- 112 - 



THE USE OF THE HISTORICAL METHOD FOR GENERATING SNOW-ICE 



CONTRIBUTIONS 



by John S. Hoffman 

 A variety of authors have estimated sea level rise in the 

 last century on the basis of tidal gauge stations. The esti- 

 mates vary between 10 cm and 15 cm. Using historical changes in 

 temperature, Hansen et al. and Gornitz et al. have varied CO2 

 increases and the heat absorption capacity of the ocean as 

 represented by the dif f usitivi ty coefficent "K" ._ For a T e 

 of 3°C, and a K of 1.2 cm 2 sec~l, almost half of the total sea 

 level rise could be accounted for. Sea level rose approximately 

 5 cm due to thermal expansion; thus, a 10 cm total rise implies 

 5 cm due to ice and snow transfer from land to sea, assuming 

 changes in other water reservoirs to be negligible. However, 

 if the historical sea level rise was actually 15 cm, then 

 10 cm was due to ice and snow contributions, giving the higher 

 two-to-one historical ratio. Barnett, the source of the 15 cm 

 estimate, attributes two-thirds of the rise to this source. £/ 

 The scenarios of future sea level are simply extrapolated past 

 ratios, one to one as the low, two-to-one as the high. This 

 ratio generates estimates within the contribution capacity of 

 the ice sheets, alpine glaciers, and other water sources on 

 land based on a review of several strands of evidence, including 

 the GISS melting estimates. 



