Question 1

What is El Niño?

Accepted Answer

El Niño is the warm phase of the El Niño–Southern Oscillation (ENSO), a natural climate cycle in the tropical Pacific Ocean. During El Niño, sea surface temperatures in the central and eastern equatorial Pacific run warmer than average, the trade winds weaken, and tropical rainfall shifts eastward — changes that ripple through weather patterns worldwide.

Question 2

Is El Niño happening right now (2026)?

Accepted Answer

Yes. NOAA has an El Niño Advisory in effect. In NOAA's Climate Prediction Center weekly index, the Niño 3.4 sea surface temperature anomaly stood at +2.6 °C in the week centred on 19 August 2026. NOAA's latest diagnostic discussion states: El Niño is strengthening, with a greater than 90% chance of a very strong event during the Northern Hemisphere fall and winter 2026-27.

Question 3

Why is it called 'El Niño'?

Accepted Answer

The name is Spanish for 'the boy' and refers to the Christ Child. Peruvian fishermen — from at least the 1600s — noticed a warm coastal current that arrived around Christmas each year and called it 'El Niño de Navidad'. The name entered scientific literature in 1892 through Peruvian naval captain Camilo Carrillo.

Question 4

What is the difference between El Niño and La Niña?

Accepted Answer

They are opposite phases of the same cycle (ENSO). El Niño means warmer-than-average sea surface temperatures in the central/eastern tropical Pacific with weakened trade winds; La Niña means cooler-than-average temperatures with stronger trade winds. Their global weather effects are roughly opposite.

Question 5

How often does El Niño happen?

Accepted Answer

Irregularly, every two to seven years. A typical El Niño develops in Northern Hemisphere summer or autumn, peaks around November–January, and decays by spring, lasting about 9–12 months in total. Since 1950, NOAA's records show 28 completed El Niño events of varying strength, with a 29th under way in 2026–27.

Question 6

How do scientists declare an El Niño?

Accepted Answer

Agencies use sea surface temperature thresholds, but definitions differ. NOAA declares El Niño when the Oceanic Niño Index (Niño 3.4 region) stays at or above +0.5 °C for five consecutive overlapping three-month seasons, with an atmospheric response. Japan's JMA uses the Niño 3 region with a five-month running mean, and Australia's BOM uses a higher +0.8 °C bar plus wind, pressure and model criteria.

Question 7

What is the Niño 3.4 index?

Accepted Answer

Niño 3.4 is the region of the equatorial Pacific between 5°N–5°S and 170°W–120°W. The average sea surface temperature anomaly in this box is the most widely used measure of El Niño strength, because temperatures there correlate best with global weather impacts. NOAA's official Oceanic Niño Index (ONI) is a three-month running mean of Niño 3.4 anomalies.

Question 8

Does El Niño make the world hotter?

Accepted Answer

Yes, temporarily. El Niño releases heat stored in the Pacific Ocean into the atmosphere, raising global average surface temperature by roughly 0.1–0.2 °C on top of the long-term warming trend. That is why record-warm years tend to follow El Niño peaks — as in 1998, 2016 and 2023–24.

Question 9

How does El Niño affect hurricanes?

Accepted Answer

El Niño typically suppresses Atlantic hurricanes by strengthening upper-level winds (vertical wind shear) that tear storms apart, while boosting hurricane activity in the eastern and central Pacific, where waters warm and shear drops. Western Pacific typhoons tend to form farther east and recurve more often.

Question 10

How strong will the 2026–27 El Niño be?

Accepted Answer

Official forecasts point to a very strong event. NOAA gives an 81% chance of a very strong El Niño (Niño 3.4 ≥ +2.0 °C) during October–December 2026, and most international models — including the European Copernicus multi-model ensemble — project a peak that could rival or exceed the record events of 1997–98 and 2015–16. Exact peak strength remains uncertain until it happens.

Question 11

Which countries are most affected by El Niño?

Accepted Answer

Impacts are strongest around the Pacific rim and the tropics: Peru and Ecuador (flooding, fisheries losses), Australia and Indonesia (drought and fire risk), India (weaker monsoon rains), the Philippines (drought), southern Africa (drought), East Africa (heavy rains and flooding), and the southern United States (wet, stormy winters). Effects vary event to event — they are shifts in the odds, not certainties.

Question 12

Can El Niño be predicted in advance?

Accepted Answer

Yes, within limits. Because the ocean stores heat slowly and visibly, models can often forecast an El Niño six or more months ahead — especially forecasts made after mid-year for the winter peak. Forecasts made in Northern Hemisphere spring are much less reliable, a known problem called the 'spring predictability barrier'.

Question 13

Is climate change making El Niño stronger?

Accepted Answer

The science is not settled on El Niño itself: the IPCC finds no model consensus on whether El Niño's ocean temperature swings will strengthen, and assigns low confidence to projected changes. What is very likely, per the IPCC, is that ENSO-related rainfall swings will intensify as the atmosphere warms — and El Niño's impacts now play out on top of a hotter baseline climate, amplifying heat extremes.

Question 14

What was the strongest El Niño ever recorded?

Accepted Answer

By NOAA's Oceanic Niño Index, the 2015–16 event holds the record with a peak of +2.8 °C, ahead of 1997–98 (+2.4 °C) and 1982–83 (+2.2 °C). Reconstructions suggest the 1877–78 event was comparably extreme and triggered famines that killed tens of millions. The ongoing 2026–27 event is forecast to challenge these records. Note that ONI values are periodically revised as NOAA updates its underlying sea surface temperature dataset, so figures quoted in older coverage can differ by a tenth or two.