GRINDELWALD, Switzerland (Reuters) - Climbing sheer rock faces has never been the safest of sports, but global warming is increasing the risk factor.
The ice that glues Alpine peaks together is slowly melting, loosening rocks and making classic European climbs like the Eiger and Matterhorn even riskier than in the past.
“Now there are routes that just can’t be done any more,” said Grindelwald mountain guide Marco Bomio.
He pointed out a slope on the Eiger’s northeast face, first climbed in 1932, which is now often too dangerous to ascend as there is too little ice and snow on the route.
After a major rockfall — which geographers say are ever more common in the Alps — guides are often called in to secure the mountainside by clearing loose rocks and binding others in nets.
“These days we make more money from rockfalls than we do as mountain guides,” Bomio said.
Elsewhere in the Alps, the Petit Dru, a sharp pinnacle of rock and ice in the Mont Blanc massif, is disintegrating and the world-renowned Bonatti Pillar route up its south-west face has disappeared.
In 2003 — a particularly hot summer in Europe, which loosened large volumes of rock — some 70 climbers had to be rescued by helicopter from the Matterhorn after a series of rockfalls swept down its sheer sides.
Two years later, a meadow in the Bernese Oberland slid into a glacier basin, taking a popular mountain restaurant with it. Last year, tourists flocked to the Eiger to witness a rock the size of two Empire State Buildings collapse to the canyon floor.
The infamous north face of the Eiger, which looms above Grindelwald, used to be about 75 percent snow and ice.
“Today it’s only a quarter. That’s the same on many routes,” Bomio said. “Good ice is better than bad rock.”
Collapsing mountainsides are not a new phenomenon. In 1806 a slide wiped out the village of Goldau, killing 457 people in one of Switzerland’s worst disasters.
In a freak occurrence last year, a boulder the size of locomotive plunged around 700 meters onto a passing car on the Swiss motorway, killing the two German tourists within.
But the trend appears to be accelerating as temperatures rise, with five major rockslides of more than a million cubic meters in the last 20 years, said Wilfried Haeberli, geographer at the University of Zurich.
“As the temperature rises, higher and until now frozen mountainsides will warm up and the number of possible crack zones — and the frequency of large falls — increases,” Haeberli said.
The problem is by no means confined to the Alps. Climbers have reported disintegrating routes and shrinking glaciers in mountain ranges around the world.
“The changes are everywhere,” said Mark Bowen, a climber and author of “Thin Ice,” a book about global warming and its impact on high mountains. “They go from Patagonia to Alaska, from New Zealand to the Alps to the Himalaya (range).”
Melting snowfields also threaten fresh water supply for a large part of the world’s population as river flows decrease, Bowen said.
“The problem is larger than our sport. Climbers are beginning to recognize this and they are in a unique position to tell the rest of the world,” he said.
Grindelwald guide Bomio said his job was becoming easier on some ridge routes that have become faster and less strenuous as the ice melts.
But with a rising permafrost line — where the temperature remains below zero degrees Celsius (32 Fahrenheit) and the ground stays frozen — Bomio’s choice of routes narrows.
“It’s at its safest in winter,” Bomio said.
“I hear it (rocks falling) when I open the window in the morning,” he said. “There will always be some kind of a risk.”
Kev Reynolds, who has written a series of guide books on hiking in the Alps and other ranges, witnessed a major rockfall last summer while researching a new route near Zermatt, on a small glacier which he had crossed only minutes before.
That alternative will not be featuring in his new guidebook.
“The Alps are falling down and glaciers disappearing. That should be obvious to all walkers and climbers who make fairly frequent trips to the mountains,” he said. “These are just a few examples of the effects of global warming.”