Climbers face more risks as Alps crumble

"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.

DIRE WARNINGS

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."