Comparison of GCM and Energy Balance Model Simulations of Seasonal Temperature Changes over the Past 18 000 Years

Abstract

The Sensitivity of a linear two dimensional Energy Balance Model (EBM) to altered surface albedo and insolation over the last 18 000 years is compared to simulators made with the NCAR Community Climate Model (CCM). The two-dimensional EBM is a more general form of that described in North et al. and allows for regionally varying albedos of ice sheets and sea ice. It is shown that the EBM's hemispherically averaged land and sea seasonal temperature departures agree excellently with the CCM's in the Northern Hemisphere. In the Southern Hemisphere the seasonal comparisons are legs favorable, although the annual-averaged oceanic temperature departures at glacial maximum agree to within 0.3°C. Since the CCM used prescribed SSTs (from CLIMAP), whereas the ERMs are calculated, our results suggest that the hemispherically averaged glacial- interglacial SST change estimated by CLIMAP is consistent with the altered energy balance requirements of the earth-atmosphere system. Results also suggest that on the largest scales the seasonal temperature field at the earth's surface may be linearly dependent on change in orbital forcing and surface albedo. We conclude that the EBM performs well enough to justify its use as an exploratory tool for investigating the effect of altered boundary conditions on the earth/s annual temperature cycle.