Are we at greater risk of avalanches?

The climate crisis is leading to a rise in extreme precipitation events, but snowfall and snow cover is reducing. It's a mixed picture.

New Delhi: The Snow and Avalanche Establishment under Defence Research and Development Organisation (DRDO) issued a yellow warning for East Sikkim (above 3,800m) and an orange warning for North Sikkim (above 3,100m) for the possibility of avalanche on April 3 and 4.

Rescue team members search for survivors after an avalanche in Sikkim on Tuesday. (REUTERS)

The warnings were issued through the National Disaster Management Authority and are available on their website. Officials, however, are not certain if the alerts reached tourists and locals.

Yellow label warning implies partly unsafe conditions and small size avalanche may be triggered on extreme slopes. Black warning implies extremely unsafe conditions and avalanches may be triggered on unexpected paths. Clearly, SASE’s warnings had underestimated the risk.

“We are not sure how many people may have got the alert. These were issued through the NDMA which disseminates disaster risk warning,” said a senior official at SASE who did not wish to be named.

India Meteorological Department had warned of moderate rainfall and snowfall starting March 31. Gangtok reported 5 cm rainfall on April 4. An intense Western Disturbance that brought thunderstorm and hail to many parts of northwest India from March 31 to April 3 also brought intense weather to the Eastern Himalayas, officials said. In short, weather conditions were favourable for heavy precipitation and disasters like a snow avalanche.

“A warning was issued five days in advance that weather will change in East Sikkim from March 31. We were expecting thunderstorms, rainfall and snowfall. So, it doesn’t come as a surprise. But we do not issue avalanche warnings and do not measure snowfall so we will not be able to comment on what exactly led to the avalanche,” said Gopi Nath Raha, head of IMD at Gangtok.

“There are two features that contributed to extreme weather over Sikkim during the past five days. 1. A very active Western Disturbance which also impacted the Eastern Himalayas 2. Heavy moisture incursion from Bay of Bengal. There was also an upper air trough. Avalanches are not very common for East Sikkim but weather conditions had also deteriorated and we had issued timely warning,” Raha added. IMD has warned that thunderstorm and rainfall are expected to continue till Thursday.

Experts said extreme precipitation (rainfall and snowfall) during a short period can act as a trigger for snow avalanches. But forecast is often challenging because of the complex interplay of contributing factors. “Avalanches can be forecast, to an extent, based on certain contributing factors. For example, how much snow has already accumulated on a steep slope and how much fresh snowfall has taken place. A sudden temperature rise or strong wind after snowfall can also act as a trigger. If there is a lot of fresh snowfall in a particular region that can also lead to an avalanche. It’s a complex phenomenon. In the case of Sikkim, the weather has been bad there for the past few days and initial observations suggest rainfall and fresh snowfall, meltwater may have contributed to it. Our team of scientists are there. We are waiting for a detailed report from them,” said Amreek Singh, scientist at Defence Geo-informatics Research Establishment, DRDO. Snow & Avalanche Study Establishment.

“We had also issued a yellow label avalanche warning for April 3 and 4 for East Sikkim through NDMA,” Singh added.

According to an Avalanche user’s guide released by SASE, avalanche danger increases with the increasing slope angle. Maximum avalanche activity is experienced between 30-degree to 45-degree slopes that are in the shade/ rather than facing the sun. Contributing factors may be new snow with wind of 10 to 25 m/s; rapid rise in temperature during a storm; first fine day after a bad weather spell; incessant rain on snow; soaked snowpack; and new snow crystals that do not bond well with ice layer.

Rumbling noises (described as whoomps) can be a warning.

Anil V Kulkarni, glaciologist and Distinguished Visiting Scientist, Divecha Center for Climate Change at Indian Institute of Science said its difficult to say if India is seeing a rising trend in snow avalanches simply because avalanches often occur in very remote mountain regions and go unrecorded.

“We have to improve our monitoring of avalanches even in remote regions to understand and prepare well for such disasters in view of climate change. We know that climate change is leading to a rise in extreme precipitation events but at the same time snowfall and snow cover are reducing. It’s a mixed picture which is why it's important to understand the implications.”

The Intergovernmental Panel on Climate Change (IPCC) in its “Climate Change 2022: Impacts, Adaptation and Vulnerability” released in February 2022 said that climate crisis impacts in mountains and their attribution to human influence have increased in recent decades with serious consequences for people and ecosystems in many mountain regions.

“Observed changes include increasing temperatures, changing seasonal weather patterns, reductions in snow cover extent and duration at low elevations, loss of glacier mass, increased permafrost thaw and an increase in the number and size of glacier lakes,” it said.

IPCC’s factsheet on mountains said: “Projected changes in hazards, such as floods and landslides, as well as changes in the water cycle, will lead to severe risk consequences for people, infrastructure and the economy in many mountain regions. Nearly all mountain regions will face at least moderate and some regions even high risks at around 2°C global warming level.”

A paper in Proceedings of the National Academy of Sciences (PNAS) published in 2018 and led by Climate Change Impacts and Risks in the Anthropocene, Institute for Environmental Sciences, University of Geneva had concluded that the climate crisis is impacting the cryosphere in high mountain ranges, thereby enhancing the probability for more and larger mass-wasting processes to occur. A snow avalanche reconstruction exercise in the Indian Himalayas showed an increase in avalanche occurrence. Statistical modelling suggests that this increase in avalanche activity is linked to climate warming. These findings contradict the intuitive assumption that warming results in less snow, and thus fewer snow avalanches in the region, the paper concluded.

According to another paper published in Frontiers in 2021, titled “Effects of Climate Change on Avalanche Accidents and Survival” with the climate crisis, the frequency and types of snow avalanches may change, affecting the rates of avalanche burial and survival. With a wetter and warmer snow climate, consequences of burial may become more severe. Blunt trauma and secondary injuries will also likely become more frequent as terrain roughness is expected to rise and snow cover to become thinner.