Oceans could rise by 8 metres

The world's oceans are likely to rise by seven to eight metres over the next 1,000 to 2,000 years, a leading Australian research institute said today, but drastic change is unlikely in the next few centuries.

The world's oceans are likely to rise by seven to eight metres over the next 1,000 to 2,000 years, a leading Australian research institute said today, but drastic change is unlikely in the next few centuries.

The estimates by the Antarctic Cooperative Research Center, based on the southern island state of Tasmania, contradict the theory that there could be a large rise in sea levels over the next century.

"We want to get away from extremist ideas about changes," said Professor Bill Budd, who led a team that made the projections based on existing estimates of global warming.

The findings are part of Australia's contribution to the Intergovernmental Panel on Climate Change, an international body that is reviewing scientific estimates on long-term climate change.

The new estimates were based on the "middle road" scenario on greenhouse gas emissions - that emissions will stabilize in 100 years at about triple the pre-industrial levels. Emissions are currently about 1.5 times that level.

The centre said any major ocean change would be associated with the melting of the two remaining ice sheets of Greenland and Antarctica.

The smaller Greenland ice sheet would, if completely melted, raise ocean levels by six metres.

Calculations suggest that warming by a few degrees might melt most of the sheet, but it would take 1,000 to 2,000 years.

The much larger Antarctic ice sheet would, if entirely melted, raise the oceans by about 55 metres. But warming of two to three degrees would have little effect because Antarctic temperatures generally remain well below the melting point of ice.

However, a one to two metre rise over the next 2,000 years could occur if glacier flow into the ocean increased because of melting of ice floating around Antarctica.

The centre said that over the next century or two there would be little melting of the ice sheets and ocean levels would be determined by thermal expansion - water expanding when it is heated - and the melting of non-polar glaciers.

The best estimate was that the oceans would rise by "several tens of centimetres per century".

"This is good news," said the institute's director, Professor Garth Paltridge.

"It tells us we are not going to drown over the next few hundred years because the Antarctic or Greenland ice caps suddenly take it into their heads to melt. There are always science fiction yarns and films which have left the public with the impression that that will happen."