CLIMATE CHANGES DURING THE PAST MILLENNIUM Michael E. Mann Department of Environmental Sciences...
-
Upload
elwin-stewart -
Category
Documents
-
view
217 -
download
0
Transcript of CLIMATE CHANGES DURING THE PAST MILLENNIUM Michael E. Mann Department of Environmental Sciences...
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 MeetingDecember 2002
INSTRUMENTAL TEMPERATURE
RECORD
GLOBAL PROXY
CLIMATE RECORDS
Annual Resolution Proxy Climate Indicators
Note: half of the surface area is between 30S and 30N
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.
Esper, J., Cook, E.R., Schweingruber, F.H., Low-Frequency Signals in Long Tree-Ring Chronologies for Reconstructing Past Temperature Variability, Science, 295, 2250-2253, 2002.
Mid-Latitude Tree RingsGreater variability?
Mid-Latitude Tree Rings
1000 1200 1400 1600 1800 2000
Greater variability?
Shindell et al, 2002 (submitted)
Volcanic Radiative Summer Cooling
Average summer surface temperature response (June-August) in the ten winters immediately following eruptions for Pinatubo.
Average winter surface temperature response (December-February) in the ten winters immediately following eruptions for Pinatubo.
Shindell et al, 2002 (submitted)
Volcanic Winter Dynamical Warming
Long-term climateresponse to volcaniceruptions: GISS GCM ensembles
Pinatubo(12 years followingeruption)
Tambora(12 years followingeruption)
Time series(1959-1999)
-0.4 -0.7
-1.2 -2.1
-0.4 -0.6
dT dF C W/m2
Shindell et al, 2002 (submitted)
European Winter Cooling During the Little Ice Age
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., Long-term Patterns of Solar Irradiance Forcing in
Model Experiments and Proxy-based Surface Temperature Reconstructions, Climate
Dynamics, 18, 563-578, 2002.
Sunspots
LIA winter cooling in Europe associated with
an NAO trend due to solar irradiance changes,
interacting w/ stratospheric
atmospheric dynamics and chemistry
Empirical
NASA/GISS Model
European Winter Cooling During the Little Ice Age
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, 2149-
2152, 2001.
Proxy basedreconstruction
GCM Solar + Volcanic patterns
Annual averagelate 17th vs late 18th Century Temperature change
Shindell et al, 2002 (submitted)
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)
Greater trend?
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)
BoreholesDetermine 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 optimally-determined 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