global signatures of the “little ice age” and “medieval climate anomaly” and plausible...
TRANSCRIPT
Global Signatures of the “Little Ice Age” and “Medieval Climate Anomaly”
and Plausible Dynamical Origins
Michael E. Mann Penn State University
with contributions from: Caspar Ammann, Raymond Bradley, Elizabeth
Crespin, Jeff Donnelly, Greg Falugevi, Fangxing Fan, Hugues Goosse, Malcolm Hughes, Klaus Keller,
Scott Rutherford, Drew Shindell, Axel Timmermann, Jonathan Woodruff, Zhihua Zhang
1th International Meeting on Statistical ClimatologyUniversity of Edinburgh, Scotland
July 13, 2010
Global Surface Temperature Changes
Climate “Proxy” Data…
Global Surface Temperature Changes
Climate “Proxy” Data…
Reconstructions of Past Climate
Climate Change 2001: The Scientific Basis, Houghton,
J.T., et al. (eds.), Cambridge Univ. Press, Cambridge, 2001
Surface Temperature Reconstructions
Surface Temperature Reconstructions
Jones, P.D., Mann, M.E., Climate Over Past Millennia, Reviews of Geophysics, 42, RG2002, doi:10.1029/2003RG000143, 2004.
Surface Temperature Reconstructions
European Winter Cooling During the Little Ice Age
El Nino
Sources of Uncertainty
Sources of Uncertainty
El Nino
Combined response to Solar +Volcanic Forcing
Ensemble mean Nino3 (100 realizations of CZ model)
40 year smooth
Palymra coral isotopes (standardized to have same mean and standard deviation as Nino3 composite series)
Mann, M.E., Cane, M.A., Zebiak, S.E., Clement, A., Volcanic and Solar Forcing of The Tropical Pacific Over the Past 1000 Years, Journal of Climate, 18, 447-456, 2005.
How did Natural Forcings Influence influence ENSO and the Tropical Pacific During the Past Millennium?
simulation
smoothed simulation result
Coral isotope reconstruction of past El Nino variations
Combined response to Solar +Volcanic Forcing
‘Little Ice Age’ wet in Kenya: El Nino-like conditions
How did Natural Forcings Influence influence ENSO and the Tropical Pacific During the Past Millennium?
Cook et al, Science, ‘04
simulation
smoothed simulation result
Coral isotope reconstruction of past El Nino variations
Combined response to Solar +Volcanic Forcing
‘Little Ice Age’ wet in southwestern U.S.:
El Nino-like conditions
How did Natural Forcings Influence influence ENSO and the Tropical Pacific During the Past Millennium?
Cook et al, Science, ‘04
simulation
smoothed simulation result
Coral isotope reconstruction of past El Nino variations
Combined response to Solar +Volcanic Forcing
‘Medieval Warm Period’ dry in southwestern U.S.:
La Nina-like conditions
How did Natural Forcings Influence influence ENSO and the Tropical Pacific During the Past Millennium?
Surface Temperature Reconstructions
Surface Temperature Reconstructions
Science (11/27/09)
Regional Time Series
Surface Temperature Reconstructions
statistical model
historical record
Model resolves ~50% annual variance in both calibration and split calibration/validation over 1870-2006
Applications: Atlantic Tropical Cyclones
statistical model
historical record
Model resolves ~50% annual variance in both calibration and split calibration/validation over 1870-2006
Applications: Atlantic Tropical Cyclones
sediments
historical record
95% uncertainties
95% uncertainties
Statistical model
Applications: Atlantic Tropical Cyclones
Surface Temperature Reconstructions
Science (11/27/09)
Surface Temperature Reconstructions
Science (11/27/09)
Model-Data Comparisons
Positive Phase of Northern Annual Mode
Science (11/27/09)
Past Natural Arctic warming
PROXIES MODEL
Paleoclimate Data Assimilation
Paleoclimate Data Assimilation
SAT
Z(800mb)
PROXIES MODEL
Past Natural Arctic warming
CONCLUSIONS
•Reconstructed La Nina-like pattern during Medieval times, and El Nino-like anomalies during the “Little Ice Age”, suggest a ‘thermostat’ response response to natural radiative forcing
•Recent hemispheric-scale warmth anomalous in at least a millennial context; can only be explained by anthropogenic radiative forcing
•Prior to the 20th century, warmth and cold was highly regionally variable
•Combination of warm tropical Atlantic and La Nina-like conditions in the tropical Pacific can explain periods of relatively high past Atlantic Hurricane activity
•Medieval warmth in high-latitude North Atlantic and parts of North America rivaled modern warmth
•Response of Northern Annular Mode/NAO to natural volcanic and solar radiative forcing appears to explain enhanced ‘Little Ice Age’ and ‘Medieval Warm Period’ temperature signal in regions such as Europe