Download Climate Changes During the Past Millennium

CLIMATE CHANGES DURING THE
PAST MILLENNIUM
Michael E. Mann
Department of Environmental Sciences
University of Virginia
Gavin A. Schmidt and Drew T. Shindell
Goddard Institute for Space Studies and Center for Climate
Systems Research, Columbia University
AGU Fall Meeting
December 2002
Annual Resolution Proxy Climate Indicators
INSTRUMENTAL
TEMPERATURE
RECORD
Note: half of the
surface area is
between 30S
and 30N
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
Mann, M.E., The Value of Multiple Proxies
Science, 297, 1481-1482, 2002.
Mid-Latitude Tree Rings
Greater variability?
Esper, J., Cook, E.R.,
Schweingruber, F.H., LowFrequency Signals in Long
Tree-Ring Chronologies for
Reconstructing Past
Temperature Variability,
Science, 295, 2250-2253,
2002.
Mid-Latitude Tree Rings
Greater variability?
1000
1200
1400
1600
1800
2000
Volcanic Radiative Summer Cooling
Average summer surface temperature response (June-August) in
the ten winters immediately following eruptions for Pinatubo.
Shindell et al, 2002 (submitted)
Volcanic Winter Dynamical Warming
Average winter surface temperature response (December-February)
in the ten winters immediately following eruptions for Pinatubo.
Shindell et al, 2002 (submitted)
Long-term climate
response to volcanic
eruptions: GISS GCM
ensembles
dT dF
C W/m2
-0.4 -0.7
Pinatubo
(12 years following
eruption)
-1.2 -2.1
Tambora
(12 years following
eruption)
Time series
(1959-1999)
Shindell et al, 2002
(submitted)
-0.4 -0.6
European Winter Cooling During the Little Ice Age
Sunspots
Negative pattern of sensitivity of Mann et al
(1998) surface temperature reconstructions
against the Lean et al (1995) solar irradiance
series for the period 1650-1850 (20 year lag,
40 year lowpass)
Waple, A., Mann, M.E., Bradley, R.S., Longterm Patterns of Solar Irradiance Forcing in
Model Experiments and Proxy-based Surface
Temperature Reconstructions, Climate
Dynamics, 18, 563-578, 2002.
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 et al,
2002 (submitted)
Boreholes
Greater trend?
Mann, M.E., Rutherford, S., Bradley, R.S., Hughes, M.K., Keimig, F.T., Optimal
Surface Temperature Reconstructions Using Terrestrial Borehole Data,
Journal of Geophysical Research, 2002 (in press)
Boreholes
Mann, M.E., Rutherford,
S., Bradley, R.S., Hughes,
M.K., Keimig, F.T., Optimal
Surface Temperature
Reconstructions Using
Terrestrial Borehole Data,
Journal of Geophysical
Research, 2002 (in press)
Boreholes
Mann, M.E., Rutherford, S., Bradley, R.S., Hughes, M.K., Keimig, F.T., Optimal
Surface Temperature Reconstructions Using Terrestrial Borehole Data,
Journal of Geophysical Research, 2002 (in press)
Boreholes
Pattern
Correlation
r=0.1 to 0.2
(depending
on weighting
of gridpoints)
Mann, M.E., Rutherford,
S., Bradley, R.S., Hughes,
M.K., Keimig, F.T., Optimal
Surface Temperature
Reconstructions Using
Terrestrial Borehole Data,
Journal of Geophysical
Research, 2002 (in press)
Boreholes
Determine rotation
in two-dimensional
state space that
yields optimal
match with
instrumental trend
pattern
This rotation
determines
optimal
projections of
EOF patterns
Mann, M.E., Rutherford,
S., Bradley, R.S., Hughes,
M.K., Keimig, F.T., Optimal
Surface Temperature
Reconstructions Using
Terrestrial Borehole Data,
Journal of Geophysical
Research, 2002 (in press)
Boreholes
Mann, M.E., Rutherford, S., Bradley, R.S., Hughes, M.K., Keimig, F.T., Optimal
Surface Temperature Reconstructions Using Terrestrial Borehole Data,
Journal of Geophysical Research, 2002 (in press)
CONCLUSIONS
•Comparisons between different proxy-based
estimates, model predictions, and optimallydetermined borehole estimates of past
hemispheric temperature trends indicate broad
consistency over the past millennium.
•Estimated and modeled patterns of surface
temperature change during the “Little Ice Age”
suggest the importance of both large-scale
radiative responses and regional atmospheric
dynamical response to both volcanic and solar
forcing