Transcript Global Climate Change: Past and Future

Global Climate Change:
Past and Future
Michael E. Mann
Department of Meteorology and
Earth and Environmental Systems Institute (EESI)
Penn State University
University of California at Santa Cruz
May 10, 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HISTORICAL DOCUMENTS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
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 take into
account the full threedimensional 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)
Modeled Internal Natural Variability Observations
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
The climate is governed by external factors, including
the intensity of solar output and volcanic aerosols
and greenhouse gas concentrations
The climate is governed by external factors, including
the intensity of solar output and volcanic aerosols
and greenhouse gas concentrations
ENHANCED GREENHOUSE EFFECT?
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
Future Surface Temperatures Trends?
Climate Change 2001: The Scientific Basis,
Houghton, J.T., et al. (eds.), Cambridge Univ.
Press, Cambridge, 2001
Possible Impacts:
North American
Drought
1998 Global Temperature Pattern
El Nino and North American
Drought
El Nino vs. North American Drought
over the Past Century
Increased Drought
Less Drought
La Nina
El Nino
Courtesy of
E.Cook
Possible Impacts:
Destructive
Potential of
Atlantic
Hurricanes
Katrina
(Aug 28 ’05)
Possible Impacts:
Destructive
Potential of
Atlantic
Hurricanes
Rita
(Sep 21 ’05)
Possible Impacts:
Destructive
Potential of
Atlantic
Hurricanes
Wilma
(Oct 19 ’05)
Hurricane Statistics
P. J. Webster, G. J. Holland, J. A. Curry, H.-R. Chang Changes in Tropical
Cyclone Number, Duration, and Intensity in a Warming Environment, Science,
309, Issue 5742, 1844-1846 , 2005.
Hurricane Statistics
Emanuel, K. (2005), Increasing destructiveness of tropical cyclones over the past 30 years,
Nature, online publication; published online 31 July 2005 | doi: 10.1038/nature03906
Climate Model Predictions
Knutson, T. K., and R. E. Tuleya, 2004: Impact of CO2-induced warming on
simulated hurricane intensity and precipitation: Sensitivity to the choice of climate
model and convective parameterization. Journal of Climate, 17(18), 3477-3495.
CONCLUSIONS
•Recent global surface temperatures are unprecedented
this century, and likely at least the past millennium
•It is difficult to explain the recent surface warming in
terms of natural climate variability
•Recent surface warming is largely consistent with
simulations of the effects of anthropogenic influence
on climate
•Possible impacts of anthropogenic climate change
this century include increased drought conditions in
the western U.S. and more destructive Atlantic
tropical storms and Hurricanes
``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