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CLIMATE CHANGES DURING THE PAST MILLENNIUM

CLIMATE CHANGES DURING THE PAST MILLENNIUM. Michael E. Mann Department of Environmental Sciences University of Virginia Gavin A. Schmidt and Drew T. Shindell Goddard Institute for Space Studies and Center for Climate Systems Research, Columbia University. AGU Fall Meeting December 2002.

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CLIMATE CHANGES DURING THE PAST MILLENNIUM

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  1. CLIMATE CHANGES DURING THE PAST MILLENNIUM Michael E. Mann Department of Environmental Sciences University of Virginia Gavin A. Schmidt and Drew T. Shindell Goddard Institute for Space Studies and Center for Climate Systems Research, Columbia University AGU Fall Meeting December 2002

  2. Annual Resolution Proxy Climate Indicators Note:half of the surface area is between 30S and 30N INSTRUMENTAL TEMPERATURE RECORD GLOBAL PROXY CLIMATE RECORDS

  3. 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.

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

  5. Mann, M.E., The Value of Multiple Proxies Science, 297, 1481-1482, 2002.

  6. Mid-Latitude Tree Rings Greater variability? Esper, J., Cook, E.R., Schweingruber, F.H., Low-Frequency Signals in Long Tree-Ring Chronologies for Reconstructing Past Temperature Variability, Science, 295, 2250-2253, 2002.

  7. 1000 1200 1400 1600 1800 2000 Mid-Latitude Tree Rings Greater variability?

  8. Volcanic Radiative Summer Cooling Average summer surface temperature response (June-August) in the ten winters immediately following eruptions for Pinatubo. Shindell et al, 2002 (submitted)

  9. Volcanic Winter Dynamical Warming Average winter surface temperature response (December-February) in the ten winters immediately following eruptions for Pinatubo. Shindell et al, 2002 (submitted)

  10. Long-term climate response to volcanic eruptions: GISS GCM ensembles dT dF C W/m2 -0.4 -0.7 Pinatubo (12 years following eruption) Tambora (12 years following eruption) Time series (1959-1999) -1.2 -2.1 -0.4 -0.6 Shindell et al, 2002 (submitted)

  11. Negative pattern of sensitivity of Mann et al (1998) surface temperature reconstructions against the Lean et al (1995) solar irradiance series for the period 1650-1850 (20 year lag, 40 year lowpass) Waple, A., Mann, M.E., Bradley, R.S., Long-term Patterns of Solar Irradiance Forcing in Model Experiments and Proxy-based Surface Temperature Reconstructions, Climate Dynamics, 18, 563-578, 2002. European Winter Cooling During the Little Ice Age Sunspots

  12. 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.

  13. Annual average late 17th vs late 18th Century Temperature change Proxy based reconstruction GCM Solar + Volcanic patterns Shindell et al, 2002 (submitted)

  14. Boreholes Greater trend? Mann, M.E., Rutherford, S., Bradley, R.S., Hughes, M.K., Keimig, F.T., Optimal Surface Temperature Reconstructions Using Terrestrial Borehole Data, Journal of Geophysical Research, 2002 (in press)

  15. Boreholes Mann, M.E., Rutherford, S., Bradley, R.S., Hughes, M.K., Keimig, F.T., Optimal Surface Temperature Reconstructions Using Terrestrial Borehole Data, Journal of Geophysical Research, 2002 (in press)

  16. Boreholes Mann, M.E., Rutherford, S., Bradley, R.S., Hughes, M.K., Keimig, F.T., Optimal Surface Temperature Reconstructions Using Terrestrial Borehole Data, Journal of Geophysical Research, 2002 (in press)

  17. Boreholes Pattern Correlation r=0.1 to 0.2 (depending on weighting of gridpoints) Mann, M.E., Rutherford, S., Bradley, R.S., Hughes, M.K., Keimig, F.T., Optimal Surface Temperature Reconstructions Using Terrestrial Borehole Data, Journal of Geophysical Research, 2002 (in press)

  18. Boreholes Determine rotation in two-dimensional state space that yields optimal match with instrumental trend pattern This rotation determines optimal projections of EOF patterns Mann, M.E., Rutherford, S., Bradley, R.S., Hughes, M.K., Keimig, F.T., Optimal Surface Temperature Reconstructions Using Terrestrial Borehole Data, Journal of Geophysical Research, 2002 (in press)

  19. Boreholes Mann, M.E., Rutherford, S., Bradley, R.S., Hughes, M.K., Keimig, F.T., Optimal Surface Temperature Reconstructions Using Terrestrial Borehole Data, Journal of Geophysical Research, 2002 (in press)

  20. CONCLUSIONS • Comparisons between different proxy-based estimates, model predictions, and optimally-determined borehole estimates of past hemispheric temperature trends indicate broad consistency over the past millennium. • Estimated and modeled patterns of surface temperature change during the “Little Ice Age” suggest the importance of both large-scale radiative responses and regional atmospheric dynamical response to both volcanic and solar forcing

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