Climate Change, ARkStorms & the Sierra NevadaMike Dettinger, US Geological Survey, Scripps
Institution of OceanographyDale 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
-4F20 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
cent
age
of
hist
oric
al 5
0-yr
floo
d
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 [email protected] w/questions or for info re: ARkStorm@Tahoe
