SPATIALLY AND SEASONALLY-SPECIFIC RESPONSES TO FORCING AS DETECTED IN PALEOCLIMATE RECONSTRUCTIONS OF PAST CENTURIES Michael E. Mann 1, Brad Adams 1, Caspar Ammann2, Ronald Miller 3, Scott Rutherford 4, Gavin A. Schmidt 3, Drew T. Shindell 3 1. Department of Environmental Sciences, University of Virginia, Charlottesville, VA 2. National Center for Atmospheric Research, Boulder, CO 3. Goddard Institute for Space Studies and Center for Climate Systems Research, Columbia University, New York, NY 4. Roger Williams University, Bristol, RI Fall AGU December 12, 2003 Also: R.S. Bradley, M.K. Hughes, M. Cane, S. Zebiak

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, , 2003 [MODIFIED: Boreholes—Rutherford and Mann (in press); Crowley & Lowery (updated)]

Greater variability in extratropics and summer!

Sensitivity to target region? Comparison between Briffa et al. NH extratropical warm- season 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, submitted, 2003.

Sensitivity to target region? Comparison between Briffa et al. NH extratropical warm- season 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, submitted, 2003.

Sensitivity to target region? 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, submitted, Comparison between Briffa et al. NH extratropical warm- season NH mean temperature reconstruction with RegEM reconstruction (a) unmasked (b) Masked (c) based on Esper et al (2002) locations only

Seasonal Spatial Patterns 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, submitted, 2003.

Influence of Natural Radiative Forcing Volcanism Solar Crowley, T.J., Causes of Climate Change Over the Past 1000 Years, Science, , 2000.

LIA winter cooling in Europe associated with an NAO trend due to solar irradiance changes, interacting w/ stratospheric atmospheric dynamics and chemistry Empirical NASA/GISS Model European Winter Cooling During the Little Ice Age 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, , 2001.

Proxy based reconstruction GCM Solar + Volcanic patterns Annual average late 17th vs late 18th Century Temperature change 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, , 2003.

Volcanic Radiative Summer Cooling Ensemble average summer (Jun-Aug) surface temperature response following eruption of Pinatubo.

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, , 2003.

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

Mid-Latitude Summers Greater variability?

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

Decadally-smoothed Mann et al NINO3 (x-1) Jones et al, Science, 2001 Solar Forcing of El Nino? Verschuren et al, Nature, 403, , 2000.

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, , Theoretical mechanism for natural radiative forcing of El Nino

Composite Nino3 (100 realizations of CZ model) Theoretical mechanism for natural radiative forcing of El Nino Tropical Volcanic radiative forcing (0.1 x W/m 2 )

Composite Nino3 (100 realizations of CZ model) Theoretical mechanism for natural radiative forcing of El Nino Response to Volcanic Forcing Tropical Volcanic radiative forcing (0.1 x W/m 2 )

Tropical volcanic radiative forcing (0.1 x W/m2) Theoretical mechanism for natural radiative 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, , Superposed Epoch Analysis AD all (7) tropical events exceeding -2 W/m2 Superposed Epoch Analysis AD All (7) tropical events exceeding -4 W/m2

Tropical volcanic radiative forcing (0.1 x W/m2) Composite Nino3 (100 realizations of CZ model) Theoretical mechanism for natural radiative forcing of El Nino 40 year smooth Tropical Solar radiative forcing (W/m 2 )

Tropical volcanic radiative forcing (0.1 x W/m2) Composite Nino3 (100 realizations of CZ model) 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/m 2 )

Theoretical mechanism for natural radiative forcing of El Nino Cobb, K.M., C.D. Charles, R.L Edwards, H. Cheng, and M. Kastner, El Niño-Southern Oscillation and tropical Pacific climate during the last millennium, Nature, 424, , 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)

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 12 th - early 13 th centuries, and El Nino-like anomalies during the late 17 th century, are reproduced by the simulated response to total (solar+volcanic) natural radiative forcing

Sensitivity to methodology? Comparison between the Mann et al (1998) and RegEM reconstruction of NH mean temperature using the Mann et al (1998) multiproxy network. 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, submitted, 2003.

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

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

Reconstructed Surface Temperatures Climate Change 2001: The Scientific Basis, Houghton, J.T., et al. (eds.), Cambridge Univ. Press, Cambridge, 2001 MAHOGANYOAKHARD PINE BALSA? Remove from network: Western U.S. ITRDB chronologies (70-86 series) Stahle Southwestern US/Mexican latewood (6-12 series) 15 th century Jacoby Northern Treeline series

Mann et al, submitted, Mcintyre and McKitrick, “Energy and Environment”, 2003.

Temperature Proxy Climate Indicators Past two millennia… 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, 2003.

Temperature Proxy Climate Indicators Past two millennia… Mann, M.E., Jones, P.D., Global Surface Temperatures over the Past Two Millennia, Geophysical Research Letters, 2003.