- 33 - 



Determining the Ratios 



Using available estimates on past temperatures and the 



rates of heat absorption in the oceans, Gornitz et al. estimated 



past sea level rise due to thermal expansion to be 4 to 5 cm 



the last century. 23/ 



o For the low scenario , a 10-centimeter estimate of 

 historical sea level rise was used, thus implying a 

 one-to-one ratio of the contribution of snow and ice 

 to thermal expansion. 



o For the high scenario , the higher sea level rise 

 estimate of 15 cm was used, thus implying a ratio 

 of two- to-one. 



Deficiencies in Our Estimates of Snow and Ice Contribution 



Although the GISS 3-D experiments yield a similar magnitude 



for the rate of sea level rise as the ratio method, we have no 



illusions about the adequacy of these projections. If estimates 



based on process models of deglaciation had been available, we 



would have used them. The ratios depend on estimates of change 



which are themselves subject to mis-estimation. Futhermore, 



the physical basis for extrapolating the historical ratio 



into the future is weak at best. Past "associations" may 



not continue in the face of much larger temperature increases. 



To remedy this situation, EPA and NASA have assembled 



a team of glaciologists , oceanographers , and climatologists , 



who, with limited funding, will use "process models" and 



judgment to estimate a range for possible meltwater runoff 



