Chapter 22 - Late Glacial Climate Variability and General Circulation Model (GCM) Experiments: An Overview

Abstract

This chapter attempts to provide an overview of general circulation model (GCM) experiments for the late glacial period, a time of rapid climate variability. Two basic approaches to modeling the late glacial climate involve the time slice approach, and the sensitivity test approach. The time slice approach attempts to model a particular past climate interval using a set of multiple boundary conditions, while the sensitivity test approach isolates the effect of one boundary condition at a time for a particular time interval. Examples are given for each approach, including studies of various forcing parameters such as changes in insolation, ice sheets, sea surface temperature (SST), ocean transports, and CO2. Despite the use of different atmospheric general circulation models (AGCMs), including the National Center for Atmospheric Research (NCAR), Geophysical Fluid Dynamics Laboratory (GFDL), Goddard Institute for Space Studies (GISS), and European Community Hamburg Model Version 3 (ECHAM3), there are similarities in the various model responses to forcing parameters. With other forcing parameters, SST and sea ice, the results are not comparable from model to model because duplicate experiments have not been made with different models. Recent focus on coupled ocean-atmosphere GCM's provides new tools for exploring ocean-atmosphere links. The iterative process of data-model comparison, and the development of new questions are essential to this pursuit.