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China will "seed" the clouds looming over its cities with rockets and chemical pellets to bring rain and so clear its polluted skies for the Olympics in 2008. China leads the world in using cloud seeding to induce rainfall. In the past five years, the practice has produced enough precipitation to fill the Yellow river, the country's second longest, four times over.
The Games will be the biggest test to date of cloud seeding.
Some studies show cloud seeding can increase precipitation by up to 30 per cent, but others are wary of the overall effect on the environment.
In the past five years, Chinese air force jets have flown nearly 3,000 flights and sowed rain-making chemicals to bring down 210 billion cubic metres of water over three million square kilometres, nearly a third of China's territory. Rain-making rockets and shells were used in 1,952 counties across the country, and 3,000 people are employed in the business, with a formidable arsenal of 7,000 cannon and 4,687 rocket launchers.
Weather specialists induced rain in early May in Beijing to help relieve drought and wash tons of dust from the Gobi desert dumped on the capital by a rash of sandstorms. Cloud seeding is also used to prevent hail and extinguish forest fires. Artificially induced rain was used to help put out three major forest fires that raged in north and north-east China for 10 days before they were subdued last Friday.