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With Delhi’s air quality plunging to severe levels each winter, the state government has renewed its call for cloud seeding as a potential intervention to reduce pollution. However, scientific assessments and governance experts warn that this approach offers limited, temporary relief and risks diverting attention from structural reforms required to address air pollution sustainably.

Why Delhi’s Air Quality Deteriorates in Winter

Delhi’s winter pollution is driven by a combination of meteorological and anthropogenic factors:

• Temperature Inversion: During winter, colder air remains trapped near the surface while warmer air lies above. This temperature inversion acts as a lid, preventing pollutants from rising and dispersing vertically.
• Low Wind Speeds: Weak winds limit horizontal movement of pollutants, causing particulate matter to accumulate in the lower atmosphere.
• Crop Residue Burning: Post-harvest stubble burning in Punjab, Haryana, and western Uttar Pradesh releases large quantities of smoke and suspended particles, which are carried to Delhi via prevailing winds.
• Dust and Urban Emissions: Vehicular emissions, construction dust, industrial exhaust, and waste burning remain trapped within the low boundary layer height, intensifying pollution.
• Post-Monsoon Stagnation: Stable high-pressure systems reduce atmospheric mixing, compounding North India’s chronic winter air quality problem.

What is Cloud Seeding?

Cloud seeding is a form of weather modification intended to enhance rainfall using chemical agents.

• Origin: First demonstrated in 1946 by Vincent J. Schaefer.
• Seeding Agents: Silver iodide, potassium iodide, sodium chloride, and dry ice are commonly used.
• Mechanism: The agents act as nuclei for condensation or ice-crystal formation, encouraging droplet growth. Once droplets become heavy, they fall as precipitation.
• Delivery Methods: Aircraft, rockets, or ground-based generators disperse particles into suitable moisture-laden clouds.

However, cloud seeding requires the presence of natural clouds with adequate moisture and cannot generate clouds on its own.

Scientific and Environmental Limitations

• Reliance on Existing Clouds: Delhi often lacks suitable cloud systems during peak pollution periods. Cloud seeding has no impact in the absence of adequate moisture.
• Weak Evidence of Effectiveness: Global scientific studies show inconsistent results. Even when rainfall occurs after seeding, establishing causality is difficult.
• Only Temporary Pollution Relief: Rain may wash away PM2.5 and PM10 temporarily, but pollution typically rebounds within 1–2 days. Secondary pollutants like ozone and sulphur dioxide remain unaffected.
• Environmental and Health Concerns: The use of silver iodide raises concerns regarding long-term ecological and health impacts due to chemical deposition. Evidence on safety is limited and inconclusive.
• Governance and Accountability Issues
  • Unpredictable outcomes may lead to public criticism.
  • Accountability becomes unclear if cloud seeding coincides with flooding or adverse weather events.

Ethical and Policy Concerns

• Misallocation of Resources: Investing in cloud seeding may divert funds from proven interventions.
• Distracting Public Attention: Temporary fixes risk undermining public trust and shifting focus away from systemic issues.
• Potential Misuse: Short-term optics may overshadow long-term environmental governance.

Real Solutions for Air Pollution Control

Experts emphasise that lasting improvement requires sustained structural action:

• Cleaner Transportation
  • Strengthening public transport
  • Transition to electric mobility
  • Enforcing emission norms
• Sustainable Energy Transition
  • Phasing down coal-based power
  • Scaling up renewables
  • Promoting clean industrial technologies
• Improved Waste Management
  • Curbing open waste burning
  • Efficient municipal systems
• Construction and Dust Control
  • Enforcement of dust mitigation norms
  • Use of green barriers and mechanised sweeping
• Agricultural Reforms
  • Subsidising sustainable stubble management
  • Promoting crop diversification in Punjab and Haryana
• Urban Planning Reforms
  • Increasing green cover
  • Reducing congestion through better mobility planning