Editorial: Cloud seeding under a cloud

The Delhi government must be consistent in implementing long-term anti-pollution measures rather than trying to nudge clouds to produce rain

Given the extent of air pollution in Delhi, the cloud seeding procedure can barely make a dent, let alone resolve the pollution problem. The recent attempt by the Delhi government to reduce pollution by inducing artificial rains came to nought. This is not surprising, because global experience shows that cloud seeding only offers conditional, short-term relief and is largely ineffective in checking pollution. The major constraint in Delhi, one of the most polluted cities in the world, is the lack of rain-bearing clouds during the pollution-prone season from October to December, when monsoon clouds retreat and atmospheric moisture is low. As a result, trials in the national capital saw only trace drizzles and minimal reduction in particulate matter due to insufficient atmospheric moisture, even though pollution levels were high. A small aircraft sprinkled silver iodide and salt particles on clouds over parts of Delhi’s sky, but 0.3 mm of rain over Noida and Greater Noida was all that came from the experiment, conducted in collaboration with IIT Kanpur. The clouds did not have enough water to pour down over the capital. Delhi’s pollution challenge is complex and deeply entrenched, requiring a multi-pronged effort. In the past, cloud seeding has been used as a drought management tool. But the jury is out on the technique’s efficacy in cleaning toxic air. Scientists had warned that the moisture content of the late autumn clouds would be insufficient to wash away the particulate matter in Delhi’s air.

Cloud seeding is a weather modification technique that involves dispersing substances such as silver iodide or sodium chloride into clouds to encourage rainfall. It has been used, with moderate success, in several countries, including China, the United States, and the UAE, mostly to tackle drought or enhance water availability. In India, it has been used intermittently in States such as Maharashtra and Karnataka for similar purposes. The pilot cloud seeding experiment aimed to induce rainfall that could temporarily wash pollutants from the atmosphere. While the desperation of the authorities is understandable, the harsh reality is that Delhi’s pollution problem cannot be dispersed with one-off, high-visibility interventions. Even if there is a small possibility of inducing rain due to cloud seeding, it is likely to be washed away on the upper side of the atmosphere, which doesn’t make any difference as far as air quality is concerned. The success of any intervention can be measured if particulate matter washes away when there is sufficient rain. Experts have warned that cloud seeding can never be a viable, long-term solution to the national capital’s worsening air pollution. The government must be consistent in implementing long-term, multi-pronged anti-pollution measures rather than depending on trying to nudge clouds to produce rain, a largely unproven method. Also, there is a need to step up investments in durable science-backed solutions.

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