We asked researchers at the National Centre for Atmospheric Science about the climate pattern known as El Niño. 

Find out what impact it had on the record-breaking temperatures recorded in 2023, whether more temperature records will be broken in 2024, and when we might expect to see a transition to La Niña.

El Niño is a climate pattern. It was first discovered in the 1600s by South American fishermen who noticed periods of unusually warm water in the Pacific Ocean, and is studied by scientists today to track its impacts on global temperatures and weather. 

El Niño occurs irregularly, roughly every 2-7 years. Its greatest impact is in the winter, and it typically lasts for about 1 year. NOAA – the National Oceanic and Atmospheric Administration in the US – officially declared the onset of El Niño in June 2023 and it continues into 2024.

Kieran Hunt, a climate scientist at the National Centre for Atmospheric Science and University of Reading, explains what El Niño is:

“El Niño is a climate pattern that is defined as anomalous warming of surface and sub-surface waters in the eastern and central tropical Pacific Ocean. More specifically, El Niño is the name given to the warm phase of a larger phenomenon called El Niño-Southern Oscillation also known as ENSO.”

The opposite climate pattern to El Niño is known as La Niña , which is defined as the cooling of surface-ocean waters of the Pacific Ocean.

Unlike El Niño which only lasts for up to 1 year, La Niña  events can last between 1-3 years. La Niña  events sometimes occur after an El Niño, however this is not always the case as the two events do not necessarily alternate.

El Niño can warm the planet significantly – up to about 0.2°C averaged over a given year.

Previous global mean temperature records have been broken in the year following big El Niños, namely 1998 and 2016.

2016 held the record as the hottest year, until it was beaten by a large margin in 2023. 

El Niño acts as a giant heat source in the tropics, in turn affecting atmospheric circulation, which then influences global climate and weather patterns worldwide. Stronger El Niño events can lead to increased global temperatures. 

2023 was confirmed as the hottest year on record. The soaring temperatures were driven by human-induced climate change, however the climate pattern El Niño also boosted the record-breaking temperatures.

Climate change causes the background temperature of the planet to be warmer, meaning periods of hot weather are likely to be more frequent and more intense. Alongside the current strong El Niño event, climate change is leading to unparalleled temperatures being recorded in recent months.

“Given that global warming has resulted in the ten hottest years on record all occurring since 2010, I think 2024 would have been likely to break the record even with a moderate El Niño. In reality, we actually had quite a strong one,” explains Dr Kieran Hunt.

In January NOAA reported that El Niño is very close to peak strength, and will continue – while gradually weakening – over the next few months. Forecasters currently expect ENSO-neutral conditions by late spring – early summer, as La Niña develops over the next 6 months.