Transcript NASA_water_2004-02

Climate Change:
Impact on water in
the western United
States
Tim P. Barnett
David W. Pierce
Scripps Institution of Oceanography
La Jolla, CA
Effect of Climate Change on
Western U.S.
• Large and growing population in a semiarid region
• How will it impact water resources?
• Use an “end-to-end” approach
Project overview
Projected change in California
snowfall...
Projected change by 2050
Downscaling: the motivation
Global model (orange dots)
vs. Regional model grid
(green dots)
How good is the Hydrological
Model?
Andrew Wood, Univ. of Washington
River flow earlier in the year
Runoff already coming earlier
Columbia Basin Options
Hydropower
Or
Salmon
California: Mandated water releases
cannot be met
Colorado River: Not enough water
to meet current demands
10 million people in Los Angeles
Los Angeles water shortage
Christensen et al., Climatic Change, to appear
Miss water treaty obligations to
Mexico
Christensen et al., Climatic Change, to appear
• Ratio of chlorophyll concentration in
spring, 2090s/2000s.
Step 1
• Begin with current state of global oceans
Why initialize the oceans?
• That’s where the heat has gone
Data from Levitus et al, Science, 2001
How good is the ocean simulation?
Pierce et al,
Climatic
Change, to
appear
Step 2
• Estimate climate change due to emissions
Global Climate Change
Simulation
• Parallel Climate
Model (PCM)
• Business as Usual
Scenario (BAU)
• 1860-2100
• Estimate Western U.S.
climate change
How well does the PCM work over
the Western United States?
Dec-Jan-Feb total precipitation (cm)
Step 3
• Downscaling and impacts
How good is downscaling?
El Nino rainfall simulation
Observations
Downscaled model
Standard reanalysis
Ruby Leung, PNNL
Results
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Reduced snow cover
Earlier snow melt
Earlier spring flood crest
Shift in ‘Run off” season
Small rainfall reductions
Columbia River basin
Columbia River flow
Andrew Wood, Univ. of Washington
Sacramento/San Joaquin River basin
Sierra snow pack
• Now and ………………….………….future?
Colorado River basin
Other impacts
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Increased wildfires
Salinification of Sacramento Delta
Extinction of Salmon in PNW?
Cities vs. Farming
More wildfires
100% more acres
burned in 2100
Less time for Salmon to reproduce
Now:
Future:
Lance Vail,
PNNL
Water use conflicts
Climate changes naturally
San Diego (CA) Union Tribune; Phil Caterion
Conclusions
• Greenhouse induced climate changes will
have a massive impact on the water
resources of the western United States.
• The fabric of life in this region will be
greatly altered by these changes….a “train
wreck” in the making.
• What you have seen is a “best case”
scenario (it could be worse and/or happen
sooner).