Meltdown

Arctic ice 'disappearing fast'
By Richard Black Environment Correspondent, BBC News website
[excerpt; emphasis added]

The area covered by sea ice in the Arctic has shrunk for a fourth consecutive year, according to new data released by US scientists. They say that this month sees the lowest extent of ice cover for more than a century.

he Arctic climate varies naturally, but the researchers conclude that human-induced global warming is at least partially responsible.They warn the shrinkage could lead to even faster melting in coming years.

"September 2005 will set a new record minimum in the amount of Arctic sea ice cover," said Mark Serreze, of the National Snow and Ice Data Center (NSIDC), Boulder, Colorado. "It's the least sea ice we've seen in the satellite record, and continues a pattern of extreme low extents of sea ice which we've now seen for the last four years," he told BBC News.

The current rate of shrinkage they calculate at 8% per decade; at this rate there may be no ice at all during the summer of 2060.

Mark Serreze believes that the findings are evidence of climate change induced by human activities. "It's still a controversial issue, and there's always going to be some uncertainty because the climate system does have a lot of natural variability, especially in the Arctic," he said. "But I think the evidence is growing very, very strong that part of what we're seeing now is the increased greenhouse effect. If you asked me, I'd bet the mortgage that that's just what's happening."

f the current trend can be ascribed in part to human-induced climate change, Mark Serreze sees major reasons for concern. "What we're seeing is a process in which we start to lose ice cover during the summer," he said, "so areas which formerly had ice are now open water, which is dark. "These dark areas absorb a lot of the Sun's energy, much more than the ice; and what happens then is that the oceans start to warm up, and it becomes very difficult for ice to form during the following autumn and winter.

"It looks like this is exactly what we're seeing - a positive feedback effect, a 'tipping-point'."

The idea behind tipping-points is that at some stage the rate of global warming would accelerate, as rising temperatures break down natural restraints or trigger environmental changes which release further amounts of greenhouse gases.

This study is the latest to indicate that such positive feedback mechanisms may be in operation, though definitive proof of their influence on the Earth's climatic future remains elusive.

Story from BBC NEWS:http://news.bbc.co.uk/go/pr/fr/-/1/hi/sci/tech/4290340.stm