Pacific Northwest National Laboratory
U.S. Department of Energy
The Effects Of Climate Change On Water Resources In The Western
United States:The Accelerated Climate Prediction
Initiative
Bill Pennell, Pacific Northwest National Laboratory
Tim Barnett, Scripps Institution of Oceanography
April 30, 2003
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The ACPI Demonstration Project
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Implementation
Ocean Data Assimilation: UCSD, NPSGlobal Climate Modeling: NCAR/LANL PCMDownscaling: PNNL & UCSDImpacts: Columbia River: UW Yakima River: PNNL Sacramento/San Joaquin
Rivers: UW, UCSD, USGS, PNNL
Wild fires: UCSD & DRI
Ocean DataAssimilation
Global ClimateModeling
Downscaling
ImpactAssessment
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Step 1
Begin with current state of global oceans
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Why Initialize the Oceans?
That’s where the heat has gone!
Data from Levitus et al, Science, 2001
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How Good is the Ocean Simulation?
Pierce et al, Climatic Change, to appear
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Step 2
Estimate climate change due to emissions
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Global Climate Change Simulations
Used NCAR/DOE Parallel Climate Model (PCM)
Three projections using the Business as Usual Scenario (BAU)
Period covered: 1860-2100
These simulations provided the basis for our projections of western U.S. climate change
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How well does the PCM work over the Western United States?
Dec-Jan-Feb total precipitation (cm)
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Projected change by 2050
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Step 3
Downscaling and Impacts
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Why do we do it?
Global model (orange dots) vs. Regional model grid
(green dots)
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It works
El Nino rainfall simulation
Observations Downscaled model Standard reanalysis
Ruby Leung, PNNL
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And It Clearly Improves PCM Simulations
PCM RCM
Absolute Bias (mm/day)
Win
ter
(DJF
)S
um
mer
(JJ
A)
Control Simulation Precipitation Biases
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Precipitation Skill Score
PCMRCM
0
0.1
0.2
0.3
0.4
0.5
1 2 3 4 5 6 7 8 9 10 11 120
0.1
0.2
0.3
0.4
0.5
1 2 3 4 5 6 7 8 9 10 11 120
0.1
0.2
0.3
0.4
0.5
1 2 3 4 5 6 7 8 9 10 11 120
0.1
0.2
0.3
0.4
0.5
1 2 3 4 5 6 7 8 9 10 11 12Eq
uit
able
Th
reat
Sco
re
Precipitation Threshold (mm/day) Precipitation Threshold (mm/day)
Columbia River Basin Sacramento-San Joaquin Basin
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So What Does the “Future” Look Like?
An Ensemble of Projected Future Climate Simulatedby the PCM
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Temperature Precipitation
PC
MR
CM
Climate Change Signals (2040-2060)
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Extreme Precipitation and Snowpack Changes
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Such Changes Would Clearly Affect Water Resources
Andrew Wood, Univ. of Washington
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And The Effects Would be Greater for Smaller River Basins
Yakima River above Parker
Mea
n M
onth
ly F
low
(m
m)
Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
010
2030
4050
6070
80
RCM HistoricBAU44BAU46BAU47
Source: Lance Vail, PNNL
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Climate Mean flow (m3/s)
Peak flow (m3/s)
Peak flow date
1/3 date
1/2 date
Freshet date
Historic 48.2 281 May 17 Mar 11 May 1 May 16
BAU44 52.0 285 Jan 25 Jan 24 Mar 14 Mar 14
BAU46 52.0 270 Feb 4 Feb 5 Mar 20 Apr 8
BAU47 54.9 262 Mar 18 Feb 17 Mar 25 Apr 21
Average altered climate change from historic
4.8 -9 -91 -34 -42 -42
Streamflow and snowmelt statistics for regulated basins. Values are medians computed from 19 years of model output for each climate. Difference in dates is given in days. Source: Lance Vail, PNNL
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With Consequences for Humans
Scenario Base 20% Increase In
Demand
20% Decrease
In Demand
20% Increase In
Storage
20% Decrease In Storage
Current Climate
5 6 0 2 11
BAU 44 7 15 2 2 17
BAU 46 9 12 3 3 14
BAU 47 3 12 0 1 16
Number of years (out of 19) with prorationing reductions greater than 25% of normal flow for current climate and for 3 BAU realizations. System forecast and operation rules based on current climate data. Note: Prorationing meansreductions to users with junior water rights. Reductions greater than 25% have significant economic impacts.Source: Lance Vail, PNNL
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Scenario Base 20% Increase In
Demand
20% Decrease
In Demand
20% Increase In
Storage
20% Decrease In Storage
Current Climate
66 304 0 20 695
BAU 44 384 928 89 160 1704
BAU 46 396 897 29 50 1396
BAU 47 119 480 0 5 1330
Total number of days (out of 19 years) with prorationing reductions greater than 25% of normal flow for current climate and for 3 BAU realizations. Normal irrigation season in the Yakima Basin runs from April through September or about 180 days. Source: Lance Vail, PNNL
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And Fish
Warm Fall Water Earlier Freshet
Spawning, Incubation, Rearing, Smolt Migration
Historical Climate
Altered Climate
Climate Change will Seriously Compress the TimeAvailable for Fall Chinook to Complete their
Spawning Cycle