Download Pacific Northwest Climate Variability and Change

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UW Climate Impacts Group
UW Climate Impacts Group
Preparing for Climate
Change in the Pacific
Northwest
UW Climate Impacts Group
UW Climate Impacts Group
UW Climate Impacts Group
A (Brief!) Overview of Global Climate
Change
A Perspective on Climate Change:
Past Climate Change
Climate change is not new on
a geologic time scale…
ex: Glaciers in the Puget Sound
region
…and systems have adjusted
ex: Species migration and
extinction
Present Day Climate Change:
What is Different?
• CO2 concentration levels
– Appear to be higher than any time in past ~
23 million yrs
• The human footprint
– Human activities altering the climate system
– Human systems based on expectation of
certain climate conditions
– Population growth, political boundaries,
resource dependency/depletion, habitat
fragmentation limit ability of natural and
human systems to tolerate rapid change
Greenhouse gases (water vapor, CO2, CH4, N2O) play a critical
role in determining global temperature
Rapid increases in greenhouse gases are
changing this natural balance
Carbon Dioxide (CO2)
• Atmospheric concentration has
increased 31% since 1750
• ~70% of CO2 emissions come
from fossil fuel burning
• Accounts for ~ 60% of
warming
From a long term perspective, these changes are enormous
Methane (CH4)
• Atmospheric concentration
has increased ~150% since
1750
• Current concentration is
highest in last 420,000 years
• Slightly more than 50% of
CH4 emissions originate from
human activities
• Accounts for ~20% of
warming
Figure source: IPCC 2001
Nitrous Oxide (N2O)
• Atmospheric concentration
has increased 17% since
1750
• Current concentration is
highest in last 1,000 years
• About 33% of current N2O
emissions originate from
human activities
Figure source: IPCC 2001
Where do these increases come from?
• Human sources:
–
–
–
–
–
–
–
Fossil fuel burning (oil, coal, natural gas) (CO2, CH4, N20)
Deforestation and land use change (CO2)
Agricultural practices (CO2, CH4, N20)
Energy extraction (CO2, CH4)
Ruminant (e.g., cows) (CH4)
Cement production (CO2)
Landfills (CH4)
• Natural sources
– Wetlands (CH4)
– Oceans, soils (CO2, N20)
– Decomposition of organic matter (CO2, CH4)
Changes in Global Average Temp
• With these changes in greenhouse gases, the
Earth’s average global temperature has been
increasing
• Since 1900, the planet has warmed 0.60.2°C
(1.10.4°F)
• The significance of this temperature increase is
more evident when you look over the longer term.
Source: IPCC 2001
How do we get perspective on these
changes?
• Instrumental data
• “Proxy” data
– Ice cores
– Pollen
– Tree rings
– Corals
– Landscape
Getting perspective (cont’d)
• Observed changes in natural systems (20th century)
– The extent and thickness of Arctic sea ice is in decline
(extent is down 10-15%; thickness is down 40%)
– Permafrost at northern latitudes is thawing
– The growing season has lengthened 1-4 days per decade
during the last 40 years in the Northern Hemisphere.
– Plants are flowering earlier, birds are arriving earlier, and
insects are emerging earlier in the Northern Hemisphere,
Getting perspective (cont’d)
• 20th century observed changes, cont’d
– Increased frequency of coral bleaching, particularly
during El Niño events
– Weather-related economic losses are increasing (partly
due to choices about where we live and work)
– Mid-elevation mountain snowpack is in decline and
melting earlier
– Glaciers are in widespread retreat
Riggs Glacier
Glacier Bay National Park
1941
2004
Nearly every glacier in
the Cascades and
Olympics has retreated
during the past 50-150
years
South Cascade
Glacier, 1928 (top)
and 2000 (right)
Photos courtesy of Dr. Ed Josberger, USGS
Glacier Group, Tacoma, WA
21st Century Global Warming
Projected range of globalscale warming by 2100:
2.5-10.5°F (1.4-5.8°C)
Warming expected through
21st century even if CO2
emissions end today due to
persistence of greenhouse
gases.
