An avalanche on 17 July 2016 killed nine yak herders from the Dungru Village in Rutog County, Ngari Prefecture, when 70 million tonnes of ice broke off from the Aru glacier in Tibet. This, and a second avalanche in September, have been linked to a local temperature rise of 1.5C, scientists say.

The Tibetan plateau used to be stable and free of avalanches, but this year two large glacier collapsed within months.

More from IBTimes UK

Witnesses said that the collapse in July took only four or five minutes to bury 3.7 square miles of the valley.

The speed of the collapse indicates the presence of a large body of meltwater in the glacier, according to a paper published in the Journal of Glaciology.

"Given the rate at which the event occurred and the area covered, I think it could only happen in the presence of meltwater," said Lonnie Thompson of Ohio State University and the Byrd Polar and Climate Research Center. Other nearby glaciers may also be vulnerable, he says.

In September the second avalanche happened when a neighbouring glacier collapsed, with no reports of casualties.

The scientists say that a large amount of meltwater beneath the glaciers is due to local temperatures rising in the region. At the nearest weather station, the average temperature has risen by 1.5C in the past 50 years.

"It makes sense that snow and ice are melting and the resulting water is seeping down beneath the glacier," Thompson says.

Analysis of satellite and GPS data shows that a large body of meltwater beneath the glacier is the only plausible explanation for the avalanches.

Tibet avalanches
On July 17, more than 70 million tons of ice broke off from the Aru glacier in the mountains of western Tibet and tumbled into a valley below, taking the lives of nine nomadic yak herders living there. The cause of the avalanche was climate change, scientists say Photo by the Chinese Academy of Sciences, courtesy of The Ohio State University.

Difficulty of prediction

Scientists at ETH Zurich in Switzerland did spot worrying signs before the September collapse, but their warnings only reached the local authorities in Tibet hours after the glacier had given way.

However, Thomson says that there is no reliable method of early warning that can be used to identify which glaciers in the region may be the next to collapse.

Tibet avalanches
Sentinel-2 satellite images from shortly before (left) and just after (right) the Aru Glacier collapse that occurred on July 17, 2016 in western Tibet. More than 70 million tons of ice flowed down the mountain, killing 9 people. Ohio State University
Climate Change