1. Global Climate Change: Past and Future
Michael E. Mann
Departments of Meteorology and Geosciences and
Earth and Environmental Systems Institute (EESI)
Penn State University
Pennsylvania Consortium for Interdisciplinary Environmental Policy and the Pennsylvania Environmental Council
Harrisburg PA
Oct 5, 2006

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

6. Greenhouse Gases and Warming
CO2
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 HISTORICAL DOCUMENTS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. Thompson, L. G. , Mosley-Thompson, E. , Davis, M. E. , Lin, P. N
Thompson, L. G., Mosley-Thompson, E., Davis, M. E., Lin, P. N., Henderson, K., and Mashiotta, T. A., 2003, Tropical glacier and ice core evidence of climate change on annual to millennial time scales, Climatic Change, v. 59, p

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

16. CLIMATE MODELS

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

18. General Circulation Models (GCMs) take into account the full three-dimensional structure of the atmosphere and ocean

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

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

23. 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
1000
1200
1400
1600
1800
2000

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

27. GREENHOUSE EFFECT?

29. ENHANCED GREENHOUSE EFFECT?

30. ANTHROPOGENIC IMPACTS
Industrial Aerosols
Greenhouse Gases
Climate Change 2001: The Scientific Basis, Houghton, J.T., et al. (eds.), Cambridge Univ. Press, Cambridge, 2001

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. Jones, P.D., Mann, M.E., Climate Over Past Millennia, Reviews of Geophysics, 42, RG2002, doi: /2003RG000143, 2004.

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

37. Possible Impacts?
Climate Change 2001: The Scientific Basis, Houghton, J.T., et al. (eds.), Cambridge Univ. Press, Cambridge, 2001

38. Gavin Schmidt, Michael Mann David Archer, Ray Pierrehumbert
``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.’’
Gavin Schmidt, Michael Mann
Eric Steig, William Connolley, Ray Bradley, Stefan Rahmstorf, Rasmus Benestad, Caspar Ammann, Thibault de Garidel,
David Archer, Ray Pierrehumbert