Explorer Pen Hadow has told how he fought off a polar bear with a saucepan.
The first man to trek to the North Pole solo said he has had 30 to 40 close calls with polar bears on annual expeditions to the Arctic.
But the closest encounter was 20 years ago when a curious animal poked its head into his tent. Unable to reach a gun in time, Mr Hadow used the nearest weapon which was a dirty saucepan from the previous night's supper.
"I think it was the noise of the vibrating saucepan catching the eyebrow of the bear that scared it away," he said. "I was enormously relieved."
Mr Hadow warned of the dangers of polar bears at the launch of his latest project to measure the effects of global warming on the Arctic.
The Catlin Arctic Survey, which last year measured the depth of sea ice around the North Pole, will this year investigate the dangers of ocean acidification.
A base camp will be set up 750 miles south of the North Pole on Ellef Rignes Island in Northern Canada.
It will not only be the most northerly point reached by scientists during the winter but the first opportunity to moniter the effects of climate change in the region at such an early point in the year.
Around a dozen people, from a Norwegian chef to the world's leading expert on ocean acidification, will be based in a few tents from early March until late April.
All will be given special training and equipment to deal with temperatures down to -40F (-40 C) and the threat of polar bears.
Mr Hadow said Polar guides with guns will accompany scientists on expedition.
"There is a risk, a real and actual risk and one has to have the equipment and techniques to be able to deal with this confrontation when it happens," he said.
The main purpose of the scientific research is to measure the effects of ocean acidification in the Arctic. Cold water absorbs more carbon dioxide than warmer seas and it is feared the Arctic Ocean is becoming more acidic as it soaks up the increasing pollution from mankind. Little is known about the phenomenon, dubbed the 'evil twin' of climate change, and scientists need to know how it is affecting important eco-systems.
Meanwhile a separate expedition of professional Polar explorers, led by mother-of-four Ann Daniels, will be trekking even further north to get the latest measurements of sea ice and send back sea water samples back to base.
Mr Hadow, who will direct the expedition from the UK, said explorers and scientists are working together to solve one of the great problems of the age.
"We know that disappearing ice cover and potential impacts of acidity are parts of some big ocean changes. Since it is widely viewed as a bell weather for wider global change, it is important we understand what is happening."
:: Grizzly bears moving north could threaten the survival of polar bears, according to a new study.
Biologists from the American Museum of Natural History in New York found grizzly bears are increasingly being spotted in the Canadian province of Manitoba, even though they are officially extinct in that particular region. Between 1996 and 2008 there were nine sightings. Last summer alone saw another three bears spotted.
It could be a problem for polar bears because grizzly bears may attack their cubs.