Estimated
atmospheric
lifetime of major
greenhouse gas
(per molecule)
Figure source: IPCC 2001
Carbon Dioxide
~60% of warming
5 to 200 years
Methane
~20% of warming
8 to 12 years
Nitrous Oxide
~6% of warming
~120 years
CF4 (Perfluoromethane)
>50,000 years
Data source: IPCC 2001
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UW Climate Impacts Group
UW Climate Impacts Group
UW Climate Impacts Group
20th century PNW climate trends
PNW Temperature Trends by Station
• Average annual
temperature
increased +1.5F in
the PNW during the
20th century (+2.3 F
in the Puget Sound)
Cooler Warmer
3.6 °F
Annual
variability
2.7 °F
present
throughout1.8 °F
the warming
0.9 °F
trend
• Almost every station
shows warming
• Extreme cold
conditions have
become rarer
• Low temperatures
rose faster than high
temperatures
Mote 2003(a)
Snow Water Equivalent Trends
• Most PNW stations
showing a decline in
snow water
equivalent
• Numerous sites in
the Cascades with
30% to 60%
declines
• Similar trends seen
throughout the western
United States - 73% of
stations show a decline
in April 1 snow water
equivalent
Decrease Increase
Trends in the Timing of Spring Runoff
Peak of spring runoff is
moving earlier into the spring
throughout western US and
Canada
• Advances of 10-30 days
between 1948-2000
• Greatest trends in PNW,
Canada, and AK
• >30% of trends are
statistically significant at
the 90% level, especially in
the PNW
+ 20 days later
- 20 days earlier
Stewart, I., Cayan, D.R., and Dettinger, M.D., 2004, Changes in snowmelt runoff timing in western North America under a
"Business as Usual" climate change scenario: Climatic Change 62, 217-232.
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21st century PNW
climate change
UW Climate Impacts Group
UW Climate Impacts Group
Projected 21st century PNW climate
• Projected rate of warming:
0.2-1.0°F (~ 0.5ºF average)
per decade through at least
2050 (compared to 1.5°F
over 20th century)
• Temperatures will increase
across all seasons; most
models project the largest
temperature increases in
summer (June-August)
• High confidence in projected
temperature changes, low
confidence in precipitation
changes
2020s
Temperature
Precipitation
Low
+ 0.7ºF (0.4ºC)
- 4%
Mean
+ 1.9ºF (1.1ºC)
+2 %
High
+ 3.2ºF (1.8ºC)
+7%
2040s
Temperature
Precipitation
Low
+ 1.4ºF (0.8ºC)
- 4%
Mean
+ 2.9ºF (1.6ºC)
+ 2%
High
+ 4.6ºF (2.6ºC)
+9%
All changes are benchmarked to average temperature and
precipitation for 1970-1999
Projected Effects on
PNW Resources
Less Snow
Warmer temperatures contribute to more winter precipitation
falling as rain rather than snow, particularly in transient (midelevation) basins
Changes in Simulated April 1 Snowpack for the Cascade Range in WA and OR
“Current” Climate
~ 2040s (+3°F)
-44%
(mm)
~ 2060s (+4.5°F)
-58%
Altered Streamflows
• If more winter rain → higher winter streamflows
• Warmer temperatures → earlier snowmelt and a shift in the
timing of peak runoff
• Lower winter snowpack → lower spring and summer flows
Projected streamflow changes in the Quinault and Yakima Rivers
+3.6 to +5.4°F
(+2 to +3°C)
(note: under new scenarios, light blue bands are more likely to be seen mid-century (2050s) rather than 2040s
Implications
•
Water supplies:
– Increased vulnerability to drought,
– Increased competition for water during
summer as demands increase with
population growth and climate change
•
Water quality:
– Altered water quality (water temp, dissolved
oxygen, salinity, nutrients, fecal coliform)
– Impacts vary with parameter and location
•
Flooding and stormwater management:
– Increased risk of winter flooding in mid- and
low-elevation basins
– Changes in urban flooding less clear
(importance of frequency and intensity of
storm events)
Implications (cont’d)
•
•
•
Hydropower:
– Increased winter generation due to higher
streamflows (but lower demand)
– Reduced summer generation due to lower
streamflows (but increased demand)
Salmon:
– Increased stress due to lower summer and fall
streamflows, warmer water temperatures, and
increased potential for winter flooding.
– Unclear how coastal or open ocean conditions will
respond
Marine ecosystem and function:
– Impacts reverberate through the food web from the
bottom-up (e.g., phytoplankton) and top-down (e.g.,
marine mammals).
– Magnitude of change hard to predict at this point but
broad reorganization of systems observed with subtle
changes in natural variability
Implications (cont’d)
•
Forests:
– Increased vulnerability to severe forest fires and insect
outbreaks
– Reduced regeneration and growth at dry low elevation
sites (with some benefit at higher elevations)
– Shifts in some species ranges over time
•
Agriculture:
– Overall impacts vary with crops and availability of water
– Increased crop yields where there is sufficient soil
moisture or irrigation water
– Increased weed growth and risk of pest outbreaks
And let’s not forget about…
• Skiing:
– Increased risk of shortened ski season at lower elevation
ski areas due to lack of snow or poor snow quality
– Could improve customer access to ski areas
How will tree growth change in a
warmer climate?
