Climate Change in California:Choosing our Future

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Climate Change in CaliforniaChoosing our Future

• October 2004

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Emissions pathways, climate change, and impacts
on California Proceedings of National Academy of
Science Published in August 2004

• Katharine HayhoeATMOS Research and Consulting
• Daniel CayanScripps Institution of Oceanography
• Christopher FieldCarnegie Institution
• Peter FrumhoffUnion of Concerned Scientists
• Edwin MaurerSanta Clara University
• Norman MillerLawrence Berkeley National Lab
• Susanne MoserNational Center for Atmospheric
  Research
• Stephen SchneiderStanford University
• Kimberly CahillCarnegie Institution

• Elsa ClelandCarnegie Institution
• Larry DaleLawrence Berkeley National Lab
• Ray DrapekUSDA Forest Service
• R. Michael HanemannUC Berkeley
• Laurence KalksteinUniversity of Delaware
• James LenihanUSDA Forest Service
• Claire LunchCarnegie Institution
• Ronald NeilsonUSDA Forest Service
• Scott SheridanKent State University
• Julia VervilleUnion of Concerned Scientists

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Climate Change in CaliforniaNew Projections

• What are the consequences of following markedly
  divergent emissions pathways?
• -- for temperature and precipitation
• -- for key climate-sensitive sectors

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Global Emissions ScenariosIntergovernmental
Panel on Climate Change (IPCC)
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Temperature Projections(change in temperature F)
HADCM3
Low
High
PCM
SUMMER
Low
High
Previous Midrange Projections
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Rising Temperatures California statewide
Projected changes in average summer temperature
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Patterns of Temperature Change2070-2099 relative
to 1961-1990Summer
LOWER EMISSIONS
HIGHER EMISSIONS
HadCM3 lower
PCM higher
HadCM3 higher
PCM lower
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Increasing HeatwavesAdditional Heatwave
days/year2090s
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Increasing Heat-Related MortalityAverage Annual
Deaths
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Diminishing Sierra Snowpack Remaining, Relative
to 1961-1990
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Precipitation ProjectionsStatewide, Winter
HadCM3 higher
PCM higher
HadCM3 lower
PCM lower
0
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Impacts on Water Supply
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Decreasing Wine Grape QualityTemperature Impacts
Wine Country (Sonoma, Napa Counties) Cool Coastal
(Mendocino, Monterey Counties) Northern Central
Valley (San Joaquin, Sacramento Counties)
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Changes in Vegetation Distribution2070-2099,
relative to 1961-1990
Temperature-driven
Fire-mediated
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California Climate Projections Summary End of
Century

• Temperature increases greater than previously
  predicted
• Higher emissions yield higher summer temperatures
• Higher scenario summer 8.5 to 18 F
• Lower scenario summer 3.5 to 9 F
• Heat waves 2-5 times more common, more intense,
  and longer lasting
• Precipitation variable, with trends towards
  slight decrease

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Impacts on Key SectorsSummary End of Century

• Substantial impacts under both emissions
  scenarios
• Impacts and adaptation costs increase with higher
  emissions
• Heat-related deaths in 5 study cities
• Increase 2-4 times in lower emissions
• Increase 3-6 times in higher emissions
• Sierra snowpack loss
• 70-90 in higher scenario and
• 30-70 lower scenario
• Lower emissions pathway is not a floor higher
  emissions pathway is not a ceiling.

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Managing Climate Change in California

• Reduce emissions of heat-trapping gases
• Transportation accounts for 49 of C02 emissions
• Electricity accounts for 30 of C02 emissions
• Minimize pressures on the environment
• reduce fire risk in forests
• Protect natural floodways
• Reduce encroachment on sensitive ecosystems
• Prepare for climatic changes that
• cannot be avoided
• Heat warning system
• Water conservation

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Comparing Historical Observations with Downscaled
Climate Model ResultsTEMPERATURE
Observed
Statistical Downscaling
Dynamical Downscaling
Wood et al., 2003
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Comparing Historical Observations with Downscaled
Climate Model ResultsPRECIPITATION
Observed
Statistical Downscaling
Dynamical Downscaling
Wood et al., 2003
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Temperature (oC)
Winter
Summer
Summer Winter
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Winter Precipitation