The Rongbuk glacier, the biggest glacier on Mount Everest's northern slopes. The photo above was taken in 1968 and the one below was taken this year (2007).
Photo: Chinese Academy of Sciences and Greenpeace

These two photographs - taken 40 years apart - show how one of the world's most spectacular ice formations, the field of ice towers ("serac forest") around Mount Everest, is shrinking. Environmental group Greenpeace, which released the photographs today, say this is global warming in action.

The photographs are of the Qinghai-Tibet plateau, which is called the world's "third pole" because it contains the biggest fields of ice outside of the Arctic and Antarctic. Its glaciers are the source of Asia's biggest rivers - Yangtze, Yellow, Indus and Ganges.

The melting of this glacier is also significant because the UN's Intergovernmental Panel on Climate Change reported last month that if current trends continue, 80 per cent of the Himalayan glaciers, the water source for a sixth of the world's population, could disappear in 30 years if the current rate of emissions is not reduced. Other reports have suggested that the impact would be lower, at about 30 per cent.

The original picture from 1968 was taken by the Chinese Academy of Sciences. Greenpeace has made three expeditions to the same area in the past two years.

The Greenpeace campaigners were unable to reach the same spot where they think the 1968 picture was taken because a smaller glacier that was there four decades ago has disappeared, making it impassable. The season in which the 1968 photograph was taken is also unknown, though there are really only two periods when the area is habitable by humans, which is April to May (spring) and September to October (autumn).

Li Yan, one of the expedition members, said climate change was transforming the ancient Himalayan landscape. The first photograph shows a long valley filled with ice towers as high as 20 metres that form the Rongbuk glacier, the biggest glacier on Mount Everest's northern slopes. The second photograph taken on April 29 this year (early spring here), shows that the ice forest has retreated dramatically.

"A big piece of the Rongbuk glacier ... has disappeared," Ms Li said.

"The demise of the ice towers is the most significant sign of global warming in the Himalayas. But this is just one example of what is happening right across the Qinghai-Tibet plateau. All the glaciers are depleting, threatening the livelihoods of millions of people."

The melting glacier has created many new lakes, which can create havoc through flooding when they burst. Unfortunately for the farmers who live in the area, the extra water has been more than offset by less and less rainfall and the hotter temperatures.

China has acknowledged that global warming is adversely affecting its environment and has pledged to reduce its emissions, but this week, along with India, another developing country and also the world's second most populous, again rejected mandatory targets because it would slow development.