Climate Change, ARkStorms & the Sierra Nevada

Mike Dettinger, US Geological Survey, Scripps Institution of Oceanography

Dale Cox, US Geological Survey, Sacramento

NOAA’s California-Nevada Applications Program

Dettinger, SFEWS, 2005

PROJECTED CHANGES IN ANNUAL TEMPERATURES, NORTHERN SIERRA NEVADA

PROJECTED TEMPERATURE CHANGES

-4F

20 of 23 in this range

0F

+4F

+8F

12F

All Drier All Wetter

Among 12 projections with high-CO2 emissions, how many models yield increasing (decreasing) precipitation?

PROJECTED PRECIPITATION CHANGES

Northern California still on the edge between more-or-less precipitation.

Percentage Change from Historical Normals

PROJECTED SNOWCHANGES

Courtesy of David Pierce, SIO

End snow szns

(9 CMIP5 RCP4.5 GCMs BCCA downscaled, VIC snow simulated)

Rain vs Snow

More changeNO change

Start snow szns

Dettinger & Culbertson, SFEWS 2008

• More rain vs snow

• Shorter snow-cover seasons

• Earlier snowmelt & runoff

Cayan et al., SWCA, 2013

16 models, A2 emissions

Northern Sierra Nevada

Median of A2 emissionsMedian of B1 emissions

Center of sliding 50-yr window

Per

cen

tag

e o

f hi

stor

ical

50-

yr f

lood

Das et al., ClimChg, 2012; JH, in rev

PROJECTED STREAMFLOW CHANGES

Distributions of 50-yr flood changes

PROJECTIONS of MONSOONS/FIRE-WEATHER

June-September, 2041-69 vs 1971-99Precipitation Temperature

June-October, 2080-99 vs 1980-99Moist Static Energy

• Reductions in summer precipitation? (Mearns et al. 2009)

• Later monsoon arrivals & withdrawals (Cook & Seager, 2013)

• More stable atmosphere, less thunderstorming (Cook & Seager, 2013)

50-yr FloodsPROJECTIONS of LARGEST WINTER STORMS (Atmospheric rivers, or pineapple expresses)

Update to Dettinger, JAWRA, 2011

Short-Term (during & immediately following storm)

• Flooding along streams & in meadows• Wind damage to structures• Deep wet snows/traffic interruptions, around Lake &

to/from Lake• Infrastructure damages/utility interruptions• Trashed snow runs

• Erosion, sediment & nutrient transports into Lake• Wind-blown tree falls• Dilution of upper layer of Lake?

“ARkStorm” Consequences at Lake Tahoe

Long-Term (month to years following storm)• Deep wet snows / continuing traffic interruptions to/from

Lake (e.g., 1986)• Continuing utility interruptions• Trashed snow runs• Expensive repairs & economic recoveries

• Forest/meadow damages• Continuing erosion/nutrient episodes• Major Lake clarity impact?• Repeated Lake clarity impacts?• Open-doors for invaders?

“ARkStorm” Consequences at Lake Tahoe

Emergency-Response Desktop Exercises coming to Tahoe/Reno/CC region, Winter 2014!

FROM CLIMATE/HYDRO MODELS & OTHER CONSIDERATIONS, WE PROJECT:• Warming by +3 to +6ºC across Sierra, likely more so at higher altitudes

• Much of Sierra in range for modest, wetter-or-drier trends

•Monsoons may be delayed/reduced

• Extreme weather/floods gets more extreme

More rain, less snow

Less snowpack

Increased winter flood risks but longer low flows

Less overall streamflow (think -5 to -15%)

Changes in aquifer recharge

Longer growing seasons

More, more severe heat waves

Fewer (but deeper?) cold snaps

Increased wildfires

Favors many invasive species

11

For much more info on these & other topics,

see the new 2013 Southwest Climate Assessment Report:

http://www.swcarr.arizona.edu

Contact mddettin@usgs.gov w/questions or

for info re: ARkStorm@Tahoe