Environment / Cloud Seeding — UPSC Mains Model Answer

Cloud seeding typically employs silver iodide, liquid propane, or hygroscopic salts such as potassium iodide and calcium chloride as nucleating agents. These substances provide condensation nuclei around which water vapour aggregates, forming droplets heavy enough to precipitate. The agents are dispersed via aircraft, ground-based generators, or artillery shells depending on terrain and cloud conditions.

Artificial rainfall washes particulate matter, nitrogen oxides, and suspended dust from the atmosphere, offering temporary relief during smog emergencies. Several cities facing hazardous Air Quality Index levels have explored emergency cloud seeding as a supplementary intervention alongside odd-even schemes and industrial shutdowns. It addresses the symptom rather than the source, making it a crisis-management tool rather than a structural solution.

India currently lacks a dedicated legislative framework governing weather modification operations. Coordination between the India Meteorological Department, state governments, and civil aviation authorities remains ad hoc. Transboundary effects — altering rainfall patterns in neighbouring regions — raise questions of inter-state equity and international norms under customary environmental law.

The long-term accumulation of silver iodide in soil and water bodies poses ecological risks that are insufficiently studied in Indian conditions. Efficacy is highly contingent on pre-existing cloud cover, humidity, and wind patterns, limiting its reliability as a pollution-control instrument during dry winter inversions when pollution peaks.