Since 2006 the railway line across the Tibetan plateau has been carrying passengers and freight across a landscape of snow-covered peaks and tundra, antelopes and wolves. China celebrates it as one of the nation’s greatest technological feats. But some experts worry that global warming may render it useless.
The impact of warming can be seen on a road that runs parallel to the line for much of its length. Trucks bump along its cracked and undulating surface, which is being ravaged by the freezing and thawing of the tundra beneath. Since the highway was built in the 1950s, the permafrost area has been shrinking and the layer above it, which is subject to seasonal thaw, has been getting deeper. The railway is vulnerable to the same process.
The vast and sparsely populated Tibetan plateau is the origin of the great river systems of China, South-East and South Asia: the Yangzi and Yellow Rivers, the Brahmaputra, the Indus, the Mekong and the Salween. The Ganges rises on the Indian side of the plateau’s Himalayan rim. These rivers, fed by thousands of Himalayan glaciers, are an ecological miracle. They support some 1.3 billion people.
But the glaciers are retreating. Chinese experts predict that by 2050 the icy area on their side of the Himalayas will have shrunk by more than a quarter since 1950. Predictions for the Indian side are gloomier still. In April a leading Indian glaciologist, Professor Syed Iqbal Hasnain, measured the East Rathong glacier in lofty Sikkim state. It appeared to have shrunk by 2.5km, or half its length, in a decade.
The average global temperature increase of 0.6°C in a century seems an insufficient explanation; but that may combine with a 3km-thick fug of pollution, known as Asian Brown Cloud, that hangs over northern India. Scientists think this haze, which is created by power stations and cooking-fires, may be radiating heat into the lower troposphere, at altitudes in which glaciers are found. Mr Hasnain estimates that Himalayan glaciers will be gone in 20-30 years. That would leave many great rivers depending on seasonal rainfall. According to the Intergovernmental Panel on Climate Change (IPCC), this may be the fate of the Indus, Ganges and Brahmaputra by 2035. Making matters worse, changes to the weather may meanwhile make the rains less reliable.
North India has two main weather systems. In the summer, south-westerly monsoonal winds reach northern
India, in an explosion of heat-busting rain,