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Northern India’s Persistent Air Crisis
Context: A new study, “Air Quality Assessment of Major Indian Cities (2015–2025)” by Climate Trends, reveals that no major Indian city recorded safe air quality levels in the last decade, with Delhi being the most polluted among 11 analysed cities.
Why do northern cities in India face the impact of pollution than their southern and western counterparts?
Northern cities such as Delhi, Lucknow, and Varanasi displayed the most severe and persistent pollution, while southern and western cities like Chennai, Mumbai, Bengaluru, and Visakhapatnam showed comparatively better — though still unhealthy — AQI levels.
- Geographical Trapping (Indo-Gangetic Plain + Himalayas): Northern cities lie in the Indo-Gangetic Plain, which is landlocked and bounded by the Himalayas to the north. Pollutants cannot disperse easily because the mountains act like a barrier, trapping emissions in the basin. In contrast, southern and western cities are coastal or open to sea winds, which help flush pollutants away.
- Winter Inversion Effect: In winter, cooler, dense air near the surface gets trapped under warmer air above, forming an atmospheric “lid.” This winter inversion reduces vertical mixing, so pollutants accumulate close to the ground. Northern plains experience stronger and longer inversion periods compared to coastal regions, worsening smog episodes.
- Dense Urban Structures: Northern megacities like Delhi have dense built-up areas that create “surface roughness.” This slows wind speeds, further limiting pollutant dispersion. Southern/western cities often have more open layouts and coastal breezes that aid ventilation.
- Seasonal Meteorology: Monsoon rains and westerly winds in summer help clean the air in northern cities, but winter is stagnant. Coastal cities (Mumbai, Chennai, Visakhapatnam) benefit from sea breezes year-round, which dilute pollutants more effectively.
- Local Emission Sources: Northern cities face higher baseline emissions from vehicles, industries, biomass burning, and seasonal stubble burning. Even when farm fires contribute less, local emissions remain elevated. Southern/western cities have relatively lower seasonal agricultural burning impact.
