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Climate Change and Global Warming

Climate Change and Global Warming. Michael E. Mann Department of Environmental Sciences University of Virginia. Waxter Environmental Forum Sweet Briar College March 14, 2002.

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Climate Change and Global Warming

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  1. Climate Change and Global Warming Michael E. Mann Department of Environmental Sciences University of Virginia Waxter Environmental Forum Sweet Briar College March 14, 2002

  2. `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

  3. THE EMPIRICAL RECORD

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

  5. Surface Temperature Changes Shaded: 20th century Boxes: since mid 19th century

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

  7. 1998 Global Temperature Pattern

  8. 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”)

  9. NORTH ATLANTIC OSCILLATION Negative Phase Positive Phase

  10. NORTH ATLANTIC OSCILLATION This NAO trend could be Anthropogenic

  11. “PACIFIC DECADAL OSCILLATION”

  12. Atlantic Multidecadal Oscillation There is evidence of multidecadal natural variability in the North Atlantic ocean circulation

  13. Greenhouse Gases and Warming CO2 Related?

  14. TREE RINGS

  15. CORALS

  16. ICE CORES

  17. VARVED LAKE SEDIMENTS

  18. HISTORICAL DOCUMENTS

  19. RECONSTRUCTED GLOBAL TEMPERATURE PATTERNS

  20. European Winter Cooling During the Little Ice Age “Little Ice Age”

  21. European Winter Cooling During the Little Ice Age 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 Shindell, D.T., Schmidt, G.A., Mann, M.E., Rind, D., Waple, A., Solar forcing of regional climate change during the Maunder Minimum, Science, 294, 2149-2152, 2001.

  22. CLIMATE MODELS

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

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

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

  26. Observations Modeled Internal Natural Variability

  27. INFLUENCE OF EXTERNAL FACTORS

  28. The climate is governed by external factors, including the intensity of solar outputand volcanic aerosolsand greenhouse gas concentrations

  29. Solar Variations

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

  31. Volcanoes

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

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

  34. GREENHOUSE EFFECT?

  35. ENHANCED GREENHOUSE EFFECT?

  36. Greenhouse Gases and Warming CO2 Related?

  37. SIMULATIONS OF CLIMATE CHANGE

  38. 1000 1200 1400 1600 1800 2000 CLIMATE FORCINGS Volcanism Solar Natural

  39. 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

  40. CLIMATE FORCINGS Anthropogenic Industrial Aerosols Greenhouse Gases

  41. 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

  42. 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

  43. 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

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

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

  46. 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 • Uncertainties remain regarding the precise sensitivity of the climate to forcing, and the regional details of expected climate changes

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