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California’s Future Climate

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Presentation on theme: "California’s Future Climate"— Presentation transcript:

1 California’s Future Climate
Lessons from Scenarios Assessments Dan Cayan Scripps Institution of Oceanography, Climate Research Division, UCSD and Water Resources Division, USGS Thanks: Mike Dettinger, Noah Knowles, Mary Tyree Funding: PIER Program, California Energy Commission RISA Program, NOAA Office of Global Programs DOE More info: http//

2 California Climate Change Scenarios Assessment some lessons learned
Gov Swartzenegger’s June 2005 Executive Order commissioned this Climate Assessment, which investigated potential climate change impacts and formed key scientific background for California’s greenhouse gas emissions legislation, AB-32 which was passed in fall 2006 Available on the web at

3 Vulnerability: response to a +3ºC warming
What fraction of each year’s precipitation historically fell on days with average temperatures just below freezing? YOSEMITE Less vulnerable More vulnerable “Rain vs Snow” Computed by Mike Dettinger from gridded historical US weather data (from Bates et al, in rev)

4 More Rain Less Snow WY Winter (Nov-Mar) SFE/P trends at western US weather stations: symbol area is proportional to study-period changes, measured in standard deviations as indicated; circles indicate high trend significance (p<0.05), squares indicate lower trend significance (p>0.05). Noah Knowles et al. 2006 in press J. Climate

5 We face significant losses of spring snowpack
Less snow, more rain Particularly at lower elevations Earlier run-off More floods Less stored water By the end of the century California could lose half of its late spring snow pack due to climate warming. This simulation by Noah Knowles is guided by temperature changes from PCM’s Business-as-usual climate simulation. (a middle of the road emissions scenario) Knowles and Cayan 2001

6 since 1985 the number of large wildfires in western U. S
since 1985 the number of large wildfires in western U.S. increased by 4X Anthony Westerling et al. Science August 2006

7 Large wildfire threat is aggravated by warmer springs and summers
Anthony Westerling et al. Science August 2006

8 Ocean Beach , February 1983 Extreme storm-forced sea levels during an extreme tide

9 Observed SFO (left) and modeled Global (right)
Observed SFO (left) and modeled Global (right). Sea level rise estimates based upon an envelope of output from several GHG emission scenarios Projected envelope of global s.l. rise observed Climate models Only provide loose guidance on The amount of sea level rise, but It is very likely that rates will increase

10 San Francisco Bay/Delta Water Levels
Confluence of sea level rise and increased flooding ~Jan Nasa /ncalifflood_amo_ _lrg.jpg

11 Uncertainty: Projected Warming Ranges Statewide annual average (°F)
14.4 10.8 9 3.6 -3.6 Higher Warming Range Medium Warming Range Temperature Change (°F) Lower Warming Range

12 Meditterranean precipitation regime remains

13 Although models unanimously indicate a warmer
climate, they are undecided if it will get wetter or dry out 6 different climate models 5 emission scenarios, IPCC SRES runs Mike Dettinger, 2005 San Fran. Estuary and Watershed Science

14 Projected patterns of precipitation changes
versus Globally, dry regions become drier?

15 Challenges Mike Dettinger, Jim Wells USGS and SIO
record streamflow in Tuolumne Meadows

16 Seasonally intensified warming?
some models suggest amplified summer warming

17 GFDL CM2.1 Jun-Aug air temp change
Climate models project 1.5-2.C ocean surface warming by end–of-century. Greater warming on land than oceans would amplify California coast-interior thermal gradient. Summer land warming is accentuated GFDL CM2.1 Jun-Aug air temp change minus GFDL CM2.1 is a medium-high sensitivity model. Other models produce less (or more) warming

18 Modeling climate over California’s complex terrain: July 10m Wind Diurnal Variation

19 Are models capable of producing realistic suite of wet and dry spells?
Distribution of Obs and simulated 5yr precip departures obs Sacramento drainage div sim sim Hist means (inches): Div Gfdl 43.13 Pcm 29.63

20 California needs a sustained modern Climate Observation Network
Douglas Alden Scripps Institution of Oceanography Installing met station Lee Vining, CA

21 Implications for Monitoring
Primary snowpack loss is above ~1500m This is to show what elevs we should be monitoring. I chose >1500m as a threshold for the next slide. Knowles and Cayan, 2004

22 Rain-snow transition zone Needs more Careful monitoing
Over all Stream gages, present-day elevational bias is small… Total number of stream gages below 1500m (red) Total number of gages above 1500m (blue) …but climate-quality HCDN subset is under-represented in crucial elevations. Top: all gages, bottom: hcdn only Red: above 1500m (~snowline), blue: below (see left and right y-axes) Key to this slide is that CA has ~5x as much area below 1500m as above. Y-axes are scaled accordingly, so that red and blue lines coincide if no gage elev bias (rel to 1500m threshold anyway). Take-home is that for all gages, avg gage dens above 1500m is ~same as below BUT HCDN avg gage dens above 1500m is ~half what it is below 1500m. Total number of HCDN gages below 1500m (red) Total number of HCDN gages above 1500m (blue) Noah Knowles, USGS)

23 …on the other hand, it can be very wet
May 16th A warm storm in the Sierra Yosemite Valley floods from a 1” rain

24 GHG Emissions Scenario
need to understand event scale phenomena projected heat wave days SRES A2 GHG Emissions Scenario

25 Need observations of 3-d, upstream atmosphere
Slide 11 Slide 11 Hydromet testbed, NOAA ETL and collaborators

26 How to effectively work and learn across disciplines?
Impacts Physical Ecological Economic Social Scenarios, not forecasts PCM. GFDL, HAD Model-based Climate Projections Human Health Forests/ Fire Agriculture Coasts Water Energy Coping Capacity/Preparedness Susi Moser, NCAR

27 Recommendations (without much discussion) :
Improved, sustained observations higher spatial resolution, more coverage 3-d atmosphere and ocean upstream California meso-micro climates including urban and agricultural settings improve insitu network, real-time communications scientific quality record keeping of economic, social measures data archeology Continued modeling at several scales, disciplines Ongoing climate simulation compute consortium Ongoing Consortium for climate simulation/prediction to knit state/campuses/labs End-to-end assessments, including eco, economic, social; close State participation Study extreme events as well as secular changes Study aerosol-clouds-precipitation Link with other regional, national, international efforts Support California State Climate Scenarios Assessments Promote CEC-PIER Annual Climate Change Conference Develop closer, better links to decision makers; strengthen outreach Fellowship program for grad students, post docs to ensure continuity, new generation

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