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Paleoclimate Reconstructions from HighResolution Proxy Data Michael E. Mann Department of Environmental Sciences, University of Virginia, Charlottesville, VA Collaborators: B. Adams, C. Ammann, R. Bradley, K. Briffa; M. Cane; A. Clement, T. Delworth; M.K. Hughes, T. Osborn; P. Jones, S. Rutherford; G. Schmidt; D. Shindell; S. Zebiak Support: NOAA/NSF Earth Systems History program Meeting on Tree Rings and Climate Tucson, Arizona April 6, 2004 Mann, M.E., Ammann, C., Bradley, R.S., Briffa, K., Crowley, T.J., Hughes, M.K., Jones, P.D., Oppenheimer, M., Osborn, T.J., Overpeck, J.T., Rutherford, S., Trenberth, K.E., Wigley, T.M.L., On Past Temperatures and Anomalous late 20th Century Warmth, Eos, 84, 256-258, 2003 [MODIFIED: Boreholes—Rutherford and Mann (in press); Crowley & Lowery (updated)] Greater variability in extratropics and summer! Mann, M.E., Ammann, C., Bradley, R.S., Briffa, K., Crowley, T.J., Hughes, M.K., Jones, P.D., Oppenheimer, M., Osborn, T.J., Overpeck, J.T., Rutherford, S., Trenberth, K.E., Wigley, T.M.L., On Past Temperatures and Anomalous late 20th Century Warmth, Eos, 84, 256-258, 2003 [MODIFIED: Boreholes—Rutherford and Mann (in press); Crowley & Lowery (updated)] Annual Resolution Proxy Climate Indicators INSTRUMENTAL TEMPERATURE RECORD GLOBAL PROXY CLIMATE RECORDS 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. Sensitivity to target region? Comparison between Briffa et al. NH extratropical warmseason NH mean temperature reconstruction with RegEM reconstruction (a) unmasked 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 revision), 2004. Sensitivity to target region? Comparison between Briffa et al. NH extratropical warmseason NH mean temperature reconstruction with RegEM reconstruction (a) unmasked (b) masked 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 revision), 2004. Sensitivity to target region? Comparison between Briffa et al. NH extratropical warmseason NH mean temperature reconstruction with RegEM reconstruction (a) unmasked (b) masked (c) based on Esper et al (2002) locations only 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 revision), 2004. Seasonal Spatial Patterns Temperature Anomaly (oC) Cold Season (multiproxy) Warm Season (MXD) 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 revision), 2004. Influence of Natural Radiative Forcing Crowley, T.J., Causes of Climate Change Over the Past 1000 Years, Science, 289 270-277, 2000. Volcanism 1000 1200 1400 1600 Solar 1800 2000 Jones, P.D., Mann, M.E., Climate Over Past Millennia, Reviews of Geophysics, in press, 2004. 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, 21492152, 2001. 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, 40944107, 2003. 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. 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. Mid-Latitude Summers Greater variability? Esper, J., Cook, E.R., Schweingruber, F.H., LowFrequency Signals in Long Tree-Ring Chronologies for Reconstructing Past Temperature Variability, Science, 295, 2250-2253, 2002. Mid-Latitude Summers Greater variability? 1000 1200 1400 1600 1800 2000 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. 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. Solar Forcing of El Nino? Decadally-smoothed Mann et al NINO3 (x-1) Jones et al, Science, 2001 Verschuren et al, Nature, 403, 410-414, 2000. 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. 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) 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 El Niño Over the Past 1000 Years, submitted, 2004. Response to Volcanic Forcing Composite Nino3 (100 realizations of CZ model) Tropical Volcanic radiative forcing (0.1 x 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 El Niño Over the Past 1000 Years, submitted, 2004. 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 Tropical volcanic radiative forcing (0.1 x W/m2) 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 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) Mann, M.E., Cane, M.A., Zebiak, S.E., Clement, A., Volcanic and Solar Forcing of El Niño Over the Past 1000 Years, submitted, 2004. 40 year smooth Theoretical mechanism for natural radiative forcing of El Nino Cobb, K.M., C.D. Charles, R.L Edwards, H. Cheng, El NiñoSouthern Oscillation and tropical Pacific climate during the last millennium, Nature, 424, 271-276, 2003. Theoretical mechanism for natural radiative forcing of El Nino Combined response to Solar +Volcanic Forcing Ensemble mean Nino3 (100 realizations of CZ model) 40 year smooth Palymra coral isotopes (standardized to have same mean and standard deviation as Nino3 composite series) Mann, M.E., Cane, M.A., Zebiak, S.E., Clement, A., Volcanic and Solar Forcing of El Niño Over the Past 1000 Years, submitted, 2004. CONCLUSIONS •Differences between estimates of extratropical and full (combined tropical and extratropical) hemispheric mean temperature changes in past centuries appear consistent with seasonal and spatially-specific responses to climate forcing. •Observations of an El Nino-like response to explosive tropical volcanic eruptions are consistent with results based on simulations with the Cane-Zebiak model •Coral evidence of La Nina-like anomalies during the 12thearly 13th centuries, and El Nino-like anomalies during the late 17th century, are reproduced by the simulated response to total (solar+volcanic) natural radiative forcing