Polar ice sheets are now melting three times faster than they did in the 1990s, a 'definitive' study of satellite data has found.
The amount of ice lost from Greenland and Antarctica is enough to raise world sea levels by almost one millimetre a year.
Since 1992, it has added more than 1cm to global sea levels - contributing around a fifth of the total rise.
About two thirds of the ice loss was from Greenland and the remainder from Antarctica, said scientists.
Until now, there has been confusion over what is happening to the ice sheets in a warming world.
Estimates have differed greatly, with some studies even suggesting gains rather than losses.
The new survey is said to be the most accurate assessment to date, ending 20 years of uncertainty.
It confirms that, with the exception of East Antarctica, both land masses are losing ice. But big differences in the pace of change were seen at each pole.
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