The Limitations of Cloud Seeding in Addressing Delhi's Air Pollution Crisis

Context

In October 2025, Delhi conducted cloud seeding trials aimed at improving air quality. Unfortunately, these efforts did not yield meaningful results. A recent study from IIT Delhi confirmed that cloud seeding cannot be relied upon as a dependable method for addressing winter air pollution in the city.

Background

In 2024, the Delhi government sought approval from the Centre to utilize cloud seeding as an emergency measure to combat spikes in winter pollution, driven by various factors:

• Delhi's air transforms into a hazardous mix of dust, smoke, and chemicals every winter.
• Decreasing temperatures, sluggish wind speeds, and temperature inversion trap pollutants close to the ground.
• Vehicular emissions and stubble burning exacerbate the air quality issues.
• The Air Quality Index often exceeds hazardous levels, leading to a search for artificial rainfall as a temporary relief measure.

Delhi has attempted multiple cloud seeding trials using a Cessna aircraft outfitted with silver iodide flares. However, these efforts have not resulted in significant rainfall over the capital. Experts highlight that effective cloud seeding necessitates specific cloud types that are typically absent during Delhi's cold and dry winters, showcasing the scientific limitations of the technique.

About Cloud Seeding

Cloud seeding is a weather modification technique that involves dispersing substances like silver iodide, potassium iodide, or dry ice into clouds to stimulate rainfall. This practice was initially tested globally in the 1940s.

Process

To artificially induce rain, clouds are injected with particles such as silver iodide, potassium iodide, or sodium chloride. These particles serve as nuclei around which cloud droplets can form. The substances can be dispersed using aircraft or ground-based generators. When sufficient droplets cluster and become heavy, they fall as rain.

Conditions Required for Cloud Seeding

• Cloud Availability: Essential, as rainfall cannot be induced without appropriate cloud formations.
• Moisture Level: Relative humidity should ideally exceed 50%.
• Instability (Convection): Adequate vertical cloud development is critical.
• Low Horizontal Wind: Strong winds can disrupt cloud formation and dispersion patterns.

Recent Findings: Artificial Rainfall Offers Only Short-Term Relief

A recent study indicates that during peak pollution months (December–January), moisture and cloud saturation levels in northern India are largely unsuitable for cloud seeding. While Western Disturbances occasionally provide opportunities, they are too infrequent for reliable intervention.

Heavy natural rainfall can reduce pollutants like PM2.5, PM10, and NOx, but light rainfall offers limited benefits. Even when air quality improves temporarily, ongoing emissions lead to a rapid resurgence of pollution levels. Furthermore, ozone levels tend to rise following rainfall.

Limitations of Cloud Seeding

• Effectiveness Difficult to Verify: It's challenging to determine if rainfall is induced or natural. Success requires a precise alignment of cloud type, moisture, and atmospheric conditions.
• Environmental Concerns: Potential risks include soil and water contamination, impacts on biodiversity, and long-term effects on groundwater and soil health.
• Ethical and Legal Challenges: Weather modification raises concerns about cross-regional impacts and jurisdictional issues.
• Not a Permanent Solution: Cloud seeding does not address the underlying causes of pollution and may distract policymakers from necessary long-term reforms.

Way Forward

To achieve meaningful and sustained improvement in Delhi’s air quality, a consistent reduction of emissions from vehicles, industries, construction activities, residential heating, and biomass burning is essential. If cloud seeding is considered, it must be guided by comprehensive scientific analysis, environmental risk assessment, and coordinated planning among states. Ultimately, India must emphasize sustainable air-quality management, resilient urban planning, and climate-adaptive development strategies.