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

Global to Regional Downscaling

GCMs ~150km downscaled toRegional models ~ 12km

Many simulationsIPCC AR4 and IPCC AR5 have been downscaledusing 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

average summer afternoon temperature

average summer afternoon temperature

3GFDL A2 1km downscaled to 1kmHugo Hidalgo Tapash Das Mike Dettinger

Temperature Change 14 GCMs X 3 RCP emissions Scenarios

IPCC 5th Assessment (CMIP5) models

Uncertainty is substantial in climate projections

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 median2100 median SWE ~ 1/3 historical median