How El Niño development during May-June is likely to affect India  

What exactly is the El Niño phenomenon, and how does it affect weather patterns around the globe and in India?

What is El Niño-Southern Oscillation?

Sea surface temperature (SST) and atmospheric pressure are the two main factors affecting global ocean circulation. The El Niño Southern Oscillation (ENSO) is a periodic ocean-atmospheric fluctuation in sea surface temperatures and air pressure across the equatorial Pacific Ocean. 

The chemical composition of ancient coral skeletons reveals that ENSO has been happening for the past thousands of years. It has three distinct phases: warm or El Niño, cold or La Niña, and neutral. 

Under normal conditions or during the neutral phase, trade winds blow from east to west along the equator in a pattern known as Walker Circulation. The eastern side of the Pacific Ocean (near South America) is cooler than the western side (near Indonesia).

The trade winds push warm surface waters towards Australia and Asia, making the western Pacific relatively warmer. The movement of warm water westward allows cold, nutrient-rich water from the deeper ocean to rise to the surface near the western coast of South America. The process is called upwelling. The nutrient-rich water helps sustain fisheries in the region. 

The warm low-pressure conditions that prevail in the western Pacific bring abundant rainfall in December over northern Australia, Southeast Asia, and New Guinea in the southern hemisphere.

What is El Niño and how does it arise? 

The term ‘El Niño’ was first used by South American fishermen in the 1600s. It comes from Spanish and literally means the Christ Child or Little Boy, as this phenomenon typically peaks around Christmas. Therefore, the full name the fishermen used was El Niño de Navidad (“The Christmas Child”). 

El Niño generally occurs every two to seven years in the central and eastern tropical Pacific Ocean and affects weather and precipitation patterns, ocean conditions, and fisheries worldwide. An El Niño typically lasts 12-18 months and weakens monsoon winds over the Indian subcontinent.

It arises due to the reversal or weakening of trade winds, which leads to the accumulation of warm water in the central and eastern Pacific. Strong and weak trade winds are linked to changes in the pressure gradient (the rate at which air pressure changes across a given distance) of the atmosphere over the tropical Pacific. This periodic disruption affects SST, atmospheric circulation, and weather patterns. 

During El Niño events, the low pressure zone moves eastward in the central Pacific, and the western Pacific experiences a weak high-pressure zone and drought-like conditions. This shift in pressure pattern is known as the Southern Oscillation. 

Tracking ENSO conditions

Monitoring of ENSO conditions focuses on changes in the average conditions of  sea surface temperatures across the equatorial Pacific Ocean. The NOAA tracks these temperature anomalies through different indices.

1. Oceanic Niño Index (ONI) – It measures the three-month absolute mean SST anomaly in a specific region of the Pacific Ocean known as Niño 3.4 (5°N–5°S, 120°W-170°W longitude).

SST anomalies of ≥ +0.5°C, sustained across at least five consecutive overlapping three-month periods, are declared as ENSO warm phase (El Niño), while anomalies of ≤ -0.5°C are called ENSO cool phase (La Niña).

2. Southern Oscillation Index (SOI) – It measures differences in sea-level pressure between Tahiti (French Polynesia) and Darwin (Australia). A high SOI indicates stronger trade winds and La Niña conditions, whereas a low SOI is associated with weaker trade winds and El Niño conditions.

3. Relative Oceanic Niño Index (RONI) – It is an advanced ENSO metric, which compares Nino 3.4 temperature values with the temperature of all tropical oceans simultaneously, adjusting for global oceanic warming. RONI aims to improve the forecast by taking into account a higher baseline as the world warms.

Based on the strength probabilities of the RONI, El Niño can be categorised as:

– Weak (0.5°C -1°C)

– Moderate(1°C -1.5°C)

– Strong (1.5°C -2°C)

– Very strong (≥ 2°C) 

Notably, the term ‘Super El Niño’ is an informal term. It is used to describe very strong El Niño event, which is likely to occur this time. However, NOAA has cautioned that ‘Stronger El Niño events do not necessarily ensure strong impacts; they can only make certain impacts more likely’.

Impact of ENSO phenomena

The impact of ENSO phenomena can be seen globally, but the most intense impacts are felt by tropical countries of South and South-East Asia, Latin America, and Africa. The impacts can vary regionally. 

El Niño conditions generally bring drier weather in southern Africa, South Asia, Southeast Asia, and Northern Brazil. In contrast, it causes heavy rainfall in Central America, northern Peru, Ecuador, and the northern and southeastern parts of South America, as well as wetter conditions in the eastern-central Pacific islands and parts of equatorial east Africa. 

El Niño years often witness higher-than-average temperatures. For example, the year 2024 became the hottest year on record, partly due to the strong El Niño event in 2023-24. These conditions could induce extreme heat, drought, wildfires, and food insecurity, and can also alter transmission patterns of vector-borne diseases.

Implications for India 

For India, the impact of El Niño can be particularly significant because of the country’s dependence on the southwest monsoon for agriculture, water resources, and overall economic stability. Historically, at least half of the El Niño years have been associated with monsoon droughts (below -10% departure from long-term average). Since 1950, out of 16 El Niño years, India has received below normal monsoon rainfall during seven years. 

This year’s IMD forecast of a below-normal monsoon can adversely affect crop yields and agricultural productivity, potentially leading to food shortages, inflation, and strained rural incomes that can further aggravate the economic difficulties. 

Reduced rainfall, prolonged dry spells, droughts, and higher temperatures could put stress on the available water resources. It could also lead to increased forest fires and heatwaves. These climatic stresses can have serious consequences for public health. 

In addition, disruptions in energy and fertiliser supplies due to the crisis in West Asia and the closure of the Strait of Hormuz can further aggravate the impact of a weak monsoon year. 

Why early forecasts matter 

ENSO is a natural phenomenon and cannot be prevented. But its impact can be reduced through proactive measures. Advanced monitoring capabilities have significantly improved the possibility of predicting the onset, intensity, and duration of El Niño events. 

Such forecasts provide valuable lead time to take proactive steps like strengthening disaster preparedness, promoting water conservation, and improving agricultural practices to reduce potential damage. 

The promotion of drought-resistant kharif crop varieties and revised sowing windows, especially in rainfall-deficient districts, may help in minimising income loss for farmers if yields fall short.

States also need to prepare their drought and heat action plans and prioritise groundwater recharge and water conservation efforts before it’s too late. Advance predictions will benefit only if we act upon them. 

Post read questions

Explain the mechanism of El Niño–Southern Oscillation (ENSO). How does El Niño influence global climatic patterns?

Examine the relationship between El Niño and the Indian Summer Monsoon. Why do all El Niño years not result in droughts in India?

Evaluate the likely impacts of a below-normal monsoon associated with El Niño on India’s rural economy. How can advances in ENSO forecasting help India improve climate resilience and disaster preparedness?

Discuss whether India’s agricultural system is adequately prepared to deal with recurrent El Niño-induced monsoon variability.

A stronger El Niño does not always guarantee stronger impacts. Examine this statement.

(Abhinav Rai is a Doctoral candidate at the Department of Geography, Delhi School of Economics, University of Delhi.) 

Share your thoughts and ideas on UPSC Special articles with ashiya.parveen@indianexpress.com.

Gear up for UPSC Prelims 2026—Practice smarter, revise faster, and succeed with our Special Quiz Magazine. (Click Here)

Click Here to read the UPSC Essentials magazine for May 2026. Subscribe to our UPSC newsletter and stay updated with the news cues from the past week.

Stay updated with the latest UPSC articles by joining our Telegram channel – IndianExpress UPSC Hub, and follow us on Instagram and X.