Antarctica is melting, adding to the inexorable rise in global sea levels, endangering millions of lives and whole economies, leading scientists said on Monday.

But while the effect is well known after years of monitoring from land and space, the reasons for the sea warming are not.

“We know sea levels will rise. We need to know by how much and why,” Anthony Payne of the University of Bristol and one of the organizers of a major scientific conference in London, told Reuters on the sidelines of the meeting at the Royal Society, Britain’s national academy of science.

“This has implications for the whole world — most people and industries are in coastal areas,” he added.

Payne said there was a net loss of mass in Antarctica as the snowfall in the center of the frigid landmass was more than offset by sea ice melting around the edges.

The key was to find out whether the process was accelerating, or whether it might stabilize or even reverse.

And the important factor was understanding the complex interaction between ocean and wind currents and how much — if any — of the warming of the seas was due to mankind’s contribution to global warming.

“We know a lot more about the ice sheets than we did before,” Payne said. “We know change is happening and that it is rapid. What we don’t know is why or what is causing it — what proportion is anthropomorphic.”

Scientists calculate that average world temperatures — which have already risen by 0.6 degrees Celsius (1.1 Fahrenheit) since 1900 — could rise by at least two more degrees this century, due in large part to greenhouse gases from burning fossil fuels.

By Jeremy Lovell

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