One of the most devastating effects of climate change in Asia is set to be rapid melting of glaciers in the Hindu Kush Himalayan (HKH) region, the source of 10 major rivers.
Temperatures are already rising faster in this vast mountainous zone than the global average, speeding up melting of glaciers that provide water for farmers, hydroelectric power plants and cities.
Rivers, including the Brahmaputra, Ganges, Indus and Mekong, are also critical for regional economies, and demand for water is growing as populations increase.
The HKH region covers all the high mountain chains of Central, South and Inner Asia and comprises thousands of glaciers, stretching from Afghanistan to Myanmar and including the Tibetan Plateau.
"This vast complex of high mountains produces one of the world's largest renewable supplies of freshwater. The Himalayan region has the largest reserves of water in the form of ice and snow outside the polar regions and that's why it is called the 'third pole'," said Dr Anjal Prakash, an associate professor at the regional water studies department of the Teri School of Advanced Studies in India.
About 250 million people live in this region and a further 1.65 billion people rely on its rivers.
The danger is that rapid melting would initially increase water flows in the next few decades. Meltwater feeding the rivers would then decline as the glaciers shrink. That could trigger unrest as nations clash over water supplies.
Dr Prakash said that even with the most ambitious goal of the 2015 Paris Agreement to limit warming to 1.5 deg C by the end of the century, temperatures in the HKH would rise 2.1 deg C and one-third of the region's glaciers would melt. If global climate efforts fail, current emissions would lead to warming of up to 5 deg C and the loss of two-thirds of the region's glaciers by 2100.
Worse, computer models also project higher rainfall in the region if temperatures rise sharply. This would lead to significant losses in glacier volume, from 36 per cent to 64 per cent, depending on the warming scenario, said Dr Prakash, a coordinating lead author of the Intergovernmental Panel on Climate Change special report.
He said nations reliant on HKH waters urgently need increased coordination and management of the region's water resources.
The rivers are the economic engines of the region. What happens to them will directly affect more than half of Asia's population, he said.