Extreme climate in the 21 st century Noah S. Diffenbaugh Department of Environmental Earth System Science and Woods Institute for the Environment Stanford University
Mar 27, 2015
Extreme climate in the 21st century
Noah S. Diffenbaugh
Department of Environmental Earth System Science
and
Woods Institute for the Environment
Stanford University
IPCC SRES Scenarios
Raupach et al., 2007
A2: > 800 ppm CO2 in 2100
Simulations test difference between:
1961-1989
2071-2099
General Circulation Model
Australia Government BOM
Nested High-Resolution Climate Model
Driver Variables• Temperature• Pressure• Winds• Geopotential Height• Specific Humidity
Driver variables passed to nested model at lateral boundaries every 6 model hours
Walker and Diffenbaugh, 2009
Diffenbaugh and Ashfaq, in review
• Increases of 100 to 560 % in occurrence and 50 to 550 % in duration
Change in Extreme Hot Event Occurrence
Diffenbaugh et al., 2005
2071-2099minus
1961-1989
Change in Extreme Cold Events
∆ Extreme Cold Frequency ∆ Extreme Cold Magnitude
2071-2099minus
1961-1989Diffenbaugh et al., 2005
Poumadere et al., 2005
Magnitude of 2003
Heat Stress
Giorgi and Diffenbaugh, 2008
2071-2099minus
1961-1989
Trapp, et al., PNAS, 2007
Change in Severe Thunderstorm Environments
• Inceases in CAPE overcome decreases in shear
Harshvardhan et al., in revision
Air Stagnation Events
IPCC SRES Scenarios
Raupach et al., 2007
A1B
Simulation between:
1950-2039
5 ensemble members=> “physically uniform”
Ensemble Mean
• Exceedence of 1951-1999 3-month maximum value
Diffenbaugh and Ashfaq, in review
Summary and Conclusions
• High-resolution nested climate models often project larger changes in health-relevant metrics than global climate models.
=> is this a real feature of the climate system?
• Near-term (decadal), local-scale climate prediction is of high value as a climate service, but is at best very challenging (and at worst impossible) from a scientific perspective.