Science - January 14, 2016

More rock fall in Alps due to warming

Rob Ramaker

On many climbing routes in the Alps climbers run more risk these days of being overtaken by rock fall, a trend related to climate change. This was revealed by geomorphologist Arnaud Temme from a comparison of mountain climbing guides of the last 150 years. He writes about his findings in Geografiska Annaler Series A.

The north side of the Eiger in Switserland, Image: Kosala Bandera

The idea came up when Temme, an amateur alpinist, was hit on the shoulders by falling rocks during a climb. ‘I had the feeling climbing was getting more and more dangerous.’ This danger mainly arose in areas which used to be permanently frozen but which now regularly thaw. Crevices then fill with water which expands with the next frost, causing rocks to break up. Only when an area has permanently thawed does the situation stabilize.

Scientists had previously found signs of increasing rock fall. They had for example studied the damage to trees, or compared historic photos with the current situation. The disadvantage of such methods, however, is that they are so local. Temme wanted to take a broader view. He studied 17 mountain guides published between 1864 and 2010. For 63 routes in the Grindelwald region, famous for the Jungfrau and the Eiger, he looked at what the authors said about the frequency of rock fall and the quality of the rock. He also looked at whether the overall assessment changed, from ‘dangerous’ to ‘highly dangerous’, for example, or even to ‘not recommended’

Temme found a tendency towards more rock fall and higher risks. Seven of the 63 routes have been scrapped and all 27 changes in the advice given were in the direction of more danger. The geomorphologist points out that the assessments of the mountain guides are subjective. It could be that climbers tolerate lower levels of risk than they used to. Nevertheless, he believes the results show a clear tendency.