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Co-organizer/Chair: Michael E. Mann, University of Virginia

Climate Change Detection / Attribution. Organizer: Martin Visbeck, Columbia University. Co-organizer/Chair: Michael E. Mann, University of Virginia. SPEAKERS: Gabi Hegerl, Duke University Drew Shindell, NASA-Goddard Institute for Space Studies. National Academy of Sciences

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Co-organizer/Chair: Michael E. Mann, University of Virginia

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  1. Climate Change Detection / Attribution Organizer: Martin Visbeck, Columbia University Co-organizer/Chair: Michael E. Mann, University of Virginia SPEAKERS: Gabi Hegerl, Duke University Drew Shindell, NASA-Goddard Institute for Space Studies National Academy of Sciences Thirteenth Annual Symposium on Frontiers of Science November 8-10, 2001

  2. Climate Change Detection / Attribution Introduction (Mann)    25 minQ&A                                                                      5 minUse of Models in Detection/Attribution (Hegerl)    25 minQ&A                                                                     5 minCauses of N.Hemisphere winter warming (Shindell)     25 minQ&A                                                                       5 minDiscussion                                                     30 min National Academy of Sciences Thirteenth Annual Symposium on Frontiers of Science November 8-10, 2001

  3. Introduction to the Problem of Climate Change Detection and Attribution Michael E. Mann Department of Environmental Sciences University of Virginia National Academy of Sciences Thirteenth Annual Symposium on Frontiers of Science November 8-10, 2001

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

  5. OVERVIEW • The Empirical Record • Model Predictions • Comparison between the two • Key Outstanding issues

  6. THE EMPIRICAL RECORD Surface Temperature Changes

  7. Climatic Research Unit (‘CRU’), University of East Anglia

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

  9. TREE RINGS

  10. CORALS

  11. ICE CORES

  12. VARVED LAKE SEDIMENTS

  13. HISTORICAL DOCUMENTS

  14. INSTRUMENTAL TEMPERATURE RECORD GLOBAL PROXY CLIMATE RECORDS

  15. RECONSTRUCTED GLOBAL TEMPERATURE PATTERNS

  16. MODEL PREDICTIONS

  17. Greenhouse Gases and Warming CO2 Related?

  18. GREENHOUSE EFFECT?

  19. ENHANCED GREENHOUSE EFFECT?

  20. SIMULATED ANNUAL MEAN TREND 1949-1997 Knutson, T.R., T.L. Delworth, K.W. Dixon, and R.J. Stouffer, Model assessment of regional surface temperature trends (1949-1997), Journal of Geophysical Research, 104, 30981-30996, 1999.

  21. Observations Modeled Natural Variability

  22. COMPARISON BETWEEN MODEL AND OBSERVATIONS

  23. OBSERVED ANNUAL MEAN TREND 1949-1997 Knutson, T.R., T.L. Delworth, K.W. Dixon, and R.J. Stouffer, Model assessment of regional surface temperature trends (1949-1997), Journal of Geophysical Research, 104, 30981-30996, 1999.

  24. SIMULATED ANNUAL MEAN TREND 1949-1997 Knutson, T.R., T.L. Delworth, K.W. Dixon, and R.J. Stouffer, Model assessment of regional surface temperature trends (1949-1997), Journal of Geophysical Research, 104, 30981-30996, 1999.

  25. Inconsistent with Natural Variability Inconsistent with Greenhouse+ Sulphate Forcing

  26. Vertical Fingerprint

  27. Greenhouse vs. Solar Vertical Fingerprint ECHAM3/LSG MODEL Climate Change 2001: The Scientific Basis, Houghton, J.T., et al. (eds.), Cambridge Univ. Press, Cambridge, 2001

  28. CLIMATE FORCINGS Anthropogenic Industrial Aerosols Greenhouse Gases

  29. 1000 1200 1400 1600 1800 2000 CLIMATE FORCINGS Volcanism Solar Natural

  30. 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

  31. Science Energy Balance Model (“EBM”) simulation

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

  33. KEY OUTSTANDING ISSUES

  34. EL NINO/SOUTHERN OSCILLATION (“ENSO”) Substantial interannual climate variability associated with ENSO, but decadal variability is also evident as well. The recent decadal trend towards El Nino conditions could be natural or anthropogenic. Multivariate ENSO Index (“MEI”)

  35. NORTH ATLANTIC OSCILLATION Negative Phase Positive Phase

  36. NORTH ATLANTIC OSCILLATION Trend in NAO in past couple decades explains enhanced recent warming in certain regions of Northern Hemisphere

  37. The “Little Ice Age”

  38. Shindell et al (Science, in press) Empirical LIA winter cooling in Europe associated with an NAO trend due to solar irradiance changes, interacting w/ stratospheric atmospheric dynamics and chemistry NASA/GISS Model

  39. NORTH ATLANTIC OSCILLATION This NAO trend could be Anthropogenic

  40. 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 • Unresolved issues regarding the precise sensitivity of the climate to forcing, and changes in ENSO, NAO, and regional responses

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