The Hindu Kush Himalayan (HKH) region, covering more than 4.2 million sq km, encompasses the highest mountain ranges in the world and contains the largest volume of ice on Earth outside of the polar regions, as well as large expanses of snow. This region is undergoing ‘catastrophic’ changes.
Scientists say the glaciers and snowpacks in HKH are melting and retreating in double quick time than the global average. It would have a devastating impact on millions of people considering HKH spans some 3,500 km in length from Afghanistan in the west to Myanmar in the east, and covering parts or all of Pakistan, India, China, Nepal, Bhutan and Bangladesh. It is home to unique cultures, highly diverse landscapes, and all of the world’s peaks above 7,000 metres.
The region hosts four global biodiversities and is an important source of water for 12 river basins, including 10 major (transboundary) rivers — the Amu Darya, Brahmaputra, Ganges, Indus, Irrawaddy, Mekong, Salween, Tarim, Yangtse, and Yellow (Huang He) – that flow through 16 countries in Asia and provide freshwater services to 240 million people living in the HKH region and 1.65 billion downstream.
As the UN Climate Conference (COP29) gets underway in Baku even as countries are indulging in hard negotiations to keep global warming within the reach of the Paris Agreement — with little success so far — The New Indian Express caught up with Miriam Jackson, Eurasia and Nordic Director of International Cryosphere Climate Initiative (ICCI). One of the world’s leading glaciologists who spent four years in Kathmandu, Nepal heading cryosphere work for the International Centre for Integrated Mountain Development (ICIMOD), Miriam gave a detailed insight into what is happening in HKH and why it is important for the world to take note of it. Excerpts:
You have co-authored State of the Cryosphere 2024, which was released during COP29. What is the scale of glacier and snow melt we are looking at? How fast is the HKH warming compared to other regions?
The glaciers of the HKH, particularly in the Eastern Himalayas, are experiencing alarming rates of melting. The loss is nearly 1 metre water equivalent (1 m w.e.) per year in the past decade. Glacier mass balance, a critical indicator of glacier health, has seen a 65% increase in mass loss, from –0.17 m w.e. per year in the 2000s to –0.28 m w.e. per year between 2010 and 2019. Projections for global warming scenarios are dire. At 1.5°C to 2°C warming, glaciers could lose 30% to 50% of their volume by 2100, rising to 55% to 75% at 3°C and 70% to 80% at 4°C.
Even the robust glaciers of West Kunlun and Karakoram are expected to shrink to half their current area under extreme warming. Snow cover is also declining, with a forecasted reduction of 1% to 26% under temperature increases between 1.1°C and 4°C. Although heavy snowfall events are becoming more frequent, their contribution to streamflow is projected to decrease across all climate scenarios. The HKH is warming at a faster rate than most regions, with a mean temperature rise of +0.28°C per decade since 1951, and localised increases of up to +0.66°C per decade in basins like the Tibetan Plateau and Brahmaputra. The HKH region as a whole is warming in double quick time compared to global average. The cryosphere (glaciers, snow and permafrost) changes are largely irreversible. The “water towers” of the HKH, critical for downstream regions, are some of the most vulnerable to these changes in the world.
The HKH region is prone to glacial lake outburst floods (GLOFs), which the report predicts may become more frequent. How many glacial lakes are marked as ‘vulnerable’ in the region? Can you explain what happened in Sikkim?
About 200 lakes have been identified as potentially dangerous. However, that doesn’t mean that other glacial lakes aren’t dangerous. Things can change fast, and the smaller lakes can also cause a lot of damage. For instance, the GLOF that hit Thamel in Nepal in August this year. In Sikkim, part of the moraine (loose material deposited previously by the glacier) collapsed into the glacial lake, probably due to permafrost thaw. This triggered the lake to flood causing extensive damage downstream.
The lake had been identified as dangerous, and previous attempts had been made to lower it. However, the urgency doesn’t seem to have been understood by the authorities.
Climate change is causing glaciers to shrink, which also causes glacial lakes to form, often at the side of the glacier or in front between the glacier and the moraine. As the glacier gets smaller, the lake usually gets bigger. There have been 311 GLOFs recorded in Afghanistan, Bhutan, Nepal, India, China and Pakistan in the past 200 years that caused 6,818 fatalities, and 243 in the past 100 years. In India, there have been 40 recorded GLOFs in the past 200 years and 6,119 fatalities.
