1. “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

2. “what a climate model is”

3. General Circulation Model (“GCM”) Australia Government BOM Laws of Physics!!!

4. Two basic parts: -“Dynamics” -Atmospheric circulation -Ocean circulation -“Physics” -Radiation -Clouds -Precipitation -Land surface fluxes -and more…..

5. Global Radiation Balance

6. From Marshall and Plumb, Elsevier, 2008 T e = [S 0 (1-a p ) / 4σ] 1/4 T e = emission temp S 0 = solar “constant” a p = planetary albedo σ = Stefan- Boltzman constant

9. Water Vapor in Air

12. Santer et al., 2007 Observed and Modeled Water Vapor Content important for greenhouse effect important for atmospheric circulation important for extreme events

13. Atmosphere and Ocean Circulation

21. “and what uncertainty means”

22. Observed “Global Warming”

23. Keeling Curve Global Warming Art

24. IPCC, 2007 Observed warming does not occur without human forcings

25. “The Future”

26. From the perspective of climate model experiments

27. IPCC SRES Scenarios Raupach et al., 2007

28. IPCC, 2007 spread within each scenario spread between scenarios

29. Climate Feedbacks Santer et al., 2007 http://internationalspacestationpictures.com/pic tures-of-earth-from-space.php NASA

30. Hawkins and Sutton, 2009 “Internal Variability” “Model” “Scenario”

33. Diffenbaugh and Scherer, 2011

34. Date of permanent exceedence of late-20 th century maximum

35. Diffenbaugh and Ashfaq, 2010 U.S.A. Summer Soil- Moisture/Temperature/Precipitation Coupling 2030-2039 minus 1980-1999

36. CBS News Joplin Tornado – May 22, 2011

40. Brooks et al. 2003

41. 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

42. Trapp et al., PNAS, 2007

43. From the perspective of the climate system

44. Giorgi, Diffenbaugh, et al., 2008 Climate Change Uncertainty

45. 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?