Does the Nepal glacier collapse signal a new climate risk?

A glacier collapse in the Nepalese Himalayas triggered devastating floods this week, killing at least 584 people and leaving more than 2,400 missing.

Scientists tell AFP the disaster raises questions about whether it signals a new kind of hazard in a world warmed by climate change.

What caused the Nepal glacier collapse floods?

According to the US Geological Survey, the floods were triggered by a glacier collapse so violent it generated energy equivalent to a magnitude 5.2 earthquake, setting off numerous landslides. Nepal had issued an alert two days earlier about the risks posed by a large body of water that formed in China's Tibet region following the collapse.

Could the glacier collapse again in the same area?

"Once you take a piece of mountain away, then there's probably another piece right beside it that's been destabilised by the removal. And so you could have a similar thing collapse," Simon Cox, principal scientist at New Zealand's GNS Science research institute, told AFP. "You may well have more material to fall down right from up at the source area, and the same thing could happen immediately again."

Could similar glacier collapses happen elsewhere?

Etienne Berthier, a glaciologist at the French National Centre for Scientific Research (CNRS), told AFP that the risk of similar events occurring elsewhere "can't rule out." He explained that such collapses reach extreme proportions in the Himalayas because the terrain and the region's high tectonic activity amplify the likelihood of events on that scale.

Other regions, such as Alaska, may have similarly "dynamic" glaciers, but Berthier noted this typically happens in completely uninhabited areas. Tristram Hales, a professor of environmental hazards at Cardiff University, told AFP there has been "a dramatic increase in the number of extremely hazardous flows such as this globally in the past decade or so," citing events in the Himalayas and Switzerland.

Scientists warn that rockfalls and landslides triggered by earthquakes or the thawing of permafrost, which is being accelerated by climate change, are more likely than entire sections of mountain coming down. These risks are greater for people when towns, roads or tourist sites are located nearby.

In the Alps, this year's extremely hot summer saw a record number of rockfalls, including some fatal ones, the vast majority of which can be attributed to the climate crisis, Ludovic Ravanel, a geomorphologist at the CNRS, told AFP recently. In Switzerland, the municipality of Randa, home to some 400 people, fears a glacier collapse in the coming days and has established safety perimeters following several rockfalls, according to the national press.

Can scientists predict when a glacier will collapse?

The disaster in Nepal was probably very hard to predict, Berthier said, adding that rock movements will need to be analyzed to see if signs of instability were visible in the preceding weeks or months. Risks are far more apparent when glacial-fed lakes form, since these can drain suddenly and catastrophically in a phenomenon known as glacial lake outburst floods (GLOFs).

In the Alps, "we are well-equipped, we monitor these lakes and check for risks of overflowing or sudden drainage," Bernard Francou, a retired glaciologist and former research director at the French National Research Institute for Sustainable Development (IRD), told AFP.

Is climate change to blame for the Nepal glacier collapse?

Several scientists urged caution about linking the latest disaster directly to climate change, even though some experts are already drawing such a connection. "While climate change is altering glaciers, snow conditions, permafrost and mountain slopes across the Hindu Kush Himalaya, it is too early to determine what role climate change played in this specific event," said the International Centre for Integrated Mountain Development (ICIMOD), an intergovernmental institute.

An "attribution study," which analyses how likely a specific event would occur in today's fossil-fuel warmed climate compared to the pre-industrial climate, will be required to draw firm conclusions either way.