El Niño and Its Effects

At a Glance

• Name Spanish for the Christ child, from Peruvian fishermen
• Frequency Every 2 to 7 years
• Threshold Niño 3.4 warming of +0.5 degrees Celsius or more, sustained
• Pressure Tahiti falls, Darwin rises; negative SOI
• Status El Niño Advisory in force in October 2026
• Exam link UPSC Prelims, Geography: El Niño and Climate Classification

Where Does It Fit?

This is the second topic of the category on El Niño and climate classification. The previous topic described the normal Pacific and the Walker Circulation, and this topic describes what happens when it breaks down. The next topic covers La Niña and El Niño Modoki. Previous topic: Walker Circulation and Normal Conditions in the Pacific. Next topic: La Niña and El Niño Modoki.

What Is El Niño and How Does It Develop?

In short: in an El Niño year the trade winds weaken, warm water flows east, and the heat and rain of the Pacific shift.

El Niño, Spanish for the Christ child, was originally the name for a warm current that appears every few years off the coast of Peru near Christmas. Today it refers to the warm phase of ENSO, the El Niño-Southern Oscillation, the combined ocean and atmospheric phenomenon. In an El Niño, the trade winds weaken or even reverse for some time. The warm pool in the west Pacific then moves east, the thermocline deepens in the east and rises in the west, and the upwelling of cold water off Peru is reduced or suppressed, as in Walker Circulation and Normal Conditions in the Pacific. The surface of the eastern and central Pacific becomes several degrees warmer than normal, the pressure falls over Tahiti and rises over Darwin, and the Southern Oscillation Index turns negative. The rising branch of the Walker Circulation shifts from Indonesia to the central Pacific. The warm ocean in turn weakens the winds even more, which is the Bjerknes feedback that makes the event grow.

It is monitored using the Niño 3.4 region of the equatorial Pacific, and the Oceanic Niño Index, ONI, which is the three-month average temperature anomaly in that area. El Niño conditions are declared when the anomaly stays at or above +0.5 degrees Celsius, together with the atmospheric response. Events are usually called weak, moderate, strong or very strong, depending on the size of the anomaly.

What Are the Effects of El Niño?

The warm waters in the east also make the Pacific release more heat to the atmosphere, so that years with strong El Niño often become records for global warmth. The years 2015 and 2016, and 2023 and 2024, were records, and 2024 was the warmest year on record. Food markets are affected through droughts in rice, wheat, palm oil and sugar producers: in July 2023, India restricted the export of non-basmati white rice, in part because of the concern about the El Niño and the monsoon.

How Does El Niño Affect the Indian Monsoon?

The link was found by Gilbert Walker. In an El Niño year, the shift of the Walker Circulation brings sinking air to the Indian region, and the south-west monsoon tends to be weak, as in Mechanism of the Indian Monsoon. The droughts of 2002, 2009, 2014 and 2015 occurred in El Niño years, with the all-India rainfall at about 81 per cent, 78 per cent, 88 per cent and 86 per cent of the long period average, respectively. In 2023 too the monsoon ended at about 94 per cent of the average, with a dry August. But the link is not perfect. Not all El Niño years are droughts, and 1997, a very strong El Niño, had a normal monsoon because a positive Indian Ocean Dipole, a warm western Indian Ocean, offset it. Some droughts happen without an El Niño. The monsoon is also helped or hurt by the Indian Ocean Dipole, the Eurasian snow cover and the Madden-Julian Oscillation, so forecasters use ENSO as one of the main predictors, not the only one.

As an analytical point, the effect of a weak monsoon on the economy is today smaller than before, because agriculture is a smaller share of the national income, there is a large buffer stock of food grains and irrigation covers more land, but rural income and food price inflation, especially in pulses, vegetables and cereals, are still exposed.

What Is the Current El Niño Status?

The United States Climate Prediction Center of the National Oceanic and Atmospheric Administration issues the monthly ENSO diagnostic discussion. In its discussion of 8 October 2026, it kept an El Niño Advisory in force, stating that El Niño was continuing to strengthen and was strong to very strong, with the Niño 3.4 index at about +2.1 degrees Celsius, and gave an over 83 per cent chance of a strong-to-very-strong event lasting through January to March 2027. Because the status changes every month, a reader should always check the latest discussion, and the India Meteorological Department and other agencies also issue their own ENSO updates. The lesson of an event of this size is that the effects on rainfall, food prices and global temperature are felt in the following months, and not just during the event itself.

Why Is This Topic Important?

• Recurring theme El Niño is asked every year
• India Monsoon and food prices
• Current affairs Strong event in 2026

What Came Next?

The next topic describes La Niña and El Niño Modoki. Next topic: La Niña and El Niño Modoki.

Key People and Terms

• ENSO El Niño-Southern Oscillation
• ONI Oceanic Niño Index
• Niño 3.4 Pacific region used to monitor ENSO
• Bjerknes feedback Self-reinforcing ocean-atmosphere loop
• Indian Ocean Dipole East-west temperature difference in the Indian Ocean
• Teleconnection Distant weather link

Exam Corner

Mains Angle

Questions ask for effects and the Indian link. These points add depth.

• Cause Weak winds and warm east
• India Weaker monsoon, but offset by IOD
• Economy Food inflation and policy response