With their boundless vistas of turquoise water framed by swaying coconut palms, the Carteret Islands northeast of the Papua New Guinea mainland might seem the idyllic spot to be a castaway.

Stuart Beck, the permanent representative for Palau at the United Nations, in 2005.

In the debate over global warming, one thing is clear: as the planet gets warmer, sea levels will rise. But how much, where and how soon? Those questions are notoriously hard to answer.

New York, Boston and other cities on North America's northeast coast could face a rise in sea level this century that would exceed forecasts for the rest of the planet if Greenland's ice sheet keeps melting as fast as it is now, researchers said on Wednesday.

Washington defended its plans to cut its greenhouse gas emissions as among the most ambitious in the world Tuesday as major economies meeting in Paris rallied around a Mexican plan to raise cash to fight climate change.

China won praise for moves to cap its surging greenhouse gas emissions at a meeting of major economies on Tuesday, even as Germany criticised the lack of progress towards a new United Nations climate treaty.

"China is very active," French Environment Minister Jean-Louis Borloo told reporters on the second day of the two-day meeting of 17 major emitters.

Rising sea levels that could wipe whole nations off the map and displace scores of millions of people are being overlooked in global climate change talks, island countries said.

Major emitters are pushing for greenhouse gas emissions cuts that are too low to prevent devastating sea rises, representatives said at the World Ocean Conference in Indonesia

France and Germany suggested on Monday that rich nations should collectively guarantee deep cuts in greenhouse gases by 2020 while giving flexibility to laggards such as the United States to catch up later.

European Commission President Jose Manuel Barroso said on Monday he was confident the world would sign a global deal to combat climate change in Copenhagen in December.

Barroso urged European industry to gear up for a green technology race instead of shoring up outdated, high-carbon business models.

A rise in concentrations of a powerful greenhouse gas over the Arctic after a decade of stability is stirring worries about a possible thaw of vast stores trapped in permafrost, experts said.

Hospitals and their emergency vehicles, which are major polluters, must join the fight against climate change, the World Health Organisation said on Friday.