Scientists seek global warming clues from dead explorers' notes

A team of scientists has examined the log books of polar adventurers going back five centuries to measure the movement of the ice cap, a key indicator of global warming.

Their preliminary findings provide a fascinating insight into the ebb and flow of the ice over the centuries.

They have discovered that 135 years ago the ice cap was 50% bigger than it is today.

However, when researchers from the Arctic Climate System Study looked back to 1700 they found the levels of sea ice were about the same as they are today.

Chad Dick, a Scots climate scientist who is co-ordinating the project, based in Norway, said this showed that whatever effect man-made global warming was having, it had not yet caused an abnormally low level of polar ice.

Among the hundreds of mariners whose information has been compiled on a database and released for use by climate scientists across the world were noted Scottish arctic explorer Sir John Ross and his nephew Sir James Clark Ross.

Sir James, who died in 1862, discovered the magnetic North Pole in 1831 after first accompanying his uncle to the Arctic in 1818. The younger Ross then turned to the Antarctic and gave his name to the Ross Sea, Ross Island, Ross Ice Shelf and Ross Dependency.

Dick, originally from Newport-on-Tay but now based in Troms, said: "Usually about half the ice disappears in the summer and comes back again in winter, but the maximum extent has reduced by about 33% compared to 135 years ago. However, some of these old results show that a long time before that - in the early 1700s - there was probably as little sea ice as there is now; there are certainly natural cycles in the amount of sea ice.

"Several changes have occurred quite rapidly over the last 20 years or so. The doomsayers are saying this is part of the ice cap disappearing and disintegrating and there are those who say this is just part of a natural cycle.

"In 10 years’ time we’ll probably know which of those two scenarios has come about."

He said the new database would help scientists test computerised models of climate change by measuring them against the reports from mariners in the past.

Dr Richard Dixon, of the environmental campaign group WWF Scotland, said the alarming reduction in levels of sea ice over the last few years was evidence of man-made global warming.

"The thing that’s worrying climate scientists is not particularly the volume of change, which is of some concern, but the speed of change, particularly because natural systems cannot adapt to the fast pace we are setting," he said.

"If you add it to all the other indicators, you’ve got a whole range of ‘smoking guns’ and we need to take that very seriously."

The reason why today’s scientists have so much historical data to work with comes down to the fact polar explorers were trying to make a fortune by finding a new trade route to the Far East.