How heatwaves are making the Swiss Alps more dangerous
High up in the natural wonder of the Alps, the climbers who spend their days among the rockfaces and glaciers have come to a grim conclusion: the mountains are falling down around them.
On Wednesday morning two alpinists lost their lives on the Matterhorn when they were hit by a rockfall, while the village of Zermatt experienced a raging flood that evening after the rupture of an underground glacier.
Though rockfalls are common in the mountains, heatwaves like the one experienced across Europe this week are exacerbating the problem, according to experts.
During heatwaves, temperatures may now surpass freezing point as high as 4,600m-4,800m altitude – higher than nearly all the Swiss Alps – causing permafrost to melt and destabilizing the rock, Valais cantonal geologist Raphaël Mayoraz told newspaper Le Temps this week.
Though erosion is a natural process, a hot summer speeds things up. If during a normal summer day, 1,000 rocks fall from a mountain like the Matterhorn, during a heatwave that could reach 1,200, said Mayoraz.
And as heatwaves arrive more frequently, the mountains become more destabilized.
In three decades the altitude at which the temperature surpasses zero degrees in summer has crept up by 300-500m on average, now regularly topping 4,000m, meteorologist Nicolas Borgognon told the paper.
“It used to be rare that it surpassed 4,500m. Now that’s no longer the case,” he said.
At the end of June, temperatures even hit positive figures at 5,000m, higher than Mont Blanc.
"The mountains are falling"
The Alps’ highest mountain is a magnet for mountaineers in the summer, where many popular routes up or through the peaks have become too dangerous to take because of the risk of falling debris.
"It's going quickly. Ten years ago, I'd have never thought that it would accelerate like this," said Ludovic Ravanel, an academic at the University of Savoie Mont Blanc who has been studying major rockfalls in the area.
"And if you look at the predictions from my climatologist colleagues, for the next 10 to 20 years, it's only going to get worse," he told AFP.
Around Mont Blanc, the warming has already left physical scars. In 2005, following a major heatwave two years earlier, a huge shard of granite called the Bonatti pillar suddenly collapsed, spewing 292,000m3 of rock into the valley below and stunning the mountaineering community.
Major rockfalls on less famous routes continue regularly, without fanfare, and would go unnoticed were it not for the work of researchers like Ravanel who tracked them for his PhD.
"There's not much time left for certain rockfaces," warned 37-year-old Ravanel, whose father was a mountain guide.
Confirmation of the decay came in a recent study based on a popular mountaineering book published in 1973 by famed climber Gaston Rebuffat called "100 Most Beautiful Routes".
Ravanel and fellow academics analysed the routes in order to measure how they had changed in the more than 45 years since the first appearance of the book, a bible for several generations of mountaineers.
A majority of them had been affected by climate change, concluded the study in June, including 26 which were "very affected" and three which no longer existed.
The team of mountain specialists at the University of Savoie Mont Blanc looked at the ice and snow coverage, as well as the extent of exposed rock and the state of the glaciers, where crevasses are widening.
The optimal climbing conditions had moved to the spring and autumn, it said, while routes in general had become more dangerous and technically more difficult.
For guides, the unpredictability of the conditions, with unexpected warm spells in winter or late snowfalls, is making a dangerous job even more nerve-wracking.
But some are keen to simply enjoy it while they can.
"I've started to accept quite a few things," admits Yann Grava, 33, who will finish his training to be a guide next year. "On average, a guide used to be able to work for about 15 years, but for me I think it'll be around 10. The mountains are falling."