Flato, G.M., 2001:
Contribution to Chapter 8 "Model Evaluation"
IPCC Third Assessment Report, Cambridge University Press (in press)


Data available from the CMIP contributors was used to evaluate existing climate models with respect to their ability to reproduce contemporary sea-ice and snow extent. Figure 8.10 illustrates the range of sea-ice extent produced by the participating models, comparing the 10th, 50th and 90th percentile ice margins with the ice edge inferred from the GISST_2.2 observationally-based data set. The comparison was made for December-February in the Northern Hemisphere and June-August in the Southern Hemisphere. The median ice edge (50th percentile) agrees rather well with observations in the Northern Hemisphere, but underestimates observed ice extent in the Southern Hemisphere.  Intermodel discrepancy (the range between 10th and 90th percentile contours) was particularly large in the North Atlantic sector of the Arctic. Figure 8.11 provides a similar illustration for Northern Hemisphere snow extent. The models' median winter (December-February) snow line agrees quite well with observations in North America, but underestimates snow extent in western Eurasia while overestimating extent in eastern Eurasia.