The icecap atop Mt. Kilimanjaro, which for thousands of years has floated like a cool beacon over the shimmering equatorial plain of Tanzania, is retreating at such a pace that it will disappear in less than 15 years, according to new studies.
The vanishing of the seemingly perpetual snows of Kilimanjaro that inspired Ernest Hemingway is one of the clearest signs that a global warming in the past 50 years appears to have exceeded typical climate shifts and is at least partly caused by gases released by human activities, a variety of scientists say.
Measurements taken in the past year on Kilimanjaro show its glaciers not only are retreating but also rapidly thinning, with one spot having lost a yard of thickness since last February, said Lonnie Thompson, a senior research scientist at the Byrd Polar Research Center of Ohio State University.
Altogether, he said, the mountain has lost 82 percent of the icecap it had when it was first carefully surveyed, in 1912.
Given that the retreat started a century ago, Thompson said, it is likely that some natural changes were affecting the glacier before it felt any effect from the large, recent rise in heat-trapping greenhouse gases from smokestacks and tailpipes. And, he noted, glaciers have grown and retreated in pulses for tens of thousands of years.
But the pace of change–echoed by similar trends on ice-capped peaks from Peru to Tibet–goes beyond anything in recent centuries.
“There may be a natural part of it, but there’s something else being superimposed on top of it,” Thompson said.
“And it matches so many other lines of evidence of warming. Whether you’re talking about bore-hole temperatures, shrinking Arctic sea ice or glaciers, they’re telling the same story.”
Thompson presented the fresh data at the American Association for the Advancement of Science annual meeting in San Francisco.
The retreat of mountain glaciers has been seen from Montana to Mt. Everest to the Swiss Alps.
In the Alps, scientists have estimated that by 2025 glaciers will have lost 90 percent of the ice that was there a century ago. Only Scandinavia seems to be bucking the trend, apparently because shifting storm tracks in Europe are dumping more snow there.
The melting is generally quickest in and near the tropics, Thompson said, with some ancient glaciers in the Andes–and the ice on Kilimanjaro–melting the fastest.
Separate studies of air temperature in the tropics, made using high-flying balloons, have shown a steady rise of about 15 feet a year in the altitude at which air routinely stays below the freezing point.
Thompson said other changes also could be contributing to the glacial shrinkage, but this rising warm zone is probably the biggest influence.
Trying to stay ahead of the widespread melting, Thompson and a team of scientists have been hurriedly traveling around the tropics to extract cores of ice from glaciers containing a record of thousands of years of climate shifts. The data may help predict trends.
Richard Alley, a professor of geosciences at Pennsylvania State University, said the melting trend and the link–at least partly–to human influence is “depressing.”
“What is a snowcap worth to us?” he said. “I don’t know about you, but I like the snows of Kilimanjaro.”
The changes in the character of Kilimanjaro are registering beyond the ranks of climate scientists.
People working in the tourism business around the mountain and surrounding national park are worried that visitors no longer will be drawn to the peak once it has lost its glimmering cap.
Douglas Hardy, a geologist at the University of Massachusetts, returned from Kilimanjaro last week with the first yearlong record of weather data collected by a probe placed near the summit.
Just before he left, he talked with the chief ranger of Kilimanjaro National Park, who expressed concern about the trend.
“That mountain is the most mystical, magical draw to people’s imagination,” Hardy said. “Once the ice disappears, it’s going to be a very different place.”
And the melting continues.
When Hardy climbed the mountain to retrieve the data, he discovered that the weather instruments, erected on a tall pole, had fallen over because the ice around the base was gone.
