India plans to change the weather to fight deadly smog

The Indian capital, New Delhi, is preparing a new weapon in the battle against deadly air pollution: cloud seeding. The experiment, which could take place as early as next week, will introduce chemicals such as silver iodide into cloudy skies to create rain and, it is hoped, wash away tiny particles hovering over one of the world’s largest cities.

The need is urgent. Delhi has already tried traffic-restricting measures, multi-million-dollar air filtration towers, and fleets of water-spraying trucks to dissolve airborne particles, but to no avail.

The use of cloud seeding, if it goes ahead, will be controversial. “This is not a good use of resources at all, because it is not a solution, it is a temporary relief,” says Avikal Somvanshi, a researcher at the Center for Science and Environment in New Delhi. Environmentalists and scientists are concerned that most of the government response is focused on mitigating pollution rather than trying to cut off its source. “There is no political intention to solve this problem, this is one of the biggest problems,” says Bhavreen Kandhari, activist and co-founder of Warrior Moms, a network of clean-air mothers.

The air is so bad that schools in Delhi and surrounding areas have announced their closure, and offices have allowed employees to work from home. The government advised children, the elderly, and those with chronic diseases to stay in their homes as much as possible. Diesel trucks, except those carrying essential goods, are no longer allowed into the city. Last week’s spells of rain cleared the air, but the respite was short-lived as air quality deteriorated again, aided by fireworks set off over the weekend to celebrate Diwali, the Hindu festival of lights.

Now, Delhi officials are seeking permission from federal agencies in India to experiment with cloud seeding. This technique involves flying an aircraft to spray clouds with salts such as silver, potassium iodide or solid carbon dioxide, also known as dry ice, to induce precipitation. Chemical molecules bind with moisture already in the clouds to form larger droplets that then fall as rain. China has used artificial rain to tackle air pollution in the past, but for cloud seeding to work properly, you need significant cloud cover with reasonable humidity, which Delhi generally lacks during the winter. If weather conditions are favourable, 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 the thick gray fog that has become a toxic ritual of winter. Smog, a dangerous mixture of harmful particles and gases, is caused by a series of unfortunate events that occur at the beginning of winter.