Pacific Northwest Climate Change and Expected Impacts

1. Pacific Northwest Climate Change and Expected Impacts Eric Salathé salathe@washington.eduClimate Impacts GroupUniversity of Washington

2. 3.6°F 2.7°F 1.8°F 0.9°F

3. Some year-by-year data

4. Global Climate System Model

5. Range of Projected Climate Change for the Pacific Northwest from Latest IPCC Climate Simulations

6. (2-10 ºF) (1.6-4.3 ºF) (0.7-1.8 ºF)

10. Reference Scenarios Three Scenarios that represent the range of expected changes for use in detailed impacts studies: ECHAM5-A2 - Mid-range IPSL-A2 -- High change GISS-B1 -- Low change +30% -30%

11. SUMMARY • Projected Pacific Northwest warming: 1/4 to 1 ºF/decade • Probably more warming in Summer than Winter • Precipitation changes uncertain – Possibly wetter winters and drier summers

12. Global models must be downscaled for regional studies

13. Downscaling Methods Used in CIG Empirical Downscaling • Assumes climate model captures temperature and precipitation trends • Quick: Can do many scenarios •Shares uncertainties with global models • Regional Climate Model • Based on MM5 regional weather model • Represents regional weather processes • May produce local trends not depicted by global models • Additional modeling layer adds bias and uncertainty

14. Washington’s economy and natural resources are sensitive to climate changes • “drought” – a water supply shortage – is our region’s greatest climate vulnerability

15. The main impact of a warmer climate: LESS SNOW for a ~3.6°F (2°C) warming Snoqualmie Pass 3022 ft

16. Springtime snowpack will decline, especially at the warmest locations + 4.1 ºF (2.3 ºC) & + 4.5% winter precipitation +2.3C, +4.5% winter precip

17. Springtime snowpack will decline, especially at the warmest locations + 4.1°F + 4.5% winter precip

18. Western Washington Precip Oct Feb Jun +3.6 to +5.4°F (+2 to +3°C) Streamflow depends on Snowpack

19. 2000 climate +4.1 ºF Reduced spring & summer flows Increased winter flows Impacts on Seattle’s water supply • reduced summertime inflows, increasing the size and extending the time of the summertime inflow-demand deficit • this is common to all our region’s municipal (surface) water supplies Oct Dec Feb Apr Jun Aug Wiley (2004)

20. Factors driving Portland Oregon’s future water supply Bull Run Watershed Climate change: supply drops by ~16% Projected population growth increases demand: +66% Warmer temperatures increase demand +18% Including the 2040s scenario for climate change impacts increases projected future supply needs by ~50% of the amount needed to meet population growth alone. Palmer and Hahn (2004)

21. Climate impacts on salmon must be added to existing stresses across their full life-cycle

22. Climate impacts on salmon must be added to existing stresses across their full life-cycle HABITAT CHANGE and DEGRADATION INCLUDING GLOBAL WARMING HARVEST PRACTICES HATCHERY PRACTICES

23. Climate change impacts on Washington’s forests • CO2 fertilization • A transient impact • a longer dry season • reduced regeneration, increased vulnerability to fires and pests (except in especially cool-wet locations) • shifts in species ranges • subalpine forests “invading” alpine meadows; a northward march--or a loss--of species?

24. Climate change sharpens the tradeoffs in a world of multiple stresses • climate change will likely intensify existing conflicts over scarce natural resources • most of our natural resources are now fully allocated and managers already grapple with difficult tradeoffs • summer water supplies for in and out of stream uses are especially vulnerable to climate warming • global warming impacts on Washington depend on both the climate change and on how we prepare

25. Correspondence of Temperature and Precipitation Trends Déry & Wood, Geophys Res Lett, 2005

26. Stormtrack and Climate Change: Influence on Precipitation J Yin, Geophys Res Lett, 2005

27. Stormtrack and Climate Change: Influence on Precipitation J Yin, Geophys Res Lett, 2005