The climate of the Earth at Last Glacial Maximum: statistical equilibrium state and a mode of internal variability

We report the results obtained for the climate of the Earth at Last Glacial Maximum based upon multi-millennium integrations of a model of the coupled atmosphere-ocean-sea ice-land surface processes, system. The model employed is the low spatial resolution (T31) paleoclimate version of the Community Climate System Model that has been developed at the National Center for Atmospheric Research (NCAR) with important input from the UCAR community. In this initial discussion of the results delivered by the model for LGM, we focus upon the primary characteristics of the statistical equilibrium state of both atmosphere and ocean. Also discussed are the characteristics of the ENSO mode of internal climate variability that the model predicts to obtain under glacial conditions. Our analysis suggests that the degree of tropical cooling at LGM is approximately 4.5degreesC over the equatorial Pacific sector, a value that is somewhat higher than has been obtained in other recent simulations of LGM climate. We also find that the strength of the ENSO phenomenon is significantly increased at LGM relative to its expression in the modern climate system. In order to achieve a statistical equilibrium representation of LGM climate, we have been obliged to integrate the coupled system for over 2000 years, a fact that has important implications for snapshot analyses of paleoclimatic state when a coupled atmosphere ocean model is employed. (C) 2003 Elsevier Ltd. All rights reserved.