Stewart et al., 2005

Recent trends:Recent trends:

Observed:Warming

Observed:Less

snowpack

Observed:Observed:Earlier Earlier snowfedsnowfedstreamflowstreamflow

Observed: Less snow/more rain

Observed: Earliergreenup dates

20 of 23 in this range

Under projected greenhouse gas increases,

all climate models yield warmer futures for the West.

Greenhouse effects1900-2100

Dettinger, 2005; Hidalgo et al, 2008

Expected changes: Temperature

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.

Expected trends:

Half models wetter, half drier

Dettinger, 2005

19 of 23 in this range

cm/m

onth

cm/m

onth

Precipitation

Enhanced deserts

Wetter poles

Net results: more severe

winter floods in at least some settings and

drier summersin most…

Changes in Sierra Nevada Outflow, 2060 – 2000

Knowles and Cayan, 2004; http://www.fs.fed.us/psw/cirmount/ /meetings/agu/pdf2006/dettinger_etal_poster_AGU2006.pdf

Projected changes:

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

San Francisco

Monterey

Bringing projections down to Devils Postpile

• Downscale global-scale projections to 12 km

• Run thru VIC land-surface hydrology model

Following projections courtesy of Hugo Hidalgo, Tapash Das & Dan Cayan (2008)

DEPO

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

The normal climate variability in the West is now being augmented with warming associated with

increases in the greenhouse effect.

MeehlMeehl et al., 2004et al., 2004

ObservedGreenhouse emissions

required

Global-average temperatures

Recent trends:

Natural conditions suffice

This global response has now been verified also at regional scales, including in the hydrology of the western US (Barnett et al., Science, 2008)

IPCC4, WG1, TSU, 2007, Fig. TS-25

Recent trends:

Historical & projected temperatures