An avalanche buried an Italian resort on Wednesday, leaving at least 30 people trapped inside and scores likely dead. Officials link the immediate cause to earthquakes in central Italy. But scientists say there's another reason that snow slides are becoming more common: climate change.
Avalanches are caused by a combination of geological factors (like the incline of a mountain or natural events like earthquakes), weather and the structure of the snow. Warmer weather can weaken a mountain's snow pack and make it more difficult for the layers of snow to stick together. Mix in another element, like particularly gusty wind or trembling earth, and you've got a mountain primed for avalanche.
Experts have been aware of this phenomenon for a while. One study found that recent changes in climate have affected the quality of mountain snow cover, which has led to more frequent avalanches and more severe ones, too. Norwegian researchers also found a link between climate change and avalanches; they're working on a plan to alleviate the worst impacts of this on roads. The Intergovernmental Panel on Climate Change warned that warming temperatures have destabilized mountain climates, leading to more avalanches, melting glaciers and more intense storms.
“Changes in snow and ice are going to strongly influence the stability of snow on a slope and the possibility of an avalanche,” Tad Pfeffer, a glaciologist with the Institute of Arctic and Alpine Research at the University of Colorado at Boulder, told Al Jazeera. “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.”
This has hit the Alps particularly hard. Weather on that mountain range is warming at a quicker pace than the global average. Additionally, snow storms are more volatile and erratic. In particular, it's taking longer for winter to descend. That means weak snow at the very bottom of the snow pack. “As more snow piled on top of the weak layer, and temperatures remained warm, the upper, moisture-laden layers became vulnerable to sliding, and it created a delicate situation that required extra vigilance,” Vice reported.
In 2015, when more than 100 people were killed in avalanches. “It was terrifyingly unstable,” skier Tyler Jones told Vice. “I've never seen anything like it,” agreed Dougal Tavener, a guide and professional skier
Similar trends have been seen at other mountain ranges as well. In the Himalayas, glaciers are melting faster than ever. The total area of Nepal's glaciers shrunk by almost a quarter between 1977 and 2010, according to the International Centre for Integrated Mountain Development. During the same time, Nepal's average temperature change was two to eight times above the global average. This has led to a dramatic increase in the number of avalanches.
“The frequency of avalanches like the one that struck at the Everest base camp last month may increase due to global warming,” Samjwal Bajracharya told Reuters in 2014.
In May 2012, more than 60 people were killed in the Mount Annapurna region of western Nepal after flash floods triggered by an avalanche washed away Nepali homes. Ten people, including nine European climbers, were also killed that year when avalanches swept away their camps on the world's eighth tallest peak, Mount Manaslu, in central Nepal.
In 2014, an avalanche on Mount Everest killed 16 Sherpas. It was the deadliest disaster in Mount Everest history. Then in 2015, another avalanche buried Mount Everest's base camp. Nineteen were killed, including 10 Sherpas.
America also had one of its deadliest avalanche seasons in 2016, thanks to weak snow packs.