The snows of Mount Kilimanjaro, immortalized by an Ernest Hemingway short story, are melting so quickly they are expected to disappear within two decades.

Researchers have found that the icefields capping Africa's highest mountain shrank by 80 per cent in the last century, from 4.6 square miles in 1912 to just one square mile two years ago, which has brought down the height of the mountain by several feet.

Climbers make their way up to the 19,000 foot summit of Mount Kilimanjaro, background, in this Oct. 19, 2001, file photo. The snow cap on the mountain, famed in literature and beloved by tourists, first formed some 11,000 years ago, but will be gone in two decades, according to researchers who say the ice fields on Africas highest mountain shrank by 80 percent in the past century. A temperature rise in recent years, measured at about a full degree since 2000, is eroding the 150-foot-high blocks of ice that gave Kilimanjaro its distinctive white cap.(AP Photo/Picture Plant, Michael Brown)

The ice covering the 19,330ft peak "will be gone by about 2020", said Lonnie Thompson, a glaciologist at Ohio State University. The process has cut water volume in some Tanzanian rivers which supply villages and hospitals.

Global warming is one reason, but scientists say it alone cannot have caused such a dramatic change. The other factors behind the transformation remain a mystery.

The disappearance of the ice could spell trouble for Tanzania's economy, which relies heavily on tourism driven by the attraction of the mountain. In the Hemingway short story "The Snows of Kilimanjaro", a disillusioned writer, Harry Street, reflects on his life while injured in an African campsite. The story was made into a film in 1952 starring Gregory Peck. "Kilimanjaro is the number one foreign currency earner for the government of Tanzania," said Professor Thompson. "It has its own international airport and some 20,000 tourists every year."

The ice-cap was deposited during an extremely wet period about 11,700 years ago, according to ice cores examined by Professor Thompson and his team, and described in a paper today in the journal Science. It was up to 165ft deep.

Since 2000, the average temperature in the area has risen by about 1C. The glacial retreat has been so rapid scientists do not think it can solely be caused by man-made global warming – although the greenhouse effect is turning mountain glaciers into an endangered species. In 1998 research showed an unprecedented warming, in which some mountain ranges such as the Alps had lost 50 per cent of their ice in the last century.

The team's research shows that Kilimanjaro has dried up before. Cores taken from the icefields revealed evidence of three catastrophic droughts that plagued the tropics 8,300, 5,200 and 4,000 years ago.

The most recent drought lasted 300 years. It rocked the Egyptian empire and threatened the rule of the pharaohs. Professor Thompson said: "Writings on tombs talk about sand dunes moving across the Nile and people migrating. Some have called this the Earth's first dark age."

Civilizations also collapsed in India, the Middle East and South America.

"Whatever happened to cause these dramatic climate changes could certainly occur again," Professor Thompson said. "Today, 70 per cent of the world's population lives in the tropics. They would be dramatically affected by events of this magnitude."

© 2002 lndependent Digital (UK) Ltd

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