Melting of polar ice sheets has added 11mm to global sea levels over the past two decades, according to the most definitive assessment so far.

More than 20 polar research teams have combined forces to produce estimates of the state of the ice in Greenland and Antarctica in a paper in Science.

Until now different measurement means have produced a wide range of estimates with large uncertainties.

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The new estimate shows that polar melting contributed about one-fifth of the overall global sea level rise since 1992; other factors include warming that causes the seawater to expand.

http://www.bbc.co.uk/news/science-environment-20543483