Hikers begin their descent to the Aletsch Glacier in the early morning from the Konkordia Hut, Switzerland, August 29, 2015. One of Europe's biggest glaciers, the Great Aletsch coils 23 km (14 miles) through the Swiss Alps - and yet this mighty river of ice could almost vanish in the lifetimes of people born today because of climate change. The glacier, 900 metres (2,950 feet) thick at one point, has retreated about 3 km (1.9 miles) since 1870 and that pace is quickening. Picture taken with long exposure. REUTERS/Denis Balibouse
