A polar explorer from Northumberland has warned global warming may soon prevent future trips to the Arctic.
Mr Dickinson is due to leave in March
Conrad Dickinson from Hexham, is due to set off in March on a 482-mile crossing from the Canadian High Arctic to the Geographic North Pole.
He and Canadian champion skier Richard Weber will each haul 330lb sledges.
But Mr Dickinson, 50, says the effects of global warming will make the trip particularly hazardous and believes he has just a 20% chance of success.
The pair will walk against shifting ice flows, climb over house-high ridges of packed snow and negotiate stretches of open water.
Only 10 people have completed the journey - rated as the toughest route to the pole.
Mr Dickinson said: "With global warming and the ice getting thinner, this is getting harder to do. I'm sure if global warming continues there will be a time when the trip will become impossible."
The carpet store businessman and former Army officer said polar bears were even more of a threat because melting ice had diminished their habitat.
Last year he and wife Hilary became the first British couple to trek to and from the South Pole.
Mr Dickinson will spend a month acclimatising in Canada before setting off.
He added: "There really is only one great journey left for me and it is this one."