Climate drivers and climate changes in the Columbia River ... · Climate drivers and climate...

Climate drivers and climate changes in the Columbia River basin

Philip MoteClimate Impacts Group

University of Washington

The Climate Impacts Group

Goal: help the Pacific Northwest become more resilient to climate variations and climate change

Supported by NOAA Climate Program Office as part of the Regional Integrated Science and Assessments (RISA) program

http://cses.washington.edu/cig/

Outline

• Interpreting regional climate variability and change

• Observed changes here

• Future climate

cses.washington.edu/cig/

Global warming

Widespread warming has occurred. Globally averaged, the planet is about 0.75°C warmer than it was in 1860, based upon dozens of high-quality long records using thermometers

worldwide, including land and ocean.

Unequivocal evidence of warming1880-2007

National Climatic Data Center

2000

1980

1960

1940

1920

1900

1880

56

57

58

59

Year

Glob

al A

nnua

l M

ean

Tem

pera

ture

(°F

)

0.92°F/century; r**2 = 0.595

Global Annual Average Temperatures

Courtesy Susan Solomon, NOAA

1990

1970

1950

1930

1910

1890

1870

1870

50

51

52

53

54

55

56

57

58

59

60

US National Annual MeanGlobal Annual MeanYear

Tem

pera

ture

(°

F)

1.0°F/century; r**2 = 0.143

0.92°F/century; r**2 = 0.595

Compared to the USA average….


1990

1970

1950

1930

1910

1890

1870

1870

50

55

60

65

70

75

Cascade Jun/JulMontana Jun/Jul

US Jun/JulUS National Annual MeanGlobal Annual Mean

Year

Tem

pera

ture

(°

F)

0.66°F/century; r**2 = 0.011

0.87°F/century; r**2= 0.070

1.0°F/century; r**2 = 0.143

0.92°F/century; r**2 = 0.595

0.33°F/century; r**2 = 0.002

US Jun/Jul

Montana Jun/Jul

Cascade, MTJun/Jul

A hot summer does not prove global warming. A cool spring does not prove global cooling.


19251946 1977


Todd Mitchell, UW/JISAO

Tree-ring based PDO index reconstructions:(ex: Gedalof and Smith 2001)

Plots courtesy of Torrence and Compo http://paos.colorado.edu/research/wavelets

Understanding global warming

IPCC Summary for Policymakers 2007

Regional attribution

Second-Order Draft Chapter 9 IPCC WG1 Fourth Assessment Report

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Do Not Cite or Quote 9-111 Total pages: 24

P.A. Stott GRL 2003

Outline



• Future climate


www.climate.washington.edu

Trend in annual mean 1907-2006

1.5°F

Challis3.6°F

Trend in annual mean 1957-2006

www.climate.washington.edu

Knowles et al. 2006

Western warming trends historically have been (andpresumably will continue to be) marked by strong sea-sonal and geographic patterns (e.g., Diaz and Quayle1980; Dettinger et al. 1995; Cayan et al. 2001). Becauseof the general wintertime maximum of snowfall andprecipitation in the region, contributions of snow towestern precipitation are likely to be most affected bywintertime (November–March) temperatures, whereaschanges in onset of snowmelt (once snow is on theground) are more likely to be sensitive to springtimetemperatures. Thus, snow deposition and snowmelt areexpected to be differently sensitive to warming trendsin different seasons, and the warming trends associatedwith snowfall and snowmelt changes may be distin-guishable by differences in their geographic patternsand rates of change. Much work has been accomplishedin mapping trends in snowmelt response; this studydocuments a parallel set of trends that has changed therelative contributions of snowfall to western precipita-tion.

In section 2, the data used and the methods appliedare discussed, and the robustness of the approach isaddressed. In section 3a, trends in winter precipitationform are presented, and in section 3b, the influence oftemperature on these trends is examined. In section 3c,the monthly patterns underlying the seasonal trends arepresented. In section 3d, the role of climate variabilityin generating trends in precipitation form is investi-gated. Finally, the main results are summarized in sec-tion 4, and their implications discussed.

2. Data and methods

The measure of snowfall that will be used in thisstudy is the snowfall liquid water equivalent (SFE), de-

fined as the precipitation totals on days for which newlyfallen snow was recorded. These data and the tempera-ture data used in this study were derived from the his-torical Summary of the Day (SOD) observations fromcooperative weather stations in the 11 westernmoststates of the conterminous United States (Fig. 1), ob-tained from the National Climatic Data Center. Theobservations used here comprise daily snowfall depth(S, actual depth as opposed to liquid equivalent), pre-cipitation (P, regardless of form), and maximum(TMAX) and minimum (TMIN) surface air tempera-ture, from October 1948 to September 2004. Because Sis not a reliable proxy for snowfall liquid equivalentsince snow density can vary significantly, and because Pobservations have no associated data flags indicatingthe precipitation form (i.e., solid, liquid, or mixed), inthis study, a nonzero value of snowfall depth (S) is usedto assign a solid form to any measured precipitation(P), thereby estimating snowfall water equivalent(SFE).

Precipitation and snowfall totals were recorded at1653 stations during some or all of this period; tempera-tures were recorded at 1517 stations. Emulating the ap-proach developed by Huntington et al. (2004) for a similaranalysis in the northeastern United States, the recordsof precipitation and snowfall at the western stationswere culled according to the following sequential steps.

1) Any cool season during which precipitation or snow-fall data were missing for 10 or more days betweenNovember and March was considered incompleteand was excluded from the analysis.

2) Any station that was missing !50% of its Novem-ber–March daily observations in any given 10-yr pe-riod was excluded.

