The Hindukush-Himalaya region, which holds the largest concentration of snow and ice outside the polar regions, is undergoing considerable cryospheric changes driven by rising temperatures, a new review paper says. Published in the journal Earth-Science Reviews, the review assessed 145 studies in the region’s cryosphere, finding that warming is resulting in more floods, increased peak flow in rivers, and frequent avalanches.
The region, which covers Tajikistan, Afghanistan, Pakistan, India, Nepal, China, Bhutan, and Myanmar, has warmed by 0.2–0.3°C per decade between 1980 and 2020, approximately twice the global average rate. However, these changes are not uniform. The central and eastern Himalaya lost close to 30% of snow cover between 1990 and 2020, causing altitudinal vegetation shifts of 8 to 20 metres annually. The Karakoram range, on the other hand, showed relative stability, which is “attributed to the westerly-driven winter precipitation and a coincident summer cooling effect,” which partially off-sets glacier loss, says the study — a phenomenon known as the ‘Karakoram anomaly.’
Seen across a 40 year timescale, almost no part of the Hindukush-Himalaya region has been left untouched by rising temperatures. Even as this holds true, the eastern Himalayas remain particularly underrepresented in academic research. Despite being the most vulnerable to glacier melt, studies into glacial lake expansion and Glacial Lake Outburst Floods (GLOFs) “are rare in the Eastern Himalaya, particularly in Bhutan and Arunachal,” the study says.
Glacial lakes have nearly doubled from 1,160 to 2,168 in the central Himalaya between 1977 and 2010. This expansion also increases the risk of GLOFs, which can have catastrophic downstream impacts. The study also notes that 681 avalanche incidents between 1982 and 2022 resulted in over 3,100 deaths, with frequency rising after 2010.
Snow and glacier melt currently contribute between 33 and 42% of annual river flow in major basins, supporting hundreds of millions of people downstream. Projections suggest peak runoff will occur around 2050 in most basins, after which meltwater contributions are expected to decline, impacting hydropower generation and raising longer-term questions about water availability. The Yarkand and Hotan basins in western China have already achieved peak flow, says the study.
Covering approximately one million square kilometres in the region, permafrost is degrading at rates that are destabilising slopes and affecting high-altitude infrastructure in the Tibetan Plateau. Active layer thickness, the uppermost layer of permafrost affected soils, is increasing by 2–23 cm annually in some areas.
Using satellite imagery and geospatial technologies to monitor changes in hard-to-reach regions can be revolutionary, says the study, particularly for the Siachen glaciers in Karakoram, Chhota Shigri, Langtang, Gurudongmar, Gomukh in the Himalaya, Chitral in Hindukush, and Wakhan in Pamir, which are not adequately monitored.
The integration of indigenous knowledge, improved transboundary cooperation, and high-resolution monitoring are highlighted as priorities for more effective adaptation planning. “Transboundary co-operation is the need of the hour. Joint monitoring frameworks, multi- lateral disaster frameworks, and data sharing protocols are essential to develop,” it says.
Banner image: The Hindu Kush mountains seen from Pakistan. Image by Ninara via Wikimedia Commons (CC BY 2.0).