Wen Xu recalls first climbing Muztagh Ata in Kashgar prefecture, Xinjiang, back in 2004. “The snow was thigh deep and we had to use snowshoes to spread our weight. Snow bridges allowed us to cross crevasses.”
The scientist and explorer has now made the trip a dozen times, to collect ice cores and bear witness to the impacts of the climate crisis. “That thick snow is now a mix of hard snow and bare ice,” he says. “We need crampons to get around up there now. The snow bridges have gradually disappeared, while the crevasses have got wider and deeper, forcing us to make long diversions to avoid them.”
Glacier melt has been accelerating in this arid north-west part of China in recent years. By 2050, glaciers smaller than half a square kilometre will disappear here, according to the latest research from the Chinese Academy of Sciences’ Tianshan Glaciological Station. That is under any climate change scenario, and taking into account possible increases in precipitation.
Experts interviewed by Dialogue Earth say glacial melt is an important symbol of global warming. Smaller glaciers may be doomed no matter what we do, but they become alert beacons for climate action as they diminish. The only effective solution to global glacier loss is rapid cuts in greenhouse gas emissions, the experts say.
Meanwhile, Unesco has proclaimed 2025 the International Year of Glaciers’ Preservation, with 21 March to become annual World Glacier Day.
What happens when a mountain glacier melts?
China’s glaciers are mostly to be found on the Qinghai-Tibet Plateau. By their seasonal melt, they feed rivers including the Yangtze, Yellow, and Yarlung Tsangpo (which flows on to become the Brahmaputra). Surveys show that between the 1970s and 2010, a fifth of China’s total glacial area melted permanently, meaning 12,442 square kilometres of glacier loss.
Dialogue Earth consulted Tian Lide, a researcher at Yunnan University’s Institute of International Rivers and Eco-security. “When we talk about glaciers melting, people think that means rising sea levels,” he said. “But that’s a risk primarily from ice caps melting in Antarctica, where 90% of the world’s ice is found, and Greenland, second in terms of ice volume.”
Mountain glaciers have nevertheless been melting with surprising speed, and with a more direct impact on human activity, Tian explains. The melt causes more water to flow, with ice dams forming at the ends of the glacier. When those dams collapse in a glacial lake outburst flood (GLOF), there can be catastrophic consequences for those living and farming downstream.
A glacial lake outburst flood is a sudden release of water from a lake formed by mountain glacier meltwater, which had been held back by ice or a moraine (rocks and sediment carried along by the glacier). These floods can be prompted by an earthquake, avalanche or the accumulation of too much meltwater. GLOFs are often extremely destructive, and a growing threat in the Himalayan watershed.
Melting mountain glaciers can also trigger dangerous ice avalanches. In July 2016, a collapse in the Ngari prefecture of western Tibet caused 600 million cubic metres of glacier to fail. Nine people from local herding families who were grazing their livestock on summer pastures were killed.
A much less obvious result of this glacial melt is methane. Between May 2022 and July 2023, a team of Chinese researchers analysed gas taken from the ice caves and meltwaters of the Laohugou No. 12 glacier – the largest valley glacier on the Qinghai-Tibet Plateau’s Qilian Mountains. Their study found that methane levels were two to three times higher than atmospheric background levels. Conversely, CO2 levels were about 2.5 times lower. This may be because the fine sediment scraped from glaciers is rich in minerals. As the sediment mixes with meltwater and atmospheric gas, it undergoes “chemical weathering” which induces CO2 absorption.
However, across a 100-year period, methane’s global warming potential is 28 times that of CO2, rising to 84 across 20 years. The methane levels at the Laohuguou No. 12 glacier prompted a headline in The Paper saying “Melting mountain glaciers are pumping greenhouse gases into the atmosphere like chimneys.”
Early warnings
The results of a seven-year scientific survey of the Qinghai-Tibet Plateau, involving a 28,000-strong expedition team, were published in August last year. They concluded that the region is getting warmer, wetter and greener. It is also getting darker. As glaciers and snow melts, and vegetation spreads, the land becomes less reflective and absorbs yet more heat.
Adequate management of downstream rivers requires more accurate and timely warnings of disasters like ice avalanches and glacial lake failures, the survey found.
Early warning is currently the best way to reduce the damage of these disasters. When an ice avalanche blocked the flow of the Yarlung Tsangpo River in 2018, scientists were able to keep a close eye on the situation with sensors and from helicopters to ensure local people were moved away from the danger. The blockage was eased 56 hours later when the water overcame it, with no loss of life.
The following year, China devised a way to monitor such blockages on the Yarlung Tsangpo. Ten-metre-high monitoring towers were installed at vulnerable sites to provide regular observations in all weathers. Real-time monitoring of water levels also began. As of May 2024, five early warnings had been issued.
