The Tibetan plateau gets a lot less attention than the Arctic or Antarctic, but after them it is Earth's largest store of ice. And the store is melting fast. In the past half-century, 82% of the plateau's glaciers have retreated. In the past decade, 10% of its permafrost has degraded. As the changes continue, or even accelerate, their effects will resonate far beyond the isolated plateau, changing the water supply for billions of people and altering the atmospheric circulation over half the planet.
The plateau's pivotal role is due almost entirely to its height. Being an average of 4 kilometres above sea level makes it peculiarly cold for its latitude--colder than anywhere else outside the polar regions. Lhasa, capital of the Tibet Autonomous Region, is by Tibetan standards relatively low-lying, at 3,650 metres--yet it is higher even than La Paz, Bolivia, the highest capital city of a country. Lhasa's year-round average temperature is 8 [degrees]C; at the same latitude Houston, Texas, has an average temperature of 21[degrees]C. The altitude makes Tibet cold, especially in winter; its snow and ice cover, by reflecting sunlight, make it colder still. The very bulk of the plateau affects how winds circulate above it, and its altitude also places the surface simply closer to the stratosphere than is normal.
The proximate cause of the changes now being felt on the plateau is a rise in temperature of up to 0.3 [degrees]C a decade that has been going on for fifty years--approximately three times the global warming rate. The questions are how much more change to expect in the future, and how severe the effects will be on the planet's climate as a whole. "Our understanding of global climate change would be incomplete without taking into consideration what's happening to the Tibetan plateau," says Veerabhadran Ramanathan, an atmospheric scientist at the Scripps Institution of Oceanography in La Jolla, California.
Perhaps surprisingly given its significance, the potential impact of the Tibetan plateau is still unfamiliar to many climatologists. One reason is that there are far fewer data available compared with the Arctic and Antarctic, which have seen a far greater number of scientific expeditions to plumb their secrets. Although fieldwork there can be tough, the plateau offers the same physical isolation coupled with political challenges, at least for Western researchers. "The plateau's remoteness, high altitude and harsh weather conditions make any research on the region very challenging," says Yao Tandong, director of the Institute of Tibetan Plateau Research, headquartered in Beijing, of the Chinese Academy of Sciences.
Yao and his colleagues should know: in the 1980s, they were among the few researchers persevering in difficult field conditions to gather data on the plateau's past climate history. They drilled ice cores, up to 300 metres long, from Himalayan glaciers 7,200 metres high. "It's all done manually, and we had to carry them down the mountain. There were no helicopters, no heavy equipment," he says. "It's -30 [degrees]C, with the wind cutting through us like a knife. It's no...
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