Recent temperature rises and heatwaves, such as those of the summers of 2015 and 2018, have had significant impacts on many climbing routes across the Alps, including those on Mont Blanc. For example, in 2015, the Grand Mulets route, previously popular in the 20th century, was blocked by virtually impenetrable crevasse fields, and the Gouter Hut was closed by municipal decree for some days because of very high rockfall danger, with some stranded climbers evacuated by helicopter.