The polar ice caps are melting so fast that the world's oceans are rising more than twice as fast as they were in the 1970s, scientists have found.
They have used satellites to track how the oceans are responding as billions of gallons of water reach them from melting ice sheets and glaciers.
The effect is compounded by thermal expansion, in which water expands as it warms, according to the study by Anny Cazenave of the National Center for Space Studies in France.
Cazenave's data show that in the past 15 years, sea levels have been rising at 3.4 mm (1/8 of an inch) a year, much faster than the average 1.7 mm (1/16 of an inch) recorded by tidal gauges over the past 50 years.
Cazenave said: "This rate, observed since the early 1990s, could reflect an acceleration linked to global warming."