Ausgabe 8/2006

Climate Research in the Death Zone Why Is Mt. Kilimanjaro Melting?

The glaciers on top of Mt. Kilimanjaro are melting, but nobody really knows why. Researchers have turned the peak into an extreme laboratory to find the answer. But it's a race against time -- the information archived in the ice must be unlocked before it melts.


"Remember this view," Lonnie Thompson yells into the storm. It's -10 degrees Celsius (14 degrees Fahrenheit) as a fierce wind rips at his old woolen cap. "This glacier will be gone forever in less than 20 years." The 57-year-old researcher hunches down and coughs, struggling with the mountain, the thin air and himself.

He stands in front of an ice wall as tall as a house, and behind him the west flank of Mt. Kilimanjaro plunges more than 3,000 meters (about 10,000 feet) to the valley below. The mountain juts up like an island from a sea of East African clouds, towering over the shimmering Serengeti, a world of zebras, giraffes and elephants so far away that one might as well be seeing it from the window of an aircraft.

Thompson, widely viewed as the pioneer of modern tropical glacier research, is a living legend among climate researchers. He's met with former US Vice President Al Gore to give him his personal assessment of climate change, and music magazine Rolling Stone has celebrated him as an "ice hunter." Where others see nothing but fields of rubble, Thompson uncovers evidence of dying glaciers and the traces of a 300-year catastrophic drought that spelled the downfall of entire civilizations. For Thompson, the ice at the top of Mt. Kilimanjaro is an archive, and he intends to use it to divine both the past and future of Africa's climate.

Working conditions in his open-air laboratory are extreme, to say the least. Though frozen, everything is constantly in flux. The steps cut into the ice yesterday are covered with snow today. Location markers suddenly disappear, blown away or knocked over by the wind. Sometimes, as Thompson lies awake in his tent at night, struggling to catch his breath and suffering the debilitating effects of high altitude headaches, he listens to the glacier's sounds: a cracking in the ice, then silence, followed by a metallic knocking sound and then a rumbling noise. And sometimes he feels as if he were standing on the twitching back of an enormous, wounded animal struggling to stay alive.

Dramatic conclusion; but premature?

The ice mountain at the equator is legendary. As recently as the 19th century, geographers were arguing over whether ice could even exist there. Nowadays, Kilimanjaro's tropical ice is once again the topic of heated discussion among experts. Is it true that the glaciers of Kilimanjaro will soon melt away completely? If so, how fast? Is this the result of global warming? And will streams fed by the glaciers dry up when they disappear?

To answer these and other questions, Thompson and many other scientists are busy studying tropical glaciers, but not all concur with Thompson's conclusions. American climate expert Doug Hardy, for example, who also happens to be climbing around on Kilimanjaro these days, is convinced that his famous colleague's dramatic conclusions are a bit premature.

But before other groups could even analyze their data, Thompson made headlines last week by publishing the results of his latest measurements. The glaciers, he announced, are receding more rapidly than previously thought, losing more than half a meter in thickness each year. Thompson -- in yet another highly controversial claim -- believes that if the ice fields disappear, much of the water supply at the base of the mountain could vanish along with them.

"We have to collect as much data as possible today, even if we're not exactly sure what it means, because in a few decades it'll be too late," says Thompson. More than 80 percent of tropical glaciers, including those on Mt. Kilimanjaro, he believes, have already vanished within the last hundred years.

A few hundred meters away, a crowd of tourists stumble down the mountain. Despite its official elevation of 5,895 meters (19,340 feet), Kilimanjaro's middle summit, a peak known as Kibo, is considered a walk-up, one that even an out-of-shape chain smoker can master. Each year about 25,000 visitors drag themselves up the dormant volcano, spend the night in giant tent camps and slide back down special one-way tracks carved into the lava sand. Generally, the groups are accompanied by vast armies of porters.

Popcorn in the "death zone"

But less than half actually make it to the summit. Those who fail are often kept back by altitude sickness, causing symptoms ranging from headaches, vomiting and insomnia to mental blackouts and cerebral edemas. Each year the mountain claims an average of six lives. Thompson and his three younger assistants, as well as another group of researchers camping nearby, also suffer from the effects of working at this high altitude. Unlike the tourists, the scientists spend about a week living and working at an altitude of about 5,750 meters (18,865 feet), where the air is only about half as dense as it is at sea level.

