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The winter of 2022 brought with it a grim reality for the residents of Mumbai, India’s bustling financial capital. A recently published study has shed light on a troubling trend: poor air quality in Mumbai, exacerbated by climate change. According to the study, Mumbai experienced its worst air quality deterioration in the country during this period, with PM2.5 levels soaring by a staggering 30 percent. The study, which analyzed data from November 2022 to January 2023, revealed that out of the 92 days in this period, Mumbai suffered from poor air quality for 66 days.
This revelation serves as a wake-up call, indicating that last year’s poor air quality in Mumbai could become a recurring issue during winters if urgent action is not taken to address the root causes—emissions at their source and climate change. While Mumbai is currently experiencing moderate air quality, with an overall Air Quality Index (AQI) of 144, the study warns that without intervention, the city could face a bleak future marked by frequent episodes of poor air quality.
Interestingly, while Mumbai grappled with deteriorating air quality, the National Capital Region (NCR) experienced a significant improvement in air quality during the same period. This disparity can be attributed to a rare weather phenomenon known as a “triple-dip” La Niña, which reduced pollution levels in North India while exacerbating them in peninsular parts of the country.
Among the cities in northern India, Ghaziabad experienced the most notable improvement in air quality, with PM2.5 levels, an ultrafine pollutant, decreasing by 33%. This was followed by Rohtak with a decrease of 30% and Noida with a decrease of 28%. Delhi saw a modest improvement of around 10%. Conversely, Mumbai observed the most significant deterioration, while other cities in peninsular India also experienced increases, including Coimbatore (28%), Bengaluru (20%), and Chennai (12%), among others.
RH Kripalani, a climate scientist at the Indian Institute of Tropical Meteorology and co-author of the report, stated that the winter of 2022-23 had coincided with the last phase of an unusual triple-dip La Nina event, marking the first occurrence of its kind in the 21st century. He mentioned that this phenomenon, influenced by climate change, had impacted the large-scale wind pattern, playing a decisive role in preventing stagnation conditions in north Indian cities and thus improving air quality.
The rise in PM2.5 levels, fueled by both natural and anthropogenic sources, poses significant risks to public health and environmental sustainability. India’s rapid economic growth has only exacerbated these challenges, with emissions from industries, transportation, and agricultural practices contributing to the deterioration of air quality.
Gufran Beig, a chair professor at the National Institute of Advanced Studies, who spearheaded the team of scientists for the project stated “The findings of the current paper suggest that we need to wake up to the fact that extreme and unusual occurrences in air pollution phenomena are directly or indirectly manifestations of climate change”.
During the La-Nina phase of the El Nino Southern Oscillation (ENSO) phenomenon over the Pacific Ocean, the western Pacific Ocean experiences warmer waters while the eastern Pacific Ocean has cooler waters. This leads to an interaction between the ocean and atmosphere, resulting in easterly winds over the equatorial Pacific during the La Nina phase. These winds can extend over South Asia, altering circulation patterns and influencing the climate of the Indian sub-continent. The recent occurrence of a triple-dip La Nina state began in the summer of 2020 and persisted until early 2023, the paper states. Additionally, aerosols emitted from both natural and anthropogenic sources can further impact the climate over the Indian subcontinent. The degree to which anthropogenic aerosols affect the climate and the underlying mechanisms remain largely uncertain, a topic that is also addressed in this paper. Thus, the findings of this research contribute to bolstering the understanding of the relationship between climate change and variability in air quality.
The intricate relationship between air quality and climate change is increasingly evident. Climate-driven phenomena such as La Niña can disrupt meteorological patterns, trapping pollutants and worsening air quality. Studies have shown that extreme weather events associated with climate change, such as heatwaves and stagnation events, are likely to intensify air pollution, posing further risks to public health.
While the impacts of climate change-related extreme weather events on air quality have been documented, quantifying these effects and their implications for public health remains an ongoing challenge. The need for comprehensive approaches to address both air pollution and climate change is more urgent than ever.
In India, crop residue burning during winter exacerbates air pollution issues, particularly in Northern regions. Meteorological conditions play a crucial role in shaping pollutant concentrations, highlighting the complex interplay between weather and air quality.
Recent research has attempted to unravel the factors driving variability in PM2.5 levels across different regions of India. The study suggests that climate change-driven disturbances in large-scale meteorological patterns significantly influenced air quality trends in the Indian subcontinent during the winter of 2022–23.
Using advanced modelling techniques and statistical analyses, researchers have explored the association between La Niña-induced changes in large-scale wind patterns and variability in particulate pollutants in 2022. The findings underscore the need for interdisciplinary research and collaboration to develop effective policies and interventions that safeguard public health and environmental sustainability.
References:
https://www.sciencedirect.com/science/article/abs/pii/S0048969724011021
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