INTERVIEW - Sea Rise Seen Outpacing Forecasts Due To Antarctica
Author: Alister Doyle
Millions of people, from Bangladesh to Florida and some Pacific island states, live less than a metre above sea level. Most of the world's major cities, from Shanghai to Buenos Aires, are by the sea.
Chris Rapley, the outgoing head of the British Antarctic Survey, said there were worrying signs of accelerating flows of ice towards the ocean from both Antarctica and Greenland with little sign of more snow falling inland to compensate.
"The ice is moving faster both in Greenland and in the Antarctic than the glaciologists had believed would happen," Rapley told Reuters during a climate seminar in Ny Alesund on a Norwegian Arctic island 1,200 km from the North Pole.
"I think the realistic view is that we will be nearer a metre than the 40 cm" in sea level rise by 2100. The UN climate panel in February gave a likely range of 18 to 59 cm this century, for an average around 40 cm.
Asked at the seminar what the upper limit for the rise might be at a probability of one percent or less, he said: "At this extremely unlikely level the maximum would be two metres."
Sceptics often dismiss such low probabilities as scaremongering. But many scientists note that people take precautions such as to insure their homes against far lower risks, such as fire.
The UN panel said that rising temperatures due to more and more greenhouse gases from human activities led by use of fossil fuels were melting ice.
Antarctica stores enough ice to raise ocean levels by about 57 metres if it ever all melted. Greenland has about 7 metres, according to UN data.
All other glaciers on land, from the Norwegian Arctic to the Himalayas, are tiny by comparison and contain only enough ice combined to raise sea levels by about 15-37 cm.
Glaciers around Ny Alesund, which calls itself the world's most northerly settlement, are also retreating fast.
The UN's Intergovernmental Panel on Climate Change (IPCC) in February hedged its forecasts by saying that "larger values cannot be excluded" but said there was too little understanding of how ice sheets react if water seeps beneath them and lubricates their slide.
Rapley said there were worrying signs of an accelerating thaw both in West Antarctica, where much of the ice sits on rocks that are below sea level, and on the Cook and Totten glaciers on the fringe of the far bigger ice mass to the East.
"The East Antarctic ice sheet is always dismissed as the big bit which sits on rock above sea level and so is much more stable. But the radar altimeters show significant discharge going on," he said.