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Meteorologists warned that global warming will bring changes to surface runoff, the frequency of droughts and floods and the water quality in some areas of China, and exacerbate the uncertainty of the country's water resources and contradictions between demand and supply.

Many Chinese and overseas meteorologists have expressed their concern over "Our future climate" -- the theme of World Meteorological Day (WMD) 2003, held annually on March 23.

They said further global warming will influence the earth's water cycle by increasing evaporation and changing the quantity and distribution of regional rainfall, which would make disasters like floods and droughts more prevalent and serious.

China, the northern areas in particular, has witnessed a sustained drop in precipitation since the rainfall in the country reached its maximum in the 1950s, revealed the China Meteorological Administration's (CMA) statistics.

Meteorologists estimated that the western regions of China will lack about 20 billion cubic meters of water from 2010 to 2030, andin 2050 the regions would still need 10 billion more cubic meters of water.

The absence of adequate water conservation facilities in the west could make the water resources system more fragile in the face of the climate changes, they said.

China will face a tougher challenge in its water security as global warming will further increase the evaporation of its seven major valleys, of which the annual natural runoff has kept falling as a whole during recent years, according to the CMA.

"The aridity caused by climate changes in drought seasons will further deteriorate the already short water supply in the northern and northwestern parts of China," said Professor Ding Yihui, CMA'sspecial adviser on climate changes.

Ding said more evaporation and less flow of water due to climate warming in certain areas would probably intensify the pollution of rivers and lower the water quality.

The CMA's statistics show the temperature in China has risen 0.4 to 0.5 degree Celsius during the past century, slightly lower than the global average increase of 0.6 degree.

"Global warming will have a more profound effect on the water cycle in China's fragile arid and semiarid areas," said Zhu Changhan, chief research fellow on climate effects with the National Climate Center, adding that the northern China area would turn warmer and drier.

Zhu said global warming would bring also about serious consequences to the agriculture and hydropower in those drought-affected areas.

However, some experts also said global warming might enhance the earth's hydrological cycle and bring more rainfall worldwide on the average.

"Precipitation is projected to intensity during the 21st century. At low latitudes, there would be decreases in some regions and increases in others while in middle to high latitudes, precipitation would be intensified," said Godwin O.P. Obasi, secretary-general of the World Meteorological Organization in his address to the WMD 2003.

Some meteorologists said global warming would closely affect China's security in sectors like food, water resources and energy.

"The real risk is that the consequences caused by climate changes are usually irreversible," cautioned CMA director Qin Dahe.

(Xinhua News Agency March 24, 2003)