If emissions continue unabated, cities like New York and Shanghai could be threatened sooner than predicted by the rising sea levels brought on by the melting of Antarctic glaciers.
The ice discharge may raise sea levels by as much as 37 centimetres (14.6 inches) this century if greenhouse gas emissions continue to grow, conclude the team led by the Potsdam Institute for Climate Impact Research.
Even with a cutback on emissions, a sea level rise of up to 23 centimetres can be expected, it says.
The Potsdam institute has challenged the IPCC's conservative projections on many counts.
Antarctica was until recently seen as a player only in the long-term.
Glaciers in the Amundsen Sea region contain enough water to raise global sea levels by 4 feet (1.2 meters), according to a Nasa report in May.
Another report in the National Geographic had quoted a recent study that the oceans can rise up to 6.5 feet (2 metres) by 2100, enough to submerge many cities along the US East Coast. A complete meltdown of the Greenland ice sheet could submerge London, it said.