New warning on global warming

2009-07-02 22:08

Wellington - New evidence shows that if global warming melts the West Antarctic ice sheet, sea levels around the world could rise by up to five metres, a New Zealand scientist said on Thursday.

Tim Naish, director of Victoria University's Antarctic Research Centre in Wellington, said the ice sheet was Antarctica's most vulnerable element and was expected to melt first, along with Greenland.

"Polar ice sheets have grown and collapsed at least 40 times over the past 5 million years, causing major sea-level fluctuations," he said in a statement issued by the university.

The most recent "interglacial" period between collapses had lasted 10 000 years, during which time global sea-level and atmospheric temperatures remained more or less constant, and human civilisation flourished, Naish said.

He said much of his research focused on an international drilling programme in the sedimentary layers of the West Antarctic ice sheet, which analysed how it behaved at a time when the world was warmer.

"We know that greenhouse gases in the atmosphere were slightly above what they are now, and the earth was two to three degrees warmer. When the West Antarctica ice sheet collapsed numerous times, it raised sea levels by up to 10 metres.

"In the past, these climate changes were happening naturally, but now we've accelerated this process, the greenhouse gases are rising and temperatures are rising faster than they ever have in the past," Naish said.

"It's one of the big issues of our time and it will have a profound effect on our future society."