In April 2014, a massive chunk of ice, known as a serac, broke off a section in the Khumbu Icefall on Mount Everest. This triggered an avalanche of snow and ice that swept down the mountain, taking the lives of 16 sherpas. It also effectively ended the 2014 Everest climbing season.
While shifting and crumbling ice has long made the Khumbu region one of the most dangerous places on the climb, the avalanche suggested that climate change is a growing threat to some of the highest peaks on Earth.
A recent study suggests that the Khumbu glacier and more than 5,500 others in the Everest region will drastically recede or completely disappear by the end of the century. But this problem isn’t unique to Everest. Glaciers are disappearing from mountains all around the world, including the Andes in South America, from Mount Rainier in Washington, and from Aconcagua, the highest peak in Asia.
“The mountains are so high and they are typically quite cold, and we were really surprised to see that the glaciers were really quite sensitive to future climate changes,” says Joseph Shea, lead author of the study and glacier hydrologist at the International Centre for Integrated Mountain Development in Nepal.
As glaciers recede, the bottom section of the snow pack melts first because of lower temperatures at the base. This shifts the snow and rock forward, shrinking the glacier. With temperatures rising in the Himalayas and around the globe, the bottom of the glacier melts away faster, making the upper portion less stable, and more dangerous for climbers.
“Climate change has made the mountain less able to handle a crowd,” says David Hahn, a Himalayan guide for RMI Expeditions who has summited Everest 15 times. “It certainly means you have less control over risk if you are mixed in with hundreds of other people in those dry and icy conditions, and as a guide you’d like to have more control rather than less.”
The south route to the summit isn’t the only place climbers are experiencing changes: in 2010, a massive serac broke off on the northern route and killed 2 climbers. But unlike the seracs people usually see in the Khumbu icefall, the ice avalanche on the northern route was considerably higher up—more than 7000 meters above sea level. Since people first started climbing the North Col route, also known as the Northeast Ridge Standard Route, climbers have only seen snow avalanches, says John All, an Everest climber and Associate Professor of Geography at Western Kentucky University. The 2010 avalanche was the first recorded ice avalanche ever seen on the route, another alarming indication that climate change was creeping up the mountain.
In addition to noting these ice avalanches, climbers like Hahn and Politte have noted that areas once covered by snow are now reduced to ice and rock, less than ideal climbing conditions for larger crowds, as it increases the risk of rock fall.
“One the snow melts away you’re on rock, and very cold temperatures make rocks super brittle,” says All. “You go from climbing a nice consolidated snow face to climbing loose, brittle rock that crumbles beneath your hand, and it’s a lot more dangerous.”
Climbing Everest, once something reserved for the most experienced climbers, is now a commercialized adventure, in which hundreds of climbers try their hand at summiting the world’s highest peak every year. But the high numbers have led to blockages and lines along various trails up the mountain that didn’t use to require a wait time.
In addition to the health issues climbers face, including the possibility of brain swelling and fluid build-up in the lungs, standing still while they wait in lines on a freezing mountain increases the risk of climbers’ developing frostbite and hypothermia. And now, with the terrain itself becoming more precarious, guides are considering making changes to how major climbing expeditions are handled.
“I think small group sizes would help on some of these peaks that are becoming more difficult, since they’ll need more management,” says Pollitte. “At one time you could climb some of these peaks with 12 people, but that isn’t always manageable now.”