Dams mask sea level rise
March 13, 2008
The findings are significant in that they increase by a third the annual rise in sea levels observed since 1961, from 1.8 mm to 2.4 mm. Rising sea levels have been attributed to thermal expansion of warming sea water and melting of polar ice caps and glaciers. According to the University of Colorado at Boulder's Institute of Arctic and Alpine Research, about 60 percent of total global sea rise from ice loss can be attributed to glaciers and ice caps, 28 percent from Greenland, and 12 percent from Antarctica.
In its 2007 report, the IPCC said it could account for only 1.1 mm of the observed annual sea level rise of 1.8 mm from 1961 to 2003. It attributed 0.4 mm of rise to thermal expansion and 0.7 mm to melting ice. Overall global average sea level rose about 17 centimeters last century.
The Taiwanese researchers used the International Commission on Large Dams' World Register of Dams to calculate the volume of water — some 10,800 cubic kilometers (2,600 cubic miles) — that is stored in more than 29,000 reservoirs worldwide. They then used data on when dams were built to calculate annual sea level rise had water not been retained by dams. They found that sea levels would have climbed by an "essentially constant" 2.46 millimeters per year over the past eight decades.