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

2

The ACPI Demonstration Project

3

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

4

Step 1

Begin with current state of global oceans

5

Why Initialize the Oceans?

That’s where the heat has gone!

Data from Levitus et al, Science, 2001

6

7

How Good is the Ocean Simulation?

Pierce et al, Climatic Change, to appear

8

Step 2

Estimate climate change due to emissions

9

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

10

How well does the PCM work over the Western United States?

Dec-Jan-Feb total precipitation (cm)

11

Projected change by 2050

12

Step 3

Downscaling and Impacts

13

Why do we do it?

Global model (orange dots) vs. Regional model grid

(green dots)

14

It works

El Nino rainfall simulation

Observations Downscaled model Standard reanalysis

Ruby Leung, PNNL

15

And It Clearly Improves PCM Simulations

PCM RCM

Absolute Bias (mm/day)

Win

ter

(DJF

)S

um

mer

(JJ

A)

Control Simulation Precipitation Biases

16

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

17

So What Does the “Future” Look Like?

An Ensemble of Projected Future Climate Simulatedby the PCM

18

Temperature Precipitation

PC

MR

CM

Climate Change Signals (2040-2060)

19

Extreme Precipitation and Snowpack Changes

20

Such Changes Would Clearly Affect Water Resources

Andrew Wood, Univ. of Washington

21

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

22

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

23

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

24

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

25

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