March 2007
Antarctic Melting May Be Speeding Up
Top scientists have recently claimed that rising sea levels and melting polar ice-sheets are fast approaching their upper limits of projections. With some human population centres already unable to cope, this latest analysis based on satellite data has served to heighten concern.
The Intergovernmental Panel on Climate Change (IPCC) report in February projected sea level gains of 18-59 centimetres this century from temperature rises of 1.8-4.0 Celsius. However, John Church, a leading marine scientist at Australia’s CSIRO Marine and Atmospheric Research Centre has gone on record stating that "observations are in the very upper edge of the projections… [and] I feel that we're getting uncomfortably close to threshold".
Past this level, parts of the Antarctic and Greenland would fast approach a point where irreversible melting would produce sea level rises that could be measured in metres rather than centimetres. At present, there has been no repeat in the Antarctic of the 2002 break-up of part of the Larsen ice shelf that created a 500 billion ton iceberg as big as Luxembourg. Nevertheless, this is not a source for complacency.
Indeed, the Antarctic Peninsula is warming faster than anywhere else on Earth and glaciers in Europe are in massive retreat. Glaciologist Tans van Ommen, of the Australian Antarctic Division paints a worrying picture: "There have been doomsday scenarios that west Antarctica could collapse quite quickly. And there's six meters of sea level in west Antarctica." Even in east Antarctica, which is insulated from global warming by extreme cold temperatures and high-altitudes, new information shows the height of the Tottenham Glacier near Australia's Casey Base has fallen by 10 meters over 15-16 years.
Scientists say the massive glacier retreat at Heard Island, 1,000 km (620 miles) north of Antarctica, is an example of how fringe areas of the polar region are melting. The break-up of ice in Antarctica to create icebergs is also opening pathways for accelerated flows to the sea by glaciers. Church has pointed out that sea levels were 4-6 meters higher over 100,000 years ago when temperatures were at levels expected to be reached at the end of this century. Moreover, van Ommen pointed to the possibility of dynamic ice-flows adding 25 percent to IPCC forecasts of sea level rise.
John Hunter, another leading figure in climate change science, has studied historical sea level information. Beginning with the assumption that we do nothing and can afford to treat the symptoms, communities would need to begin raising sea walls. Hunter continues: "there's lots of places where you can't do that and where you'll have to put up with actual flooding", showing that there is no easy fix. This has already happened in the south of England, where local councils could not afford to protect even most residential coastal areas from sea water erosion, and land is continuing to be claimed by the ravages of the sea. Cutting through the science of the issue, senior research scientist at CSIRO, Steve Rintoul, gave a chilling warning. The 100 million people around the world currently living within a metre of the present-day sea level “will need to go somewhere”, but at present, no one seems to know where that somewhere is.
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