Concept2 stories
El Niño-Southern Oscillation
In one line: ENSO is a recurring cycle of ocean warming and cooling in the equatorial Pacific, coupled with swings in air pressure called the Southern Oscillation.
Three phases
- El Niño: the central and eastern Pacific is warmer than normal; trade winds weaken. It tends to weaken India's monsoon.
- La Niña: the same region is cooler than normal; trade winds strengthen. It tends to favour a good monsoon.
- Neutral: neither condition holds.
Events recur every two to seven years. Scientists track them through sea surface temperature in the Niño 3.4 region and through the pressure difference between Tahiti and Darwin.
Why it is in the news
A strong El Niño in 2026 coincided with a monsoon 12.6% below normal. The Hindu explainer shows that El Niño alone does not settle the outcome.
Where to go next
- Indian Ocean Dipole
- IMD monsoon forecasting
El Niño-Southern Oscillation in the news
- Explained: Why even a strong El Niño does not guarantee a poor Indian monsoon 2 November 2026
The Pacific cycle behind El Niño and La Niña
- El Niño, heat deaths and why parched Maharashtra cannot declare drought yet 24 September 2026
The Pacific driver of India's monsoon
Previous-year questions on this
- 2017 · GS1 · 15 marks What characteristics can be assigned to monsoon climate that succeeds in feeding more than 50 percent of the world population residing in Monsoon Asia?
- 2014 · GS1 · 10 marks Most of the unusual climatic happenings are explained as an outcome of the El-Nino effect. Do you agree?
- 2014 · GS3 · 12.5 marks Drought has been recognised as a disaster in view of its spatial expanse, temporal duration, slow onset and lasting effect on various vulnerable sections. With a focus on the September 2010…
- 2017 · Prelims With reference to 'Indian Ocean Dipole (IOD)' sometimes mentioned in the news while forecasting Indian monsoon, which of the following statements is/are correct? 1. IOD phenomenon is characterised…