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Global warming swells Tibetan lakes

Scientists had earlier found that global warming had caused glaciers to melt fast at Mt Qomolangma, threatening balance of global water resources.

india Updated: Apr 13, 2006 14:09 IST

Gesang Cering, a shepherd, habitually wakes up at midnight to check if his house is flooded. He often sees water oozing out of the ground, a phenomenon researchers attribute to global warming.

He has also noticed that lake Naigri Puencog, some eight kilometres from his home village in Nagqu Prefecture in northern Tibet, often swells.

"The pasture near the lake is flooded from time to time; in winter, it is often covered with ice," he says.

Many herders have witnessed similar situations. In many lake areas, water springs out of formerly dry places, roads are flooded, and alkali is found no more in what used to be alkaline lakes.

Even the oldest people in the village cannot explain the abnormal phenomenon. Some say it is inauspicious and invite lamas (Buddhist monks) to perform rituals, hoping to dispel the evil spirits.

"It is actually caused by global warming," says Bendo, a senior engineer with Remote Sensing Application Research Centre of the Tibet Autonomous Region.

Bendo and his colleagues have been studying the floods in Nagqu since August 2005.

They conducted site surveys of five lakes in the prefecture and analysed changes in the sizes of the lakes over the past two decades with remote sensing mapping.

"We found rises in rainfall as well as in air and ground temperatures in lake areas but declines in water evaporation, exposure to sunlight, and thickness of snow and frozen earth," he said. "We therefore decided global warming caused the lakes to swell."

Bendo said the average water level in Naigri Puencog and two other inland lakes rose by 12.6 meters in the recent two decades, flooding an average 40.8 square km of pasture, cropland and roads.

Despite the damages to the pastures and roads, many people say the local climate is milder than before as it gets warmer and rains more often.

However, experts say the impact of global warming is not always positive in Tibet.

In Ngari Prefecture in western Tibet, for example, the warm but arid climate has had a negative effect on the local ecology, says Bendo.

Known as the "roof of the world", the Qinghai-Tibet Plateau is very sensitive to climate changes.

Chinese scientists had earlier found that global warming had caused glaciers to melt fast at Mount Qomolangma, threatening the balance of global water resources.

"Tibet's responses to global warming will provide valuable firsthand information to worldwide researchers on climate changes," says Bendo.