1. Dan Cayan USGS Water Resources Discipline Scripps Institution of Oceanography, UC San Diego much support from Mary Tyree, Mike Dettinger, Guido Franco and other colleagues Sponsors: California Energy Commission NOAA RISA program California DWR, DOE, NSF Planning for climate change in California substantial shifts on top of already high climate variability Calit2 100G and Beyond UCSD 2/26/2013

2. Global to Regional Downscaling GCMs ~150km downscaled to Regional models ~ 12km Many simulations IPCC AR4 and IPCC AR5 have been downscaled using statistical methods INCREASING VOLUME OF CLIMATE SIMULATIONS in comparison to 4th IPCC (CMIP3) GCMs : Latest generation CMIP5 models provide: more simulations higher spatial resolution more developed process representation daily output is more available

3. average summer afternoon temperature average summer afternoon temperature 3 GFDL A2 1km downscaled to 1km Hugo Hidalgo Tapash Das Mike Dettinger

4. Temperature Change 14 GCMs X 3 RCP emissions Scenarios IPCC 5 th Assessment (CMIP5) models Uncertainty is substantial in climate projections

5. HOW MUCH CALIFORNIA SNOW LOSS ? Initial projections indicate substantial reduction in snow water for Sierra Nevada+ declining Apr 1 SWE: 2050 median SWE ~ 2/3 historical median 2100 median SWE ~ 1/3 historical median