Transcript Slide 1
A Brief History of Climate Change Sensitivity Work JISAO Center for Science in the Earth System Climate Impacts Group and Department of Civil and Environmental Engineering University of Washington April, 2003 Dennis P. Lettenmaier Hydrology, water resources, and climate • Hydrologists and water resources engineers have always had to deal with climate, it wasn’t just “discovered” • But, the classical assumption is equivalent to statistical stationarity, “the future will resemble the past” • Unfortunately, the future may not be like the past, which greatly complicates planning Natural Flow at Lee Ferry, AZ Natural Flow at Lee Ferry Stream Gage 30 Annual Flow (BCM) 25 allocated 20.3 BCM 20 Currently used 16.3 BCM 15 10 5 0 1900 1910 1920 1930 Annual Flow 1940 1950 10 Year Average 1960 1970 1980 Running Average 1990 2000 Evolution of interest in climate change in hydrology • ~1977 NAS/NRC report (various papers, basically said “we know how to deal with this”) • Late 1980s AAAS study (Schaake paper evaluating water balance issues, SE U.S.) • Late 1980s EPA Reports to Congress • 1990s IPCC reports USNA (~40 papers cited on water resources and climate) UW interest in hydrology, water resources, and climate change • Hydrologic sensitivities of the Sacramento-San Joaquin River basin, California, to global warming (WRR, 1990) • Climatic sensitivity of California water resources (JWRPM, 1991) • Sensitivity of Pacific Northwest water resources to global warming (Northwest-Environmental-Journal, 1992) • Water resources implications of global warming: A U.S. regional perspective (Climatic-Change, 1999) • Effects of climate change on hydrology and water resources in the Columbia River basin (JAWRA , 1999) Effects to Snowpack Effects to Streamflow Number of Storage Failures no optimization More Storage Less Storage optimization U.S. Climate Change Study Basins (Lettenmaier et al. 1999) aug jun apr 60 feb 70 dec 80 oct 90 Average Flow (cfs) Flood Control Snake River Navigation Snake Irrigation McNary Fish Flow Lower Granite Fish Flow Grand Coulee Recreation Non-Firm Energy Firm Energy VIC/ColSim 2040’s 100 Current Climate ECHAM4 2040's HadCM2 2040's HadCM3 2040's PCM 2040's 50 DALLES 600000 500000 400000 Base ECHAM4 300000 HadCM2 200000 HadCM3 PCM 100000 0 Current Climate 2040 Composite Scenario Inflow to Chester Morse Lake Columbia River at The Dalles 9/2 8/5 7/8 6/10 5/13 4/15 3/18 2/18 aug jun apr feb dec 0 1/21 100000 12/24 2040s 200000 Base 2020s 2040s 11/26 300000 2020s 10/29 Base 9000 8000 7000 6000 5000 4000 3000 2000 1000 0 10/1 400000 Inflow (acre-ft) 500000 oct Average Flow (cfs) 600000 So what is the issue for this meeting? • The fundamental implications of global warming for snowmelt dominated and transient snow rivers in the west have been well understood in the academic community for a decade or longer. • Lots of questions about specifics, climate model uncertainty, etc. However, a) all models show there is a problem in snowmelt dominated watersheds, and b) the models are consistent with what’s been observed over the last half century or so. • Almost all the studies are academic – few examples where the studies have been done by the water management agencies, using their own tools and models • We are to the point where the question is no longer whether climate change is an issue, but rather how to incorporate it into the planning process (and preferably internalize it at the agency level)