Rare ‘triple-dip’ La Nina phenomenon behind unusual air quality trend in India in 2022-23, finds a study

The study by a team of scientists led by Gufran Beig stressed that besides local emissions, rapidly changing climate is a significant factor affecting air quality. (Image: PTI)

According to a new study released on Sunday, an unusual triple-dip La-Nina event, extended by climate change, triggered a strange trend in the 2022-23 winter season where air quality improved in north India while peninsular India recorded an increase in pollution levels.

The three consecutive years of La Niña conditions (2020-23) had widespread impacts on the ocean and climate across the world. It is a rare “triple-dip” phenomenon.

The study by a team of scientists led by Gufran Beig stressed that besides local emissions, rapidly changing climate is a significant factor affecting air quality. Beig is a Chair Professor at the National Institute of Advanced Studies.

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The study is published in the Elsevier Journal. It shows that the air quality deteriorated in peninsular Indian cities in the 2022-23 winter season but improved in the northern part of the country, contrary to the trends seen in recent decades.

Among the north Indian cities, Ghaziabad registered the most important progress with a reduction of 33 percent, followed by Rohtak (30 percent) and Noida (28 percent). Delhi, being the most critical and landlocked city, showed a gain of about 10 percent.

On the opposite, Mumbai registered the highest deterioration with a 30 percent increase in PM2.5 levels, followed by other peninsular Indian cities like Coimbatore (28 percent), Bengaluru (20 percent), Chennai (12 percent), etc.

The dominance of higher northerly winds at the transport level forced an influx, trapping pollutants in peninsular India and raising PM2.5 concentration. The condition was aggravated by relatively slower winds near the surface in peninsular India.

Conversely, weak western disturbances, unusual wind patterns, and the lack of rain, clouds, and faster ventilation led to a significant improvement in air quality in north India.