Global warming 'past the point of no return'

Satellites monitoring the Arctic have found that the extent of the 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 that such a loss of Arctic sea ice in summer has not occurred in hundreds and possibly thousands of years. It is the fourth year in a row that the sea ice in August has fallen below the monthly downward trend - a clear sign that melting has accelerated.

Scientists are now preparing to report a record loss of Arctic sea ice for September, when the surface area covered by the ice traditionally reaches its minimum extent at the end of the summer melting period.

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 when the ice of the Arctic failed to recover significantly.

Arctic specialists at the US National Snow and Ice Data Centre at Colorado University, who have documented the gradual loss of polar sea ice since 1978, believe that a more dramatic melt began about four years ago.

In September 2002 the sea ice coverage of the Arctic reached its lowest level in recorded history. Such lows have normally been followed the next year by a rebound to more normal levels, but this did not occur in the summers of either 2003 or 2004. This summer has been even worse. The surface area covered by sea ice was at a record monthly minimum for each of the summer months - June, July and now August.

"This will be four Septembers in a row that we've seen a downward trend. The feeling is we are reaching a tipping point or threshold beyond which sea ice will not recover."