Antarctica is melting faster than expected , a conference was told earlier this week.
Professor Peter Barrett of Victoria University's Antarctic Research Centre told the Annual Antarctic Conference in Auckland that the rate of ice loss was up 75 percent since 1996, and was increasing quickly.
The loss of glaciers at the edges of Antarctic was causing a sea-level rise of 0.4mm a year,
With the global ice loss from Greenland, Antarctica and other glaciers suggested sea levels would rise between 80cm and 2m by 2100, Prof Barrett said.
Research centre director Professor Tim Naish, led a team of researchers who drilled deep into the Antarctic rock and discovered ancient records from the last time atmospheric CO2 reached the level it was now approaching.
They found that 3 million to 5 million years ago, seas were warm enough to melt a large chunk of Antarctica's ice when atmospheric CO2 was only slightly higher than today.
Prof Naish said west Antarctica's ice would melt before the larger east Antarctic ice sheet because it sat below sea level and warmed with the ocean.
However, he said the research raised unresolved questions about how much atmospheric CO2 would need to rise to increase temperatures by 2degC or more.
CO2 concentration in the atmosphere is now around 387 parts per million, up from about 280ppm at the start of the Industrial Revolution.
NZPA