Kolkata's Air: Blame Winter's Stagnation, Not Just Smog

A recent study by Climate Trends reveals that Kolkata's winter air pollution is significantly influenced by meteorological factors and climate change, moving beyond solely emissions-based concerns.

The analysis highlights that atmospheric stagnation, characterized by low wind speeds and high humidity, is a major amplifier of pollution across Indian cities, including Kolkata. During winter, weak ventilation in Kolkata prevents pollutants from sources like biomass and waste burning from dispersing, leading to their accumulation near the ground.

While Kolkata's PM2.5 levels do not reach the extremes seen in Delhi or Patna, the city experiences moderate to high pollution during winter months due to prolonged stagnant conditions. This results in a pronounced seasonal contrast, with significantly lower pollution during the monsoon season.

For instance, winter averages in 2024 and 2025 ranged between 77.2 and 80.9 µg/m³, with monthly peaks reaching alarming levels like 99.7 µg/m³ in January 2024. Conversely, monsoon averages dropped to around 20-21 µg/m³ in 2024 and 2025. Experts emphasize that pollution control strategies must integrate dispersion modeling with emissions inventories, recognizing the impact of local and regional sources and winter boundary-layer dynamics.