Could you elaborate on how this glacier loss and snow retreat impact both highland and downstream water availability?
With accelerated glacier melt, ‘peak water’ will be reached around mid-century in most HKH river basins, and overall water availability is expected to decrease by the end of the century. At higher elevations, an increase is expected (more melt or more rainfall). However, the variability from basin to basin is large, and due to the large uncertainty in future precipitation projections, it is estimated that the future discharge remains low. More confident projections of precipitation, snow water equivalent, as well as both evaporative and subsurface fluxes will be crucial to improving our ability to accurately determine future water availability in the HKH.
In addition to glaciers, mountains also store water in the form of snow. In fact, seasonal freshwater in many mountain and lowland regions is dependent on annual snowfall, and meltwater from snow is of greater importance than meltwater from glaciers in many areas. However, snowfall has become less consistent in many mountain watersheds, with extremes of “snow drought” alternating with high amounts of snow, or wet snow, that increase the risks of avalanche and flood, such as in the Hindu Kush Himalaya in winter 2023-2024. In many mountains, it now appears that snow generally is following the same downward trajectory as glaciers. Snowfall is reducing as temperatures rise above freezing at higher altitudes, with precipitation that would have fallen as snow in past decades, increasingly coming down as rain, and often in the form of hazardous extreme rainfall.
As a result, seasonal snowpack will not form, which in turn will lead to loss of stored water in the snow and in underground aquifers. A decreasing extent and duration of snowpack has already been observed in many mountain areas.
The report highlights the need for a rapid shift to low-emission pathways to mitigate cryosphere loss. What immediate actions do you believe are most feasible for countries in the HKH region to prevent further glacier and snowpack loss?
Every fraction of a degree of global temperature rise substantially impacts the loss of the mountain cryosphere. New research reinforces the need for drastic emissions cuts. Due to warming to-date, mountain and downstream populations must be prepared for current steep losses to continue through at least mid-century. However, a sharp strengthening of climate action towards the 1.5°C limit will determine the future after that point. We need to preserve as much glacier ice, snow and the ecosystem services as possible to minimise the catastrophic events in the second half of this century. The next Nationally Determined Contributions (NDCs) due in February next year must commit to a credible 1.5°C goal. This requires course correction to a minimum of 40% reduction in human-induced GHG emissions by 2030, and stronger commitments and implementation of actions in the near-term 2030–2040 timeframe.
Considering the report’s emphasis on the irreversibility of permafrost thaw, what unique challenges does permafrost degradation pose for the HKH region, and what measures are in place to monitor and mitigate its impact?
In the Arctic, one of the main risks of permafrost thaw is increased methane emissions. This isn’t such a big problem in the HKH, except on the Tibetan plateau. However, there is significant infrastructure at high elevation, such as roads, trekking infrastructure, hydropower etc, as well as in valleys immediately below steep slopes with permafrost. As permafrost thaws, slopes can be destabilised and cause landslides — destroying lives and property. Landslides can also block rivers, thus forming a lake that can then subsequently burst in a flood.
The report discusses the compounding risks of ocean acidification and warming. Could similar risks affect high-altitude lakes in the HKH?
Not in the same way, but there could definitely be increased sedimentation, different chemistry in the water and the lakes may become smaller.
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Tough facts
Nearly all of these changes cannot be reversed on human timescales, and they will grow with each additional fraction of a degree of warming and CO2 concentrations in the atmosphere
Ten million people are currently at risk of catastrophic flooding hazard events from glacial lake outburst floods, especially in Alaska, High Mountain Asia, and Iceland. In Asia alone, the frequency of these events is expected to triple by the century’s end without substantial emission reductions
Under a high emissions scenario, two-thirds of Mount Everest’s famous East Rongbuk Glacier is projected to be lost by 2100. In addition to being an iconic part of the Asian water tower, East Rongbuk has climbing and cultural significance
Recent findings on ice retreat in the Eastern Himalayas show climate change directly links to glacier instability that drives cascading hazards