- VI - 



REPORT SUMMARY AND FINDINGS 



Concentrations of atmospheric CO2 and other greenhouse gases 

 will continue to increase in coming decades. Two National Academy 

 of Sciences panels have concluded that higher levels of these 

 gases will almost certainly produce a large global warming. 

 That warming, by thermally expanding the oceans and by causing 

 the transfer of ice and snow resting on land to the oceans, 

 should raise sea level substantially faster than the rise that 

 has taken place during the past century. 



Although current knowledge is inadequate to make a precise 

 prediction of future sea level rise, it is sufficient to predict 

 the likely range. Many factors were considered in generating 

 the estimates of sea level rise contained in this report: 

 population and productivity growth, atmospheric and climatic 

 change, and oceanic and glacial response. High and low assump- 

 tions for these principal determinants of sea level rise were 

 derived from the literature. When linked together the various 

 assumptions allowed the estimation of nigh and low paths of future 

 sea level rise. Based on this work, the following findings can 

 be stated: 



(1) GLOBAL SEA LEVEL WILL ALMOST CERTAINLY RISE IN COMING DECADES. 



A global rise of between 144 cm (4.8 feet) and 217 cm 

 (7 feet) by 2100 is most likely. 



A global rise as low as 56 cm (1.9 feet) or as high as 

 345 cm (11 feet) by 2100 cannot be ruled out. 



- Along most of the Atlantic and Gulf Coasts of the United 

 States, the rise will be 18 to 24 cm (0.6 to 0.8 feet) 

 more than the global average. 



(2) ESTIMATES OF FUTURE SEA LEVEL RISE CAN BE USED TO REDUCE 

 ITS ADVERSE IMPACTS. 



Sea level rise will increase shoreline retreat, erosion, 

 flooding, and saltwater intrusion in coastal areas. 

 Important economic impacts could result. 



Many, if not most of the adverse economic impacts of sea 

 level rise can be avoided if timely actions are taken in 

 anticipation of these effects. 



- Professionals and policymakers need to assess the 

 vulnerability of forthcoming decisions and the existing 

 infrastructure to sea level rise. 



