Record pollution in New Delhi: India experiments with cloud seeding against smog

In New Delhi the sky has become a laboratory. On October 23, for the first time in the country’s history, India attempted to “seed” the clouds to cause artificial rain, in the hope of reducing the toxic cloud that has been suffocating the capital for days.
The project, the result of collaboration between local authorities and the Indian Institute of Technology in Kanpur, represents an unprecedented experiment for one of the most polluted cities on the planet.

The test was conducted with a small Cessna plane over Burari, north of the federal territory of Delhi. “During the flight, cloud seeding rockets were launched,” explained Manjinder Singh Sirsa, the capital’s environment minister. The objective was to verify the ability of clouds to generate precipitation and test the technical coordination between the different agencies involved.

The art of making it rain: the cloud seeding technique

The cloud seeding technique, invented in the 1940s, involves the release of compounds such as silver iodide into the atmosphere to encourage the condensation of water vapor and stimulate the formation of rain.
Used in the past to fight drought or mitigate hailstorms, today it is rediscovered as a possible tool against urban pollution. However, the scientific community remains divided: the results are often uncertain and the potential ecological consequences not fully understood.

What the Texas case teaches

A recent study published in Atmosphere (Al Homoud et al., 2024) analyzed over five years of cloud seeding operations in West Texas, showing how seeding can significantly change the physical properties of clouds.
In the case of Tom Green County, small clouds experienced an average increase in duration of 53.6 percent, area by 47.1 percent, and volume by 63.6 percent, with an increase in precipitation of up to 150 percent compared to unseeded clouds.
The largest clouds showed smaller effects (between +27% and +33%), while the type B ones showed only 5–6%.

The researchers also highlighted that effectiveness is highly dependent on local weather conditions — particularly humidity, winds and water content — elements that can make an operation successful or a complete failure.

A useful comparison for New Delhi

Applying these results to the context of the Indian capital, it emerges that the challenge is not only technical but also climatic. The atmosphere of New Delhi, saturated with fine particulate matter, could alter the condensation mechanisms and reduce the efficiency of silver iodide particles, according to the same principle observed in Texas: denser aerosol clouds react less to seeding.

The Texas study also suggests that artificial rain produces immediate but not long-lasting results. In Texas, the years 2015-2016 showed a clear increase in precipitation, but by 2017 the values ​​returned to levels similar to the pre-experimental ones. This confirms that seeding can enhance individual rainfall events, but cannot stably modify the rainfall regime of a region.

Wash away the smog or address its causes?

In New Delhi, where PM2.5 particulate matter reaches peaks up to 60 times above the WHO limits, artificial rain could temporarily wash away the smog, but would hardly resolve the structural causes – traffic, agricultural combustion, industry.
As the authors of Atmosphere (2024) point out, “the effectiveness of cloud seeding depends on the correct alignment of meteorological conditions and integration with long-term environmental policies”.

New Delhi therefore looks to the sky, but the answer could be found closer to the ground: in the construction of systemic environmental governance and a culture of sustainability capable of reducing emissions at the root.
The rain may perhaps clean the air for a day, but the real challenge – scientific, political and social – is learning not to pollute it.