LHASA, April 11 (Xinhua) -- Gesang Cering habitually wakes up at midnight to check whether his house or sheepfold is flooded again, as he has often seen water oozing, or sometimes even spouting out from ground since year 2000, particularly in winter.

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

    "The pasture near the lake is flooded from time to time; in winter, it's often covered with ice," the man said.

    Many local 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's inauspicious and invite lamas to perform Buddhism rituals, hoping to dispel the evil spirits.

    "It's actually caused by global warming," said Bendo, a senior engineer with Remote Sensing Application Research Center of the Tibet Autonomous Region.

    Bendo and his colleagues have been studying the floods in Nagqusince Aug. 2005. They conducted site surveys to five lakes in the prefecture and analyzed 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 kilometers 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.

    "It's getting more comfortable here," said Zhang Jianhua who has been working in Nagqu for 11 years. "The once lifeless hills are covered in green. We used to wear jackets in summer but nowadays shorts and T-shirts are enough."

    But 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, said Bendo.

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

    "Tibet's responses to global warming will provide valuable first-hand information to worldwide researchers on climate changes," said the expert.

    Chinese scientists found in an earlier research that global warming had caused glaciers to melt fast at Mount Qomolangma, the world's highest area, threatening the balance of global water resources. Enditem