里程碑报告：喜马拉雅冰川消融速度是此前的两倍半

20 June 2023

Building on the 2019 Hindu Kush Himalaya (HKH) assessment report, a major study from the International Centre for Integrated Mountain Development (ICIMOD) provides the most complete assessment of snow, ice, and permafrost in the Himalayas to date. The report draws on recent scientific advances to map the extensive links between cryosphere, water, ecosystems, and society in the HKH region.

ICIMOD finds that 70-80% of current glacier volume in this region will disappear by 2100 under a high emission scenario, but keeping the global temperature average to 1.5°C could limit glacier loss to 30%, and also help preserve the region’s essential snow cover. Snowmelt provides freshwater for major rivers such as the Amu Darya (supporting up to 79% of its flow), the Indus (40%), and Helmand (77%). Over 120 million farmers in the Indus, Ganges and Brahmaputra basins depend on this snowmelt for their livelihoods.

Even with very low emissions and 1.5°C however, the HKH will face serious impacts in terms of species loss, ecosystem structure and productivity. HKH ecosystem services directly support 240 million people in the high altitude regions, and aid a further 1.65 billion people downstream. Species decline and extinction has already been observed at today’s temperatures, and further habitat degradation will dramatically increase as glaciers retreat, snow melts and permafrost thaws.

The HKH has warmed by +0.28°C on average per decade since the 1950s, rendering it highly vulnerable to rapid ice loss, with irreversible changes occurring to downstream water supplies as temperatures rise. Melting glaciers also increase the risk of hazards such as glacial lake outburst floods (GLOFs) and landslides, both of which are projected to increase over coming decades. 200 glacier lakes across the HKH region currently pose a dangerous risk to downstream communities, and researchers anticipate that the risk of GLOFs could spike by the end of the century unless rapid and far-reaching emissions reductions keep peak temperatures close to 1.5°C, a hard adaptation limit for millions of people across Asia.

Two billion people living within these mountains and downstream river valleys depend on melting ice and snow for freshwater resources, and the availability of this water is expected to peak mid-century and then decline as rising temperatures shrink both glaciers and snowpack. Cryosphere plays an essential role in the livelihoods, agriculture, hydropower and infrastructure underpinning societies across the Hindu Kush Himalaya. The report makes clear that urgent policy action is needed to enhance adaption measures, support those already affected by cryosphere loss; and not least, mitigate global emissions to uphold 1.5°C as a guardrail for the billions reliant on the HKH region.

https://hkh.icimod.org/hi-wise/hi-wise-report/