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California’s Future Climate
Lessons from Scenarios Assessments
Dan Cayan
Scripps Institution of Oceanography, Climate Research Division, UCSD
and
Water Resources Division, USGS
Thanks: Mike Dettinger, Noah Knowles, Mary Tyree
Funding:
PIER Program, California Energy Commission
RISA Program, NOAA Office of Global Programs
DOE
More info:
http//:meteora.ucsd.edu/CAP/
California Climate
Change Scenarios
Assessment
some lessons
learned
Gov Swartzenegger’s
June 2005 Executive Order
commissioned this
Climate Assessment, which
investigated potential climate
change impacts and formed key
scientific background for
California’s greenhouse gas
emissions legislation, AB-32
which was passed in fall 2006
Available on the web at
http://www.climatechange.ca.gov/b
iennial_reports/2006report/
Vulnerability: response to a +3ºC warming
What fraction
of each year’s
precipitation
historically fell
on days with
average
temperatures
just below
freezing?
YOSEMITE
Less vulnerable
More vulnerable
“Rain vs Snow”
Computed by Mike Dettinger from gridded
historical US weather data (from Bates et al, in
rev)
More Rain
Less Snow
WY 1949-2004
Winter (Nov-Mar) SFE/P trends at western US
weather stations: symbol area is proportional to
study-period changes, measured in standard
deviations as indicated; circles indicate high
trend significance (p<0.05), squares indicate
Noah Knowles et al. 2006
lower trend significance (p>0.05).
in press J. Climate
We face significant losses of spring snowpack
• Less snow,
more rain
• Particularly at
lower elevations
• Earlier run-off
• More floods
• Less stored
water
By the end of the century California could lose half of its late spring
snow pack due to climate warming. This simulation by Noah
Knowles is guided by temperature changes from PCM’s Business-asusual climate simulation. (a middle of the road emissions scenario)
Knowles and Cayan 2001
since 1985 the number of large wildfires in western U.S. increased by 4X
Anthony Westerling et al. Science August 2006
Large
wildfire
threat is
aggravated
by warmer
springs and
summers
Anthony Westerling et al. Science August 2006
Ocean Beach , February 1983
Extreme storm-forced sea levels during an extreme tide
Observed SFO (left) and
modeled Global (right). Sea
level rise estimates based
upon an envelope of output
from several GHG emission
scenarios
Projected envelope of global s.l. rise
observed
Climate models
Only provide loose guidance on
The amount of sea level rise, but
It is very likely that rates will increase
San Francisco Bay/Delta
Water Levels
Confluence of sea level rise and increased flooding
~Jan 3 2006
Nasa
http://earthobservatory.nasa.gov/Newsroom/NewImages/Images
/ncalifflood_amo_2006004_lrg.jpg
Uncertainty: Projected Warming Ranges
Statewide annual average (°F)
o
T e m p e raChange
tu re C h a(°F)
nF)
ge (
Temperature
14.48
10.86
9
Higher Warming
Range
4
Medium
Warming Range
Lower
Warming Range
3.6 2
00
-3.6
-2
1975
2000
2025
2050
2075
2100
A1 H ad C M 3
A1 P C M
A2 H ad C M 3
A 2 G F D L 2 .1
A2 P C M
B1 Had CM3
B 1 G F D L 2 .1
B1 PCM
Meditterranean precipitation regime remains
Although models unanimously indicate a warmer
climate, they are undecided if it will get wetter or dry out
6 different climate models
5 emission scenarios,
IPCC SRES runs
Mike Dettinger, 2005
San Fran. Estuary and Watershed Science
Projected patterns of precipitation changes
2090-2099 versus 1980-1999
Globally, dry regions become drier?
Challenges
Mike Dettinger, Jim Wells USGS and SIO
record streamflow in Tuolumne Meadows
Seasonally intensified warming?
some models suggest amplified summer warming
Climate models project
1.5-2.C ocean surface warming
by end–of-century.
Greater warming on land
than oceans would amplify
California coast-interior thermal
gradient.
Summer land warming
is accentuated
GFDL CM2.1 is a medium-high
sensitivity model. Other models
produce less (or more) warming
GFDL CM2.1 Jun-Aug air temp change
2070-2099 minus 1961-1990
Modeling climate over California’s complex terrain:
July 10m Wind Diurnal Variation
Are models
capable of
producing
realistic
suite of
wet and dry
spells?
Distribution of
Obs and simulated
5yr precip departures
Hist means (inches):
Div2 36.02
Gfdl 43.13
Pcm 29.63
obs
Sacramento drainage div
sim
sim
California needs a sustained
modern Climate Observation Network
Douglas Alden
Scripps Institution
of Oceanography
Installing met station
Lee Vining, CA
Implications for
Monitoring
Primary snowpack loss is above ~1500m
Knowles and Cayan, 2004
Rain-snow
transition zone
Needs more
Careful
monitoing
Over all Stream gages, present-day elevational bias is small…
Total number of stream
gages below 1500m
(red)
Total number of gages
above 1500m (blue)
…but climate-quality HCDN subset is under-represented in crucial elevations.
Total number of HCDN
gages below 1500m
(red)
Total number of HCDN
gages above 1500m
(blue)
Noah Knowles, USGS)
…on the other hand, it can be very wet
May 16th 2005 A warm storm in the Sierra
Yosemite Valley floods from a 1” rain
need to understand event scale phenomena
projected heat wave days
SRES A2
GHG Emissions Scenario
Need observations of
3-d, upstream atmosphere
Slide 11
Hydromet testbed,
NOAA ETL and collaborators
How to effectively work and learn across disciplines?
Impacts
-Physical
-Ecological
-Economic
-Social
Scenarios, not forecasts
PCM. GFDL, HAD
Model-based
Climate Projections
Human
Health
Agriculture
Coasts
Water
Forests/
Fire
Energy
Coping Capacity/Preparedness
Susi Moser, NCAR
Recommendations
(without much discussion)
:
Improved, sustained observations
higher spatial resolution, more coverage
3-d atmosphere and ocean upstream
California meso-micro climates including urban and agricultural settings
improve insitu network, real-time communications
scientific quality record keeping of economic, social measures
data archeology
Continued modeling at several scales, disciplines
Ongoing climate simulation compute consortium Ongoing Consortium for
climate simulation/prediction to knit state/campuses/labs
End-to-end assessments, including eco, economic, social; close State participation
Study extreme events as well as secular changes
Study aerosol-clouds-precipitation
Link with other regional, national, international efforts
Support California State Climate Scenarios Assessments
Promote CEC-PIER Annual Climate Change Conference
Develop closer, better links to decision makers; strengthen outreach
Fellowship program for grad students, post docs to ensure continuity, new generation