Climate change impacts and adaptation in the Pacific Northwest Dennis P. Lettenmaier Department of Civil and Environmental Engineering and Climate Impacts Group University of Washington American Geophysical Union Fall Meeting San Francisco December 17, 2008

Outline of this talk 1)The UW Climate Impacts Group – the scientific basis 2)Statewide climate impact assessment 3)Adaptation inferences 4)Lessons learned, and evolving issues

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

Have we seen changes in 20 th century climate in the PNW? UW Climate Impacts Group

PNW Temperature Trends by Station Average annual temperature increased +1.5  F in the PNW during the 20th century Almost every station shows warming Extreme cold conditions have become rarer Low temperatures rose faster than high temperatures Annual variability present throughout the warming trend 3.6 °F 2.7 °F 1.8 °F 0.9 °F Cooler Warmer Mote 2003(a) In contrast: No clear 20 th century trend in precipitation …

Decrease Increase Trends in Snow Water Equivalent Similar trends seen throughout the western United States - 73% of stations show a decline in April 1 snow water equivalent Most PNW stations show a decline in snow water equivalent Numerous sites in the Cascades with 30% to 60% declines

Is This Climate Change? Are these changes due entirely to climate change? NO Are these changes due entirely to natural climate variability? NO …but it would seem to have an increasing influence The trends are consistent with global climate change projections, and The trends are generally consistent across the Western U.S.

Accelerated warming: °F (~ 0.5ºF average) per decade through at least 2050 (compared to 1.5°F over 20th century) Warming is expected during all seasons with the largest temperature increases likely in summer (June-August) Precipitation variability continues, and average postive in winter, negative in summer High confidence in projected temp changes, less in precipitation changes 2020sTemperaturePrecip Low 1.1  F (0.6  C) - 9% Average 2.2  F (1.2  C) + 1% High 3.4  F (1.9  C) + 12% All changes are benchmarked to average temperature and precipitation for sTemperaturePrecip Low 1.6  F (0.9  C) - 11% Average 3.5  F (2.0  C) + 2% High 5.2  F (2.9  C) + 12% Projected 21 st Century PNW Climate Change ongoing statewide impact assessment

Spring snowpack is projected to decline as more winter precipitation falls as rain rather than snow, especially in warmer mid-elevation basins Snowpack will melt earlier with warmer spring temperatures Lower Spring Snowpack

Shifts in Streamflow, Yakima River basin

Puget Sound Basin Variations in impacts within and between systems (A1B) Seattle, springtime snowmelt peak disappears 2080s Tacoma, less transition, more constrained storage Everett, more interannual variability in storage TacomaEverettSeattle

Seattle water supply system Reliability impacted only by warmest and driest scenarios by 2020s Likelihood of storage below 50%, 25%, and 10% active capacity indicates system sensitivities

Impacts on stream temperatures

Shifts in energy production and demand

Changes in precipitation maxima

Preparing for Climate Change A Guidebook for Local, Regional, and State Governments Climate Science in the Public Interest

Motivation for writing grew out of October 2005 King County climate change conference Written by the CIG and King County, WA in association with ICLEI – Local Governments for Sustainability Written to compliment ICLEI’s “Climate Resilient Communities” Program Focused on the process (not a sector), and written for a national audience

Water management adaptation options Expand and diversify existing water supplies  Improve regional water system connectivity  Groundwater cyclic storage  Purchase water rights  Add capacity to existing reservoirs Develop new or alternate water supplies  Develop new groundwater sources  Construct new surface water reservoirs  water reuse  new technologies (desalination )  Rainwater harvesting Reduce demand/improve efficiency  Increase water conservation  Water pricing  Reduce outdoor water demands  Update building codes  Financial incentives for substitution  Reduce system losses Implement operational changes  Rebalance flood rule curves Improve hydrologic forecasting  Optimize reservoir management  Shift hydropower generation schedules  Revise maintenance schedules  Artifical groundwater recharge using existing irrigation systems Increase ability to transfer water between uses and users  Improve drought forecasting capability  Update drought management plans to recognize changing conditions  Increase emergency aid assistance for droughts  Improve coordination between stakeholders during drought

Zoning rules and regulations Taxation (including tax incentives) Building codes/design standards Utility rates/fee setting Public safety rules and regulations Issuance of bonds Infrastructure development Permitting and enforcement Best management practices Outreach and education Emergency management powers Partnership building with other communities General Implementation Tools

Concluding comments 1)We are in the process of a major shift from assessment to adaptation 2)More attention needs to be paid to uncertainties, and how best to incorporate what we know (and don’t know) in the planning process 3)There is a general lack of understanding in the scientific community of the planning, design, and decision processes, both at the technical and nontechnical levels 4)At the technical level, we lack the tools needed to perform risk assessment under nontstationary conditions. More thought needs to be given to ensemble, vs multimodel ensemble methods