Scientists look to forecast smog more precisely(2)

Beijing, which witnessed frequent prolonged smoggy weather last winter, recently adopted an emergency program to handle air pollution. Cars with odd and even license plates will be allowed on roads on alternating days and schools will close when a red air pollution alert, the highest, is issued.

With a population of more than 20 million and 5.37 million vehicles, Beijing consumes 23 million tonnes of coal and seven million tonnes of fuel a year.

Vehicle exhaust, coal burning and floating dust contribute 22 percent, 16.7 percent and 15.8 percent to PM2.5 respectively in the city, according to the Beijing Environmental Protection Bureau. PM2.5, airborne particulate measuring less than 2.5 microns in diameter, can be inhaled by people.

The emissions of pollutants far exceeded what Beijing's environment is capable of bearing, said Liu Xianshu, director of the environmental monitoring department of the bureau.

"The demands of every citizen in food, travel and accommodation, are direct creators of the sources of pollutants," said Yu Jianhua, another official of the bureau.

The Chinese government aims to cut the density of inhalable particulate matter by at least 10 percent in major cities nationwide by 2017.

PM2.5, a key indicator of air pollution, should fall by about 25 percent from 2012 levels in Beijing and surrounding provincial areas by 2017, according to the government plan.

Regional joint efforts are important to tackle air pollution. Beijing has signed deals to cooperate with surrounding provinces in battling air pollution.

If pollutants in Tianjin affect Beijing, then Tianjin should be persuaded to take action with detailed scientific data on how much pollutants it contributes to Beijing, said Wang.