It is getting hotter on the roof of the world
Kunda Dixit
The Tibetan Plateau is heating up faster than the global average due to climate change, and scientists say this will ultimately reduce the flow of Asia’s mighty rivers originating there.
The plateau has an average elevation of 4,000m, is rimmed by the Himalaya, Karakoram, Pamir and Tien Shan mountain ranges, and is called the ‘Third Pole’ because it has the largest store of frozen water on the planet after the polar regions.
But the glaciers, snowfields and permanently frozen ground on the ‘roof of the world’ are thawing, making Tibet’s lakes bloat by 58.5 cubic km just in the past 40 years.
“The plateau is filling up like a goblet. Its cryosphere is already undergoing a catastrophic and irreversible ecological shift, and the current direction of climate change in the next 50 years will directly impact the region and the world,” warns Martin Mills of the Scottish Centre for Himalayan Research.
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Mills prepared a paper for the Scottish Parliament titled ‘Climate Change on the Third Pole’ that lays out the process and consequences of uncontrolled global heating on the plateau and regions downstream.
The Tibetan Plateau is a hot spot in more ways than one — besides the effect of the climate crisis, it is also a geopolitically sensitive region with territorial disputes that erupt into frequent border skirmishes. There is little cooperation between countries that share the Himalayan watershed to study and mitigate the impact of climate change.
The plateau is the source of the Indus and its tributaries that flow into the Arabian Sea, the Ganga and Yarlung Tsangpo (Brahmaputra) that flows down to the Bay of Bengal, the Burmese rivers, the Mekong and China’s Yellow and Yangtze Rivers.
When glaciers on the Tibetan Plateau and the Himalaya melt in spring, their waters keep the rivers flowing in the dry season. However, because of climate change there will be less and less ice to feed these rivers in future.
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The plateau is warming 2-4 times faster than the global average, and its impact is already being seen in shrinking glaciers and expanding lakes. While those changes are visible, there is also the hidden thawing of the permafrost — the ‘underground icebergs’ beneath the plateau. When the frozen ground melts, it destabilises mountain slopes, leading to destructive landslides.
“As snowfall turns into rain, the Tibetan Plateau is becoming progressively warmer and wetter,” Mills told the Dialogue for Our Future conference convened by the Dalai Lama in Dharamsala last week.
He said the impact of these changes in the next 50 years will include increased flooding south of the Himalaya, desertification of river headlands in Tibet, loss of fresh water sources to mountain communities, and damage to infrastructure from permafrost melting.xit
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The main driver for these changes is warming of the planet’s atmosphere because of fossil fuel burning, but that is exacerbated by the deposition of ‘black carbon’ pollution particulates that makes the ice lose its reflectivity and melt even faster.
The location and elevation of the Tibetan Plateau means there is a fragile balance in its water cycle — the accumulation of winter snow, melting ice in spring, and rain in the lower reaches during the monsoon. This process regulates water in the rivers so there is consistent flow through the year.
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More importantly, Himalayan glaciers keep rivers flowing in the dry season when water is needed most downstream. Nearly 20% of the annual flow of the Indus, for example, is glacier-fed, and it is 9% in the Ganga — but this is vital for agriculture and household because it comes down during the dry pre-monsoon months.
‘The mean temperatures on the Tibetan Plateau are increasing at between 0.28-0.61o Celsius per decade, and this will significantly destabilise its capacity to regulate water supplies across the year, undermining regional water security of the wider continental area,’ the Scottish Centre for Himalayan Research says in its report.
The report estimates that up to 1.4 billion people in northern India, Pakistan, south-east Asia, and 23% of the population of China depend on dry season meltwater from the Tibetan Plateau before the rainy season starts.
‘The thawing of the cryosphere on the Tibetan Plateau presents a fundamental threat to human carrying capacity in many parts of Asia … and the impact of these hydrological shifts will be most strongly felt in the upper sections of those rivers,’ the report warns.
Nepal’s main rivers mostly start from glaciers in southern Tibet, and their flow will also be impacted -- adding to the danger of trans-border glacial lake outburst floods.
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Climate change models suggest that dry season flow of Himalayan rivers will actually increase as ice from ever higher elevations begin to melt, but with the glaciers all but gone, it will eventually slow to a trickle.
Chinese scientists studying the plateau have estimated that the area under permafrost will be reduced by half between 2030-2050 if current warming trends continue. With the underground ice melting away, it is easier for surface water to seep into the soil rather than drain into rivers, further reducing dry season flow.
“We can foresee water scarcity leading to food insecurity in Asia, as well as increased flood risk during the monsoon,” Diana Liverman, a professor at the University of Arizona who was co-author of the IPCC’s Special Report on Global Warming of 1.5o C.
She told the Dharamsala conference: “The good news is that we have seen increasing action on adaptation, but there are limits to adaptation for people in countries that are dependent on glacier and snow melt.”
Experts at the conference said that this means there is no option but to take drastic steps to halve global carbon emissions by 2030, eliminate the use of coal, further expand the shift to renewable energy, and reduce consumption.
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