Veteran explorer sets off on 'The Coldest Journey'

(CNN) -- A six-month trek across the world's last great wilderness, fighting through harsh winter conditions, near permanent darkness and temperatures as low as -90 degrees Celsius.

It sounds like an impossible mission, but one that Ranulph Fiennes, legitimately known as the world's greatest living explorer, could not resist attempting.

Dubbed "The Coldest Journey," the five-man expedition, led by the 68-year-old Fiennes, will be the first to attempt to complete the almost 4,000-kilometer (2,485-mile) journey across Antarctica in winter.

In doing so, they hope to find out more about how climate change is affecting the polar ice cap and raise $10 million for the blindness charity Seeing Is Believing -- adding to the more than $20 million Fiennes has already raised for charities from past expeditions.

The British-born explorer has previously been the first person to reach both the North and South Poles by land and the first to cross Antarctica on foot. He has also reached the summit of Mount Everest and Switzerland's notorious Eiger. His latest challenge, however, is likely to be his hardest yet.

Read: Drought-hit trees face race to adapt

As well as the bitter cold, they will have to cope with life on the Antarctic Plateau, with the reduced levels of oxygen that comes from being located at 3,800 meters (12,470 feet) equivalent altitude. What's more, they will have to do all this without the safety net of emergency rescue support, as aircraft cannot reach inland during the winter months.

"All the expeditions we've done in 40 years if something had gone wrong in a nasty place, you can press a beacon. A ski plane can come in," Fiennes told CNN. "This is the first time that if we run into problems like that, there is no help, because in Antarctica in winter all the rescue facilities shut off."

Despite his advancing years and a number of health scares -- he suffered heart problems while making an earlier attempt to climb Everest and amputated five of his fingers using an electric drill from his garden shed after losing them to frostbite - Fiennes is sanguine about his chances of success.

"I don't think about not coming back, because I mean, more people get killed on the roads here [London] than they do in Antarctica. I mean, I had a massive heart attack reading a magazine on an airplane. You don't need to go to Antarctica to pop it."

Read: Rising sea level puts island nations like Nauru at risk

Compared to the early polar explorers of the 1900s, Fiennes's team will benefit from some innovative equipment, including boots with electrically-heated insoles, battery-powered heated clothing, radar to spot dangerous crevasse fields and a specially designed breathing apparatus to enable them to survive at temperatures that will regularly reach -70 degrees Celsius and perhaps even lower.

Their list of supplies is also exhaustive, with support sledges carrying 7,300 tea bags, 4,400 packets of soup, 230 kilograms of chocolate and 165 rolls of toilet paper (12 sheets per man, per day). If they are left stranded the supplies are enough to keep them alive for 365 days, a realistic prospect given significant uncertainty about whether the support vehicles carrying their supplies can continue operating at temperatures of -70 degrees Celsius.

Read: How severe weather impacts global food supply

As one of the last great wildernesses on Earth, Antarctica, especially in winter, might as well be the moon, in terms of its isolation.

The continent has been protected from territorial disputes and exploitation by The Antarctic Treaty since the 1960s. However, the major powers are split over how to manage and protect the waters around the continent.

A recent meeting of the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) which is made up of 24 nations and the European Union failed to reach a consensus.

There is also another looming unknown facing the continent and that is climate change. A major part of Fiennes' expedition will involve collecting data on how global warming is affecting the Antarctic icecap during the winter. Up until now this has been an almost blank canvas of scientific research, with teams unable to penetrate during winter months.

With the help of high-tech equipment and GPS, the team will track changes in the mass of the ice caps, collect samples and map the height of the Antarctic landmass.

Gallery: First woman to cross Antarctic solo

Having set sail from London, Fiennes and his team plan to arrive in Antarctica after Christmas and begin the trek itself in early March. A typical day will start at 6:30 a.m. as the expedition team aim to cover 35 km a day. If all goes to plan this will finish in September, giving Fiennes plenty of time to ponder the luxuries he will miss most during the dark and cold winter months.

"My personal thing is have a hot bath. I love hot baths, foam baths. And, you know, to me that's better than any sort of amphetamine."