Source: The Indian Express. Relevance: GS Paper l (Geography – Climatology)


This marks the initial occasion of connecting air quality in Indian urban areas to a La Nina occurrence — and consequently, to climate change, which is amplifying the intensity of both El Nino and La Nina.

Why in the News:

  • Recent research shows a unique La Niña event, extended by climate change, led to an unusual weather pattern in the winter of 2022-23 in India.

  • During a rare "triple-dip" La Niña from 2020 to 2023, air quality in northern India improved, but pollution levels in peninsular India increased during the winter of 2022-23.


  • India's monsoon rainfall is significantly influenced by El Niño and La Niña events (periodic warming and cooling in the eastern Pacific Ocean that impacts worldwide weather).

  •  A new study by Indian researchers suggests that these weather phenomena might also impact air quality.

Reasons for Poor Air Quality in Indian Cities:

  • There are several meteorological factors that contribute to the trapping of pollutants in the lower atmosphere levels. These factors include temperature, moisture, heaviness in air, wind speed, and direction.

  • Northern Indian Cities: From October to January, cities in northern India, particularly Delhi, often experience very high concentrations of PM2.5.

  •  Southern Indian Cities: In contrast, the western and southern regions of the country typically have lower pollution levels due to their proximity to oceans.

Understanding El Niño and La Niña:

  • El Niño and La Niña are two opposing climate trends that deviate from normal conditions and typically last for nine to twelve months but can sometimes extend.

  • Occurrence: These events occur irregularly, every two to seven years on average (El Niño is more frequent than La Niña), and together they form the El Niño-Southern Oscillation (ENSO) cycle according to scientists.

  • Characteristics: El Niño is typically referred to as the warm phase, characterised by a band of warmer water spreading from west to east in the equatorial Pacific Ocean, while La Niña is identified as the cold phase, marked by a band of cooler water spreading east-west.

  • Impacts : Both El Niño and La Niña can have global repercussions, affecting weather patterns, wildfires, ecosystems, and economies.

Findings of the New Study - Impact of La Niña on Air Quality in India:

  • Research Team: The study was conducted by researchers from the National Institute of Advanced Studies (Bengaluru) and the Indian Institute of Tropical Meteorology (Pune).

  • Monsoon Rainfall: The monsoon rainfall in India is known to be significantly affected by El Niño and La Niña events, which are the alternating warming and cooling of the eastern Pacific Ocean that impact weather globally.

  • Air Quality Impact: This is the first time that air quality in Indian cities has been associated with a La Niña event, and indirectly linked to climate change, which is exacerbating the severity of both El Niño and La Niña.

  • Normal Scenario: Typically, northern Indian cities, especially Delhi, witness very high concentrations of PM2.5 during the months of October to January.  

  • Winter 2022: However, the winter of 2022 displayed a significant deviation from this norm. Northern Indian cities, including Delhi, were cleaner than usual, while cities in the west and south, like Mumbai, Bengaluru, and Chennai, experienced worse-than-usual air quality.

  • PM2.5 Concentrations: In Delhi, PM2.5 concentrations saw a reduction of about 10%. Conversely, Mumbai witnessed a 30% rise, and Bengaluru registered a 20% rise in PM2.5 concentrations.

  • Investigation: The researchers initially set out to investigate this unusual behaviour and discovered the potential effects of La Niña.

  • La Niña Event: Not all La Niña events may result in noticeable changes in wind circulation over India, but this particular event was particularly strong.

  • Impact on Air Circulation: The impact on air circulation only became apparent in the third year of La Niña, suggesting a possible cumulative effect.

  •  El Niño Effect: It was not entirely clear at the time whether El Niño would produce an opposite effect on air quality over India.

What are PM2.5 and PM10 pollutants:

  • PM10 Definition: PM10 refers to particulate matter that is 10 micrometers or less in diameter.

  •  PM2.5 Definition: PM2.5, generally described as fine particles, refers to particulate matter that is 2.5 micrometers or less in diameter.

  •  Impact: PM2.5 is more likely to travel into deeper parts of the lung and can induce tissue damage and lung inflammation.

National Clean Air Programme (NCAP):

  • NCAP Launch: The Ministry of Environment, Forest and Climate Change (MoEFCC) launched the NCAP in 2019.

  •  Objective: The aim of the NCAP is to improve air quality in 131 cities, which includes non-attainment cities and Million Plus Cities, across 24 States/UTs by engaging all stakeholders. 

Research conducted by experts from the National Institute of Advanced Studies and the Indian Institute of Tropical Meteorology has uncovered a significant relationship between La Niña events and air quality in India. This newly established link highlights the critical role of climate variability in evaluating air quality and its consequences for public health and environmental policy in India.

Advait IAS