Kilimanjaro's ice cap

During the political debates over global warming, Kilimanjaro’s vanishing ice cap became an iconic image of the negative consequences of anthropogenic climate change, but climatologists and glaciologists have discovered that decreased snowfall, enhanced exposure to solar radiation, ice-sheet locations and shapes, and other factors are more important than climate change in explaining the disappearing ice.

Background

Kilimanjaro—which, at 5,895 meters, is Africa’s highest mountain—is of volcanic origin, based in its location alongside a rift zone created by the Earth’s spreading crust. Its trio of volcanic peaks gradually became inactive, first Shira, then Mawenzi, and finally Kibo, the highest. Ice and snow gathered on Kilimanjaro’s upper slopes during the late Pleistocene epoch, about eleven thousand years ago. Ice cores taken from the mountain’s glaciers revealed a history of expansions and contractions of the ice cap, with the contractions occurring during periods of drought eighty-three hundred, fifty-two hundred, and four thousand years ago. Periods of expansion resulted from climatic conditions that were warmer and wetter than those of today. Since the late twentieth century, Kilimanjaro’s ice sheets have been confined to Kibo.

One-half million years ago, early human inhabitants of the Rift Valley first saw this majestic mountain, but its names derive from a much later period. African tribes called it the “white” or “shining” mountain, because of its ice cap. Its present name most likely comes from the Swahili, “Kilima Njaro,” meaning “Mountain of Greatness” because of its massive height and bulk. The first European to see the mountain was a German missionary who published an account of his African explorations in 1849. This not only sparked interest in searches for the source of the Nile but also in the scientific study of Kilimanjaro and its ice sheets.

Vanishing Ice Sheets

In the late nineteenth century, explorers created maps and drawings of the mountain and its environs. From these, scholars derived an estimate that, in 1880, ice covered about 20 square kilometers of Kilimanjaro’s principal peak. In 1889, two Europeans were the first to reach Kilimanjaro’s summit, and they brought back information about the extent and depth of the ice sheets. In the twentieth century, photographs from the mountain’s base and, later, from airplanes, provided benchmarks by which the shrinkage of the ice cap could be measured. In 1912, a precise map was constructed based on photogrammetric evidence. At that time, the ice sheets had diminished to 12.1 square kilometers, though they still existed on all sides and descended to about 4,400 meters. From 1912 to the early twenty-first century, Kilimanjaro’s icefields were periodically surveyed, and the data gathered indicated that the time of greatest contraction had been from about 1880 to 1950.

Ernest Hemingway, an American writer, made Kilimanjaro’s ice cap world famous through his popular short story, “The Snows of Kilimanjaro,” (1936) which was made into a successful Hollywood movie in 1952. By the early 1950s, the mountain’s icefields had diminished to 6.7 square kilometers. Sufficient data had been collected to determine that the rarely observed trickles of meltwater were unable to account for the retreating glaciers. Some scientists began to attribute glacial contraction to the of summit ice into water vapor under the influence of the tropical sun in dry air at below-freezing temperatures. However, during the second half of the twentieth century, as evidence multiplied that midlatitude mountain glaciers were shrinking because of global warming, some scientists extended this explanation to such equatorial mountain glaciers as Kilimanjaro’s.

Aerial photographs of Kibo’s ice sheets had been supplemented by satellite pictures, and this new information showed that, although the ice cap’s contraction had slowed since 1953, over 85 percent of its area had vanished during the last century. In 2019, the glaciers on the mountain covered only 1.5 square kilometers (0.60 square miles), compared to 11.4 square kilometers (4.4 square miles) in 1912. In 2022, the United Nations predicted that Kilimanjaro's ice cap would be gone by 2050, mainly because of climate change.

Since the “Snows of Kilimanjaro” were famous as well as photogenic, it was natural for advocates of greenhouse gas (GHG) reduction to use dramatic images of the mountain’s disappearing ice cap to bolster their cause. Greenpeace advocates held a news conference from Kilimanjaro’s summit, and, most significantly, former vice president Al Gore argued in a very successful documentary film and companion book, both entitled An Inconvenient Truth (2006), that the vanishing ice cap was evidence of global warming. The movie’s Academy Award and the book’s bestseller status helped popularize the images of Kilimanjaro’s vanishing ice, which Gore associated with carbon-dioxide-induced global warming.

Significance for Climate Change

Although many scientists agreed that temperate-zone mountain glaciers were retreating because of global warming, an increasing number of climatologists and glaciologists believed that the specific case of Kilimanjaro’s ice loss was caused by other factors. Data collected from balloons, satellites, and an automatic weather station on one of Kibo’s icefields revealed that reduced precipitation of ice and snow in desiccated air, along with extensive exposure to solar radiation in below-freezing temperatures, led to the accelerated sublimation of ice and snow. Fluctuating weather systems in the Indian Ocean, which influenced humidity and cloud cover over Kilimanjaro, may also have played a role.

Context

Most scientists familiar with the data held that global warming had little or no effect on the ice decline. These scientists chided global-warming enthusiasts for their misuse of Kilimanjaro’s vanishing ice cap to support their views on climate change, but they also criticized global-warming deniers who overgeneralized the Kilimanjaro case to include midlatitude glaciers. Kilimanjaro can therefore serve as a cautionary tale of how politics and overheated rhetoric often lead passionate advocates to distort scientific data and images in unacceptable ways. Despite the reason for the disappearance, the loss of Kilimanjaro’s ice caps would have severely negative effects on the surrounding areas, including the loss of drinking water, irrigation, hydroelectric energy production, and tourism income.

Key Concepts

• ice cap: semipermanent glacial crown of ice atop a mountain or other geologic formation
• sublimation: the conversion of a solid directly into a gas, bypassing its liquid state
• volcano: a usually mountainous rift in Earth’s crust caused by erupting through fissures onto the planet’s surface

Bibliography

Bowen, Mark. Thin Ice: Unlocking the Secrets of Climate in the World’s Highest Mountains. New York: Macmillan, 2005.

Gore, Al. An Inconvenient Truth: The Planetary Emergency of Global Warming and What We Can Do About It. Emmaus, Pa.: Rodale Books, 2006.

"Iconic World Heritage Glaciers to Disappear by 2050, Warns UNESCO United Nations." United Nations, 3 Nov. 2022, news.un.org/en/story/2022/11/1130157. Accessed 20 Dec. 2024.

Kornei, Katherine. "Kilimanjaro's Iconic Snows Mapped in Three Dimensions." Eos, 3 Mar. 2017, eos.org/articles/kilimanjaros-iconic-snows-mapped-in-three-dimensions. Accessed 17 Oct. 2018.

Michaels, Patrick. Meltdown: The Predictable Distortion of Global Warming by Scientists, Politicians, and the Media. Washington, D.C.: Cato Institute, 2004.

Mote, Philip W., and Georg Kaser. “The Shrinking Glaciers of Kilimanjaro: Can Global Warming Be Blamed?” American Scientist 95 (July/August, 2007): 318-325.