Unexpected rise in sea levels: "We seem to be stepping on the gas pedal"

Sea level rise was unexpectedly high last year, according to NASA 's latest analysis of satellite data. But it's the longer-term trend that's more worrying.

The annual rate of sea level rise has more than doubled in the past 30 years, with global sea levels rising by about 10 centimeters since 1993.

"We seem to be putting our foot on the gas pedal," Benjamin Hamlington, a research scientist in the Sea Level and Ice Group at NASA's Jet Propulsion Laboratory, told CNN International. He said global sea levels have been steadily rising while other climate signals fluctuate.

That spells trouble for the future. Scientists predict that global average sea levels will rise by about 15 centimeters by 2050. But the future after 2050 is very murky.

"We have a very large uncertainty band. The numbers are rising very quickly," said Dirk Notz of the University of Hamburg.

He told CNN that the world could see an additional 1 metre (3ft) of sea level rise by 2100, and that level could take hundreds of years to reach. Scientists don't yet know enough to predict what will happen.