TWO-METRE RISE IN OCEANS UNSTOPPABLE

ScienceDaily News reports that experts have told a climate conferene at Oxford University that a rise of at least two metres in the world's sea levels is now almost unstoppable.

'The crux of the sea level issue is that it starts very slowly but once it gets going it is practically unstoppable,' said Stefan Rahmstorf, a scientist at Germany's Potsdam Institute and a widely recognised sea level expert. 'There is no way I can see to stop this rise, even if we have gone to zero emissions.'

He said the best outcome was that after temperatures stabilised, sea-levels would only rise at a steady rate 'for centuries to come,' and not accelerate.

Most scientists expect at least 2 degrees Celsius warming as a result of man-made greenhouse gas emissions, and probably more. The world warmed 0.7-0.8 degrees last century.

Rahmstorf estimated that if the world limited warming to 1.5 degrees then it would still see a two-metre rise in sea-levels over a period of centuries, causing some island nations to disappear. His best guess was a one-metre rise this century, assuming three degrees warming, and up to five metres over the next 300 years.

'There is nothing we can do to stop this unless we manage to cool the planet. That would require extracting the carbon dioxide from the atmosphere. There is no way of doing this on the sufficient scale known today' he said.

Scientists say that ice melt acquires a momentum of its own--for example warming the air as less ice reflects less heat, warming the local area.

'Once the ice is on the move, it's like a tipping point which reinforces itself,' said Wageningen University's Pier Vellinga, citing various research.

He thinks that above a two-degree rise in global average temperature there is a 50% chance that the Greenland ice-sheet will disintegrate, which 'will result in about a seven-metre sea-level rise, and the time frame is about 300-1000 years.'

Speakers in Oxford used history to back up their arguments on rising seas. They said that three million years ago the planet was 2-3 degrees warmer and the sea 25-35 metres higher, and 122,000 years ago 2 degrees warmer and 10 metres higher.