‘Climbers are more at risk from rockfall today than they were 150 years ago,’ says Arnaud Temme, Professor in Geomorphology at Wageningen University and author of the study. The conclusion was reached following analysis of 150 years worth of Bernese Alps climbing guidebooks, putting the increase down to the warming temperatures being seen across the Alpine region. ‘I looked at hazard warnings over various climbing routes, with a view to finding out differences over time,’ he says.
Weather can take its toll on rocks. During winter months, water freezes in cracks expanding them. In the summer, the ice melts leaving behind a more unstable rock face. This is a natural weathering process that helps shape mountainsides.
‘However, warmer temperatures increase the risk of this weathering process,’ says Temme. ‘They cause permafrost degradation, which means that more locations that used to be locked in permafrost are now alternating between frozen and melted.’ Fewer rockfall warnings from the old guides indicated to Temme that permafrost used to keep the rock face more stable.
‘As another hazard, warmer temperatures lead to melting of permanent snowfields, which exposes rock faces and rock slopes that have not been at the surface for a long time - sometimes thousands of years. The rocks contained in the snow are often lying precariously on those faces and slopes.’
While rockfall danger has increased, Temme says the sport is still less dangerous than it was 150 years ago: ‘Climbers have already countered some of the dangers by declaring routes unclimbable, and changing the ascent of some others.’ Meanwhile, drastic improvements in equipment, weather forecasting and search and rescue teams help to keep climbers as safe as possible.