“what a climate model is, and what uncertainty means” noah s. diffenbaugh department of...
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“what a climate model is, and what uncertainty means”
Noah S. Diffenbaugh
Department of Environmental Earth System Science and Woods Institute for the Environment
Stanford University
“what a climate model is”
General Circulation Model (“GCM”)
Australia Government BOMLaws of Physics!!!
Two basic parts:
-“Dynamics”- Atmospheric circulation- Ocean circulation
-“Physics”- Radiation- Clouds- Precipitation- Land surface fluxes- and more…..
Global Radiation Balance
From Marshall and Plumb, Elsevier, 2008
Te = [S0(1-ap) / 4σ] 1/4
Te = emission temp
S0 = solar “constant”
ap = planetary albedo
σ = Stefan-Boltzman constant
Water Vapor in Air
Santer et al., 2007
Observed and Modeled Water Vapor Content
• important for greenhouse effect• important for atmospheric circulation• important for extreme events
Atmosphere and Ocean Circulation
“and what uncertainty means”
Observed “Global Warming”
Keeling Curve
Global Warming Art
IPCC, 2007
• Observed warming does not occur without human forcings
“The Future”
From the perspective of climate model experiments
IPCC SRES Scenarios
Raupach et al., 2007
IPCC, 2007
• spread within each scenario
• spread between scenarios
Climate Feedbacks
Santer et al., 2007
http://internationalspacestationpictures.com/pictures-of-earth-from-space.php
NASA
Hawkins and Sutton, 2009
“Internal Variability”
“Model”
“Scenario”
Diffenbaugh and Scherer, 2011
Diffenbaugh and Scherer, 2011
Date of permanent exceedence of late-20th century maximum
Diffenbaugh and Ashfaq, 2010
U.S.A. Summer Soil-Moisture/Temperature/Precipitation
Coupling2030-2039 minus 1980-1999
CBS News
Joplin Tornado – May 22, 2011
Brooks et al. 2003
Severe Thunderstorm Environments
• Convective Available Potential Energy (CAPE)
Brooks et al., 2003
Pole-equator temperature gradient
Thermal Wind Equation
S6
• Vertical Wind Shear
Trapp et al., 2007
Trapp et al., PNAS, 2007
From the perspective of the climate system
Giorgi, Diffenbaugh, et al., 2008
ClimateChangeUncertainty
How do we make decisions when:
1. we don’t know the level of climate forcing in the future?
2. we don’t understand every process that could be important for climate change impacts?
3. The phenomena that matter most for climate change impacts may exceed the limits of predictability?