FIG. 1. (a) Trends in fraction of winter (Nov–Mar) precipitation falling on snowy days (SFE/P), 1949–2004: redindicates decreasing snowfall fractions; symbol radius is proportional to study period changes, measured in stan-dard deviations of the detrended time series as indicated; circles indicate high trend significance ( p " 0.05), andsquares indicate lower trend significance. (b) The WY2004 winter SFE/P vs WY1949 winter SFE/P, with significantSFE/P trends highlighted with squares. Dashed line is the least squares fit to all data points.

4546 J O U R N A L O F C L I M A T E VOLUME 19

Fig 1 live 4/C

Trends in snowfall equivalent

Trends in April 1 snow water equivalent, 1950-2000neg pos

Mote et al. 2005

As the West warms,

winter flows rise and summer flows

drop

Stewart et al.J. Climate 2005

Attribution

“up to 60% of the climate related trends of river flow, winter air temperature and snow pack [in the Western US] between 1950-1999 are human-induced.” - Barnett et al. 2008

Outline



• Future climate


Estimating future climate

• How much GHGs will there be?

Estimating future climate

• How much GHGs will there be?

• How responsive is the climate?

Summary for Policymakers IPCC WGI Fourth Assessment Report

Page 21 of 21

Figure SPM-7. Solid lines are multi-model global averages of surface warming (relative to 1980-99) for the

scenarios A2, A1B and B1, shown as continuations of the 20th

century simulations. Shading denotes the plus/minus

one standard deviation range of individual model annual means. The number of AOGCMs run for a given time

period and scenario is indicated by the coloured numbers at the bottom part of the panel. The orange line is for the

experiment where concentrations were held constant at year 2000 values. The gray bars at right indicate the best

estimate (solid line within each bar) and the likely range assessed for the six SRES marker scenarios. The

assessment of the best estimate and likely ranges in the gray bars includes the AOGCMs in the left part of the figure,

as well as results from a hierarchy of independent models and observational constraints (Figs. 10.4 and 10.29)

[To be changed:

Change annotation from cnstant composition to year 2000 constant concentration.

Colour central bar in grey bars and lettering to match A2, A1B, B1 curves as appropriate.

Drop model numbers and move to caption].

IPCC 2007

CO2 up 35%

more GHGs

mor

e se

nsiti

vity

Temperature change2080-99 minus 1980-99

Averaged over 21 global models; IPCC Fig 11.12

Final Draft Chapter 11 IPCC WG1 Fourth Assessment Report

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Precipitation change2080-99 minus 1980-99

Averaged over 21 global models; IPCC Fig 11.12

Final Draft Chapter 11 IPCC WG1 Fourth Assessment Report

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2020s change in temp

DJF MAM JJA SON Annual-1

0

1

2

3

4

5

6

degr

ees F

0

1

2

3

Deg

rees

C

B1

A1B

1.8oF 1.7oF

0.7oF

3.6oF

2.2oF 2.1oF

0.4oF

3.6oF

2.5oF

3.2oF

1.0oF

5.3oF

1.9oF 1.9oF

0.1oF

3.3oF

2.1oF 2.3oF

1.1oF

3.3oF


DJF MAM JJA SON Annual0

2

4

6

8de

gree

s F

0

1

2

3

4

5

Deg

rees

C

B1

A1B

2.5oF 3.2oF

1.0oF

5.1oF

2.9oF 3.6oF

1.0oF

5.4oF

3.9oF

5.1oF

1.5oF

7.9oF

2.7oF

3.6oF

1.3oF

5.2oF

3.0oF

4.1oF

1.5oF

5.2oF


DJF MAM JJA SON Annual0

2

4

6

8

10

12

14

degr

ees F

0

1

2

3

4

5

6

7

Deg

rees

C

B1

A1B

4.2oF

5.7oF

1.3oF

9.1oF

4.5oF

6.1oF

1.3oF

9.7oF

6.0oF

8.3oF

2.5oF

12.5oF

4.2oF

6.2oF

2.4oF

8.8oF

4.9oF

7.1oF

2.8oF

9.7oF

2020s change in precip

DJF MAM JJA SON Annual

-4

-2

0

2

4

6

8

Inch

es

-8

-4

0

4

8

12

16

20

cm

B1

A1B

2.0% 2.1%

-13%

22%

1.3% -0.2%

-10%

9%

-3.0% -7.9%

-29%

12% 5.9% 2.8%

-10%

19%

1.6% -0.1%

-9%

12%



-4

-2

0

2

4

6

8

Inch

es

-8

-4

0

4

8

12

16

20

cm

B1

A1B

2.6% 5.1%

-13%

26%

3.3% 3.9%

-10%

16%

-4.6%-12.0%

-30%

16% 5.1% 4.7%

-10%

20%

2.0% 1.9%

-11%

11%



-4

-2

0

2

4

6

8

Inch

es

-8

-4

0

4

8

12

16

20

cm

B1

A1B

7.1% 9.0%

-10%

41%

3.2% 5.8%

-7%

21%

-11.3% -15.8%

-37%

14% 5.7%

8.9%

-11%

35%

2.9% 4.3%

-9%

19%

Downscaling

Difference in projected winter temperature (°C)

Texture of warming: Regional model minus global model for 2050s

Conclusions

• human influence on climate emerging from noise at smaller scales (western N. Am.)

• Observed PNW changes: 1.5°F warming, corresponding hydrologic shifts

• Future climate: 0.5°F/decade warmer, precip?, rest depends on us

Climate drivers and climate changes in the Columbia River ... · Climate drivers and climate...

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