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CHAPTER 3 



THE APPROACH, ASSUMPTIONS, AND MODELS 

 USED TO ESTIMATE SEA LEVEL RISE 



Estimating global sea level rise requires considering all 

 of the possible changes in the social and natural systems that 

 could influence future climate and sea level. £/ Existing 

 scientific knowledge is inadequate to make a precise prediction 

 of the extent of these changes. Consequently, we generated a 

 range of estimates, called scenarios. 



Each scenario used a different set of assumptions (see 

 Figure 3-1). For each factor that could affect sea level, a 

 range of assumptions was developed by consulting the literature 

 and the appropriate scientists. Thus, the full set of 

 assumptions covered the likely ranges for each factor, although 

 not necessarily the most extreme possibilities. 



Models were selected that allowed various assumptions 

 to be combined to generate yearly estimates of sea level 

 rise. The models were chosen for their ability to accomplish 

 this task in a reliable, flexible, and cost-effective manner. 



Many scenarios were generated, but four critical ones 

 were named. The "low scenario" consists of the most conservative 

 assumptions for each factor, while the "high scenario" consists 

 of the least conservative. Although the determinants of sea 

 level rise are not likely to be all at the high ends or low 

 ends of their ranges, these possibilities cannot be ruled out. 



