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Frozen Secrets

Ten percent of the earth's surface is covered by glaciers. While these frozen peaks are the planet's largest reservoirs of drinking water, they are also home to precious relics of the distant past. Like tree rings, each layer of ice provides information on past years, such as temperature and precipitation. With global warming - an environmental concern but a boon for glaciologists - these treasures are gradually being released. In 1991, for example, hikers in Italy discovered a corpse lying at an altitude of over 3,000 metres.

• Documentary