As Delhi considers using cloud seeding to tackle the unprecedented smog choking it, it could be useful to look at another country that used the method --- China.
Cloud seeding is an artificial way to create rainfall. It is done either by using artillery to fire shells containing rain-inducing chemicals such as silver iodide into the cloud cover or by dropping chemicals from aircraft.
The Chinese government has used cloud seeding technology in the past not only to create artificial rain but also to clear air pollution using induced precipitation. Most famously, the technology was apparently used to keep the skies over Beijing blue during the 2008 August Olympics.
China even offered its cloud seeding technology to India to artificially induce rain in regions affected by drought when a team of top meteorological scientists from Beijing, Shanghai and Anhui visited Maharashtra in May to study the drought patterns in the state.
The Chinese government believes the technology works.
Earlier this year, the ministry of finance allocated 199 million yuan ($ 29.8 million) to support weather modification operations by local authorities.
“Weather modification usually refers to cloud-seeding practices that involve shooting various substance into clouds, such as silver iodide, salts and dry ice, to bring on the formation of larger raindrops and trigger downpours, as well as clear smog and clouds,” Xinhua, the official news agency, said in a report.
The money, the report added, will be used to relieve drought, bring about artificial rain and prevent hailstones by using aircraft, guns and rockets.
However, caution must be exercised before emulating China’s approach.
First, it isn’t clear how often authorities in Beijing use the technology to clear smog or whether it is effective at times of chart-busting pollution.
Second, the technique is only successful if the conditions are conducive to rain; there must be a cloud there to begin with so that enough moisture could be generated for rain.
And third, experts warn of secondary air and water pollution as an outcome of the chemicals used in the process – the chemicals used in creating rain and clearing the air could in turn leave behind residues of pollution.
Like New Delhi, whose pollution problem was exacerbated by Diwali crackers, Beijing has to tackle a similar problem during week-long Chinese New Year celebrations that take place at the beginning of every year. The tradition is to burst crackers to drive away evil spirits much like during Diwali.
China has dealt with this by spreading anti-pollution awareness among people and acknowledging the harm that crackers cause. The measures seemed to have been effective.
“The municipal environment monitoring centre monitored a firework spree on the eve of Spring Festival (China's Lunar New Year) on Sunday night that drove up the PM2.5 reading to as high as 700 mg ((micrograms) per cubic metres,” Xinhua said in a report in February this year.
“However, with a rising awareness of air protection, the capital city has witnessed a big fall of firework consumption. From Sunday to Monday morning, sanitation workers swept away 413 tonnes of firework clastic on the streets, down by 33.8% from the same period of last year,” Xinhua reported.