El Nino Explained for UPSC

Source: Indian Express
GS I: Salient features of World’s Physical Geography.   GS III: Disaster Management, Environment, Agriculture

Overview

1. News in Brief
2. El Niño
3. Reasons for the Strengthening El Niño
4. Impact of El Niño on India
5. India’s Preparedness

Why in the News?

The US National Oceanic and Atmospheric Administration (NOAA) has estimated an 81% chance of the current El Niño becoming very strong during October–December.

News in Brief

• The India Meteorological Department (IMD) has cautioned that a stronger El Niño may lead to below-normal monsoon rainfall over parts of the country.
• If this happens, it could be one of the strongest El Niño events since 1950.
• IMD has also indicated that the present El Niño is likely to continue into 2027, with possible impacts on agriculture, water availability, and the economy.

El Niño

• El Niño is the warm phase of the El Niño–Southern Oscillation (ENSO), a large-scale ocean–atmosphere climate phenomenon over the tropical Pacific Ocean.
• It develops when sea surface temperatures in the central and eastern equatorial Pacific become warmer than normal, weakening the trade winds and altering global weather patterns.
• Although it originates in the Pacific, its effects are felt across many regions, including India.
• El Nino and La Nina, the two phases of ENSO (El Niño–Southern Oscillation) and can trigger extreme weather, droughts, and heatwaves across the globe.
• Over the Indian Ocean Region it can adversely affect rain.
• The ENSO phase and intensity of El Niño and La Niña is determined by monitoring the surface temperature of a specific region of the Pacific Ocean called the Niño 3.4 region.
• This region is the standard reference area used by meteorological agencies such as NOAA.
• El Niño is declared when the sea surface temperature (SST) anomaly in this region is at least +0.5°C (along with supporting atmospheric conditions).

During El Niño

• Trade winds weaken or may even reverse.
• Warm surface waters shift eastward towards South America.
• Upwelling along the Peru coast weakens.
• The central and eastern Pacific become warmer than normal.
• Rainfall shifts eastward, while India, Australia, and Indonesia often experience reduced rainfall.

During La Niña

• Trade winds become stronger than usual.
• Upwelling along the Peru coast intensifies.
• The eastern Pacific becomes cooler than normal.
• Rainfall increases over the western Pacific, often supporting a stronger Indian monsoon.

Classification of El Niño Intensity

• The Niño 3.4 Index measures SST anomalies in the central equatorial Pacific.

Reasons for the Strengthening El Niño

• The current El Niño is strengthening due to a combination of oceanic and atmospheric factors:
  • Warm subsurface waters in the Pacific are supplying additional heat to the ocean surface.
  • Weakening trade winds allow warm surface waters to spread eastward across the Pacific.
  • Positive ocean–atmosphere feedback further reinforces the warming and weakens the trade winds.
  • Eastward movement of warm water increases sea surface temperatures in the central and eastern Pacific.
  • High ocean heat content provides the energy needed to sustain and intensify the event.
  • Climate change may increase the frequency and intensity of extreme El Niño events, although research on its exact influence is still evolving.

Impact of El Niño on India

• Monsoon – Weakens the Southwest Monsoon, causing delayed onset, prolonged dry spells, uneven rainfall, and below-normal precipitation.
• Agriculture & Water Resources – Affects Kharif crops, lowers yields, increases irrigation demand, and reduces reservoir levels, river flows, and groundwater availability.
• Economy & Energy – Lower farm output can fuel food inflation, reduce rural incomes, and increase dependence on thermal power due to lower hydropower generation.
• Environment & Health – Increases the risk of heatwaves, droughts, forest fires, water scarcity, and heat-related illnesses, while also affecting biodiversity.
• Note:
  • El Niño is only one of the factors that influence the Indian monsoon.
  • Its impact depends on the interaction of other climate systems such as the Indian Ocean Dipole (IOD), Madden–Julian Oscillation (MJO), Western Disturbances, Eurasian snow cover, Arabian Sea warming, and local atmospheric conditions.
  • A positive IOD can partly offset the adverse effects of El Niño, which is why not every El Niño year results in drought.

India’s Preparedness

• Improved seasonal forecasts by the India Meteorological Department (IMD).
• Expansion of the Doppler Weather Radar network for better weather monitoring.
• Reservoir and water resource management to address rainfall deficits.
• Promotion of climate-resilient agriculture and drought-tolerant crop varieties.
• Drought contingency plans for vulnerable regions.
• Pradhan Mantri Fasal Bima Yojana (PMFBY) to provide crop insurance.
• Pradhan Mantri Krishi Sinchayee Yojana (PMKSY) to promote micro-irrigation and efficient water use.
• Implementation of the National Disaster Management Plan (NDMP) for disaster preparedness and response.

Key Takeaways

UPSC Prelims and Mains Practice Question

Consider the following statements:

1. El Niño is associated with warming of the central and eastern equatorial Pacific Ocean.
2. El Niño generally strengthens the Indian Summer Monsoon.

Which of the statements given above is/are correct?

A. 1 only
B. 2 only
C. Both 1 and 2
D. Neither 1 nor 2

Answer: A

Mains Practice Question

Q. Discuss the impact of extreme El Niño events on India’s agriculture, water security, disaster management and economic growth. Suggest suitable adaptation strategies. (15 Marks)

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