More than 4,000 climbers have scaled the 8,850-meter (29,035-foot) summit since 1953, when it was first conquered by New Zealand climber Edmund Hillary and Sherpa Tenzing Norgay. The numbers have skyrocketed in recent years along with guided expeditions charging up to $75,000 to help even novice trekkers reach the peak. More than 800 climbers tried during the 2013 spring season, and there were likely at least as many signed up this year.
But some, spooked by Friday's disaster, have already packed up and left.
The legendary Apa Sherpa, who holds the record in summiting Everest 21 times, has been warning about rising risks from climate change for years. When he first summited the mountain in 1990, the trails were covered in thick layers of packed ice and snow. "Now, the trail is full of bare and exposed rock," he said, making it harder for climbers to gain footholds with their spiky metal crampons meant for digging into ice.
"The danger level has significantly risen for climbers," said Apa, 53, who now lives in Draper, Utah, and last conquered Everest in 2011.
Newly exposed rubble and rock can also cascade in rock avalanches — as now happens on the Eiger in the Swiss Alps during summertime.
Meanwhile, heavier snow storms would lead to more snow accumulating, raising avalanche risks. Shifting wind patterns may also affect how snow and ice behave. Glacier movement could change, and an increase in melt water trickling down could cause a glacier to move more quickly.
"Changes in snow and ice are going to strongly influence the stability of snow on a slope and the possibility of an avalanche," said American glaciologist Tad Pfeffer with the Institute of Arctic and Alpine Research at the University of Colorado, Boulder.
"The danger in mountaineering is a combination of what's going on in the natural world and what the climbers are doing," Pfeffer said. "People will get in trouble if they rely on what they knew in the past. They have to have their eyes open and not go somewhere or do something simply because it worked out five years earlier."
AP writer Binaj Gurubacharya contributed to this report from Katmandu, Nepal. Follow Katy Daigle on Twitter at http://twitter.com/katydaigle.
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