Retreating mountain glaciers in Bhutan.

Photo credit: ©NASA/Jeffrey Kargel

This satellite image shows the termini of several glaciers in the Himalayan mountains of Bhutan. The glaciers have been receding over the past few decades, and lakes have formed on the surfaces and near the termini of many of the glaciers.

Himalayan glaciers are among the fastest retreating glaciers globally due to the effects of global warming, and this will eventually result in water shortages for hundreds of millions of people who rely on glacier-dependent rivers in China, India and Nepal.

Climate change results from a complex process that scientists are only beginning to understand. Glaciers are indicators of long-term temperature changes, with their advances and retreats bearing geological evidence of climatic change. Glaciers in many parts of the world are currently in retreat because of climate change. Ice cores drawn from glaciers can yield further clues to the climates of the past.

Vast quantities of fresh water are tied up in the world's many melting glaciers. When Montana's Glacier National Park was created in 1910 it held some 150 glaciers. Now fewer than 30, greatly shrunken glaciers, remain. Many of the world’s freshwater glaciers are shrinking, as warming temperatures melt them away. Some have disappeared all together. The glaciers on both Mount Everest and Mount Kilimanjaro are among those glaciers noticeably decreasing as temperatures climb.

Some experts are forecasting the melting of half the Arctic’s summer sea ice by the end of the 21st century. If Greenland’s massive ice sheets were to melt, something that could occur over the very long term, they could raise the sea level by 7 metres (23 feet).

Higher temperatures threaten other dangerous consequences: drought, disease, floods, lost ecosystems. And from sweltering heat to rising seas, global warming's effects have already begun.

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