In August, 2024, several homes in Thame village in Nepal’s Namche region were swept away in a flood caused by a glacial lake bursting its banks. An estimated 135 of the village’s 370 residents were displaced.
As global temperatures rise with climate change, there is increasing danger of more such glacial lake outburst floods, warned scientists at the International Centre for Integrated Mountain Development who monitored the Thyangbo lake using satellite imagery.
It isn’t just the residents of the Himalayas who are vulnerable to such disasters. Global warming is accelerating glacier melt, decreasing snow cover, increasing permafrost thaw and prompting more extreme rainfall events and natural hazards, according to Mountains and Glaciers: Water Towers, the United Nations World Water Development Report 2025 released on March 21. Nearly 2 billion people depend on glaciers, snow and mountain runoff for water for drinking, washing, and agriculture.
To draw attention to the challenge, the United Nations General Assembly has designated 2025 as the International Year of Glaciers’ Preservation. March 21 every year will be marked as the World Day for Glaciers.
On the frontlines
At a press conference ahead of the release of the United Nations report, French glaciologist Heidi Sevestre described the plight of those on the frontlines of climate change by narrating a story about a yak herder whom she met in 2010 in a Nepalese village off the main trekking trail to Everest Base Camp.
He had been out attending a wedding, a three-day walk away and fell asleep in his home after returning late in the night. In the morning, he could barely recognise his village: in his absence, a massive glacial lake outburst flood had wrecked the valley in 1985.
Glacial lakes are formed as the result of retreating glaciers. For many of them, a portion of a glacier moraine acts as a dam. If that wall gives way, massive floods could result.
The United Nations report noted that glaciers in the Hindu Kush Himalaya region and the Hengduan, Tien Shan and Qilian mountains are disappearing at an alarming rate: 65% faster in 2011-2020 than in the previous decade. They are melting faster than the global average.
Yet of the 50,000 glaciers in the Hindu Kush region, only 28 are monitored, said Abou Amani, director of the division of water sciences and secretary of the intergovernmental hydrological programme at Unesco.
This region encompasses 5 million sq km of high mountains, with 100,000 sq km of glaciers. Often referred to as the Third Pole or the water tower of Asia, it stores more ice and snow than any other region outside the Antarctic and Arctic. The Third Pole is the origin of more than ten river systems that sustain nearly 2 billion people in several parts of Asia.
Early warning systems
Amani called for urgent action to study more glaciers and set up early warning systems in risk-prone areas. Residents need to understand that their daily lives are affected by the melting glacier, he said, and to understand the connection between glaciers and climate change. However, finding funding for data collection, monitoring and early warning systems is a gigantic challenge, he said.
There are more than 25,000 glacial lakes in the Hindu Kush Himalaya region, of which 47 potentially dangerous glacial lakes lie within the Koshi, Gandaki, and Karnali river basins of Nepal, the Tibet Autonomous Region of China, and India, said the International Centre for Integrated Mountain Development .
This region is a global hotspot for risk from glacial lake outburst floods: approximately one million people live within 10 km of a glacial lake, according to the report.
More dire news came from the World Meteorological Organization’s State of the Global Climate 2024 report, which confirmed that the years from 2022 to 2024 witnessed the largest three-year loss of glaciers on record.
The organisation said that the World Glacier Monitoring Service estimates that glaciers (separate from the continental ice sheets in Greenland and Antarctica) have lost a total of more than 9,000 billion tons since records began in 1975.
“This is equivalent to a huge ice block the size of Germany with a thickness of 25 meters, said Michael Zemp, the Director of the Service. The 2024 hydrological year marked the third year in a row in which all 19 glacier regions experienced a net mass loss.
A study in Nature found that from 2000 to 2023, the global glacier mass loss totalled 6,542 billion tons – or 273 billion tons of ice lost per year. This amounts to the amount of water the entire global population currently consumes in 30 years, assuming three litres per person per day.
Importantly, glaciers are currently the second-largest contributor to global sea-level rise, after the warming of the ocean. Between 2000 and 2023, glacier melt contributed 18 mm to global sea-level rise. Even this small rise has a huge impact as “every millimetre sea-level rise exposes an additional 200,000 to 300,000 people to annual flooding”, said Zemp.
The World Meteorological Organization said in a press release that the first-ever World Day for Glaciers on March 21 will sound the alarm that accelerating glacier melt risks unleashing an avalanche of cascading impacts on economies, ecosystems and communities at a global level.
Meena Menon is visiting postdoctoral fellow at the Leeds Arts and Humanities Research Institute, University of Leeds.
