United Nations experts have warned that the deadly flood in northern India, sparked by a cratering glacier, was not an isolated incident but the result of a rapidly warming planet. They warn the disaster, which has left many feared dead, is a precursor of what is to come unless drastic measures are taken to slow climate change.

The flood in the Indian Himalayan state of Uttarakhand was caused by a glacier breaking away and falling into the valley, sending a surge of water downstream that engulfed villages. Floodwaters submerged the Rishi Ganga hydroelectric project at around 3700 metres above sea level, washed it away completely and severely damaged a 520-megawatt dam under construction. The sudden flood tore through the valley, killing dozens of people and trapping hundreds more in construction tunnels.

Data suggests that, in the coming years, global warming will cause mountain temperatures to rise twice as fast as the global average, whittling away glaciers and threatening communities in the Himalayas, and further afield.  

“Glaciers around the world are under siege,” said Matthias Jurek, a mountain ecosystem expert with the United Nations Environment Programme (UNEP). “Unless we can limit global warming, support monitoring, early warning and adaptation measures, disasters like the one in Uttarakhand will, unfortunately, become more common.”

As a Carbon Brief factcheck points out, initial reports suggested that a “glacial lake outburst flood” was a possible cause of the event. Glacial lakes form behind natural dams created by debris collected at the front of glaciers and then left behind as glacier fronts retreat. An earlier Carbon Brief had explained that thousands of such lakes around the world are expanding as glaciers melt in response to rising temperatures. If the natural dam breaks, glacial lakes can cause potentially catastrophic outburst floods.

A recent study published in Scientific Reports, had just reported that the “retreat of glaciers in the HMA [high mountains of Asia] of 20 years appears to be associated with more frequent landslides, and larger landslides…If climate warming continues, the area of glaciers will further decrease.”

In regions like the Himalaya, the problem of rising temperatures is three-fold: it leads to the melting of mountain glaciers, which can spark floods. It also decreases glacial coverage, which leads to a reduction in the long-term availability of water for people, agriculture, and hydropower. Finally, as glacier cover diminishes and the area is replaced by water or land, the albedo – the amount of light that is reflected without being absorbed on a surface – also decreases. This could increase solar energy absorbed, leading to more warming.

UNEP experts state that glaciers are often referred to as the “water towers” of the world, with half of humanity depending on mountains for their water needs. The Tibetan Plateau alone is the source of 10 of Asia’s biggest rivers and provides water to 1.35 billion people, or 20 per cent of the world’s population. In the Paris Agreement, Member States committed to limit global temperature increases to well below 2°C, and preferably to 1.5°C, compared to pre-industrial levels. Slowing global warming would help save glaciers, but countries must also prepare mountain ecosystems for an inevitable increase in temperatures. The best way is through adaptation, in other words, introduce a change into the ecosystem that will help combat the impact of global warming.

The World Glacier Monitoring Service, a Switzerland-based organization that works closely with UNEP, monitors global glacial change. In the 1960s, its data showed, glaciers were largely in a steady state but since the 1970s glacial loss has increased rapidly, almost doubling every decade until present. They note that this ice loss “leaves no doubt about ongoing climate change.”

“Our ecosystem-based adaptation projects are restoring forests and shrubs on mountain slopes, which helps prevent both floods and landslides by holding the soil together and regulating the flow of surface water run-off,” said Jessica Troni, Head of the Climate Change Adaptation Unit at UNEP in a press release.

UNEP states that while ecosystem-based adaptation projects cannot stop glaciers from melting, they can significantly reduce the disastrous impacts. Further, they can help mountain communities to adapt to a warmer climate, for example by promoting drought-resistant crops.

And, it is not just melting glaciers that cause landslides and floods in mountainous regions. In Nepal, for example, increased monsoon rainfall and a decrease in winter rain, a result of climate change, has led to crop losses due to droughts and floods, placing communities at risk from food insecurity.