Triple dip La-Nina and Air quality in India

GS Paper 2

 Syllabus: Geography

Source: IE

 Context: Research has identified climate change as a primary cause of poor air quality in Mumbai during the winter of 2022. The study, titled “Triple dip La-Nina, unorthodox circulation and unusual spin in air quality of India,” links the city’s high pollution levels to delayed wind reversals and less frequent calm winds triggered by La Nina and Climate Change.

What is Triple Dip La Nina?

It refers to an unusual and prolonged La Nina phenomenon lasting three consecutive years, which significantly impacts global weather patterns. La Nina typically involves cooler-than-average sea surface temperatures in the central and eastern Pacific Ocean, leading to various climatic effects worldwide, such as altered rainfall patterns, increased tropical cyclone activity, and shifts in temperature gradients.

• WMO had stated in August 2022 that for the first time this century, La Nina would span three consecutive northern hemisphere winters to become a ‘triple dip’ La Nina.

What does the study indicate?

During the winter of 2022–23, an unusual trend reversal in pollution levels, particularly PM2.5, was observed in India. South-Western regions experienced unusually poor air quality, while North India showed relatively cleaner air, contrary to typical patterns.

Factors responsible for this included:

1. Triple-dip La Niña event: The winter coincided with the last phase of an unusual triple-dip La Niña event, affecting atmospheric conditions.
2. Change in wind direction: Normally, winds blow from Punjab towards the Gangetic plains, carrying pollutants from stubble burning towards Delhi. However, during the winter of 2022, wind circulation changed to a north-south direction.
   1. This led to air pollutants from Punjab and Haryana bypassing Delhi, resulting in lesser pollution in the capital and surrounding areas.
3. Instead, pollutants flew over western and southern regions, contributing to the poor air quality observed in South-Western India.

Mumbai’s Air Pollution:

1. Air quality in Mumbai deteriorated significantly, with 66 out of 92 days between November 2022 and January 2023 categorized as “poor” or “very poor.”
2. In comparison, Delhi experienced 79 days of “Poor” and “Very Poor” AQI during the same period. (Data from SAFAR – Ministry of Earth Sciences).

Reasons:

Mumbai benefits from its coastal location, which aids in naturally cleansing its air. Strong surface winds and sea breezes help rapidly disperse pollutants, maintaining better air quality.

However, last winter, Mumbai experienced a rare “triple dip” in La Niña, associated with climate change. This prolonged La Niña phase led to infrequent wind reversals from the sea, trapping pollutants in the lower atmosphere for longer durations and deteriorating air quality despite Mumbai’s usual cleansing mechanisms.

Increasing variability of the El Nino-La Nina system:

• Variability: as seen from the chart below, the ENSO system has been becoming more unpredictable as sudden changes to strong El Nino or La Nina are seen.
• Climate change: Warmer ocean temperatures, driven by climate change, can intensify El Niño events, leading to more frequent and intense occurrences. Similarly, La Niña events can also be influenced by climate change, affecting their frequency and severity.
• Tropical weather: Extremities in the impact of this variability are also strong. Tropical cyclones and precipitation have been observed to increase with this ENSO variability.
• Regional variation: On the other hand, the ENSO variability has also induced chaos in regional weather systems as impacts of rainfall and droughts have finer variability within African or Asian climates.

Its impact on India:

• Triple dip: The continuance of La Niña into 2023 is not bad news from the Indian standpoint, but it is not the same for all its constituent regions.
  • El Niño tends to weaken the Indian monsoon, leading to droughts, while La Niña strengthens it, causing floods. Climate change-induced extremes in ENSO events could result in more erratic and intense monsoon seasons, impacting agriculture, water resources, and livelihoods.
  • Observationally, the extremities of monsoon in intensity and regional spread have increased. Parts of the same state like in Maharashtra have seen floods and droughts.
• Variation: The variability makes the Indian monsoon model used by IMD less relevant as there is mathematical chaos in input variables.
• Cyclones: The variability has also drastically affected Indian Ocean cyclogenesis. Empirically, the Arabian Sea branch has observed increased cyclogenesis compared to historical averages.
• Science: The robustness of Indian weather science is impacted which makes early warning systems (EWS) on floods, droughts, cyclones etc less reliable.

Conclusion:

Thus, there is a great need to conduct scientific research and study on the variability of ENSO as even highlighted by the 2021 Nobel Prize in physics in this field of study. Indian Earth Science ministry and other bodies must also work for the protection of its citizens from these extremities.

Insta Links:

• El Nino

Prelims Links: