Climate Change Impacts on Water in CaliforniaClimate Change Center at BerkeleyRESEARCH STRATEGYGlobal CO2 emissionsGlobal warmingTemperature record 1000-2000 ADProgression of IPCC Statements In summary:Corroborating evidenceRecent California StudiesThe new impact analysesHow are the new versions of these climate models different? IPCC Emissions Scenarios CO2 Concentrations Temperature Projections Time LagsPatterns of Temperature Change 2070-2099 relative to 1961-1990 SummerDiminishing Sierra Snowpack % Remaining, Relative to 1961-1990Impact on Sierra snow packPrecipitation Projections Statewide, WinterEvidence that change is occurringPotential ImpactsFlood potentialChange in inflow to reservoirsMore frequent dry yearsDrought persistence (CALSIM)Drought persistence (WEAP)Water deliveries CVP South of Delta Annual Deliveries under climate change scenarios PCM B1-A2 and GFDL B1-A2 for 2070-2099 Water rightsEconomic impactImpact in lowest 15% of yearsUrban impactsPopulationPer capita water useImplication CaveatSources of new supply?Working assumptionTwo distinct consequencesEconomic costsShortage costs to urban usersCost to residential usersCost of outagesCost to Southern CaliforniaFor more informationClimate Change Impacts on Water in CaliforniaMichael HanemannCalifornia Climate Change CenterUC Berkeley2Climate Change Center at Berkeley• Economic and policy analysis re:– Impact on water in California– Impact on California agriculture– Impact on energy in California– Urban growth impact on water and energy– Impacts on California economy– Cap-and-trade and other policies for GHG reduction in California3RESEARCH STRATEGY• The expectation is that, in California (and much of the West) California will reduce the effective water supply, because of the reliance on storage in the snowpack, and reduce the reliability of water supply.• Strategy is to first measure the existing reliability of supply for water users in California, and ascertain the economic effects associated with differences in the degree of reliability.• Then assess the change in reliability for users as a result of climate change.• Then estimate the economic consequences of the changes in reliability.• This involves not only climate and hydrology but also engineering, economics, institutions and law.4Global CO2 emissions• For the past 150,000 years, the atmospheric carbon dioxide concentration has been between about 200 and 280 ppm.• In the pre-industrial age it was 280 ppm, and then it started rising about 150 years ago. • It is now over 360 ppm and is rising at an increasing rate.• With business as usual it may be nearly 1,000ppm by the end of this century, and will continue rising.5Global warming• Global-average surface temperature has increased by about 0.1o F/decade over the last century.• In the past 3 decades, it has increased by about 0.5o F/decade.• The 1990s were the warmest decade in the last 1,000 years in the Northern Hemisphere. The ten warmest years on record all occurred since 1990.6Temperature record 1000-2000 ADSource: IPCC WG1, Third Assessment Report (2001)7Progression of IPCC Statements1990:the size of warming is broadly consistent with predictions of climate models but it is also of the same magnitude as natural climate variability1995:the balance of evidence suggests a discernible human influence on global climate.2001:most of the warming observed over the last 50 years is attributable to human activities.8In summary:• The climate changes (temperature, CO2 concentrations) experienced in past 40 years are unprecedented in history of modern society, with respect to both the magnitude of change and the speed of change.9Corroborating evidence• There has been a widespread retreat of glaciers during the past 50 years.• Reduction of about 2 weeks in annual duration of lake and river ice over 20thcentury.• In past 30 years, snow melt in the Sierras is occurring 1-3 weeks sooner than average over previous 70 years.• Birds are now migrating, and flowers now blooming, 1-3 weeks earlier than past record.10Recent California Studies• Hayhoe et al., Proceedings of the National Academy of Sciences, August 24, 2004.• Governor’s Report on climate change http://www.climatechange.ca.gov• UC Berkeley study on Managing Greenhouse Gas Emissions in California http://calclimate.berkeley.edu11The new impact analysesThe new analyses contrast two global emission scenarios: (i) business as usual with continuing high rate of growth in greenhouse gas (GHG) emissions; and (ii) sustained global effort to reduce GHG emissions by 2100.The analyses use statistical downscaling to translate the larger scale climate model results to California with finer resolution.12How are the new versions of these climate models different? • The new versions of both models are somewhat more pessimistic with regard to precipitation than the previous two versions.• The new versions are substantially more pessimistic with regard to the increase in summer-time temperature.• The latter result may be due to improved modeling of the linkage between surface temperature and ambient air temperature.13IPCC Emissions ScenariosCO2ConcentrationsHigher (A1fi)Lower (B1)Previous(IS92a)14Temperature Projections1010-202468101960 1980 2000 2020 2040 2060 20802100Temperature Change (°C)-202468101960 1980 2000 2020 2040 2060 2080-202468101960 1980 2000 2020 2040 2060 20802100Temperature Change (°C)-2024681960 1980 2000 2020 2040 2060 2080 2100Temperature Change ( °C)HadCM3 A1 PCM A1HadCM3 B1 PCM B1-202468-2024681960 1980 2000 2020 2040 2060 2080 21001960 1980 2000 2020 2040 2060 2080 2100Temperature Change ( °C)HadCM3 A1 PCM A1HadCM3 B1 PCM B1-202468WINTERSUMMERHADCM3LowHighPCMLowHighPrevious Midrange ProjectionsPrevious Midrange Projections15Rising TemperaturesCalifornia statewide Projected average summer temperature changes16Time Lags• The temperature trajectories for the two emission scenarios remain fairly intertwined until about 2045.• They illustrate the fact that California’s future climate for next 40 years is already determined by past emissions.• Emission reductions initiated now show a significant effect after about 2045, with their impact increasing over time.17Patterns of Temperature Change2070-2099 relative to 1961-1990SummerHadCM3 higherHadCM3 lower PCM higherPCM lowerLOWER EMISSIONS HIGHER EMISSIONS14.418.0 °F10.87.23.60.0-3.618Diminishing Sierra Snowpack% Remaining, Relative to