Post on 16-Oct-2020
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….
Courtesy Susan Solomon, NOAA
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.
Courtesy Susan Solomon, NOAA
19251946 1977
http://cses.washington.edu/cig/
http://cses.washington.edu/cig/
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
Understanding global warming
IPCC Summary for Policymakers 2007
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Do Not Cite or Quote 9-111 Total pages: 24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
• Interpreting regional climate variability and change
• Observed changes here
• Future climate
cses.washington.edu/cig/
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
• Interpreting regional climate variability and change
• Observed changes here
• Future climate
cses.washington.edu/cig/
Estimating future climate
• How much GHGs will there be?
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
2040s change in temp
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
2080s change in temp
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%
2040s 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
2.6% 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%
2080s 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
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