Recent trends:
Observed:
Warming
Observed:
Less
snowpack
Observed: Less
snow/more rain
Observed:
Earlier snowfed
streamflow
Stewart et al., 2005
Observed: Earlier
greenup dates
Expected changes: Temperature
Greenhouse
effects
1900-2100
Under projected
greenhouse gas increases,
all climate models yield
warmer futures for the West.
Dettinger, 2005; Hidalgo et al, 2008
20 of 23 in this range
Expected trends:
Precipitation
cm/month
cm/month
19 of 23 in this range
Dettinger, 2005
Wetter poles
Half models
Enhan
wetter, half drier
ced de
serts
Most climate projections fall
within a fairly narrow range of
precipitation changes in much of
the West. In Northern California,
"small change" is most common
projection.
Projected changes:
Changes in Sierra Nevada Outflow, 2060 – 2000
Net results:
more severe
winter floods in
at least some
settings and
drier summers
in most…
Knowles and Cayan, 2004; http://www.fs.fed.us/psw/cirmount/
/meetings/agu/pdf2006/dettinger_etal_poster_AGU2006.pdf
Projected changes:
Soil moisture, 2050-99 minus 1950-99
(VIC land-surface hydrology model forced by downscaled CNRM global climate model)
Das et al, in prep
Projected changes:
Northern Sierra Nevada soil moisture, 1950 to 2099
(VIC land-surface hydrology model forced by downscaled CNRM global climate model)
Das et al, in prep
Bringing projections down to Devils Postpile
• Downscale
global-scale
projections to
12 km
• Run thru
VIC landsurface
hydrology
model
San Francisco
DEPO
Monterey
Following projections courtesy of Hugo Hidalgo, Tapash Das & Dan Cayan (2008)
See Jeton et al 1996,
USGS WRIR 95-4260,
For discussion of why this
happens
Finally, some thoughts on
the issue of cold air in
DEPO
…A few data plots from our DEPO
weather station
Managing for a cold refugia is going to require info:
How does cold air drainage at DEPO work, and how
will it fare under generalized warming?
•Need met data at Pass
•Need temperature transects up entry road and along
river
•Need wind data at DPO and entry
•Need an analog setting with longer history
•A high-resolution weather model to crystallize the
hypothesis would be very useful
Recent trends:
The normal climate variability in the West is now
being augmented with warming associated with
increases in the greenhouse effect.
Global-average temperatures
Natural conditions suffice
Observed
Greenhouse emissions
required
Meehl et al., 2004
Recent trends:
This global response has now been verified also at regional scales,
including in the hydrology of the western US (Barnett et al., Science, 2008)
Historical &
projected
temperatures
IPCC4, WG1, TSU, 2007, Fig. TS-25