Transcript presentation

Climate Change in the Pacific Northwest:
Impacts and Planning
Philip Mote
UW Climate Impacts Group
University of Washington
Climate Science in the
Public Interest
Science of climate change
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Thousands of peer-reviewed scientific papers
Intergovernmental Panel on Climate Change (IPCC)
Major reports in 1990, 1996, 2001
Conclusions:
 “An increasing body of observations gives a collective picture of a
warming world and other changes in the climate system.”
 “There is new and stronger evidence that most of the warming
observed over the last 50 years is attributable to human activities.”
Carbon dioxide: up 32%
Methane: up 150%
Global average temperature
0.8
degrees Celsius
0.4
0
-0.4
-0.8
1860
1880
1900
1920
1940
1960
1980
2000
Could these measurements be
wrong?
 Urbanization?
 Perhaps 10% of warming; lots
of natural evidence
 Warming patterns very big
 Stations too sparse?
 Satellite measurements  Surface definitely warming;
troposphere warming 1960show no warming?
2001 but not 1979-2001
The South Cascade
glacier retreated
dramatically in the
20th century
1928
Courtesy of the USGS
glacier group
2000
Trends in timing of spring snowmelt (1948-2000)
+20d later
–20d earlier
Courtesy of Mike Dettinger, Iris Stewart, Dan Cayan
Decrease Increase
Mote 2003(b)
those satellite observations
Models: troposphere should warm faster than surface
But satellites show little warming (0-5 miles) since 1979: does this
mean that surface measurements are unreliable?
those satellite observations
Models: troposphere should warm faster than surface
But satellites show little warming (0-5 miles) since 1979: does this
mean that surface measurements are unreliable?
Some evidence that it’s not natural
 Rate of change appears to be unusual
 Pattern of change matches that expected from
increasing greenhouse gases
 Solar, volcanic forcing would have led to
cooling in the past ~30 years
Long-term context
source: Mann et al., EOS
Carbon dioxide: up 32%
Solar output varies - but not much
Figure courtesy of NOAA National Geophysical Data Center
Natural Climate Influence
Human Climate Influence
All Climate Influences
Temperature change, 2071-2100 minus 1961-1990
Main Impact: Less Snow
Less snow, earlier
melt:
 More water in
winter
 Less water in
summer
April 1 Snow Extent for the
Columbia River Basin
Snake River at Ice Harbor
140000
120000
Flow (cfs)
100000
base
comp 2020
comp 2040
80000
60000
40000
20000
0
O
N
D
J
F
M
A
M
J
J
A
S
Reduced summer flows ==> shortages for irrigation, fish, hydro;
less concern over flooding
Increased winter flows ==> more hydro production
Simulated Natural Flow in the Willamette River at the Confluence with the Columbia
Conclusions
 Earth is warming as greenhouse effect
strengthens
 Regional climate change will take many forms,
some of which we cannot predict
 Warming is virtually certain and has profound
impacts: loss of snowpack, reduction in
summer water supply, hardships for salmon
and forests
 Some prudent steps can be taken now to
reduce vulnerability
Enhanced greenhouse effect
CO2
CH4
CFCs
O3
N2O
0
0.2
0.4
0.6
0.8
W/m2
1
1.2
1.4
1.6
Decrease Increase
and climate damage
Floods
Low summer
streamflow, high temp
????
Estuary conditions: prey, predators,
competitors
Consequences
 Reduced summer flow in most rivers is likely
 More difficulty supplying water for agriculture,
hydropower, fish, recreation
 Likelihood of snow-driven (springtime)
flooding will decrease
 Likelihood of rain-driven (winter) flooding will
increase
21st century temperature change
IPCC (www.ipcc.ch)
Projected PNW Climate Change
Projected changes
in average annual
PNW temperature
and precipitation
for the decades of
the 2020s and
2040s.
2020s
Temperature
Precipitation
Low
+ 0.5°C
+ 1.5 %
Mean
+ 1.5°C
+ 6.9%
High
+ 2.5°C
+ 14.4 %
2040s
Temperature
Precipitation
Low
+ 1.5°C
- 3.3 %
Mean
+ 2.3°C
+ 7%
High
+ 3.2°C
+ 13.7 %
Based on an increase in equivalent CO2 of 1% per
year. Benchmarked to the decade of the 1990s.