FIGURE 1-3 



ESTIMATED GLOBAL WARMING DUE TO A DOUBLING OF GREENHOUSE 



GASES: DIRECT EFFECTS AND CLIMATIC FEEDBACKS 



c a> 



— i— 



<D 2 



°?CU 



C k_ 



CO o> 



o E 



<D 



o 1 - 



NOTE: Although Hansen et al. estimate a positive feedback from the clouds, a negative feedback 

 cannot be ruled out. 



Sources: Adapted from: HANSEN, J.E., A. LACIS, D. RIND, and G. RUSSELL, 1984. Climate 

 Sensitivity to Increasing Greenhouse Gases. In Greenhouse Effect and Sea Level Rise: A 

 Challenge for This Generation, edited by M.C. Barth and J.G. Titus. New \brk: Van Nostrand 

 Reinhold, p. 62. 



A global warming could raise sea level by expanding ocean water, melting mountain glaciers, 

 and causing ice sheets in Greenland and Antarctica to melt or slide into the oceans. Four major 

 reports have assessed the possible significance of these factors, as shown in Table 1-1 and Figure 

 14. All predict that the global warming will cause the rate of sea level rise to accelerate. 



Revelle (1983) estimated that Greenland and mountain glaciers could each contribute 12 cm 

 to sea level in the next century, and that thermal expansion could contribute 30 cm. Based on 

 current trends, Revelle concluded that other factors could contribute an additional 16 cm, for a 

 total rise of 70 cm, plus or minus 25 percent. Hoffman et al. (1983) developed a variety of sea 

 level rise scenarios based on high and low assumptions for all the major uncertainties. They 

 estimated that sea level was most likely to rise between 26 and 39 cm by 2025 and 91 to 137 cm 

 by 2075. 



