Thirteen of the world's 14 peaks taller than 8,000-meters have been climbed in winter. But one still remains unclimbed — the 8,611 metres (28,251 feet) K2, the world's second tallest that straddles Pakistan and China.

Climbers say that avalanches are an ever-present risk, and in winter temperatures can fall to -50C (-58F). Winds blow up to 200km/h (124mph) that’s equal to cyclone Fani, the most severe storm that travelled more than 900 kilometres (570 miles) from the Indian state of Odisha and blew nearly two dozen tents at Everest’s Camp 2, at 6,400 metres in May last year.

It is also considered to be a technically very difficult mountain to climb and has been dubbed “killer mountain” for the sheer number of climbers that have lost their lives on the mountain.

“It’s the planet's toughest and most dangerous mountain to climb,” said Kami Rita Sherpa, who has climbed Everest a record 24 times.

Eighty-four climbers have died attempting to climb K2, and only 306 have reached its summit. The death and success ratio is roughly one death for every three successful climbs.

In contrast, 6,507 mountaineers have climbed Everest from the Nepal side since Tenzing Norgay Sherpa and New Zealander Edmund Percival Hillary first set foot atop the world's highest peak in May 1953.

In the summer of 1954, Italian climbers Achille Compagnoni and Lino Lacedelli became the first persons to reach the summit of K2.

“K2 is 237 metres lower than Everest, but it is much challenging to climb even in the best conditions. That’s in summer,” said Kami Rita. “The weather in winter is beyond imagination. The weather is good only for 2-3 hours a day.”

Kami Rita, who had climbed the K2 in the summer of 2014, said as far as K2 is concerned he is retired.

But now a massive 55-member group of climbing veterans from around the world, including 27 Sherpas from Nepal, has set its sight on one of the most daring missions on the planet, which many mountaineers still call an “impossible project”.

The extreme mission, that may cost more than Rs200 million, is being handled by Kathmandu-based Seven Summit Treks, which also devised the expedition.

Chhang Dawa Sherpa, the youngest mountaineer to have climbed all the 14 highest peaks, is leading the K2 winter mission.

Spanish climber Sergi Mingote, who has been attempting to climb all eight-thousanders without supplemental oxygen within 1,000 days, is the co-leader of the expedition. Mingote’s plan had come to a halt, after seven successful summits, due to Covid-19 related restrictions.

Nepali climber Nirmal "Nims" Purja, who smashed the record for taking the shortest time to climb all 14 of the world's 8,000-meter-high mountains and had also announced his plans to climb bid K2 in the winter of 2020-21, has joined the group. Through his website nimsdai.com, he has described K2 winter ascent as “the last great mountaineering challenge.”

The Post’s attempt to contact Purja went unsuccessful.

Other climbers include Noel Hanna from Britain, Arnold Coster from the Netherlands, Atanas Skatov from Bulgaria, Waldemar Kowalewski from Poland, Antonis Sykaris from Greece and Luis Carlos Garranzo Ibanez from Spain. Slovenian, Romanian, Swiss, Italian, Chilen, American and Finnish mountaineers are also part of the 55-member mission.

The two-month-long expedition will begin from December 21 and ends by February 28.

“Ten Sherpa climbers left for Pakistan on Sunday,” said Thaneshwor Guragain, manager of Seven Summit Treks. “The remaining 17 climbers from Nepal are scheduled to join them on December 18 and others from around the world will join the expedition by December 20.”

The bid to climb K2 in the winter has attracted mountaineers for long.

The mountain has been attempted more than 30 times in winter but all expeditions have been unsuccessful with the highest point reached being 7,400 metres.

Last winter, Spanish mountaineer Alex Txikon, led one of the two expeditions to K2 comprising mostly Sherpa climbers. But it was unsuccessful. Several expeditions have failed in past years, mainly because of unstable climate, mountaineers said.

“The K2 winter feat is very tough. If any member of the team climbs, it will be another milestone in the mountaineering history—the first winter ascent of the world's second-tallest mountain,” said Kami Rita. “Even Sherpas who have climbed Everest multiple times are scared to climb K2.”

K2 is a rocky mountain up to 6,000 metres and beyond it becomes an ocean of snow, according to Seven Summit Treks.

“It’s difficult even to reach the base camp of K2. We have to trek on the glacier for a week to reach the base camp and there aren’t any lodging and fooding facilities on the way up,” said Kami Rita, who has plans to lead two expeditions on Everest in spring next year.

According to Kami Rita, one spot in particular is infamous in K2. That’s Bottleneck, a perilous couloir about 300 metres below the summit, which was the site of a 2008 tragedy in which 11 people were killed in an avalanche.

“Winter brings with it a whole different level of danger and challenge. Numerous teams have attempted since 1987-88, but all have fallen short, Purja writes in his website describing it as a personal project.

“Not only do the sheerness of the slopes and overall exposure create a technically challenging climb, but the weather is also always the great opponent on K2 all year round.”