Global warming has caused the ice in the main shipping passage between Europe and Asia to melt, fully clearing the historically impassable route for the first time in history.

Sea ice in the Northwest Passage, which links the Arctic ocean to the Pacific, has shrunk in the Arctic to its lowest level since satellite measurements began 30 years ago, the European Space Agency said.

The route is now "fully navigable", according to ESA, lending strength to the possibility that the passage in the Canadian Arctic is a cheaper option to the Panama Canal for many shippers.

Leif Toudal Pedersen, of the Danish National Space Centre, described the drop in the Arctic sea ice as "extreme".

"We have seen the ice-covered area drop to just around 3 million square km," he said, about 1 million sq km less than previous lows in 2005 and 2006.

Although the Northeast Passage through the Russian Arctic remains partially blocked, Pedersen said the images they have received suggest it may well open sooner than expected.

September and March generally mark the annual minimum and maximum extent respectively of Arctic sea ice.

Some scientists have predicted the Arctic would be ice free as early as 2040.

Explorer Sir John Franklin was trapped by ice while attempting to navigate the passage during the most disastrous expedition in British history in 1845.

The crew fled the icebound vessels to march 200 miles south towards safety, apparently resorting to cannibalism and surviving for up to three years before starving to death in temperatures as low as minus 60C.

telegraph.co.uk

So the Franklin expedition was about 150 years too early.