India’s capital, New Delhi, is preparing a new weapon in the fight against deadly air pollution: cloud seeding. The experiment, which could take place as early as next week, would introduce chemicals such as silver iodide into a cloudy sky to generate rain and, it is hoped, remove the fine particles that hang over one of the world’s largest cities.
The need is desperate. Delhi has already tried traffic restriction measures, multi-million-dollar air filtration towers and the use of fleets of water spray trucks to dissolve airborne particles, but without success.
The use of cloud seeding, if carried out, would be controversial. “It’s not at all a good use of resources because it’s not a solution, it’s like a temporary relief,” says Avikal Somvanshi, a researcher at the Center for Science and Environment in New Delhi. Environmentalists and scientists worry that most of the government’s response will focus on mitigating pollution rather than trying to cut off its source. “There’s just no political intent to solve this, that’s one of the biggest problems,” says Bhavreen Kandhari, activist and co-founder of Warrior Moms, a network of mothers demanding clean air.
The air is so bad that schools in and around Delhi have announced closures and offices are allowing employees to work from home. The government has advised children, the elderly and people with chronic illnesses to stay home as much as possible. Diesel trucks, except those transporting essential goods, can no longer enter the city. Last week’s spells of rain cleared the air, but the respite was short-lived as air quality worsened again, helped by firecrackers set off over the weekend to celebrate Diwali, the Hindu festival of lights.
Now, officials in Delhi are asking India’s federal agencies for permission to attempt cloud seeding. The technique involves flying an airplane to spray clouds with salts such as silver or potassium iodide or solid carbon dioxide, also known as dry ice, to induce precipitation. Chemical molecules attach to moisture already in clouds to form larger droplets that then fall as rain. China has used artificial rainfall to combat air pollution in the past, but for cloud seeding to work properly, significant cloud cover with reasonable moisture content is needed, which Delhi generally lacks during winter. If weather conditions are favorable, scientists leading the project at the Indian Institute of Technology in Kanpur plan to carry out cloud seeding around November 20.
Until then, at least, Delhi will remain shrouded in a thick gray haze, which has become a toxic winter ritual. Smog, a dangerous cocktail of harmful particles and gases, is the result of a series of unfortunate events that occur at the beginning of winter.