The Pacific Northwest has wet winters and dry
summers  potential for summer moisture stress
• Growth may decrease in dry, eastside forests
• Growth may decrease slightly in low-elevation,
westside forests
• Growth will increase in many high-elevation
forests
Are forests responding to climatic change?
Growth increases at
high elevation
From McKenzie et al. (2001)
Regeneration increases at high elevation
throughout western North America
What could cause these patterns?
How will climate change affect wildfire?
Years with fire area > 80,000 ha
Warm-phase PDO
Cool-phase PDO
Idaho
14
7
Oregon
14
5
Washington
10
2
TOTAL
38 (73%)
National Forest data, 1916-2005
14 (27%)
Area burned, western U.S.
5x106
Total Wildfire Area Burned 1916-2002
USFS, NPS, BLM, BIA Lands
Acres burned
4x106
Warm PDO
Cool PDO
Warm PDO
6
3x10
2x106
1x106
0
1920
1930
1940
1950
1960
1970
1980
1990
2000
3x106
Fire suppression 
Fire
exclusion
 1916-2002
Fuel accumulation
WA, OR,
ID Wildfire
Area Burned
3x106
Some fire
2x106
USFS, NPS, BLM, BIA Lands
 Much less fire 
Lots of fire
Future wildfire?
Analysis of wildfire data since 1916 for
the 11 contiguous Western states shows
that for a 2oC increase that annual area
burned will be 2-3 times higher.
From McKenzie et al. (2004), Conservation Biology 18:890-902
Stress interactions, disturbance
Increased fire risk
• Higher fire frequency
• Higher fire intensity,
esp. in eastside forests
Increased insect outbreaks
• Postfire stress
• Low vigor stands with
high stem density
Carbon in forest ecosystems
Carbon dioxide (CO2) is emitted by human activities
-- Fossil fuel combustion (autos, industry)
CO2 is emitted by natural processes
-- Fire, decomposition, respiration
Trees conduct photosynthesis by assimilating CO2, a
limiting factor for productivity and growth.
Forests take up and store large quantities of carbon on a
global and regional basis
-- But annual uptake in Washington only ~20% of
emissions
Forest carbon budgets
Storage (quantity) vs. uptake (rate)
Young forest
Storage
Uptake
Mg/ha
Mg/ha/yr
50-100
5-10
Old forest
400-1000+
(600?)
+ 1.0?
Responding to Climate Change:
Mitigation and Adaptation
• Mitigation activities focus on reducing emissions of
greenhouse gases
– Ex: Kyoto Protocol, West Coast Governors’ Climate
Change Initiative
• Adaptation activities focus on developing the capacity
to manage the change that occurs as mitigation
strategies are debated and enacted.
– Ex: Developing more robust water supply systems,
migration corridors for wildlife, relocation of coastal
communities in NW Alaska
• “Mitigate we might, adapt we must”
Can forest management help mitigate
climate change?
Best case scenario: On a global basis, forests could store
up to one-third of total carbon emissions.
Longer rotations; bigger effect on westside than eastside
Retain woody debris on site or utilize it for products
Extend the life cycle of wood products; encourage
recycling, re-use
Protect forests from crown fire (suppression, fuel management)
Potential market for carbon credits?
Can forest management help adapt
to climate change?
Use nursery stock tolerant to low soil moisture, high
temperature
Use a variety of genotypes in nursery stock
Consider planting mixed species stands
Retain woody debris on site
Maintain "healthy" stands
-- Appropriate stocking (density)
-- Reduce risk from insects, fungi
Cooperate with your neighbors!
Climate change will force resource managers and planners to
deal with increasingly complex trade-offs between different
management objectives. Planning for climate change is
needed if the region is to adapt to climate change.
USFWS
WA Dept. of Ecology
Climate Impacts Group
Climate Impacts Group
Planning for Climate Change
Planning for climate change is needed if the region is to
adapt to climate change. Options for policy makers, planners,
and resource managers include:
• Become familiar with effects of climate change
• Recognize that the past is not a dependable guide to
the future
• Take actions to increase the adaptability of regional
ecosystems to future change
• Monitor regional climate and ecosystems for ongoing
change
• Expect surprises and design for flexibility to changing
conditions.
Planning Opportunities….
• National Forest management plans
• Northwest Forest Plan
• Watershed planning
• Salmon recovery
• Water supply and water quality management
• Local land use planning
• Flood control planning
• Nearshore and coastal planning
Summary
• Warming will continue. The PNW will continue warming
through the 21st century even if greenhouse gas
emissions were stopped today. Even the lowest
projected warming would alter PNW climate significantly.
• Human choices matter. Human activities affect PNW
ecosystems and ultimately affect the resilience of these
systems (negatively or positively).
• Knowledge and tools for planning exist. Taking early
action will increase capacity to adapt to changes,
monitor resource conditions, and design for flexibility.