Sea levels rising: studiesFrom: By Matthew Denholm, The...

Sea levels rising: studies
From: By Matthew Denholm, The Australian
February 01, 2006

THE world's worst fears about global warming and rapid sea-level rise will be realised or exceeded, according to two new reports.

Australian climate change research published yesterday found the average level of the oceans had risen 19.5cm since 1870 and the rate was increasing.

The study provides the first evidence of a 20th-century acceleration in sea-level rise and supports predictions the world's oceans will rise 31cm above 1990 levels by 2100.

A separate report released in Britain paints an ever more alarming picture, suggesting ice sheets may be melting, raising the prospect of sea levels rising by 5m over several centuries.

British Prime Minister Tony Blair said the research clearly showed that "the risks of climate change may well be greater than we thought".

"It is now plain that the emission of greenhouse gases, associated with industrialisation and economic growth from a world population that has increased six-fold in 200 years, is causing global warming at a rate that is unsustainable," Mr Blair writes in a foreword to the research.

Published in the report Avoiding Dangerous Climate Change, it warns of large-scale disruption if temperatures rise above 3C - within the range of climate change models for this century.

The author of the Australian research, internationally renowned CSIRO chief research scientist John Church, said it was now clear there would be significant sea-level rise without major changes to human behaviour.

"Clearly, sea-level rise will be reported in metres unless we have a substantial decrease in greenhouse gas emissions," Dr Church told The Australian.

He said his study, conducted with CSIRO scientist Neil White using data from tide gauges and satellite measurements, vindicated sea-level rise projections by the UN's Intergovernmental Panel on Climate Change.

"Although predicted by models, this is the first time a 20th-century acceleration has actually been detected."

The study concludes that sea levels rose an average 16cm during the 20th century, with a rough year-on-year increase of 1.7cm.

It finds that sea level rise began during the first half of the 19th century, when global sea level was about 20cm below current levels. A comparison of sea-level benchmarks carved in rock on the Isle of the Dead, near Port Arthur in Tasmania in 1840, and the height of ancient Roman fish tanks, indicated little sea level increase until 1800.

The study, part of Australia's Climate Change Science Program, is likely to be considered at the IPCC's global climate change assessment next year.

The British research, based on a forum of scientists at Exeter last February, includes a warning from British Antarctic Survey head Chris Rapley that the West Antarctic Ice Sheet may be starting to melt.

Scientists believe the melting of the ice sheet would eventually raise sea levels around the world by 5m.

"The last IPCC report characterised Antarctica as a slumbering giant in terms of climate change. I would say it is now an awakened giant," Professor Rapley writes. "There is real concern."

The report warns a delay of even five years in reducing greenhouse gas emissions "could be significant".

The Federal Opposition said the findings highlighted the need for Australia to sign the Kyoto Protocol.