How Rising Temperatures Likely Contributed to Nepal's Deadly Flood
About 160 people have died and hundreds remain missing after flash floods struck the Nepal-Tibet border region, with scientists pointing to a glacier collapse worsened by global warming as the likely trigger.
Flash floods that struck the mountainous border area between Nepal and Tibet on Wednesday have killed roughly 160 people, with hundreds more still missing, including dozens of international tourists. Footage shared on social media shows people fleeing a wall of water that swept away buildings and vehicles.
Early analysis of satellite imagery, along with reports from Nepal's government, suggests the floods were likely set off by a landslide after a large chunk of a glacier broke away and fell hundreds of feet. Joseph Shea, an associate professor of geography at the University of Northern British Columbia, says glaciers in the region are clearly retreating and becoming less stable.
Since 2000, the world's glaciers have lost about 5 percent of their ice overall, though some regions have been hit far harder. Nepal's glaciers shrank by nearly a quarter in area between 1970 and 2010, and more than 160 smaller glaciers in the country have disappeared completely. One recent study estimates that up to 40 percent of the world's glacial ice could vanish if warming isn't kept below 1.5 degrees Celsius.
Shea explains that as glaciers retreat, they lose the ability to hold sediment in place, which can trigger landslides, while also leaving behind large dammed lakes at higher elevations. A landslide falling into one of these lakes can cause it to overtop and the dam to collapse catastrophically — an event known as a glacial lake outburst flood. Two such floods hit Nepal last year, and researchers warn that millions of people worldwide live in areas at risk from similar events.
Wednesday's disaster, however, appears to have stemmed more directly from a mass of ice collapsing into the valley below. Daniel Shugar, a geologist at the University of Calgary, told The New York Times that satellite imagery indicates a roughly 2,000-foot-wide piece of ice may have fallen nearly 4,000 feet, pulverizing into water on impact. He told Reuters that snow present on the glacier earlier in the week may have melted due to warm temperatures, though he cautioned it's still too early to draw firm conclusions about the cause. The US Geological Survey noted the collapse and resulting debris flow were forceful enough to register as a magnitude 5.2 seismic event.
Similar glacier collapses have caused destruction elsewhere, including one in Switzerland last year that buried a town, and a 2022 collapse in Italy that killed 11 mountaineers — both linked to rising temperatures. Shea notes that in summer, warming, melting and abundant meltwater combine with thawing alpine permafrost to loosen ice and rock that would otherwise remain frozen in place.
