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Estimates of the Last Century's Sea Level Rise 



In the last century, measurements of tidal heights have 

 been collected in harbors around the world. On the basis of these 

 measurements, several researchers have concluded that worldwide 

 sea level has been rising. (See Table 3-2 on the next page.) 



Differences between sea level rise estimates can be attri- 

 buted to several factors that make precise interpretation of the 

 data difficult. Tidal gauges are influenced by local conditions 

 that do not influence worldwide sea level, such as river flow, 

 weather, and emergence or submergence of land. Furthermore, 

 they are not distributed uniformly, and large parts of the 

 oceans are unmeasured. 



To overcome these problems, the various researchers employed 

 different approaches. Some researchers averaged all available 

 stations. Others chose a few stations in each typical geographic 

 zone and assumed them to be "representative." At least one 

 group of researchers also attempted to factor out local tectonic 

 influences ,_2_1/ Despite the differences, however, the estimates 

 of sea level rise have been remarkably similar. Most of the 

 researchers have concluded that worldwide sea level has risen 

 between 10 and 15 centimeters in the last century. 22/ 



