TAG: GS 1: GEOGRAPHY
THE CONTEXT: In the winter season of 2022-23, India experienced an anomalous air quality trend, attributed to a rare “triple-dip” La Niña phenomenon, as revealed by a recent study led by Chair Professor Gufran Beig and his team at the National Institute of Advanced Studies.
EXPLANATION:
- The study, published in the Elsevier Journal, sheds light on the intricate interplay of climate change and local emissions in influencing air quality across the subcontinent.
Triple-Dip La Niña Phenomenon:
- The study highlights the occurrence of three consecutive years (2020-23) of La Niña conditions, a rare “triple-dip” event.
- ‘Triple Dip’ La Niña is a period where the La Niña period extends for up to three consecutive winters and results in multiyear cooling of the surface temperature of the equatorial Pacific Ocean.
- For example, the current La Niña episode was started in September 2020, prevailed for the last 24 months, and looks set to continue for another six months, and has thus been classified as a ‘triple dip’ La Niña.
- La Niña, known for impacting ocean and climate patterns globally, took an unprecedented turn, leading to diverse consequences in India’s air quality during the winter season.
- Contrasting Trends in North and Peninsular India: Contrary to the established trends of air quality in recent decades, the 2022-23 winter season witnessed a unique phenomenon where northern India experienced improved air quality, while peninsular India faced escalating pollution levels.
North India’s Air Quality Improvement:
- Among the northern cities, Ghaziabad exhibited the most significant progress with a remarkable 33 percent reduction in 5 levels.
- Rohtak and Noida followed closely with reductions of 30 percent and 28 percent, respectively.
- Even the capital city, Delhi, displayed a positive shift with a 10 percent gain.
Peninsular India’s Deteriorating Air Quality:
- In stark contrast, peninsular Indian cities experienced a deterioration in air quality during the same period.
- Mumbai led the unfortunate trend with a substantial 30 percent increase in PM2.5 levels.
- Other cities like Coimbatore, Bengaluru, and Chennai witnessed rises of 28 percent, 20 percent, and 12 percent, respectively.
Meteorological Factors Influencing Air Quality:
- The study identifies meteorological factors as crucial contributors to these divergent trends.
- Higher northerly winds at the transport level in peninsular India led to the trapping of pollutants, causing an increase in PM2.5 concentration.
- This condition was exacerbated by slower winds near the surface in peninsular regions.
- Conversely, north India experienced improved air quality due to weak western disturbances, unusual wind patterns, and the absence of rain and clouds, facilitating faster ventilation.
Climate Change as a Significant Factor:
- The research underscores the role of rapidly changing climate as a significant factor influencing air quality.
- The triple-dip La Niña event, exacerbated by climate change, created a complex interplay of meteorological conditions, impacting pollution levels in distinct ways across the country.
La Nina:
- La Niña is the opposite of El Niño.
- La Niña sees cooler than average sea surface temperature (SST) in the equatorial Pacific region.
- Trade winds are stronger than usual, pushing warmer water towards Asia.
- On the American west coast, upwelling increases, bringing nutrient-rich water to the surface.
- Pacific cold waters close to the Americas push jet streams — narrow bands of strong winds in the upper atmosphere — northwards.
- This leads to drier conditions in Southern U.S., and heavy rainfall in Canada.
- La Niña has also been associated with heavy floods in Australia.
- Two successive La Niña events in the last two years caused intense flooding in Australia, resulting in significant damage.
Conclusion:
- The findings of this study not only unravel the intricate dynamics of a rare triple-dip La Niña event but also emphasize the need for a comprehensive understanding of local emissions and global climate patterns to predict and manage air quality in the face of a changing climate. The anomalous trends observed in the 2022-23 winter season serve as a stark reminder of the interconnectedness of natural phenomena and human-induced factors in shaping environmental conditions.