PORT OF SPAIN: For Maldives President Mohamed Nasheed, the cold scientific numbers of the climate debate add up to the very survival of his tropical Indian Ocean state.

If global temperatures rise just 2 degrees Celsius (3.6 degrees Fahrenheit), "we won't be around, we will be underwater," he told Reuters in Trinidad and Tobago, where he and other leaders of the 53-nation Commonwealth pledged support for a definitive climate deal in Copenhagen next month.

World leaders seeking to thrash out a binding global treaty to curb greenhouse gas emissions and limit global warming cite an estimate by scientists that the world must limit average global warming to 2 degrees Celsius to avoid dangerous climate change, such as rising sea levels and flooding.

Nasheed tells his fellow heads of state that 2 degrees Celsius warming would risk swamping the sand-rimmed coral atolls and islets, dotted with palm trees and mangrove clumps, that form his small country.

If U.N. predictions are correct, most of the low-lying Maldives will be submerged by 2100. "Really, we are sandbanks, very precarious and delicate," Nasheed said.

The archipelago has a population of some 400,000 islanders, whose livelihood from fishing and tourism is already being hit by climate change.

"Ocean temperatures have risen and during the last four years we've had very bad fisheries," the president said.

"A number of islanders are having to relocate themselves because of erosion ... (and) of course, with sea water rise, the water table is being contaminated," he added.

This disruption of sewage and water systems was also causing outbreaks of disease like Chikungunya, a viral disease transmitted to humans by the bite of infected mosquitoes.

The Maldives and 41 other low-lying coastal and small island countries that form the Alliance of Small Island States are on the front line of the climate change threat that will occupy some 90 heads of state and government at Dec. 7-18 U.N. climate talks in Copenhagen.

UNDERWATER CABINET MEETING Nasheed, 42, is pushing world leaders to set even more stringent curbs to limit greenhouse gas emissions -- the 2 degrees Celsius warming figure is associated with a concentration of greenhouse gases in the atmosphere of 450 parts per million of CO2 equivalent.

"We want to see if we can get that down to 350 parts per million. But they're talking about, if anything, 450 ... . With 450, we've really lost it. It's really, really not enough for us and a number of other small island states," he said.

Nasheed said that even a rise of 70 centimeters (27.6 inches) in the ocean level in the next 40 years would wipe out 30 percent of the dry land area of his country.

At the Commonwealth summit in Port of Spain, the Maldives leader did receive a sympathetic response to his plea for "fast track money" to help small and vulnerable states counter the effects of global warming and sea level rise.

The Commonwealth, swinging its weight behind momentum for a climate deal in Denmark next month, backed a plan to establish a Copenhagen Launch Fund, starting next year and building to $10 billion annually by 2012.

Nasheed said this money could be used to create anti-flooding and sea-rise defenses like breakwaters.

He said the funds could also be used in poor states like the Maldives to finance the transfer of technology from rich nations. He mentioned biological engineering techniques aimed at shoring up coastlines, such as developing genetically modified coral to form barrier reefs. More mangroves could also be planted to secure soil from erosion.

"You have to understand local conditions, and consult with the people and see what is best for them," said the president, who last month donned scuba gear to hold the world's first underwater Cabinet meeting in a symbolic cry for help over rising sea levels.

Citing what he called island mentality -- "you are confined to this little space with horizon all around you" -- Nasheed said many Maldives inhabitants would oppose being relocated to avoid a potential climate change catastrophe.

"We have been there for the last ... 2,000 years, and it's very, very difficult for us to convince anyone to move," he said.

But people grasp the significance of climate change. "Unlike evolution, which is hard to sell for traditional societies ... climate change is very much in line with what the Scripture is talking about, the End," Nasheed said.