NEW DELHI, India – It’s that time of year again in the capital of the world’s most populous country. 40 million people cough for weeks on end, splattering with toxic pollution.
It’s like clockwork these days. At the beginning of every winter, a gray haze settles over New Delhi and its nearby satellite cities. A toxic mix of exhaust fumes, smoke and dust that blurs the horizon and stings the lungs.
The day comes a week after firecrackers rang out in the sky, adding to the smoke as people celebrated Diwali, the annual Hindu festival of lights. The new government in Delhi, led by Prime Minister Narendra Modi’s Bharatiya Janata Party, believes the answer lies in “sowing clouds” and artificially producing rain to clear away the smoke, perhaps for mitigation rather than prevention.
What is the Delhi government doing?
On Tuesday afternoon, a small aircraft sprayed small amounts of silver iodide and sodium chloride compounds into clouds over Delhi, creating artificial rain.
The cloud seeding trial is aimed at tackling worsening air quality in the capital during the winter months.
The plane took off from Kanpur, a city in Uttar Pradesh state, 500 kilometers from New Delhi. In consultation with scientists from the Indian Institute of Technology (IIT) branch in the city, they conducted a cloud seeding exercise over parts of the capital.
Last week, the government conducted a test flight and reported it was successful. Delhi Chief Minister Rekha Gupta said this was a “necessity” for the country and a pioneering step to address New Delhi’s persistent environmental problems.
Why is Delhi suffocating?
Every winter, Delhi’s air becomes a dense and toxic mixture of dust, smoke and chemicals.
As temperatures drop, slow winds and a weather pattern called a “temperature inversion” trap pollutants closer to the ground.
The fine particles, known as PM2.5, are small enough to enter the bloodstream and accumulate from exhaust fumes from vehicles, factories and construction dust, and the burning of crop stubble in neighboring agricultural states creates plumes of black carbon and smoke.
These mix with gases such as nitrogen dioxide and sulfur dioxide in the air, forming new particles that are even more harmful. As a result, a gray, suffocating fog blankets the city.
The deadly mixture of airborne particles damages the lungs, and long-term exposure is thought to be associated with heart and lung disease, respiratory infections, and adverse birth outcomes.
Diwali firecrackers have only added to the suffocation of Delhi, which lives up to its reputation as one of the world’s most polluted cities.
How does cloud seeding work?
In a sense, it’s like “poking” the sky and making it rain. Scientists select clouds to “seed” according to their type, height, and atmospheric conditions and layer structure to estimate moisture distribution.
Then, a loaded plane or drone sprays tiny particles of salt (usually silver iodide) into the moisture-filled cloud. These act like “seeds” and provide the water vapor with something to stick to. As more water droplets gather around these particles, the particles become heavier until they fall as rain. By doing so, it is hoped that the pollution around us will be washed away.
Images shared by the Indian Institute of Technology Kanpur on Tuesday showed material being ejected from a flare attached to a plane flying over cloudy skies.
Is it effective?
Scientific results are mixed. Professors Shahzad Ghani and Krishna Achuta Rao, professors at the IIT Delhi Center for Atmospheric Sciences, said in a column in The Hindu on October 24 that cloud seeding cannot create natural clouds and the evidence that seeding reliably increases rainfall remains weak and controversial.
What’s more, experts are concerned that the buildup of large amounts of these salts in the soil after rain could actually harm the ecosystem.
Experts argue that artificial rain will only provide a temporary respite to New Delhi’s everlasting problems.
“Cloud seeding is just another gimmick in a series of similarly unscientific ideas, like smog towers, suggesting that flashy interventions can take the place of serious structural solutions,” Ghani and Achyutarao write.
