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Climate over the Past Millennium or So
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  1. Michael E. Mann Department of Environmental Sciences, University of Virginia, Charlottesville, VA* Climate over the Past Millennium or So Collaborators: C. Ammann, R. Bradley, K. Briffa; M. Cane; A. Clement, M.K. Hughes, T. Osborn, P. Jones, S. Rutherford, G. Schmidt, D. Shindell, S. Zebiak Symposium on Whole Earth Systems (Honoring Stephen Schneider) Stanford University Stanford, CA Feb 10, 2005 *New Affiliation as of Fall ’05: Dept. of Meteorology and Earth & Environmental Systems Institute, Pennsylvania State University, University Park, PA

  2. ``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, Amy Clement

  3. Surface Temperature Changes Gray: back to beginning of 20th century Boxes: back to mid 19th century

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

  5. TREE RINGS

  6. CORALS

  7. ICE CORES

  8. VARVED LAKE SEDIMENTS

  9. HISTORICAL DOCUMENTS

  10. Annual Resolution Proxy Climate Indicators INSTRUMENTAL TEMPERATURE RECORD GLOBAL PROXY CLIMATE RECORDS

  11. Reconstructed Surface Temperatures Mann, M.E., Bradley, R.S., Hughes, M.K., Global-Scale Temperature Patterns and Climate Forcing Over the Past Six Centuries, Nature, 392, 779-787, 1998.

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

  13. Jones, P.D., Mann, M.E., Climate Over Past Millennia, Reviews of Geophysics, 42, RG2002,doi:10.1029/2003RG000143, 2004.

  14. 1000 1200 1400 1600 1800 2000 CLIMATE FORCINGS Volcanism Solar Natural Crowley, T.J., Causes of Climate Change Over the Past 1000 Years, Science, 289 270-277, 2000.

  15. CLIMATE FORCINGS Anthropogenic Industrial Aerosols Greenhouse Gases Climate Change 2001: The Scientific Basis, Houghton, J.T., et al. (eds.), Cambridge Univ. Press, Cambridge, 2001

  16. Jones, P.D., Mann, M.E., Climate Over Past Millennia, Reviews of Geophysics, 42, RG2002,doi:10.1029/2003RG000143, 2004.

  17. Seasonal Spatial Patterns Temperature Anomaly (oC) Warm Season (MXD) Cold Season (multiproxy) Rutherford, S., Mann, M.E., Osborn, T.J., Bradley, R.S., Briffa, K.R., Hughes, M.K., Jones, P.D., Proxy-based Northern Hemisphere Surface Temperature Reconstructions: Sensitivity to Methodology, Predictor network, Journal of Climate (in press), 2005.

  18. Volcanic Radiative Summer Cooling Ensemble average summer (Jun-Aug)surface temperature response following eruption of Pinatubo. Shindell, D.T., Schmidt, G.A., Miller, R., Mann, M.E., Volcanic and Solar forcing of Climate Change During the Pre-Industrial era, Journal of Climate, 16, 4094-4107, 2003.

  19. Volcanic Winter Dynamical Warming Ensemble average winter (Dec-Feb)surface temperature response following eruption of Pinatubo. Shindell, D.T., Schmidt, G.A., Miller, R., Mann, M.E., Volcanic and Solar forcing of Climate Change During the Pre-Industrial era, Journal of Climate, 16, 4094-4107, 2003.

  20. 1000 1200 1400 1600 1800 2000 Influence of Natural Radiative Forcing Crowley, T.J., Causes of Climate Change Over the Past 1000 Years, Science, 289 270-277, 2000. Volcanism Solar “Maunder Minimum”

  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. Annual average late 17th vs late 18th Century Temperature change Proxy based reconstruction GCM Solar + Volcanic patterns Shindell, D.T., Schmidt, G.A., Miller, R., Mann, M.E., Volcanic and Solar forcing of Climate Change During the Pre-Industrial era, Journal of Climate, 16, 4094-4107, 2003.

  23. Volcanic Forcing of El Nino? Adams, J.B., Mann, M.E., Ammann, C.M., Proxy evidence for an El Nino-like Response to Volcanic Forcing, Nature, 426, 274-278, 2003.

  24. Theoretical mechanism for natural radiative forcing of El Nino Cane, M.A., A.C. Clement, A. Kaplan, Y. Kushnir, D. Pozdnyakov, R. Seager, S.E. Zebiak, and R. Murtugudde, Twentieth-Century Sea Surface Temperature Trends, Science, 275, 957-960, 1997.

  25. Theoretical mechanism for natural radiative forcing of El Nino Composite Nino3 (100 realizations of CZ model) Tropical Volcanic radiative forcing (0.1 x W/m2)

  26. Theoretical mechanism for natural radiative forcing of El Nino Mann, M.E., Cane, M.A., Zebiak, S.E., Clement, A., Volcanic and Solar Forcing of The Tropical Pacific Over the Past 1000 Years, Journal of Climate, 18, 447-456, 2005. Response to Volcanic Forcing Composite Nino3 (100 realizations of CZ model) Tropical Volcanic radiative forcing (0.1 x W/m2)

  27. Superposed Epoch Analysis AD 1649-1868 Superposed Epoch Analysis AD 1000-1999 all (7) tropical events exceeding -2 W/m2 All (7) tropical events exceeding -4 W/m2 Theoretical mechanism for natural radiative forcing of El Nino Mann, M.E., Cane, M.A., Zebiak, S.E., Clement, A., Volcanic and Solar Forcing of the Tropical Pacific Over the Past 1000 Years, Journal of Climate, 18, 447-456, 2005. Tropical volcanic radiative forcing (0.1 x W/m2)

  28. Theoretical mechanism for natural radiative forcing of El Nino Composite Nino3 (100 realizations of CZ model) Tropical Solar radiative forcing (W/m2) Tropical volcanic radiative forcing (0.1 x W/m2) 40 year smooth

  29. Theoretical mechanism for natural radiative forcing of El Nino Response to Solar Forcing Composite Nino3 (100 realizations of CZ model) 40 year smooth Tropical Solar radiative forcing (W/m2) (40 year smooth) Mann, M.E., Cane, M.A., Zebiak, S.E., Clement, A., Volcanic and Solar Forcing of the Tropical Pacific Over the Past 1000 Years, Journal of Climate, 18, 447-456, 2005.

  30. Theoretical mechanism for natural radiative forcing of El Nino Combined response to Solar +Volcanic Forcing Palymra coral isotopes (standardized to have same mean and standard deviation as Nino3 composite series) Ensemble mean Nino3 (100 realizations of CZ model) Mann, M.E., Cane, M.A., Zebiak, S.E., Clement, A., Volcanic and Solar Forcing of the Tropical Pacific Over the Past 1000 Years, Journal of Climate, 18, 447-456, 2005. 40 year smooth

  31. Theoretical mechanism for natural radiative forcing of El Nino

  32. Theoretical mechanism for natural radiative forcing of El Nino Courtesy of E.Cook

  33. CONCLUSIONS • Proxy reconstructions and model simulations both suggest that late 20th century warmth is anomalous in the context of the past 1000-2000 years • Primary source of differences between various reconstructions appear to be related to issues of seasonality and spatial representativeness • Important differences between estimates of extratropical and full (combined tropical and extratropical) hemispheric mean temperature changes in past centuries appear consistent with seasonally- and spatially-specific responses to climate forcing. • Forced changes in large-scale atmospheric circulation such as the NAO, and internal dynamics related to El Nino, may play an important role in explaining regional patterns of variability and change.