On 26 August, an ice-and-rock collapse high in the Himalayas near Nepal’s border with China triggered a sudden flood surge that entered Nepal through northern Rasuwa District. Communities were among the first and hardest hit, with more than a thousand people killed and thousands more remain missing, as the flood travelled downstream, damaging settlements and infrastructure.
Although the precise trigger of the collapse remains under investigation, experts say climate change had helped create the conditions for such failures by accelerating glacier retreat, thawing permafrost and increasing meltwater in the high Himalayas.
“Nepal’s mountains have been sending warnings for a decade [through] thinning glaciers, retreating snowlines, permafrost turning to slush under roads and hydropower plants we kept building anyway,” said Anjal Prakash, professor of public policy at the Foundation for Liberal And Management Education (FLAME) University and an Intergovernmental Panel on Climate Change (IPCC) author.
“We didn’t lack the science, as researchers have tracked this decline for fifty years. We lacked the political will to act on it,” he said in a statement released by the Global Strategic Communications Council (GSCC) on Tuesday, arguing that the failure lay in lack of policy for land use decisions and continued fossil fuel emissions rather than in a shortage of warning systems. “No siren can outrun a mountainside collapsing in seconds.”
The disaster in Nepal, which involved a bedrock failure and glacier collapse followed by cascading flood impacts, has renewed scrutiny of how roads, hydropower facilities and settlements are planned in an increasingly unstable high-mountain environment.
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We didn’t lack the science, as researchers have tracked this decline for fifty years. We lacked the political will to act on it.
Anjal Prakash, professor of public policy, Foundation for Liberal And Management Education (FLAME) University
Alton Byers, a mountain geographer and glaciologist at the University of Colorado Boulder, said the immediate trigger for such events can vary, from gravity and meltwater to an earth tremor or extreme weather, but warming makes the conditions for failure more likely.
Permafrost, he said, acts as a form of “cryospheric glue” that has held together high-altitude rock, soil, boulders and glacier systems for millennia. As temperatures rise, that frozen ground softens, weakening the stability of mountain slopes, likening it to a “stick of butter” taken out of the refrigerator until it becomes mushy and no longer has the ability to hold together, he added.
Warming can also increase meltwater at high elevations, lubricating the contact point between rock and ice and increasing the likelihood of slippage, he said in a webinar on Tuesday. Retreating glaciers can further remove the support they once provided to adjacent rock masses – a process known as buttressing, he added.
“If these factors converge, it may take only a trigger – such as gravity or an earth tremor – to set off a collapse. The result can be the sudden release of huge masses of bedrock and glacial ice, as happened last week. What began as a bedrock failure and glacier collapse then set off a cascade of events that resulted in this tragic flood,” said Byers, who has studied the Himalayas, Andes and many other ranges for more than three decades.
The scientific evidence for accelerating Himalayan change has strengthened over recent decades.
A March 2026 report by the International Centre for Integrated Mountain Development (ICIMOD) found that glaciers across the Hindu Kush Himalaya are rapidly shrinking, with ice loss accelerating since 2000.
Across 50 years of observations, about 89 per cent of recorded years showed negative glacier mass balance. The report said the decline is affecting water availability, increasing the risk of glacial-lake outburst floods and endangering the livelihoods of nearly 2 billion people dependent on the region’s river systems.
The Rasuwa disaster should therefore not be treated as an isolated event, Prakash said, but as a warning about exposure created by development decisions in climate-vulnerable terrain.
“The real failure sits upstream,” he said, pointing to settlements and infrastructure built on riverbanks and in hazard-prone areas, alongside global emissions that are accelerating glacier and snow loss.
Research has also highlighted the role of black carbon from fossil fuel combustion and biomass burning in warming Himalayan snow and ice.
A 2025 Climate Trends analysis reported rising black carbon concentrations in parts of the Indian Himalayas, where deposited particles darken snow, reduce its ability to reflect sunlight and accelerate surface heating.
Separate research published in Science Direct in January 2025 identified shrinking snow cover and degrading permafrost as major climate-change markers with consequences for river flows, landslides, erosion and high-altitude infrastructure.
For Prakash, the policy lesson is clear: early-warning systems remain vital, but they must be paired with climate resilient land use planning, infrastructure assessments that account for changing mountain conditions, emissions cuts and stronger regional monitoring.
“Until governments treat the Himalayas as a climate frontline rather than a postcard backdrop,” he said, “Rasuwa won’t be the last name we’re forced to memorise.”
From early warning to preparedness
The Nepal flood shows why Himalayan risk reduction cannot rely on early warning technology alone, according to Dr Farooq Azam, senior cryosphere specialist and intervention manager at ICIMOD. Sudden ice-rock and debris avalanches can unfold too quickly and begin too high or out of sight for conventional systems to provide a meaningful alert, he said.
“This was an unprecedented and unexpected disaster,” Azam said in the same statement released by GSCC. “There was simply no detection and no time to issue a warning. The event was a sudden-onset hazard that could not be captured by conventional warning systems.”
Early warning systems can still save lives where hazards provide enough lead time, including through changing water levels, rainfall forecasts or monitoring of known glacial lakes, he said. But identifying the likely failure point of an ice-rock avalanche is far more difficult. Breakpoints may lie beneath glaciers or bedrock and may not be visible through satellite imagery or from the ground.
That distinction is critical for Himalayan communities and infrastructure exposed to fast-moving, cascading hazards. Once an ice-rock avalanche begins, it can release large volumes of rock and ice within seconds, transform into a high-velocity debris flow and travel far downstream, carrying water, sediment and boulders in its path.
Research published in Nature in March said rapid glacier retreat, permafrost degradation and extreme precipitation can destabilise steep Himalayan slopes, while the avalanches themselves remain difficult to model and predict because their triggers and failure mechanisms vary widely.
The focus, Azam said, must therefore shift from warning devices alone to preparedness through stronger land-use planning, more resilient infrastructure and better public awareness of high altitude hazards.
“We need to reconsider how infrastructure is planned in the Himalayas,” he said. “Environmental impact assessments are routinely conducted before infrastructure is built but increasingly, there is a need to assess how changing environmental and mountain conditions could affect that infrastructure over its lifetime.”
