World nearing point of no return on global warming

A record loss of sea ice in the Arctic this summer has convinced scientists the Northern Hemisphere may have crossed a threshold beyond which the climate may never recover.

Scientists fear the Arctic has now entered an irreversible phase of warming which will accelerate the loss of the polar sea ice that has helped keep the climate stable for millennia.

They believe global warming is melting the Arctic so rapidly it is beginning to absorb more heat from the sun, reinforcing a vicious cycle of melting and heating.

The greatest fear is that the Arctic has reached a "tipping point" beyond which nothing can reverse the continual loss of sea ice and with it the massive glaciers of Greenland.

Arctic sea ice this August has reached its lowest monthly point on record, dipping an unprecedented 18.2 per cent below the long-term average.

Experts believe such a loss has not occurred in hundreds and possibly thousands of years. It is the fourth year in a row the sea ice in August has fallen below the monthly downward trend - a clear sign melting has accelerated.

Sea ice naturally melts in summer and reforms in winter but for the first time on record, this annual rebound did not occur last winter.

Scientists analysing the latest satellite data will announce a significant shift in the stability of the sea ice, the Northern Hemisphere's major "heat sink" that moderates climatic extremes.

"The changes we've seen over the past few decades are nothing short of remarkable," said Mark Serreze, of the scientists at the Snow and Ice Data Centre in the US.

He said the melt in September is probably going to be at least as comparable to September 2002, the worst year to date.

"The feeling is we are reaching a tipping point or threshold beyond which sea ice will not recover."

Sea ice floats on the surface of the Arctic Ocean and its neighbouring seas and normally covers an area of some 7 million sq km during September - about the size of Australia. However, in September 2002, this dwindled to about 16 per cent below average.

Last month's record low strongly suggests that this September will see the smallest coverage of Arctic sea ice ever recorded.

Computer models suggest the Arctic will be entirely ice-free during summer by the year 2070 but some scientists now believe even this dire prediction may be over-optimistic.

- Independent