Even from the top of a 16,000-foot pass, Tibet's Naimona'nyi looks formidable, and the closer we get to it, the larger it looms, until, finally, its ice-glazed face disappears behind the steep, rock-strewn ridge we have yet to climb. At 25,242 feet, Naimona'nyi is the highest mountain in southwestern Tibet and the 34th highest in the world.
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Below us runs a glacier-fed river turned milky by pulverized rock. The fall equinox has passed, and shrubs and grasses are turning crimson and gold. "Look at all the colors," Lonnie Thompson exclaims, delighted that winter is finally on the way. The onset of bitter cold might seem an odd thing to welcome, but, he says cheerfully, "for the ice it's good."
Thompson, one of the world's foremost glaciologists, is the leading authority on high-altitude glaciers of the tropics and near tropics, and he is as renowned in scientific circles for his physical courage as for the pathbreaking publications that stream from his lab. "An absolute hero," says Gavin Schmidt, a climate modeler at NASA Goddard.
This is Thompson's 51st major ice-coring expedition. All told, he has spent more than three and a half years at elevations above 18,000 feet. He has endured frostbite and altitude sickness. He rode a Mongolian pony for three days through driving snow and rain on a 1986 expedition to China's Qilian Shan mountains. During a 1993 expedition to Huascarán, the highest mountain in Peru, he crawled across a yawning crevasse on a rickety wooden ladder; camped at 19,800 feet, he was trapped inside a tent as hurricane-force winds carried it toward a precipice. He averted a fall only by stabbing an ice ax through the tent floor.
Ice is like a time capsule that preserves the abrupt shifts in climate that have changed the course of human history. From the Quelccaya ice cap—a cap is larger than a glacier—in southern Peru, Thompson and his colleagues pieced together the droughts and floods that unhinged pre-Incan civilizations. In layers of ice cored from the Dasuopu glacier high in the Himalayas, they identified the dusty fingerprints of monsoon failures that have punished the Indian subcontinent with recurrent famine since A.D. 1440. Now Thompson, who is based at Ohio State University, is using high-altitude ice samples to come to grips with global warming.
"What really stands out," he says, "is how unusual the last 50 years have been compared to at least the last 2,000 and perhaps the last 5,000 years." Rising temperatures are rapidly reducing the ice that permanently caps high mountains around the world. Well before the end of this century, much, and in some areas most of it, will be gone. The loss is a harbinger of even larger, potentially catastrophic, consequences.
Thompson, I'm relieved to learn, does not intend to climb to the top of Naimona'nyi, which was not successfully summited until 1985. But the plan that he has devised with Yao Tandong, director of the Chinese Academy of Sciences' Institute for Tibetan Plateau Research and Thompson's longtime collaborator, is in some ways even more daunting. From our present elevation, about 16,000 feet, they aim to hike another 4,000 feet to the head of a massive ice field in the shadow of Naimona'nyi's highest peak. They will remain there for as long as it takes to drill down to bedrock and extract two or three continuous cores of ice, each hundreds of feet long.
We wait days for Yao's team to assemble a sufficient number of yaks. We breakfast, Chinese-style, on steamed bread and pickled vegetables and sort through gear to pass the time. Thompson is clearly eager to get under way. Finally, a jangle of bells announces the arrival of a small herd of yaks, bringing the number of pack animals to about 18. The yak herders load our stuff onto the backs of these curious bovines, excellent climbers with horns like buffaloes and tails like horses.
Then Thompson and his five-member team are off, with Vladimir Mikhalenko, an ice driller from the Russian Academy of Sciences' Institute of Geography, leading the way. Following close behind are chief driller Victor Zagorodnov, glaciologist Mary Davis, graduate student Natalie Kehrwald and geochemist Ping-Nan Lin, all from Ohio State University (OSU). Thompson waves cheerily. "It'll be a walk in the park," he promises.
Half an hour later, I head out with my husband, Thomas Nash, a physicist and photographer; we trail a second group of hikers led by Yao, which will meet up with Thompson's group later in the day. The sharp incline is unrelenting, and I find that I am soon reduced to a rhythm of ten steps followed by a pause in which I suck in an equal number of breaths. In this tortured fashion, I eventually reach 18,400 feet, at which point the scenery explodes.