The principal glacier of the world’s biggest tropical ice-cap could disappear within five years as a result of global warming, one of the world’s leading glaciologists predicted yesterday.

The imminent demise of the Qori Kalis glacier, the main component of the Quelccaya ice cap in the Peruvian Andes, offers the starkest evidence yet of the effects of climate change, according to Lonnie Thompson, of Ohio State University.

Although scientists have known for decades that Qori Kalis and the other Quelccaya glaciers are melting, new observations indicate that the rate of retreat is increasing, Professor Thompson said. When he visits this summer, he expects to find that the glacier has halved in size since last year, and he believes that Qori Kalis will be gone within five years.

“This widespread retreat of mountain glaciers may be our clearest evidence of global warming as they integrate many climate variables,” Professor Thompson told the American Association for the Advancement of Science conference in San Francisco. “Most importantly, they have no political agenda.”

The Quelccaya ice-cap, covering 17 square miles (44 sq km) in the Cordillera Oriental region of the Peruvian Andes, is the world’s largest tropical ice mass. Qori Kalis, its biggest glacier, has receded by at least 0.6 miles (1.1km) since 1963, when the first formal measurements were made from aerial photographs. The rate of retreat has increased: between 1963 and 1978, it shrank by 6.5 yards (6m) a year, a rate that has now risen tenfold to 65 yards annually.

Professor Thompson predicted six years ago that the celebrated snows of Kilimanjaro would be gone from Africa’s highest mountain by 2015, and he now thinks that that estimate may have been too conservative. He said: “Tropical glaciers are the canaries in the coalmine for our global climate system, as they integrate and respond to most of the key climatological variables — temperature, precipitation, cloudiness, humidity and radiation.”

A critical piece of evidence from almost fifty scientific expeditions to seven shrinking tropical ice-caps points to global warming as the reason for their decline. In all but one case, snowfall has increased as ice volume has fallen. More snow should mean advancing glaciers, unless rising temperatures are melting the extra precipitation and the ice tongues themselves.

Hasty retreat

- Quelccaya, in Peru, is the largest tropical ice-cap, at

- 17 square miles (44 sq km)

- Height: 18,600ft (5,670m)

- Biggest glacier: Qori Kalis

- Rate of retreat 1991-2005: 65 yards (60m) a year

Source: Ohio State University

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