HOLIVAR2006 Abstracts
Reconstructions of climate over the past two millennia.
Michael E. Mann
Earth System Science Center, Department of Meteorology, The Pennsylvania State University, Pennsylvania, PA 16802, USA
Contact: Michael E. Mann (mann@psu.edu)
Both reconstructions from climate 'proxy' data (e.g. tree rings, ice cores, corals) and climate model simulations, suggest that late 20th century warmth is anomalous in the context of the past 1000-2000 years. Various alternative reconstructions differ in their details however. Many of these differences appear to be related to issues of seasonality and spatial representativeness. Statistical methodologies for reconstructing past large-scale temperatures from proxy data have now been tested using a long forced simulation of the NCAR CSM 1.4 coupled model. Analyses of synthetic 'proxy' networks produced from the model suggest that existing proxy-based climate reconstructions are likely to yield reliable estimates of past temperature variations within estimated uncertainties. Important differences between estimates of extratropical and full (combined tropical and extratropical) hemispheric mean temperature changes in past centuries appear consistent with seasonal and spatially-specific responses to climate forcing. Forced changes in large-scale atmospheric circulation such as the NAO, and internal dynamics related to El Nino, may play an important role in explaining regional patterns of variability and change in past centuries.
Michael E. Mann is an Associate Professor in the Departments of Meteorology and Geosciences, and Director of the Earth System Science Center (ESSC) at Penn State University. He received his undergraduate degrees in Physics and Applied Mathematics from the University of California at Berkeley, a M.S. degree in Physics from Yale University, and a Ph.D. in Geology and Geophysics from Yale University. Current areas of research include model/data comparisons aimed at understanding the long-term behaviour of the climate.