Climate Change RMJOC Study Summary

Transcription

1 Climate Change RMJOC Study Summary Erik Pytlak Weather and Streamflow Forecasting Bonneville Power Administration Portland, OR IPCC: International Panel on Climate Change Established by the United Nations in 1988 Lead international ti research body on climate change Reports on State-of-the-Science on climate change and latest/best forecasts every 5 years Last report (IPCC-4) published in 2007 Used outputs from about a dozen Global Climate Models (GCMs) from the Coupled Model Intercomparison Project (CMIP-3) A subset of the CMIP-3 models were used for the RMJOC Study 1

2 Greenhouse Gas (GHG) Emission Scenarios: IPCC-4 "Source: Climate Impacts Group, University of Washington, Consensus Forecasts of Temperature and Precipitation Changes from IPCC AR4 GCMs Between late 20 th Century and mid 21 st Century Warming and precip response strongest at the poles/subarctic Summer warming strongest in the center of continents Drying strongest in southwest US/Great Basin (but they didn t model the North American Monsoon well) Pacific Northwest on several dividing lines (between subarctic/temperate/great Basin, continent/coast) 2

3 RMJOC Study Base Assumptions 1-6 F (1-4 C) warming by the 2040s Precip range from 15% decrease to 20% increase by the 2040s This uses downscaled data Model Input: Natural Streamflows at The Dalles for 2020 s 600, , 's Natural Flow at TDA: 70 year avg. 500, , ,000 Qn (cfs) ' 350, , , , , ,000 50,000 - Oct Nov Dec Jan Feb Mar Apr I Apr II May June July Aug I Study 21: Base Study 23: MW/D Study 24: LW/W Study 25: MC Aug II Sep Study 26: C Study 27: MW/W Study 28: LW/D 3

4 Model Input: Natural Streamflows at The Dalles for 2040 s 600, 's Natural Flow at TDA: 70 year avg. 550, , , ,000 Qn (cfs) ' 350, , , , , ,000 50,000 - Oct Nov Dec Jan Feb Mar Apr I Apr II May June July Aug I Aug II Sep Study 21: Base Study 29: LW/W Study 30: MC Study 31: LW/D Study 32: C Study 33: MW/D Study 34: MW/W RMJOC Study Results Most of the scenarios increase fall-winter-spring flows and generation Most of the scenarios decrease summer flows and generation Some scenarios actually yield more annual generation Most scenarios show very modest winter flow increases from Canada Canadian Rockies winter precip remains snow, even in some of the warmest scenarios Some scenarios concentrate diminished summer flows on the Snake/Lower Columbia More scenarios show drier summers in this part of the basin than wetter 2.0 C Change in Avg Columb bia Basin Temperature More Warming, Drier 28 Less Warming, Drier 21 Base Case 27 More Warming, 26 Central 24 Less Warming, Change 25 Minor Change More Warm, Drier Less Warm, Drier Central Change Minor Change More Warm, Less Warm, % Change in Avg Columbia Basin Precip 4

5 More Takeaways: RMJOC Study Represents a reasonable range of climate change outcomes Temperature increases ( C by the 2040s) are modest compared to other scientifically valid scenarios Dataset reasonably captures the uncertainty in future Pacific Northwest precipitation (-5% to +10% by the 2040s) Dataset captures where it may get wetter (Canada) and drier (southern Idaho/southern Oregon) Streamflow timing is the most likely hydroclimate variable to change Increased winter flows, decreased summer flows, earlier spring peak Less precip falling as snow, more falling as rain at mid elevations, particularly in the US part of the basin /warmer snowpack that s easier to melt earlier in the spring Temperature-induced load increases likely overwhelmed by population load growth Load shape is likely to change, though (less winter/more summer load) Sneak Peek: IPCC-5 IPCC-5 is underway, using next generation of climate models (CMIP-5) Initial results to be published: September 2013 Final report to United Nations: September 2014 Using a new CO 2 emissions approach IPCC-4: SRES: Special Report on Emissions Scenarios Discrete, fixed CO 2 forecasts IPCC-5: RCP: Representative Concentration Pathways Ensemble, several possible outcomes within a certain range More robust and capture larger range of possible CO2 outcomes So far, the new IPCC (CMIP-5) models, for the Pacific Northwest are trending Warmer than previous forecasts, but with a slightly larger range of uncertainty t Still showing a large range of possible annual precip outcomes, but somewhat drier summers compared to previous runs, Still highlighting the most likely areas for wetter (Canada) and drier (southern Idaho) IPCC-5 is suggesting that RMJOC was a good, valid study, although temperatures are on the cool side of the new uncertainty range 5

6 Forecast Temperature Change, late 20 th Century to mid 21 st Century SRES: CIMP 3/IPCC-4 (2007) RCP: CMIP 5/IPCC-5 (2012) RCP 4.5 is the B1/conservative IPCC-4 carbon dioxide emission scenario RCP 8.5 is the A2/aggressive IPCC-4 carbon dioxide emission scenario Preliminary regional takeaways: Forecast is for an even warmer Pacific NW by the 2050s IPCC-5: +2.2 to 3.5 C IPCC-4/RMJOC: to 2.8 C Better agreement that summers will warm even more than the other seasons This does NOT necessarily translate to similar increases in water temperatures (particularly small, dynamic bodies of water like rivers) Source: Abatzoglou, et al.,, 2012 (Pac NW Climate Change Workshop, Boise, ID) 11 Forecast Precipitation Change, late 20 th Century to mid 21 st Century SRES: CIMP 3/IPCC-4 RCP: CMIP 5/IPCC-5 RCP 4.5 is the B1/conservative IPCC-4 carbon dioxide emission scenario RCP 8.5 is the A2/aggressive IPCC-4 carbon dioxide emission scenario Preliminary regional takeaways: Precip forecast almost as uncertain in Pacific NW by the 2050s as the previous IPCC IPCC-5: -2% to +10% IPCC-4/RMJOC: -3% to +14% Better agreement that summers will be drier, with other months slightly wetter Source: Abatzoglou, et al.,, 2012 (Pac NW Climate Change Workshop, Boise, ID) 12 6

7 The Future: More work ahead Change from to RCP8.5 CO 2 scenario, CMIP-5 composite 7