Transcript No Slide Title

Global Climate Change:
Past and Future
Michael E. Mann
Departments of Meteorology and Geosciences and
Earth and Environmental Systems Institute (EESI)
Penn State University
Pennsylvania Consortium for Interdisciplinary
Environmental Policy and the Pennsylvania Environmental Council
Harrisburg PA
Oct 5, 2006
`The balance of evidence
suggests that there is a
discernible human influence
on global climate '
Intergovernmental Panel on Climate Change
(United Nations), Second Assessment Report, 1996
`There is new and stronger
evidence that most of the
warming observed over
the last 50 years is attributable
to human activity'
Intergovernmental Panel on Climate Change
(United Nations), Third Assessment Report, 2001
THE DATA
Surface Temperature Changes
Climatic Research Unit (‘CRU’),
University of East Anglia
CO2
Related?
Greenhouse
Gases and
Warming
TREE RINGS
CORALS
ICE CORES
VARVED LAKE SEDIMENTS
HISTORICAL DOCUMENTS
RECONSTRUCTED
GLOBAL
TEMPERATURE
PATTERNS
Reconstructed Surface Temperatures
Climate Change 2001: The
Scientific Basis, Houghton, J.T.,
et al. (eds.), Cambridge Univ.
Press, Cambridge, 2001
Thompson, L. G., Mosley-Thompson, E., Davis,
M. E., Lin, P. N., Henderson, K., and Mashiotta,
T. A., 2003, Tropical glacier and ice core evidence
of climate change on annual to millennial time
scales, Climatic Change, v. 59, p. 137-155.
From “Wikipedia”
Reconstructions of Northern Hemisphere mean temperatures
for the last 1000 years and instrumental record (black line)
CLIMATE MODELS
The climate represents a coupled system
consisting of an atmosphere, hydrosphere,
biosphere, and cryosphere
General Circulation
Models (GCMs) take
into account the full
three-dimensional
structure of the
atmosphere and ocean
GCMs do a fairly
good job of
describing the
seasonal cycle in
surface
temperature
This alone doesn’t
guarantee that they
should do a good
job in describing
climate change!
January Temp (observations)
January Temp (model)
INFLUENCE OF EXTERNAL FACTORS
The climate is governed by external factors, including
the intensity of solar output and volcanic aerosols
and greenhouse gas concentrations
Solar Variations
Solar Variations
The climate is governed by external factors, including
the intensity of solar output and volcanic aerosols
and greenhouse gas concentrations
Volcanoes
1000
1200
1400
1600
1800
2000
The climate is governed by external factors, including
the intensity of solar output and volcanic aerosols
and greenhouse gas concentrations
GREENHOUSE EFFECT?
ENHANCED GREENHOUSE EFFECT?
ANTHROPOGENIC IMPACTS
Greenhouse
Gases
Industrial
Aerosols
Climate Change 2001: The
Scientific Basis, Houghton, J.T.,
et al. (eds.), Cambridge Univ.
Press, Cambridge, 2001
SIMULATIONS OF CLIMATE CHANGE
Simulated Annual Global Mean
Surface Temperatures
Climate Change
2001: The
Scientific Basis,
Houghton, J.T., et
al. (eds.),
Cambridge Univ.
Press, Cambridge,
2001
Forced Model
simulations
Simulated Annual Global Mean
Surface Temperatures
Climate Change
2001: The
Scientific Basis,
Houghton, J.T., et
al. (eds.),
Cambridge Univ.
Press, Cambridge,
2001
Forced Model
simulations
Simulated Annual Global Mean
Surface Temperatures
Climate Change
2001: The
Scientific Basis,
Houghton, J.T., et
al. (eds.),
Cambridge Univ.
Press, Cambridge,
2001
Forced Model
simulations
Jones, P.D., Mann, M.E., Climate
Over Past Millennia, Reviews of
Geophysics, 42, RG2002,
doi:10.1029/2003RG000143, 2004.
Future Surface Temperatures Trends?
Climate Change 2001: The Scientific Basis,
Houghton, J.T., et al. (eds.), Cambridge Univ.
Press, Cambridge, 2001
Possible Impacts?
Climate Change 2001: The Scientific Basis,
Houghton, J.T., et al. (eds.), Cambridge Univ.
Press, Cambridge, 2001
``RealClimate is a commentary site on climate science by
working climate scientists for the interested public and
journalists. We aim to provide a quick response to developing
stories and provide the context sometimes missing in
mainstream commentary.’’
Gavin Schmidt, Michael Mann
Eric Steig, William Connolley, Ray Bradley, Stefan Rahmstorf,
Rasmus Benestad, Caspar Ammann, Thibault de Garidel,
David Archer, Ray Pierrehumbert