The famous Snows of Kilimanjaro that cap Africa's highest mountain are melting so fast they could be gone within two decades, according to a study of the mountain's ice fields that used data going back nearly a century. Scientists believe global warming rather than local weather changes is chiefly to blame for the rapid loss of ice from the Tanzanian peak. A study comparing new measurements with those taken in 2000 show that a layer of ice between six and 17 feet thick has vanished from the summit since that time. Not only are the mountain's glaciers retreating at an unprecedented rate, but its remaining ice is thinning. The researchers predict that if current conditions persist, the mountain could be ice-free as early as 2022. Scientists made their forecast after combining data from aerial photographs and ground measurements of ice thickness. They found that the total area of Kilimanjaro's ice fields had shrunk by nearly 85% between 1912 and 2007. More than a quarter of the ice present in 2000 was now gone. The team, led by Professor Lonnie Thompson, from Ohio State University in the US, pointed out that the snows had survived intact for 11,700 years. Even a 300-year-long drought around 4,200 years ago made little impact on the mountain's ice fields. The chief cause of the current trend was likely to be a fundamental shift in climate, although local changes in cloud cover and snowfall may also be having an effect. Similar patterns had been seen elsewhere in Africa on Mount Kenya and the Rwenzori Mountains, as well as in the South American Andes and the Himalayas. "The fact that so many glaciers throughout the tropics and subtropics are showing similar responses suggests an underlying common cause," said Thompson. "The increase of Earth's near-surface temperatures, coupled with even greater increases in the mid-to-upper tropical troposphere (lower atmosphere), as documented in recent decades, would at least partially explain the observed widespread similarity in glacier behaviour."