Transcript Climate over the Past Millennium or So

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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missing in mainstream commentary.’’
Gavin Schmidt, Michael Mann
Eric Steig, William Connolley, Ray Bradley, Stefan Rahmstorf,
Rasmus Benestad, Caspar Ammann, Amy Clement
Surface Temperature Changes
Gray: back to beginning of 20th century
Boxes: back to mid 19th century
Surface Temperature Changes
Climate Change 2001: The Scientific
Basis, Houghton, J.T., et al. (eds.),
Cambridge Univ. Press, Cambridge,
2001
TREE RINGS
CORALS
ICE CORES
VARVED LAKE SEDIMENTS
HISTORICAL DOCUMENTS
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.
Reconstructed Surface Temperatures
Climate Change 2001: The
Scientific Basis, Houghton, J.T.,
et al. (eds.), Cambridge Univ.
Press, Cambridge, 2001
Jones, P.D., Mann, M.E., Climate Over Past Millennia, Reviews of Geophysics,
42, RG2002, doi:10.1029/2003RG000143, 2004.
CLIMATE FORCINGS
Volcanism
1000
1200
1400
1600
1800
Solar
Natural
Crowley, T.J., Causes of
Climate Change Over the
Past 1000 Years, Science,
289 270-277, 2000.
2000
CLIMATE FORCINGS
Anthropogenic
Greenhouse
Gases
Industrial
Aerosols
Climate Change 2001: The
Scientific Basis, Houghton, J.T.,
et al. (eds.), Cambridge Univ.
Press, Cambridge, 2001
Jones, P.D., Mann, M.E., Climate
Over Past Millennia, Reviews of
Geophysics, 42, RG2002,
doi:10.1029/2003RG000143, 2004.
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.
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.
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
“Maunder
Minimum”
1800
2000
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 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.
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
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)
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.
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) (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.
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 the Tropical Pacific Over the Past 1000 Years, Journal of
Climate, 18, 447-456, 2005.
Theoretical mechanism for natural
radiative forcing of El Nino
Theoretical mechanism for natural
radiative forcing of El Nino
Courtesy of E.Cook
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.