Glaciers and water security
The Taklamakan is China’s largest desert. Yet in August 2024, this north-western expanse flooded. Lü Xinsheng, chief forecaster at the Xinjiang Meteorological Bureau, told media that high temperatures are rapidly melting the snowpack and glaciers surrounding the desert. The tributaries of the Tarim River swelled and the river eventually burst its banks, turning parts of the Taklamakan into temporary inland seas.
This is not the first time the Taklamakan has flooded. In August 2022, a lake appeared in the southern portion of the desert, causing some people online to speculate incorrectly that climate change could turn the desert into something like an oasis. Chen Yaning, of the Chinese Academy of Sciences’ Xinjiang Ecology and Geography Institute, says: “Changes to glaciers and the hydrological cycle caused by the climate will increase the uncertainty of water supplies, while glacial melting will impact on future water security in the area.”
The aforementioned Chinese Academy of Sciences’ Tianshan research reaches a similar conclusion. Faster melting will increase the flow of water through rivers, to a point. But once these flows have peaked, they will go into a steady decline.
“Many are worried that their sources of water will dry up once the glaciers are gone,” says Tian Lide. “It depends on the river, though. Glacial and snow melt accounts for almost 80% of the water flowing into the Indus [River]. But glacial meltwater from the Sanjiangyuan (Three River Source) region accounts for 9.13% of the flow of the Yangtze, and 2.24% of the Yellow River’s flow. In many cases, glacial melt accounts for only a small part of a river’s total flow – most of the water comes directly from precipitation.”
Tian explains how precipitation and glacial meltwaters contribute to rivers in different ways: heavy rainfall will quickly increase river levels and may cause floods, but levels will fall equally quickly when rains ease; glaciers are a more stable source of water because they melt steadily, thus providing a sustained water source for those living downstream.
Glacial melt also plays a big role in regulating seasonal changes. In the cold of winter, glaciers grow. As temperature rise in summer, they release more water, providing a steady source of water when it is needed most. That function will weaken as glaciers diminish, meaning droughts and floods could become more frequent and intense.
What can be done?
Scientists have tried a number of methods to slow glacial melt.
In 2023 and 2024, Chinese scientists attempted to “wrap up” the Tianshan No. 1 glacier. This involved laying insulating and reflective materials (often textiles) on the glacier’s surface to keep it cool and slow the melting.
Similar techniques have been used since the early 2000s to protect glaciers in the Alps. Research has found that wrapping can reduce snow and ice melting by 50-70%.
Commenting for a 2023 Scientific American article, glaciologist Matthais Huss from the University of Fribourg said the textiles approach is only worthwhile in lucrative ski areas. It is not feasible to cover the world’s glaciers in this way. Huss calculated that covering Switzerland’s 1,000 largest glaciers could prevent two thirds of the volume of ice lost every year, but would cost USD 1.52 billion annually.
In September, a Chinese Academy of Sciences research team took a snow-making machine to the Dagu Glacier in Sichuan, central China. The team aimed to turn Dagu’s meltwater back into snow and thereby slow its shrinkage. The outcomes of the intervention remain unclear. But Tian tells Dialogue Earth that, regardless, such methods are only currently suitable for glaciers of value to, for example, science or tourism. They cannot reverse the overall global trend of glacial loss. He says the only way to do that is by rapid cuts in greenhouse gas emissions.
A 2022 Unesco report agrees. In the long term, its authors say, a third of the glaciers across Unesco’s World Heritage glacierised sites will disappear by 2050, regardless of any measures taken. If global warming can be limited to 1.5C relative to pre-industrial levels, it adds, there is hope that the remaining two-thirds could be saved.
Priceless ice
Alongside their efforts to slow melting, Yunnan University glaciologists are racing to collect ice cores from the Qinghai-Tibet Plateau. Such material could yield potentially vital climate data. For example, analysis of air bubbles trapped in the ice can enable scientists to infer historical temperatures and greenhouse gas concentrations.
Many countries are preserving ice cores taken from polar or mountain glaciers in cold stores at research institutions or universities. But risks remain. In 2017, a freezer failure at the University of Alberta in Canada damaged part of the world’s largest collection of ice core samples from the Canadian Arctic. Some scientists have come up with a safer way of storing these samples: a vault has been built in Antarctica, where ice cores can be stored, hopefully, forever.
Wen Xu explains that current technology only allows limited data to be extracted from ice cores. With the glaciers still melting, future researchers may not be able to obtain ice cores themselves. The stored cores, however, will be available and could be studied using advanced techniques not yet developed. “These will be valuable research materials for future study,” he says.
