Climate Change in the. Pacific Northwest. Impacts, Choices, and Change

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1 Climate Change in the UW Climate Impacts Group Pacific Northwest Impacts, Choices, and Change UW Climate Impacts Group Philip Mote, Lara Whitely Binder Climate Impacts Group Center for Science in the Earth System Joint Institute for the Study of the Atmosphere and Ocean University of Washington Climate science in the public interest ATMS 211 May 23, 2007 UW Climate Impacts Group

2 The Climate Impacts Group 1st of 8 U.S. Regional Integrated Sciences and Assessment (RISA) teams Areas of study: Water resources Salmon Forests Coasts [Agriculture, Human Health] UW Climate Impacts Group Objectives Increase regional resilience to climate variability and change Produce science useful to (and used by!) the decision making community

3 Key Trends in 20 th Century Climate Average annual temperature increased +1.5 F in the PNW during the 20th century Temperature Trends ( F per century), since 1920 Cooler Warmer 3.6 F 2.7 F 1.8 F 0.9 F Mote 2003(a), updated

4 Key Trends in 20 th Century Climate Average annual temperature increased +1.5 F in the PNW during the 20th century Decrease Increase April 1 snowpack has decreased throughout the PNW with losses of 30-60% at many individual stations ( )

5 Nearly every glacier in the Cascades and Olympics has retreated during the past years South Cascade Glacier, 1928 (top) and 2000 (right) Photos courtesy of Dr. Ed Josberger, USGS Glacier Group, Tacoma, WA

6 Trends in Spring Runoff Peak of spring runoff is moving earlier into the spring throughout western U.S. and Canada Stewart et al. J Climate 2005

7 And What About Trends in Precipitation? Std Anomalies Relative to PNW CA CRB GB Regionally Averaged Cool Season (Oct-Mar) Precipitation Anomalies Little evidence of a consistent trend in the PNW but coherence and variability seem to have increased noticeably throughout the West around 1973

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9 Is This Human-induced Climate Change? Are these changes attributable entirely to natural climate variability? NO Are these changes attributable entirely to greenhouse gases? NO but a climate change signal may be emerging

10 QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture.

11 And what about the PNW in the 21st century? UW Climate Impacts Group

12 Projected 21 st Century PNW Warming Mean change: +2 F (2020s), +3 F (2040s) Rate of change expected to be 3x greater Warming expected in all seasons +1.9ºF ( ºF) +2.9ºF ( ºF) Changes relative to More detail on the CIG scenarios is available at:

13 Projected Changes in PNW Precipitation Modest increases (+2%) in annual average precipitation Most of the increase comes in the winter months (but in what intensity?) Projected increase in average does not exceed range of 20 th century averages Projected changes in monthly PNW precipitation. The lines show changes associated with warm (IPSL-A2), cool (GISS- B1), and middle-of-the-road (ECHAM5-A2) climate change scenarios Note: there is high confidence in projected temp changes, less in precipitation changes

14 Changes Relative to the 20 th Century 2080s

15 Lower Spring Snowpack Spring snowpack is projected to decline as more winter precipitation falls as rain rather than snow, especially in warmer mid-elevation basins +4 F, +4.5% winter precip Snowpack will melt earlier with warmer spring temperatures April 1 Snowpack

16 Streamflow Impacts Higher winter streamflows Earlier and lower peak runoff (mid/high basins) Lower late spring streamflow Lower, warmer summer streamflows Projected streamflow changes in the Quinalt and Yakima Rivers ~2050s to 2080s ~2050s to 2080s +3.6 (~2050s) to +5.4 F (~2080s)

17 Implications for Water Management Increased demand among competing uses (M&I, habitat, irrigation, water quality navigation, recreation, hydropower) Increased risk of winter flooding in many basins (changes in urban flooding less clear) Water systems must manage longer and more extreme drawdown periods that in the past Bottom line: Increased competition for water and increased vulnerability to drought

18 Salmon Impacted Across Full Life-Cycle Floods Warm, low streamflow?? Early peak flows

19 Climatic Change and Tree Growth Responses Subalpine forests: longer, warmer growing seasons, shorter snowpack duration = growth increase Mid elevation forests: warmer summers, lower snow pack = growth depends on precipitation change Low elevation forests: warmer summers, potentially less summer precipitation = large growth decrease Subalpine forests (Max. ~ 8000 ft.) Mid elevation forests Sea level Olympic Forests (Maritime Climate) Low elevation forests Western Cascades Forests Eastern Cascades Forests (Continental Climate)

20 Fire and Insects Increased vulnerability to fires and insect outbreaks due to a longer dry season (except in especially coolwet locations) BC outbreak of the mountain pine beetle has killed 100 billion board feet Lack of extreme cold, killing temperatures and current forest practices has allowed the beetle to thrive in epidemic numbers beetle killed pines in BC Beetle photos from

21 Sea Level Rise and Plate Tectonics Relative sea level rise may be greatest in South Puget Sound (~3ft by 2100) and least near Neah Bay (~1ft by 2100) Likely to increase pace and extent of erosion and nearshore habitat loss Sea Level Rise Scenarios

22 Marine and Ecosystem Function Climate change likely to impact several key parameters, e.g. water temperature, salinity, stratification, dissolved oxygen, nutrient availability (direction/magnitude of impact varies with parameter, location, time of year) Climate change will affect the Puget Sound ecosystem from the bottom-up (e.g., via impacts to phytoplankton) and top-down (e.g., via impacts to salmon, marine mammals) The ultimate impact of climate change on any individual species depends on how changes move through the food web and the ecosystem s ability to adapt to rapidly changing conditions

23 Skiing Recreation Increased risk of shortened ski season at lower elevation ski areas due to lack of snow or poor snow quality. Could improve customer access to ski areas. Other winter activities also likely to be affected (e.g. cross-country, snowmobiling) Hiking Fires/forest closures can affect summer tourism. Earlier access to low elevation trails?

24 Responding to Climate Change: Mitigation and Adaptation Mitigation activities Focus on reducing emissions of greenhouse gases Adaptation activities Focus on developing the capacity to manage the change that occurs as mitigation strategies are debated and enacted. Focus of the CIG.

25 Summary Global and regional climate is already changing These changes are expected to continue in the coming decades Changes in snowpack and streamflow caused by rising temperatures will have important consequences for resources across the Pacific Northwest The information and the tools to begin planning for climate change exist now