time. Without adaptations, current projections of the medium (A1B) emissions scenario estimate this value will increase to 32% (15% to 54% range) in the 2020s and will increase further to 36% in the 2040s and 77% in the 2080s. * (results are compared to )

Hydrology and water resources * Compared with average

Energy changes in the demand for and production of hydropower in Washington

Energy Annual hydropower production is projected to decline by a few percent due to small changes in annual flow, but seasonal changes will be substantial. Winter hydropower production is projected to increase by about % by the 2020s, % by the 2040s, and 7%-10% by the 2080s (compared to water year ) Summer energy production is projected to decline by 10% by the 2020s, 15% by the 2040s, and 20% by the 2080s. At the same time summer cooling demands may increase by 400%

Energy Changes in system-wide hydropower production in the Columbia system for three future time frames: large declines in summer, slight increases in winter.

Agriculture & Economics changes in the expected production of high-value crops in Washington (apples, potatoes, wheat)

Agriculture In the absence of water limitations, the projected impact of climate change on eastern Washington agriculture will not be severe. Likely changes in yields from climate alone are increases in winter wheat (2-8% by the 2040s), decreases in irrigated potatoes (15% by the 2040s) and decreases in apples (3% by the 2040s). However, the combination of warming and elevated CO 2 could provide significant potential benefits that offset these declines. There is some uncertainty about whether the CO 2 effect is transient, but for well managed crops in eastern WA, the beneficial effect of elevated CO 2 will most likely be positive.

Salmon changes in the quality and quantity of salmon freshwater habitat in Washington

Salmon and Ecosystems Rising stream temperature will reduce the quality and quantity of freshwater salmon habitat substantially. The duration of temperatures causing thermal migration barriers and extreme thermal stress (where weekly water temperatures exceed 70°F) are predicted to quadruple by the 2080s. Water temperatures for Western Washington stations are generally cooler, and predicted impacts on thermal stress are significant but less severe.

Salmon and Ecosystems August Mean Surface Air Temperature and Maximum Stream Temperature Historical ( ) 2040s medium (A1B) * Projections are compared with average

Changes in Flood Risks Floods in western WA will likely increase in magnitude due to the combined effects of warming and increasingly intense winter storms. In other parts of the State, changes in flooding are smaller, and in eastern WA projected reductions in flood risk are common due to loss of spring snow cover.

Forests changes in the productivity, distribution and disturbance of forest ecosystems in Washington

Forests The area burned by fire regionally (in the U.S. Columbia Basin) is projected to double or triple (medium scenario, (A1B)), from about 425,000 acres annually ( ) to 0.8 million acres in the 2020s, 1.1 million acres in the 2040s, and 2.0 million acres in the 2080s. Due to climatic stress on host trees, mountain pine beetle outbreaks are projected to increase in frequency and cause increased tree mortality. Climatically suitable habitat for pine species susceptible to mountain pine beetle is likely to decline dramatically by the 2040s.

Forests Changes in areas of potential pine species’ ranges in Washington. Combined with impacts of fire and pine beetle, these areas are likely to see significant change (Data: Rehfeldt et al. 2006, multiple IPCC scenarios).

Coasts impacts in coastal areas of Washington

Coasts A previous study involving the Climate Impacts Group found that sea level rise in Puget Sound might be as little as 6” or as much as 50” by Sea Level Rise (SLR) will shift the coastal beaches and increase erosion of unstable bluffs, endangering houses and other structures built near the shore or near the bluff edges. Shellfish will possibly be negatively impacted by increasing ocean temperatures and acidity, shifts in disease and growth patterns, and more frequent harmful algal blooms (HAB).

Urban Stormwater Infrastructure changes in storms and demands on urban stormwater infrastructure in Washington

Urban Stormwater Infrastructure Drainage infrastructure designed using mid-20th century rainfall records may be subject to a future rainfall regime that differs from current design standards. Results from regional climate models suggest increased extreme rainfall in late autumn in western Washington. Hydrologic modeling of two urban creeks in central Puget Sound suggest overall increases in peak annual discharge over the next half-century, but only those projections resulting from one of the two RCM simulations are statistically significant. Magnitudes of projected changes vary widely, depending on the particular basin under consideration and the choice of the underlying global climate model.

Human Health impacts of heat waves and climate-related air pollution on health in Washington

Human Health In Washington, climate change will lead to larger numbers of heat-related deaths due mainly to hotter summers and population growth. For example in Seattle a medium climate change scenario projects 101 additional deaths for people over 45 by 2025 and another 50% increase by 2045 Although better control of air pollution has led to improvements in air quality, warmer temperatures threaten some of the sizeable gains that have been made in recent years.

Human Health Percent Increase in Risk of Death, and Number of Deaths Each Day for All Non- Traumatic Causes by Heat Event Duration, Greater Seattle Area,

Adaptation fundamental concepts for planning for climate change and options for adapting to the impacts identified in the above sectors

Climate change impacts over the next few decades are virtually certain. Impacts beyond this timeframe will be greatly influenced by how successfully we reduce greenhouse gas concentrations both in the near-term and over time. State and local governments, businesses, and residents are on the “front line” when it comes to dealing with climate change impacts. Decisions with long-term impacts are being made every day, and today’s choices will shape tomorrow’s vulnerabilities. Adaptation Options and Opportunities

Conclusions Adaptation to climate change impacts is necessary because the projected impacts within and across sectors are large. To the extent that it can be identified, quantified, and mitigated, uncertainty is a component of planning, not a reason to avoid planning. Many sectors report different impacts in different systems (e.g., snowpack response at low vs. high elevations, fire response in the western Cascades vs. Blue Mountains, different species of salmonids, different crops etc.), but the natural spatial and temporal complexity of these systems is a key part of planning for the future. By understanding the direction and magnitude of projected climate changes and its impacts, we can better manage risks and capitalize on opportunities to reduce impacts.

JISAO/CSES Climate Impacts Group The Climate Impacts Group Climate science in the public interest UW Climate Impacts Group