As brutal as conditions on the mountain are, the researchers can't exactly complain when it comes to meals. A long caravan of more than 40 porters carried the two teams' equipment and supplies up the mountain, an effort that's reflected in their fare: eggs, porridge and toast for breakfast, popcorn and homemade potato chips as snacks before dinner.

Despite the calories, the scientists seem to become weaker as the days pass. At this altitude, the "death zone," -- the altitude at which the human body begins to steadily deteriorate -- begins. After a night of confusing dreams, the scientists often wake up feeling so exhausted that a task as simple as tying shoelaces becomes a challenge. After a few days, their eyes become swollen, their cheeks begin to collapse, their noses are sunburned and jokes become a rarity.

Thompson has been punishing his body like this for the past 30 years. As far back as 1976, he was studying tropical ice samples he obtained from Peru's Quelccaya ice field, at an altitude of more than 5,000 meters (about 16,400 feet).

He's been collecting drill cores from the world's tallest mountains ever since -- more than four tons of material from 15 countries, all stored away at Ohio State University. "In a few decades you'll have to come to my university if you want to see the remains of a tropical glacier," says Thompson. After each sentence, he has to bend over and struggle for air. Despite the fact that he has asthma, Thompson has probably spent more time at such high altitudes than anyone else -- a grand total of more than three and a half years. But he has no interest in alpine sports. "I just don't understand why people would come up here for fun." So what's his motivation? "I guess I'm just stubborn," he says.

"Equator has been woefully ignored"

Thompson was widely derided when he set out for the Quelccaya ice shelf in 1976. Back then climate researchers saw no point in studying tropical ice. One of his first expeditions almost failed when the helicopter carrying the team's heavy ice-drilling equipment began lurching from side to side in the thin air. The pilot immediately turned back, forcing Thompson to make do with porters. But the incident came with a silver lining, as it prompted Thompson to develop a portable solar-powered drill to take advantage of the intensity of sunlight at high altitudes -- an unforgiving 1,000 watts per square meter. Whereas temperatures plunge to polar levels at night, noonday temperatures inside a tent can climb to 40 degrees Celsius (104 degrees Fahrenheit). Thompson once even developed a sunburn on his gums after breathing through his open mouth for too long.

In the end, his Peruvian drill cores proved to be a sensation. They provide precise geological documentation of many climatic events of the past 1,500 years, including the eruption of a volcano, Mt. Huaynaputina, in 1600. Thompson's essays, some of which he wrote in his tent, have appeared in publications such as Science.

"The history of our climate can teach us how global warming will affect the tropics," says Thompson. "That's why it's so important that we obtain the data from glacial ice. The polar regions have been researched to no end, but the areas near the Equator have been woefully ignored."

Thompson developed a reputation beyond the world of climatology when he obtained the first drill cores from Mt. Kilimanjaro in 2000. His results were surprising. The mountain's tropical glaciers, he found, developed about 11,700 years ago. Paradoxically, this was precisely at the time when the last great ice age ended in the north. In other words, the climate of the tropics is "asynchronous" with that of the north; it follows a different cycle.

Like the ebb and flow of ocean tides, the African glaciers have expanded and contracted over the centuries. But beginning in about 1880, tropical glaciers began receding more rapidly and more abruptly than in the past. In places where extensive ice caps reached down to altitudes of 4,500 meters (14,750 feet) only a hundred years ago, all that remains today are narrow glacier strips and isolated chunks of ice in a moonlike landscape of lava sand. Thompson managed to turn Kilimanjaro into a symbol of global warming -- and he has triggered a heated scientific debate in the process.

Climatologist Doug Hardy is among Thompson's adversaries in the world of glacier research. "The phrase global warming is misleading, as are the alarmist reports of the complete disappearance of all glaciers on Kilimanjaro," says Hardy. The American scientist acts as a weatherman of sorts for the ice-capped mountain. And although he and Thompson work closely together, Hardy disagrees with much of what Thompson says, arguing that Thompson's speculations are excessive and his predictions far too premature.


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