Hastenrath found further evidence in sailing expedition reports from the same period. "Ships along the East African coast recorded very fast equatorial winds around 1880," he said. "Just like today, swift westerlies are always linked with drier seasons in East Africa, so it's very likely Kilimanjaro had a dry period around this time."
Along with a higher risk of evaporation, a drop in precipitation also makes for a dark glacial surface, made up of old, dirty snow. A darker glacial surface absorbs more solar radiation than fresh, white snow (like a blacktop playground baking in the sun).
Global warming began to take effect in East Africa by the early 20th century.
"The warming increases humidity, and as the air gets more moist, it hinders evaporation," Hastenrath explained. "The energy saved from evaporation is instead spent on melting. That might seem like a good thingto stop evaporation of the glaciersbut it's certainly not. Melting is eight times more energy-efficient than evaporation, so now, with global warming, the glaciers are disappearing eight times faster than before."
Now scientists are scrambling to learn as much as they can from a vanishing resource. "Kilimanjaro's glaciers are the only source for tropical ice core records for the whole continent of Africa," Hardy explained. "There's been somewhat of a scramble to collect data."
The glacial ice core samples (or rods) hold vital atmospheric and climatic recordsinformation that is key to understanding tropical weather patterns over the past millennia. The bottommost layer of the ice records air and climate data as far back as 11,500 years ago, near the end of the last major Ice Age.
On many glaciers, collected surface water is already filtering into the porous ice below and tainting the weather archives.
"Some scientists are even trying to collect enough core samples to store some in freezers," Hardy said. "So they can undertake analyses both now and later, when more sophisticated technology is available."
For many, though, more superficial concerns of an ice-free Kilimanjaro are almost as important as the history buried deep below the surface.
"If the ice disappears, it'll be an aesthetic disaster," said Hastenrath, who has climbed the peak three times. "There's hardly anything more beautiful than the glaciers on Kilimanjaro."
Will other would-be tourists feel the same way? Ever mindful of the economic pearl shining 19,340 feet (5,895 meters) above them, the surrounding villages can't help but worry that tourists will lose interest if Kilimanjaro loses its glaciers.
Tourism brings more foreign currency into Tanzania than any other industry, and Kilimanjaro's ice-covered peak is a major East African draw. "The sad reality is that the loss of Kilimanjaro's glaciers probably has to affect the local economy," Hardy said.
It's uncertain whether there is enough time to salvage the glaciers before they disappear altogether, but hordes of scientists are willing to try. Some have suggested covering Kilimanjaro's ice cap with a bright white coverinspired by those used in England to protect cricket fields from the elementsas a membrane to seal the glaciers, prevent evaporation and reflect solar radiation.
"Some of these ideas are just pipe dreams," Hardy said, "but as points of discussion about the importance of Kilimanjaro to Africaand to the whole worldthey are very interesting."
The Final Meltdown
Could anything have saved the portion of the Furtwängler Glacier that Keipper saw crumble? Probably not. The entire glacier is predicted to disappear well before the other fields.
When it was drilled for ice core samples in 2000, the Furtwängler was completely water-saturated. Some scientists attribute the overflow to volcanic vents, heating the base of the glacier and melting the bottom layer of ice. Others, including Hardy and Lonnie Thompson, who released the 2000 Ohio State University report, believe that colder air surrounding the glacier kept its walls frozen even as portions of the interior melted away.
"If enough of that water pressure built up, it seems likely that there was enough energy to burst through the frozen glacier wall," Hardy said.
The Furtwängler Glacier may continue to disappear in massive chunks, just like the icy boulders Keipper and his colleagues saw tumble down the crater floor. If conditions remain as they have, the rest of Kilimanjaro's ice will follow suit, but rather than exploding, they will steadily and stealthily evaporate into African air.
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