Despite having a firm scientific understanding, even the scientific community was somewhat curious—after all, some of the country’s top institutions were leading the effort.
The science behind cloud seeding is quite fundamental. It is a weather modification technique, in which chemicals, such as silver iodide, sodium chloride, or similar compounds, are injected into certain types of clouds to forcefully induce rainfall. These particles act as cloud condensation nuclei, potentially leading to rain.
However, cloud seeding works only on a specific class of clouds known as hygroscopicclouds, which already contain abundant liquid water and respond effectively to the introduction of extra nuclei of chemicals injected. In contrast, clouds lacking these characteristics are generally resistant to such external interventions, making seeding largely ineffective.
Another aspect is also well documented that such kind of specific clouds are abundant up to 50 per cent in pre- and post -monsoon periods, but they are hardly present during the winter time—to be more precise, during end of October to January time, with five to 10 per cent probability only. This is the time when pollution peaks and we need control strategy. So, it is seasonally misaligned with the air pollution issue.
Where does combining the probabilities of overall 50 per cent possibility under ideal conditions and, within it, five to 10 per cent chance during the winter time, lead us? This technique looks understandable for drought control, because such pre-conditions are not attached there and we need rain at a larger window. In addition, we need these clouds only when there is an extreme air pollution event, not on any day in winter. Moreover, the stakes are high in terms of finances and scientific institutions. I leave it to the wisdom of the reader to decide as to how far this adventure is okay.
Finally, cloud seeding was carried out on October 28, 2025. Three distinct narrative/opinions have since emerged: (a) it was a success with a significant reduction in particulate matter; (b) it achieved modest success, producing light drizzle in parts of Delhi with some positive outcomes; and, (c) it was a failure.
The implementing scientific agency leaned toward the second view of partial success. Why was it called partial? Because the target clouds lacked sufficient moisture, a condition that expert agencies were expected to assess and ensure beforehand. Whether their technical advice was formally sought, and if so, what assessment they provided, remains unclear.
We should perhaps thank nature that the drizzle—if it indeed resulted from cloud seeding—did not occur under chilly conditions; otherwise, it could have been scientifically counterproductive and even harmful. While a good spell of rain can effectively wash out particulate pollutants, drizzle during cooler weather can trigger a process known as secondary aerosol formation. In such cases, pollutant particles find cool surfaces to coagulate and multiply, leading to a rapid increase in ultra-fine particulates and, consequently, pollution levels. The underlying reality remains that emission generation is a continuous process—it quickly rebuilds and, in interaction with prevailing weather conditions, restores pollution levels. Any relief, therefore, is likely to be short-lived—perhaps lasting only a day or less.
Nevertheless, the cloud seeding trial will fulfil two aspirations: it attends to the curiosity of many and the honest post-event analysis will likely settle the debate on its scientific sanctity.
Air pollution of Delhi remains a long standing issue, and its mitigation must be rooted in coordinated, year-round actions targeting persistent sources of pollution.
(Views are personal)
