A new El Niño is developing – and it could be one of the strongest on record

What is El Niño? 

El Niño is one half of a global climate cycle known as the El Niño–Southern Oscillation (ENSO). Its opposite phase is La Niña. The ENSO plays out across the tropical Pacific, shifting between El Niño and La Niña phases every few years, with effects that can ripple across the entire planet. 

The current El Niño follows an unusually persistent “triple-dip” La Niña, following La Niña conditions which lasted for three consecutive years from 2020 to early 2023. 

To understand what’s changing and what that means, it helps to know what typical (or “neutral”) conditions look like. 

Ordinarily, steady trade winds blow east to west across the equatorial Pacific, dragging warm surface water toward Asia and Australia. That leaves a gap behind it off the coast of South America, which cold, nutrient-rich water rises up to fill. Meanwhile, warm water piled up in the west feeds rising air, clouds and heavy rain, while air sinks over the cooler eastern Pacific. Together, this forms a huge loop of moving air known as the Walker Circulation - one of the engines of global weather. 

During El Niño, the trade winds weaken and can sometimes briefly reverse. Warm water that had accumulated and deepened the thermocline in the western equatorial Pacific moves back towards the central and eastern Pacific and releases heat to the atmosphere, while the usual upwelling of cold water off South America weakens. As a result, sea-surface temperatures become much warmer than normal across the central and eastern tropical Pacific 

The effects of El Niño are not limited to the Pacific. Changes in tropical rainfall and rising air can influence atmospheric circulation around the world, affecting jet streams, storm tracks, monsoons and rainfall patterns. These knock-on effects, sometimes called “teleconnections”, help explain why El Niño can bring drought to Indonesia, influence the Indian monsoon and increase rainfall elsewhere in the Americas. 

How strong could this El Niño be?  

The 2026/27 El Niño could be exceptionally strong, potentially ranking among the strongest ever recorded. 

In August, the National Oceanic and Atmospheric Administration (NOAA) estimated a more than 90% chance of a very strong El Niño during autumn and winter, and a 69% chance that it could exceed the strength of previous El Niños recorded since 1950. 

Sea-surface temperatures in the central Pacific are already much warmer than normal 

In July, temperatures in this region were around 1.4–2°C above average. By mid-August, one measure had reached around 2.7°C above average, elevating this event into the ‘super’ El Niño category and Met Office forecasts suggest temperatures could rise even further - above 3°C - later in 2026.  

For comparison, a ‘typical’ El Niño warms the central Pacific by around 1–2°C at its peak, highlighting how unusual this event could be. 

The latest World Meteorological Organization forecast, issued on 3 September, is even more striking. Its models suggest temperatures in the central Pacific could average around 3.6°C above normal between September and November, with the event expected to peak around November or December, making this the strongest recorded El Niño event in over a century. 

It’s important to note that the exact peak remains uncertain, reflecting both differences between the forecasting models and the natural unpredictability of the climate system. 

What could the global impacts be? 

El Niño doesn't cause the same weather everywhere. Instead, it shifts the likelihood of certain weather patterns, with effects extending far beyond the Pacific. 

Australia, Southeast Asia, India, southern Africa and parts of the Amazon typically face greater risks of heat and drought, while other parts of the Americas tend to become wetter. In the US, El Niño can increase the likelihood of heavy rain and storms affecting California and the Southwest. 

Consequences beyond the weather 

Warmer waters off South America can disrupt marine ecosystems, causing widespread coral bleaching and mortality, while changes in rainfall can affect crops and water supplies. Strong El Niño events have previously disrupted supplies of commodities including cocoa, coffee, sugar, and rice.

El Niño can also bring severe heat and drought to tropical forests. Many of these forests are already under pressure from climate change and deforestation, and extreme conditions can increase tree mortality, reduce growth and affect wildlife and local communities. 

In some major El Niño events, these impacts have also affected the role tropical forests play in the global carbon cycle. Forests that would normally absorb carbon dioxide from the atmosphere can temporarily become net sources of CO₂ when severe heat and drought cause trees to die or reduce their growth. 

Some impacts are already emerging. Low water levels have affected operations at the Panama Canal, while drought is affecting agriculture in parts of Central America. India's 2026 monsoon season has also seen a significant rainfall shortfall, consistent with the influence of a strengthening El Niño. 

It’s important to remember that these are typical patterns associated with El Niño, not guarantees. Other climate influences and natural variations also play a role, meaning the effects can differ considerably from one El Niño to another. 

What about the UK? 

For Scotland and the rest of the UK, the link is real but far less direct. El Niño's influence competes with other atmospheric and oceanic forces, so it can't tell us on its own whether the coming winter will be wet, dry, mild or cold. 

However, current forecasts suggest the strengthening El Niño could raise the likelihood of wetter, stormier conditions across north-west Europe, including the UK, through autumn and early winter. Later in the season, El Niño has sometimes instead been linked to colder, calmer spells in the UK. The key point is that these are shifts in probability, not firm predictions - other factors in the ocean and atmosphere will also determine its effects. 

Is climate change affecting El Niño? 

El Niño is a natural climate phenomenon and is not responsible for the long-term rise in global temperatures, which is driven primarily by human economic activity. 

However, today's El Niño is developing against a backdrop of a much warmer planet. This means that droughts that are caused by El Nino intensify because more water is lost from the soil and vegetation under warmer conditions.  El Niño releases heat from the ocean into the atmosphere, temporarily adding to global temperatures. The Met Office expects 2027 to very likely overtake 2024 as the warmest year on record, partly because of this El Niño. 

Scientists are still investigating whether climate change is affecting the frequency or characteristics of El Niño events. What is clear is that today's events are occurring on a warmer baseline, which can increase the risks associated with extreme heat and other climate impacts.

How School of GeoSciences research is helping us understand El Niño 

Researchers in the School of GeoSciences are helping us to understand why El Niño events can have very different effects from one event to another. 

Their work shows that it is not just how much the Pacific warms that matters, but where the warming occurs. Different patterns of warming can lead to different effects on rainfall and weather around the world. Research is also examining how human influences, including air pollution, can alter the background climate and affect El Niño. 

This is particularly relevant to the 2026–27 event. Its impacts will depend not only on how strong El Niño becomes, but also on where the Pacific is warming and how the event interacts with our changing climate.