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Insights into Climate Dynamics from Paleoclimate Data
Michael E. MannDepartment of Environmental Sciences
University of Virginia
Richard Foster Flint SymposiumDynamical Paleoclimatology
In Honor of the Memory of Barry SaltzmanYale University, New Haven, CT
November 3, 2001
Interannual Through Millennial Timescales
OVERVIEW
•The Instrumental Record
•Proxy indicators and paleoclimate reconstructions
•Model/Data comparisons
•Conclusions
Collaborators• Rob Allan• Ray Bradley• Keith Briffa• Ed Cook• Curt Covey• Tom Crowley• Heidi Cullen• Rosanne D’Arrigo• Tom Delworth• Chris Folland• Malcolm Hughes
•Malcolm Hughes•Phil Jones•David Karoly •Tim Osborn•Jonathan Overpeck•David Rind•Scott Rutherford•Gavin Schmidt•Drew Shindell•Ron Stouffer•Anne Waple
•The Instrumental Record
•Proxy indicators and paleoclimate reconstructions
•Model/Data comparisons
•Conclusions
Instrumental Surface Temperature Record
Grayshaded: 1902-1993
Checkboard: 1854-1993Climatic Research Unit (‘CRU’), University of East Anglia
Instrumental Surface Temperature Record
“Niño3” El Niño
Climatic Research Unit (‘CRU’)University of East Anglia
Instrumental Surface Temperature Record
Instrumental Surface Temperature Record
Climate Change 2001: The Scientific Basis, Houghton, J.T., et al. (eds.), Cambridge Univ.
Press, Cambridge, 2001
Five leading patterns of global temperature variation during the 20th century.
Instrumental Surface Temperature Record
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.
•The Instrumental Record
•Proxy indicators and paleoclimate reconstructions
•Model/Data comparisons
•Conclusions
TREE RINGS
CORALS
ICE CORES
VARVED LAKE SEDIMENTS
HISTORICAL DOCUMENTS
tree-ring; + PCs of dense tree-ring networks, ice core C coral Early instrumental/historical (temperature) Early instrumental/historical (precipitation)
Annual Resolution Proxy Climate Indicators
Baffin Island Canada Sediment Core
Hughen et al, Holocene 10, 1: 9-19 (2000).
Fisher et al (eds. Jones, P. D., Bradley, R. S. & Jouzel, J.) (Springer-Verlag Berlin Heidelberg, Berlin, 1996).
Ice CoreMongoliaTree Ring
D'Arrigo, R. et al, Geophysical Research Letters 28, 543-546 (2001).
Annual Resolution Proxy Climate Indicators
INSTRUMENTAL TEMPERATURE
RECORD
GLOBAL PROXY
CLIMATE RECORDS
Annual Resolution Proxy Climate Indicators
Five leading patterns of global temperature variation during the 20th century.
Instrumental Surface Temperature Record
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
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
VERIFICATION
Reconstructed Surface Temperatures
Climate Change 2001: The Scientific Basis, Houghton, J.T.,
et al. (eds.), Cambridge Univ. Press, Cambridge, 2001
Instrumental Surface Temperature Record
“Niño3” El Niño
Cold-season Nino3 index
Reconstructed Surface Temperatures
Climate Change 2001: The Scientific Basis, Houghton, J.T.,
et al. (eds.), Cambridge Univ. Press, Cambridge, 2001
•The Instrumental Record
•Proxy indicators and paleoclimate reconstructions
•Model/Data comparisons
•Conclusions
Modeled Natural Variability Observations
Climate Forcings
Anthropogenic
Greenhouse Gases
Industrial Aerosols
Natural
1000 1200 1400 1600 1800 2000
Volcanism
Solar
Climate Forcings
Relationship between Northern Hemisphere Temperature and Potential Predictors
Volcanism
Greenhouse Gases
Temperature
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.
Solar Irradiance
Simulated Annual Global Mean Surface Temperatures
Climate Change 2001: The
Scientific Basis, Houghton, J.T., et
al. (eds.), Cambridge Univ.
Press, Cambridge, 2001
HADCM3 Coupled Ocean-Atmosphere Model
Science
Climate Change 2001: The
Scientific Basis, Houghton, J.T., et
al. (eds.), Cambridge Univ.
Press, Cambridge, 2001
Future Surface Temperatures Trends
Trend in NAO in past couple decades explains enhanced recent warming in certain regions of Northern Hemisphere
North Atlantic Oscillation
“Little Ice Age”
North Atlantic Oscillation
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 et al, in press)
Empirical
North Atlantic Oscillation
Atlantic Multidecadal Oscillation
Atlantic Multidecadal Oscillation
Atlantic Multidecadal Oscillation
Atlantic Multidecadal Oscillation
A clear 50-70 year timescale signal apparently centered in the Atlantic is evident from
proxy-reconstructions of SST during the past few centuries
The GFDL coupled model exhibits a robust 50-70 year timescale signal, which is insensitive to model
resolution
Atlantic Multidecadal Oscillation
ModelObservations
Atlantic Multidecadal Oscillation
Atlantic Multidecadal Oscillation
The signal in the model represents a modulation
of the intensity of the North Atlantic THC with
oceanic feedbacks
Signal is oceanic in origin, but is modified
by the atmosphere
CONCLUSIONS
•Proxy-based reconstructions of Hemispheric temperature variations over past millennium are consistent with model-based estimates of both forced and internal climate variability
•20th century warming is inconsistent with natural climate variability, but can be explained by anthropogenic influence on climate
•Little Ice Age temperature reconstructions consistent with enhancement of NAO-type pattern in response to past solar variations produced in recent model simulation
•Internal multidecadal pattern of climate variability consistent with intrinsic model of ocean-atmosphere variability evident in long control simulations of coupled ocean-atmosphere models.