This January 2, 2005, file photo, released by Greenpeace, shows a view of Kandolhudhoo island, Maldives. Members of a US disaster assessment team visited the island where several of its some 3,500 inhabitants died when the 2004 Asian tsunami hit. Scientists have long warned that the Maldives will be wiped out by rising sea levels in the coming decades, but in 2009 some recent data is challenging that dire prediction. [Shanghai Daily]

Such data is inconclusive, however - and with few available records, the Indian Ocean remains one of the world's least understood oceans.

Yin Jianjun, an assistant research scientist who monitors sea levels at Florida State University, said the drop in the Maldives could be caused by increased evaporation in the Indian Ocean. Evaporation makes water more dense, thus lowering sea levels.

Yin said the Maldives' defiance of the global trend of rising sea levels could be temporary. "I don't think the Maldives will disappear in a few decades, but maybe in another hundred years it will become a very serious situation," he said.

Other scientists think coral reefs may help save the islands. Under normal conditions, reefs can grow centimeters every year, allowing them to keep up with at least some sea level rise. The reefs form natural barriers that protect islands from being eroded by rising sea levels.

But rising tides and temperatures may conspire to stunt the corals' growth. As sea levels rise, light conditions underwater worsen, making it difficult for the reefs to expand; their health also depend upon relatively cool waters.

"One of the US$64,000 questions is whether corals will be able to grow fast enough to keep up with sea level rises," Cooper said.

Many scientists estimate that by 2100, global sea levels will rise by 91 centimeters, due to melting ice caps in Greenland and Antarctica. But because no one knows how fast these will melt, that figure comes with a significant margin of error.

"That is a huge question which limits our ability to predict what is going to happen in the Maldives," said Steve Nerem, a professor at the Colorado Center for Astrodynamics Research.

Scientists are unsure if water from the melting ice caps might hang around Greenland and Antarctica, or if they will spread out across the Earth's oceans - and if they do, how fast that spread will happen.

Though uncertainty about future sea level rises may be good news for the Maldives - and for tourists seeking their sandy beaches - most scientists urge the country to make contingency plans.

"We just don't know enough to be confident one way or the other," Overpeck said. "And in this case, if you make a mistake, you lose an island. You lose a nation."

(Shanghai Daily May 19, 2009)