Chinese experts say the climate of the Qinghai-Tibet Plateau, where the country's two longest rivers originate, has warmed and experienced slightly more rainfall during the past four decades.

The headwaters of the Yangtze and the Yellow River in the central eastern parts of the Plateau experienced average temperature rises of 0.8 degree Celsius and 0.7 degree Celsius in a decade from 1971 to 2004, according to Yang Jianping, a noted expert with the Chinese Academy of Sciences (CAS).

Yang has led a team of researchers from CAS Institute of Environment and Engineering in Cold and Arid Region to conduct meteorological analysis and compare the region's climate changes with other parts of the Qinghai-Tibet Plateau, China and elsewhere in the world.

Researchers found the area where the Yangtze River originates became warmer in 1971, whereas the same phenomenon was not witnessed at the source of the Yellow River until 15 years later.

"It's also noteworthy that neither of the two sources has clear symptoms of 'warm winter' -- the source of the Yangtze has become warmer mainly in spring, summer and autumn, while autumn and winter have both turned warmer at the source of the Yellow River," Yang said.

Yang and his peers have found the sources of the two rivers have had slightly more rainfall, particularly in spring and winter since the mid 1980s.

"Their amounts of rainwater in summertime have remained more or less the same over the past four decades," said Yang.

He concludes the sources of the Yangtze and the Yellow River are more sensitive to global climate changes compared with other parts of the world.

"In fact, climate change starts in these areas before spreading to other parts of the plateau," he said.

The scientists also found conspicuous environment degradation at the headwaters of the two leading rivers since the mid 1980s, including thawing of glaciers, shrinkage of frozen earth and drying of wetland and lakes leading to desertification.

"Such changes have affected the ecosystems at the sources of China's two longest rivers as well as their lower reaches," said Yang, adding that it is crucial to pinpoint the climate changes before finding proper solutions to tackle the problems.

Known as the "roof of the world," the Qinghai-Tibet Plateau encompasses China's Tibet Autonomous Region, Qinghai Province, and some parts of Xinjiang Uygur Autonomous Region, Gansu Province, Sichuan Province and Yunnan Province. The plateau covers an area of 2.5 million sq km, about one-fourth of China's land territory.

The plateau is the source of numerous rivers running through China and other countries in south and east Asia. Due to its special geological structure, the "roof of the world" is vulnerable to environmental changes and experts say each environmental index change in the area will inevitably be followed by world climate and environmental changes.

(Xinhua News Agency March 29, 2005)