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centimeter per year. }J_/ (See Appendix C for details and 

 possible sources of error.) Snowfall accumulation increased 

 in the run, but was overwhelmed by additional melting. This 

 contrasted sharply with the results of the model runs using 

 today's temperature and C0 2 f which showed almost stable 

 levels of ice and snow on land. 



These results need to be analyzed in greater depth than 

 was possible for this study, and model experiments should be 

 made with a more realistic treatment of ice sheet decay. 

 Studies should also be made using other GCMs , and collateral 

 evidence should be reviewed and integrated into the analysis. 

 Nevertheless, these two GCM experiments provide evidence that 

 a global warming would decrease the mass of the ice sheets 

 by the melting and ensuing runoff. 



One aspect of the GISS results that particularly needs 

 more analysis is the runoff of meltwater, not all of which 

 will escape to the sea. In many fringe areas of the ice sheets, 

 where much of the melting will take place, most of the water 

 probably will run off into the ocean; however, the percentage of 

 runoff will be low in the antarctic interior. Water that does 

 not run off will percolate into the ice and refreeze, which may 

 cause ice softening and crevasing. 



Glaciologists should use GCM outputs and information about 

 glaciers and the topography of the land underlying ice to 

 estimate the percentage of meltwater that will run off. They 

 should also consider the degree to which changes in the physical 



