Insights into Climate Dynamics from Paleoclimate Data

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




•Conclusions

Instrumental Surface Temperature Record

Grayshaded: 1902-1993

Checkboard: 1854-1993Climatic Research Unit (‘CRU’), University of East Anglia


“Niño3” El Niño

Climatic Research Unit (‘CRU’)University of East Anglia


http://www.cru.uea.ac.uk/cru/demos/temrecmontage/


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.


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.




•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HISTORICAL DOCUMENTS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).


INSTRUMENTAL TEMPERATURE

RECORD

GLOBAL PROXY

CLIMATE RECORDS


Five leading patterns of global temperature variation during the 20th century.




Reconstructed Surface Temperatures


VERIFICATION


Climate Change 2001: The Scientific Basis, Houghton, J.T.,

et al. (eds.), Cambridge Univ. Press, Cambridge, 2001


“Niño3” El Niño

Cold-season Nino3 index


Climate Change 2001: The Scientific Basis, Houghton, J.T.,

et al. (eds.), Cambridge Univ. Press, Cambridge, 2001




•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



Solar Irradiance

Simulated Annual Global Mean Surface Temperatures

Climate Change 2001: The

Scientific Basis, Houghton, J.T., et

al. (eds.), Cambridge Univ.


HADCM3 Coupled Ocean-Atmosphere Model

Science

Climate Change 2001: The

Scientific Basis, Houghton, J.T., et

al. (eds.), Cambridge Univ.


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”


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


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


ModelObservations



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.

Insights into Climate Dynamics from Paleoclimate Data

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