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Interpreting the observed sea level rise will be difficult. 

 Many factors that cause short-term variations in global 

 temperature and sea level have not been modeled, including the 

 internal dynamics of the climate system, changes in ocean 

 circulation, and year-to-year fluctuations in volcanic activity. 

 Thus, if the sea rises 9 to 13 centimeters by 2000 (the most 

 probable range), then it will be difficult to determine the 

 amount of this rise caused by the greenhouse warming, as 

 opposed to temporary fluctuations caused by other factors, 

 unless better monitoring and research is undertaken. It will 

 be even more difficult to determine the percentage of the rise 

 that should be attributed to thermal expansion versus glacial 

 contribution. Better research and monitioring could help 

 ensure that our ability to forecast sea level rise improves as 

 additional data becomes available. 



UNDERSTANDING THE SOURCES OF DIFFERENCES BETWEEN SCENARIOS CAN 

 HELP FOCUS RESEARCH PRIORITIES 



The estimates of thermal expansion vary by a factor of four. 

 However, the greatest source of uncertainty is the rate of 

 transfer of snow and ice from land to sea, which varies by a 

 factor of eight between the low and high scenarios. Unfortunately, 

 there has been insufficient funding of coordinated work between 

 glaciologists , climate modelers, and Southern Hemisphere 

 oceanographers to estimate this important source of sea level 

 rise . 



Examining the sources of uncertainty is a first step 

 toward developing research priorities. Figure 6-1 shows the 



