China must make long-term preparations to face this abnormal meteorological phenomenon, said the experts at the International Symposium on Climate Change which opened in Beijing Monday.

The "north drought and south flood" phenomenon began affecting China in the late 1980s and was comparatively stable, and would probably remain so till 2030, said Zhang Guocai, an expert from the National Meteorological Center of China.

North China had received a higher annual average rainfall than the south from the 1950s to 1970s, but lower since the 1980s, said Ding Yihui, a special advisor on climate change with the China Meteorological Administration.

"Especially since the 1990s, the significant decrease in precipitation has been observed over most parts in north China, while in south China, marked increases in precipitation have been observed," Ding said.

Figures show 33.3 million hectares of farmland were damaged and the Yellow River dried up for 222 days in the severe drought which hit the north in 1997. While in 1998, the unprecedented flooding of the Yangtze River affected 180 million people and caused losses of 29 billion yuan (US$3.5 billion).

Possible causes of the phenomenon included change in tropical cyclones from the Indian Ocean and the change of air pressure over Lake Baikal, the world's deepest freshwater lake, in Russia, according to Ding.

Some experts also explained the precipitation pattern through the climatic consequences of black carbons or sulfate aerosols emitted through human activities.

(Xinhua News Agency March 31, 2003)