1. Global Climate Change: Past and Future 2006 Scott Margolin Lecture in Environmental Affairs Middlebury College Middlebury VT March 7, 2006 Michael E. Mann Department of Meteorology and Earth and Environmental Systems Institute (ESSI) Penn State University

2. `The balance of evidence suggests that there is a discernible human influence on global climate ' Intergovernmental Panel on Climate Change (United Nations), Second Assessment Report, 1996

3. `There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activity' Intergovernmental Panel on Climate Change (United Nations), Third Assessment Report, 2001

4. THE DATA

5. Climatic Research Unit (‘CRU’), University of East Anglia Surface Temperature Changes

6. Greenhouse Gases and Warming CO 2 Related?

7. TREE RINGS

8. CORALS

9. ICE CORES

10. VARVED LAKE SEDIMENTS

11. HISTORICAL DOCUMENTS

12. RECONSTRUCTED GLOBAL TEMPERATURE PATTERNS

13. Reconstructed Surface Temperatures Climate Change 2001: The Scientific Basis, Houghton, J.T., et al. (eds.), Cambridge Univ. Press, Cambridge, 2001

14. Reconstructions of Northern Hemisphere mean temperatures for the last 1000 years and instrumental record (black line) From “Wikipedia”

15. CLIMATE MODELS

16. The climate represents a coupled system consisting of an atmosphere, hydrosphere, biosphere, and cryosphere

17. General Circulation Models take into account the full three- dimensional structure of the atmosphere and ocean

18. This alone doesn’t guarantee that they should do a good job in describing climate change ! GCMs do a fairly good job of describing the seasonal cycle in surface temperature January Temp (observations) January Temp (model)

19. Modeled Internal Natural VariabilityObservations

20. INFLUENCE OF EXTERNAL FACTORS

21. The climate is governed by external factors, including the intensity of solar output and volcanic aerosols and greenhouse gas concentrations

22. Solar Variations

24. The climate is governed by external factors, including the intensity of solar output and volcanic aerosols and greenhouse gas concentrations

25. Volcanoes

26. The climate is governed by external factors, including the intensity of solar output and volcanic aerosols and greenhouse gas concentrations

28. GREENHOUSE EFFECT?

30. ENHANCED GREENHOUSE EFFECT?

31. SIMULATIONS OF CLIMATE CHANGE

32. Simulated Annual Global Mean Surface Temperatures Climate Change 2001: The Scientific Basis, Houghton, J.T., et al. (eds.), Cambridge Univ. Press, Cambridge, 2001 Forced Model simulations

33. Simulated Annual Global Mean Surface Temperatures Climate Change 2001: The Scientific Basis, Houghton, J.T., et al. (eds.), Cambridge Univ. Press, Cambridge, 2001 Forced Model simulations

34. Simulated Annual Global Mean Surface Temperatures Climate Change 2001: The Scientific Basis, Houghton, J.T., et al. (eds.), Cambridge Univ. Press, Cambridge, 2001 Forced Model simulations

35. Climate Change 2001: The Scientific Basis, Houghton, J.T., et al. (eds.), Cambridge Univ. Press, Cambridge, 2001 Future Surface Temperatures Trends?

36. Possible Impacts: North American Drought

37. 1998 Global Temperature Pattern

38. El Nino and North American Drought

39. El Nino vs. North American Drought over the Past Century Increased Drought La Nina El Nino Less Drought Courtesy of E.Cook

40. Katrina (Aug 28 ’05) Destructive Potential of Atlantic Hurricanes Possible Impacts:

41. Rita (Sep 21 ’05) Destructive Potential of Atlantic Hurricanes Possible Impacts:

42. Wilma (Oct 19 ’05) Destructive Potential of Atlantic Hurricanes Possible Impacts:

43. Hurricane Statistics P. J. Webster, G. J. Holland, J. A. Curry, H.-R. Chang Changes in Tropical Cyclone Number, Duration, and Intensity in a Warming Environment, Science, 309, Issue 5742, 1844-1846, 2005.

44. Emanuel, K. (2005), Increasing destructiveness of tropical cyclones over the past 30 years, Nature, online publication; published online 31 July 2005 | doi: 10.1038/nature03906 Hurricane Statistics

45. Climate Model Predictions Knutson, T. K., and R. E. Tuleya, 2004: Impact of CO2-induced warming on simulated hurricane intensity and precipitation: Sensitivity to the choice of climate model and convective parameterization. Journal of Climate, 17(18), 3477-3495.

46. Climatological Surface Temperatures January [source: NOAA Climate Prediction Center]

47. Surface Temperature Pattern January ’06 [source: NOAA Climate Prediction Center]

48. Surface Temperature Anomaly Pattern January ’06 [source: NOAA Climate Prediction Center]

49. Temperature Anomaly Pattern (January ’06) Climate Change 2001: The Scientific Basis, Houghton, J.T., et al. (eds.), Cambridge Univ. Press, Cambridge, 2001

50. CONCLUSIONS Recent global surface temperatures are unprecedented this century, and likely at least the past millennium It is difficult to explain the recent surface warming in terms of natural climate variability Recent surface warming is largely consistent with simulations of the effects of anthropogenic influence on climate Possible impacts of anthropogenic climate change this century include increased drought conditions in the western U.S. and more destructive Atlantic tropical storms and Hurricanes

51. ``RealClimate is a commentary site on climate science by working climate scientists for the interested public and journalists. We aim to provide a quick response to developing stories and provide the context sometimes missing in mainstream commentary.’’RealClimate Gavin Schmidt, Michael Mann Eric Steig, William Connolley, Ray Bradley, Stefan Rahmstorf, Rasmus Benestad, Caspar Ammann, Thibault de Garidel, David Archer, Ray Pierrehumbert