Context:

• Delhi’s winter air pollution is likely to intensify due to the combined effects of vehicular emissions, stubble burning, firecrackers and unfavourable meteorological conditions.
• An exceptionally strong El Niño event could worsen the situation by weakening winds, reducing rainfall and trapping pollutants near the ground.
• The challenge highlights the need to shift from fragmented, city-centric measures to science-based, regional airshed management.

Reassessing the Sources of Air Pollution:

• PM₂.₅ versus PM₁₀:
  • PM₂.₅ (fine particulate matter) consists of particles with a diameter of 2.5 micrometres or less. It can penetrate deep into the lungs and enter the bloodstream, posing serious health risks.
  • PM₁₀ consists of particles with a diameter of 10 micrometres or less and includes coarser dust particles.
  • According to the findings under SAFAR (System of Air Quality and Weather Forecasting and Research), the transport sector accounted for approximately 40% of Delhi’s PM₂.₅ emissions.
• Policy priorities and measurement gaps:
  • The National Clean Air Programme (NCAP) has historically emphasised reductions in PM₁₀ concentrations, encouraging attention to road dust and construction activities.
  • While dust control is necessary, an excessive focus on PM₁₀ reduction can divert attention from combustion-related sources such as vehicles, biomass burning and waste burning.
  • The key concern: Air-quality policies must address the pollutants most harmful to health rather than rely disproportionately on a single performance indicator.

Super El Niño - A Potential Winter Pollution Multiplier:

• El Niño:
  • It refers to the periodic warming of the central and eastern equatorial Pacific Ocean, which alters atmospheric circulation and influences weather patterns worldwide.
  • It does not directly generate pollution but can worsen air quality by creating conditions that restrict pollutant dispersion.
• How El Niño could aggravate Delhi’s pollution?
  • Weaker winds: Reduced wind speeds over northern India could prevent PM₂.₅ from dispersing, allowing emissions from vehicles, stubble burning, biofuels and open waste burning to accumulate.
  • Fewer western disturbances: They bring winter precipitation to northwestern India. If their frequency or influence declines, fewer rain events may remove pollutants from the atmosphere, prolonging dry and polluted conditions.
  • Temperature inversion and stagnant air: Stable atmospheric conditions and surface temperature inversions can suppress vertical mixing, trapping pollutants close to the ground and sharply increasing their concentrations.
• Together, these factors could produce prolonged and severe pollution episodes across Delhi and the Indo-Gangetic Plain.

Stubble Burning:

• The challenge of accurate monitoring:
  • Punjab and Haryana have experienced substantial rainfall deficits, affecting agricultural conditions.
  • Early monsoon rainfall in some areas enabled earlier paddy sowing, potentially advancing harvesting and the associated period of stubble burning.
  • Evidence suggests that some farmers may have shifted stubble burning from morning to evening.
  • MODIS-based fire detection, widely used for monitoring agricultural fires, may consequently miss some incidents because satellite observations capture fires only under particular observational conditions.
  • However, the actual effect of rainfall deficits on paddy yields, harvesting patterns and the extent of stubble burning remains uncertain.
• Policy implication:
  • Authorities should strengthen ground-level verification and use multiple monitoring methods rather than rely exclusively on satellite fire counts.
  • Accurate measurement is essential for assessing the effectiveness of mitigation measures.

The Critical November Pollution Window:

• The festive season, including Diwali-related firecracker emissions, coincides with winter pollution and the stubble-burning period.
• Historically, November 5–10 has been particularly challenging for Delhi’s air quality.
• Weak winds could create an atmospheric trap in which emissions from vehicles, agricultural fires, firecrackers and other sources accumulate rapidly.
• Preventive measures should therefore be intensified during this critical period, including -
  • Strict enforcement of firecracker restrictions.
  • Timely support for farmers to adopt alternatives to burning.
  • Reduced vehicular emissions and effective public transport.
  • Targeted restrictions on polluting activities when meteorological conditions deteriorate.
  • Real-time monitoring and coordinated emergency responses.

Way Forward - From City-Centric to Airshed-Based Management:

• Short-term measures: Implement winter action plans, strengthen pollution forecasting, monitor agricultural fires more accurately and coordinate emergency interventions across neighbouring States.
• Medium-term measures: Expand access to crop-residue management machinery, incentivise in-situ and ex-situ residue utilisation, improve public transport and strengthen regional emission inventories.
• Long-term structural reforms:
  • Airshed-based governance: Treat the Indo-Gangetic Plain as an interconnected pollution system rather than managing Delhi in isolation.
  • Institutional coordination: Establish mechanisms for joint planning and accountability among States and urban and rural authorities.
  • Science-led policymaking: Align funding and performance indicators with health-relevant pollutants, particularly PM₂.₅, alongside PM₁₀.
  • Climate-informed planning: Integrate seasonal forecasts, climate projections and meteorological conditions into pollution-control strategies.

Air-Quality Research and Management:

• The National Air Quality Resource Framework of India (NARFI), developed by the National Institute of Advanced Studies (NIAS) under the Office of the Principal Scientific Adviser, provides a framework for strengthening air-quality research and management.
• Where a full airshed is too extensive for practical implementation, smaller satellite airsheds can offer operational units for coordinated action.

Conclusion:

• Delhi’s winter pollution is not merely a local emissions problem; it is the product of regional pollution sources interacting with adverse weather and climate variability.
• A durable solution requires coordinated airshed governance, reliable scientific monitoring and sustained action across short-, medium- and long-term horizons.