Agence France-Presse | November 11, 2009

BEIJING (AFP) – Chinese scientists artificially induced the second major snowstorm to wreak havoc in Beijing this season, state media said, reigniting debate over the practice of tinkering with Mother Nature.

After the earliest snow to hit the capital in 22 years fell on November 1, the capital was again shrouded in white Tuesday with more snow expected in the coming three days, the National Meteorological Centre said.

The China Daily, citing an unnamed official, said the Beijing Weather Modification Office had artificially induced both storms by seeding clouds with chemicals, a practice that can increase precipitation by up to 20 percent.

The office refused to comment on the report when contacted by AFP. On Tuesday, an official had said the storm was "natural".

City weather officials have previously said that such methods are aimed at alleviating a drought over much of north China, including Beijing, that has lingered for more than a decade.

But residents have griped about the flight delays, traffic snarls, cancelled classes and other inconveniences of a surprise snow storm, saying officials could warn them if they are planning to toy with the clouds.

Beyond the day-to-day hassles, experts said the weather manipulation had other undesirable side-effects in the longer term, the paper reported.

"No one can tell how much weather manipulation will change the sky," Xiao Gang, a professor in the Institute of Atmospheric Physics at the Chinese Academy of Sciences, told the paper.

"We should not depend too much on artificial measures to get rain or snow, because there are too many uncertainties up in the sky."

Zhao Nan, a Beijing engineer, was quoted as saying the more than 5,500 tonnes of erosive snow-melting chloride used on city roads Tuesday -- nearly half the annual allotment -- could "erode steel structures of buildings".

In 2005, the snow-melting agent was responsible for killing 10,000 trees in Beijing and decimating 200,000 square metres (2.15 million square feet) of grassland, the paper said, citing official statistics.

Despite a massive effort to clear the capital of snow that involved over 15,000 workers, many roads remained blocked, while highways into Beijing and in neighbouring Hebei and Shanxi provinces were closed, state press reports said.