How difficult is it to predict glacial disasters?

A geological disaster that recently struck along the China-Nepal border has once again drawn attention to glaciers.

Glaciers are often seen as "victims" of global warming. But glacier retreat, permafrost degradation and the expansion of glacial lakes, combined with extreme weather and complex geological conditions, may also increase the risks of ice avalanches, glacial lake outbursts, landslides and debris flows.

As monitoring and early warning technologies for extreme weather and climate events continue to advance, can glaciers in remote, high-altitude areas be monitored and warnings issued before disasters occur? CGTN interviewed Zhang Dongqi, a research scientist at the Institute of Global Change and Polar Meteorology, Chinese Academy of Meteorological Sciences, and Ma Lijuan, a research scientist with the Division of Climate Change Monitoring and Projection, National Climate Center, about glacial disasters, climate change, monitoring and early warning.

CGTN: We often think of glaciers as victims of climate change. Are we now also seeing glaciers becoming sources of hazard? Are ice-rock avalanches and other glacier-related hazards becoming more frequent or more severe?

Zhang Dongqi: Glacial disasters have always existed. They occurred less frequently during periods of stable climate and consequently attracted less attention. Against the backdrop of global warming, glacial disasters are becoming more frequent, causing greater losses and drawing increasing attention. Analysis of the past several decades, or even the past 10 to 20 years, shows that ice-rock avalanches and other glacier-related disasters have indeed been increasing in frequency, and their severity is also increasing. Both factors are at play. Global warming has led to a higher incidence of cryospheric disasters in recent decades. The expansion of human activity, advances in satellite remote sensing and other monitoring methods have also enabled us to detect more disasters in remote areas, including some that did not cause casualties in the past but left clear traces.

Ma Lijuan: Against the backdrop of a warming climate, glaciers in High Mountain Asia, with the Qinghai-Xizang Plateau as the core region, have been retreating and losing mass, while permafrost has been degrading and snow cover has been decreasing, with these trends intensifying since the 1990s. This has led to glacier instability and increases in the number and area of glacial lakes. Cryosphere-related disasters, such as ice and snow avalanches, glacial lake outbursts, glacier-related debris flows and snowmelt floods have occurred more frequently. Studies show that glacier collapse events have increased since at least 1950, while the number of thermokarst ponds and the occurrence of permafrost retrogressive thaw slump have increased since the 1970s. Since 2015, abrupt cryosphere events have been continuously observed across large areas of High Mountain Asia.

China has completed three glacier inventories: the first covering 1978-2002, the second covering 2008-2015 and the third covering 2023-2026. A comprehensive assessment shows that the area of glaciers on the Qinghai-Xizang Plateau declined from 51,000 square kilometers to 44,000 square kilometers and then to 39,000 square kilometers over the past 60 years. According to the second comprehensive scientific expedition to the Qinghai-Xizang Plateau, both the number and area of glacial lakes on the plateau increased by more than 20% from 1990 to 2020.

CGTN: How does a warming climate change the physical conditions that keep glaciers and mountain slopes stable? Can we say that climate change increases the risk of glacier collapse, even if we cannot say it directly caused this particular event?

Ma: Temperature, precipitation and topography are the three necessary conditions for glacier formation and development. Since the 1960s, the Qinghai-Xizang Plateau and surrounding areas have warmed significantly, with the rate of warming clearly higher than the global average over the same period. High-temperature events have become more frequent, while annual precipitation has also fluctuated upward, with greater extremes. Climate warming has accelerated glacier mass loss, increased glacier movement and reduced the stability of their internal structures, providing dynamic conditions for glacier surges and ice avalanches.

Meanwhile, glacier meltwater has increased the number of glacial lakes and rapidly expanded their area. Combined with extreme temperatures, extreme precipitation and loose geological conditions, this has contributed to the increased frequency of glacial lake outburst disasters.

Based on information from investigations so far, the event (on August 26) was triggered first by an ice-rock avalanche. The site is located in an area of maritime glaciers on the southern slope of the central Himalayas. Under the long-term influence of climate warming, glacier ice temperatures have risen and glacier flow has accelerated, while the internal structure of the glaciers has gradually become less stable and mountain slopes have become increasingly fractured.

Climate change is an important long-term risk factor for glacier melting. The direct cause of this event was geological environmental changes resulting from glacier instability.

CGTN: Can we predict when a glacier or ice mass is likely to collapse? What signs should scientists be looking for before a major collapse?

Zhang: If enough monitoring equipment is deployed and the data can be analyzed in a timely manner, we can basically predict whether a glacier has the potential to collapse, but predicting the exact timing of a collapse is very difficult. At present, glaciers are mostly located in remote, high-altitude areas where monitoring is inadequate, making it very difficult to predict ice avalanches. Signals from multiple aspects, including geological and meteorological factors, need to be monitored, such as whether an earthquake has occurred in the area where the glacier is located, whether there has been sustained or sharp warming recently, and whether there has been prolonged or extreme precipitation. In addition, where monitoring conditions permit, signals such as stress and deformation within the glacier itself require particular attention.

Ma: Mountain glaciers are distributed in cold, high-altitude regions, where systematic field observations are difficult to conduct on a regular basis, resulting in relatively limit first-hand observational data. The continued development of advanced observation technologies is creating new opportunities for routine monitoring. However, establishing a comprehensive early warning system remains a long-term challenge. It is necessary, in light of the complex terrain of the Qinghai-Xizang Plateau and the characteristics of typical glacial disasters, to build a coordinated Earth system observation network, with a focus on strengthening dynamic monitoring of high-risk glaciers and glacial lake areas. At the same time, research into the disaster-causing mechanisms of typical glacial disasters should be deepened, a comprehensive early warning indicator system established, and future trends assessed and anticipated, so as to scientifically prevent and proactively respond to the impacts and disaster risks posed by changes in high-altitude glaciers.

Recent disaster events show that glacial disasters often result from a complex chain of interacting factors, including earthquakes loosening mountain slopes, glacier retreat, permafrost thaw, fractured geological conditions, prolonged heat or precipitation, and extreme weather and climate conditions. These factors can become coupled over long periods, triggering large-scale cascading disasters. All of these factors should be incorporated into an effective monitoring and early warning system for routine monitoring.

CGTN: What can satellites and other monitoring technologies tell us about an unstable glacier or mountain slope? How much warning time could an effective monitoring system realistically give communities downstream?

Zhang: Before a disaster occurs, technologies such as remote sensing and field monitoring can provide information on whether a glacier is potentially unstable and the degree of danger it poses. After a disaster occurs, these technologies can provide information on its location, extent and impact. Different types of disasters allow for very different warning times. When a monitoring system is fully functional and operating effectively, the warning time for a glacial lake outburst may be measured in days. But ice avalanches and snow avalanches are extremely difficult to warn for, and the warning time may be much shorter, potentially on the order of minutes.

CGTN: What are the biggest gaps in our current early-warning systems?

Zhang: Inadequate monitoring – including limited monitoring coverage that cannot cover all high-risk glaciers, and limited monitoring methods that rely mainly on satellite remote sensing data while lacking field monitoring data – is currently the biggest weakness in the early warning system for glacial disasters. It is recommended that a multi-layered "air-space-ground" three-dimensional observation and sensing system be developed to improve the rapid detection and precise identification of disasters and provide solid support for early warning.

Ma: The United Nations' Early Warnings for All initiative identifies four key elements of an early-warning system: disaster risk knowledge, monitoring and forecasting, warning dissemination and communication, and preparedness and response. For glacier-related hazards, all four areas remain underdeveloped, and there is an urgent need to establish an integrated monitoring and forecasting system.