Explainer: Can artificial rain fix Delhi air?

THE Delhi government was set to conduct cloud seeding trials from October 7 to 11 to tackle the city’s persistent air pollution, but the experiment was postponed due to unfavourable weather conditions. Environment Minister Manjinder Singh Sirsa said the trial could be conducted “any day” once the India Meteorological Department (IMD) confirms a clear-weather window. The project, backed by IIT-Kanpur, involves dispersing silver iodide and salts into clouds to induce rainfall artificially. The idea is that the rain would wash pollutants from the atmosphere, particularly particulate matter, offering temporary relief to residents during the winter smog season.

What is cloud seeding

IIT-Kanpur Director Prof Maninder Agarwal explains that cloud seeding is a weather modification technique used to enhance rainfall. It works by introducing substances — most commonly silver iodide or potassium chloride — into clouds, which act as nuclei around which moisture condenses, forming raindrops. Globally, cloud seeding has been used since the 1940s, primarily to address droughts and water shortages in arid regions.

In China, large-scale cloud seeding has been deployed to induce rainfall before major events like the Beijing Olympics or in drought-prone regions. Dubai uses cloud seeding to supplement its scarce rainfall. However, experts note that these initiatives were aimed at increasing water supply, not controlling urban air pollution.

Why doubts persist

Sunil Dahiya, founder of the environmental think tank Envirocatalysts, expressed scepticism over the scientific rationale for Delhi’s experiment. “It is very difficult to understand, from a scientific perspective, that to reduce air pollution — a year-long problem and a health emergency — measures are being taken that don’t systematically cut down pollution at the source,” he said.

Dahiya explained that Delhi’s air pollution largely originates from vehicles, construction dust, small-scale industries, and even crop burning in neighbouring states. “Instead of tackling pollution at the source, cloud seeding offers a temporary and localised solution. The polluted air parcel will come from upwind directions within minutes to hours, and Delhi will again be polluted,” he said. “If you conduct this experiment during a period when there is already rainfall, it is very difficult to assess its impact scientifically,” he noted.

Global lessons

Dahiya clarified that no major city has relied on cloud seeding to control air pollution. “China’s success in reducing urban pollution came from cutting emissions at the source,” he said. Beijing, once one of the world’s most polluted cities, offers a stark contrast to Delhi. Over two decades, Beijing relocated polluting industries, upgraded coal-based power plants with flue gas desulphurisation (reducing sulphur emissions by 95 per cent), transitioned to cleaner fuels, and enforced strict vehicle emission norms.

“India adopted similar regulations in 2015, but progress has been slow, with only 12-15 per cent of coal plants implementing the technology until recently. And now, this year, the notification mandating the installation of flue gas desulphurisation at power plants has been taken away. Now there is a licence to pollute,” he added.

London, New York, and Mexico City have also successfully reduced air pollution through stringent regulation, technological upgrades, and cleaner fuels, Dahiya said.

Costs, risk, long-term solutions

The Delhi cloud seeding pilot project is estimated to cost Rs 3-4 crore. Dahiya cautioned about unintended results. “Inducing rain artificially alters moisture distribution. That moisture might have otherwise rained elsewhere. There could be consequences on micro-climatological patterns, which we do not fully understand.”

According to him, the real gains will come from systemic emission reductions using monitoring tools. Cutting emissions at the source — cleaner fuels, better industrial practices, vehicle norms — is what will provide lasting air quality improvement, Dahiya concluded.