Ice caps melting faster

British scientists have warned that global warming is melting polar ice caps in Antarctica much faster than previously thought, it was reported on Wednesday.

Experts from the research body British Antarctic Survey believe that the rise in sea levels around the world caused by the melting may have been under-estimated.

Vast ice blocks were slowly collapsing into the sea off Antarctica, increasing the threat from the rising level of the world's oceans, the scientists said.

Their discovery that the West Antarctic ice sheet was unstable overturned the previous international consensus that it would take 1 000 years for the floating ice to respond to rising temperatures, the Daily Telegraph said on Wednesday.

The scientists said that far from gaining in mass, as expected, due to increased snowfall in polar regions, the West Antarctic sheet was losing 250 cubic kilometres of ice a year.

This meant that Antarctica was contributing at least 15% of the current two millimetre annual rise in sea levels.

"The previous view was that the West Antarctic ice sheet would not collapse before 2100. We now have to revise that judgement.

We cannot be so sanguine," Chris Rapley, director of the survey, told an international conference on climate change in Exeter (southwest Britain).

Four years ago the United Nation's international scientific panel had concluded that, over a 100-year timescale, the West Antarctic ice sheet was a "slumbering giant", said Rapley. The new discovery showed, however, that it was "a giant awakened."