Last year, two important studies revealed the full extent of the threat that climate change poses to the Himalaya. The first was an assessment report of the state of the Hindu Kush Himalaya (HKH) region by the Kathmandu-based International Centre for Integrated Mountain Development (ICIMOD). According to the study, the region is profoundly at risk from global heating. It’s conclusions were stark: the HKH has lost 15% of its glaciers since 1970, and as much as 90% of it may be gone by 2100; increasing melt will lead to widespread downstream flooding in the region's 10 major river basins (including the Ganga, the Brahmaputra and the Indus) followed by extreme water stress as the glaciers pass peak melt. This would invariably lead to migration and conflict. It also found that winter snowfall is decreasing and the number of winter days is also shrinking. The number of warm nights is increasing, at 1.7 nights every decade.
This was followed by the UN Intergovernmental Panel on Climate Change’s (IPCC) Special Report On The Ocean And Cryosphere In A Changing Climate (SROCC), which arrived at much the same conclusions as the earlier report. The SROCC stated that glaciated mountain systems—and especially the HKH— could exhaust most of their water by 2050. The climate change assessment report released by India's Ministry of Earth Sciences (MoES) earlier this year made the same points. It also said that the Himalaya would see a 2.4 degree Celsius warming by 2100. In a business-as-usual scenario, the Himalaya would warm by 4.6 degrees Celsius.
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These are nightmare scenarios, and given the fact that most reports are cautious when making projections, it wouldn’t be surprising if the situation is actually worse. And new details are emerging all the time. For instance, earlier in November, a new study published in Nature Climate Change revealed how wind-blown dust is accelerating Himalayan snow melt. The report, Dust Dominates High-Altitude Snow Darkening And Melt Over High-Mountain Asia, is the result of a collaboration between researchers from five international institutions (including IIT Madras). It notes that dust blowing in from Africa and Asia in spring and summer is darkening Himalayan snow, reducing its reflectivity and increasing the melt. This is especially a problem at higher altitudes of 4,500m.
The researchers have used data from remote sensing satellites and computer simulations for their findings. The report says that although dust is natural, there’s more of it in the air due to changes in land-use patterns. On the other hand, due to increasing temperatures, the circulation patterns of dust in the atmosphere have also changed. While it’s a relatively well known fact that black carbon from atmospheric pollution has a similar effect on Himalayan snow, the report states that the influence of dust on snow-darkening is even more of a problem at altitudes of above 4,000m. “Due to global warming, snow cover at lower elevations will occur less frequently or totally disappear compared with snow cover at higher elevations in HMA (High-Mountain Asia),” the report states.
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FIRST PUBLISHED05.11.2020 | 10:03 AM IST
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