Climate over the Past Millennium or So

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• Climate over the Past Millennium or So

Michael E. Mann Department of Environmental
Sciences, University of Virginia,
Charlottesville, VA
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
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mainstream commentary.
Gavin Schmidt, Michael Mann
Eric Steig, William Connolley, Ray Bradley,
Stefan Rahmstorf, Rasmus Benestad, Caspar Ammann,
Amy Clement
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Surface Temperature Changes
Gray back to beginning of 20th century
Boxes back to mid 19th century
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Surface Temperature Changes
Climate Change 2001 The Scientific Basis,
Houghton, J.T., et al. (eds.), Cambridge Univ.
Press, Cambridge, 2001
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TREE RINGS
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CORALS
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ICE CORES
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VARVED LAKE SEDIMENTS
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HISTORICAL DOCUMENTS
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Annual Resolution Proxy Climate Indicators
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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.
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Jones, P.D., Mann, M.E., Climate Over Past
Millennia, Reviews of Geophysics, 42, RG2002,
doi10.1029/2003RG000143, 2004.
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CLIMATE FORCINGS
Volcanism
Solar
Natural
Crowley, T.J., Causes of Climate Change Over the
Past 1000 Years, Science, 289 270-277, 2000.
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CLIMATE FORCINGS
Anthropogenic
Industrial Aerosols
Greenhouse Gases
Climate Change 2001 The Scientific Basis,
Houghton, J.T., et al. (eds.), Cambridge Univ.
Press, Cambridge, 2001
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Jones, P.D., Mann, M.E., Climate Over Past
Millennia, Reviews of Geophysics, 42, RG2002,
doi10.1029/2003RG000143, 2004.
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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.
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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.
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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.
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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
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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.
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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.
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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.
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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.
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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)
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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)
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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)
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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
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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.
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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
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Theoretical mechanism for natural radiative
forcing of El Nino
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Theoretical mechanism for natural radiative
forcing of El Nino
Courtesy of E.Cook
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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.