What is El Niño and should you be worried about it?

The World Meteorological Organization (WMO) is ringing the alarm bells about El Niño conditions brewing in the Pacific, set to influence temperatures and rainfall patterns across the globe.

The warning comes after a record-breaking late May heatwave in Europe and a devastating five-day heatwave in parts of India. 

But experts believe that for some, it could get even hotter very soon.

"It is really alarming, because it means that we could break records for the hottest year on record, either this year or next year, depending on how long this El Niño lasts," says Dr Chloe Brimicombe, a climate scientist at Oxford University.

WMO forecasts indicated there was an 80% chance the world could experience El Niño as soon as this month, with warming ocean temperatures in the Pacific signaling a "super" El Niño might be on its way.

The prediction became reality on Thursday, when the US National Oceanic and Atmospheric Administration (NOAA) formally declared that El Niño had begun.

What is El Niño?

Characterized by a sustained period of warmer-than-average sea surface temperatures, El Niño emerges across the central and eastern equatorial Pacific Ocean.

This phenomenon is a primary component of the natural El Niño-Southern Oscillation (ENSO) cycle, which oscillates between distinct warm (El Niño) and cool (La Niña) phases.

These climatic events occur without a fixed timetable, varying significantly in both intensity and duration with irregular intervals between episodes.

"It's a natural phenomenon that's been occurring in that region for millennia," Dr Brimicombe explains, "El Niño causes warmer baseline temperatures across the world.

"With climate change, baseline temperatures are already rising, and then on top of this, we have El Niño, which causes these temperatures to rise further."

While every El Niño is unique, meteorologists note that stronger events typically trigger more widespread and pronounced global impacts, ranging from intensified rainstorms and flooding in certain regions to extreme heat, drought, and wildfires in others.

Is there a 'super' El Niño on the way?

For an El Niño event to be officially declared, sea surface temperatures within the tropical Pacific must typically rise at least 0.5 degree Celsius above established long-term climatological norms.

By comparison, a "super" El Niño occurs when these oceanic temperatures surge significantly higher, exceeding the average by more than two degrees.

"Forecasts are suggesting that it could be the strongest on record," says Dr Brimicombe.

"The last time that we saw a really strong El Niño was around 2015, and this caused prolonged drought in some regions, which also led to famine because of food insecurity. 

"Large-scale flooding was also seen in regions, which is why people are very concerned, if this is the most extreme, [about] what this could do to weather patterns globally."

Is El Niño the cause of higher temperatures?

Historically, many of the warmest years on record have occurred during El Niño events. The phenomenon conveys heat into the atmosphere and tends to raise global average temperatures by around 0.2C.

However, the warming it causes is added to a long-term rise in global temperatures driven by climate change; as such, when a strong El Niño develops in today's warmer climate, it could push global temperatures to exceptionally high levels.

1998 was a landmark year for global temperatures and, at the time, the warmest year ever recorded, with El Niño playing a major role in raising temperatures.

More recently, even cooler La Niña years have been warmer than some of the strong El Niño years of the past, highlighting how much the underlying climate has warmed.

This is clearly illustrated by the fact that the three most recent La Niña years were still significantly warmer than the powerful El Niño year of 1998.

Today, almost two decades later, the baseline temperatures have continued to increase as a result of climate change.

"This could be a taste of the normal climate in the future if we don't mitigate against climate change emissions," warns Dr Brimicombe.

"We know that extreme weather events are becoming more intense and more frequent as a result of changing climate, and this [could be] used as a window into our future if we don't mitigate and we don't have adaptation against these extreme weather events."

2023 marked the first year in which global temperatures reached 1.4C above pre-industrial levels.

Last year was one of the three warmest years on record, continuing the trend of extraordinary global temperatures, with the past 11 years being the 11 warmest on record.

According to the UK's Met Office, with a particularly strong El Niño, it's likely that next year could be the first one above 1.5C when compared with pre-industrial levels, the critical threshold identified by climate scientists, and  established under the 2015 Paris Agreement, to prevent the most catastrophic and irreversible impacts of climate change.

It is important to note, however, that while scientists generally agree that El Niño can temporarily raise global temperatures, the effect of climate change on El Niño and La Niña themselves is less certain.

The Intergovernmental Panel on Climate Change has concluded that there is currently no clear evidence that climate change is making these events more frequent or more intense.

"We would need more research to be able to say whether climate change could, in the future, cause a change in the cyclical nature of El Niño," says Dr Brimicombe.

Does it impact weather as well?

But the effects of El Niño extend beyond temperature changes.

It can also influence weather patterns around the world, including the number of tropical storms and rainfall distribution.

During El Niño years, there are typically more tropical storms in the Pacific Ocean but fewer in the Atlantic.

Rainfall patterns also shift, often bringing wetter conditions to the southern United States and the Gulf of Mexico, while causing drier weather in tropical regions such as Southeast Asia, Australia, and central Africa.

So how worried should you be?

For most people, El Niño is not something to panic about, but it is something worth paying attention to because it can significantly influence weather patterns around the world.

A strong El Niño can increase the likelihood of extreme weather events that can, in turn, cause disruptions to agriculture, water supplies, fisheries, and ecosystems across the globe.

That said, the effects vary a lot depending on where you live.

Some places experience relatively minor changes, while others can see serious flooding, drought, crop losses, or health impacts from heat.

In Europe, El Niño's effects are usually indirect and less dramatic than in tropical regions.

It can slightly influence winter weather patterns, but it does not typically cause the kind of severe disruptions seen in Pacific or equatorial regions.

Scientists monitor El Niño closely because strong events can temporarily push global temperatures to record highs.

However, El Niño itself is a natural climate pattern; it is not a disaster in its own right.

"You shouldn't be apprehensively worried about it; I would be aware of what El Niño is and the impact it has on my local weather, and then take measures that I would usually take to prepare for that weather," Dr Brimicombe explains.

She believes that one of the best things that people can do about El Niño is to talk about it.

"There is a lot of misinformation around what atmospheric ocean oscillations are, not just in the case of El Niño, but also in the case of, for example, the Gulf Stream near the UK and the breakdown of that.

"We don't understand these things in detail, and that's why we do research, to try and understand them better, so that we can say what the impacts are and say what the interventions could be so that we can actually improve people's lives and protect them from the most damaging impacts," she adds.

What is of particular concern is how these extreme weather impacts may become more severe when layered on top of existing vulnerabilities such as ongoing climate change, extreme heat, and water stress.

"We know that we can stop it from becoming more extreme if we transition to net zero," Dr Brimicombe explains.

"And that's really important to stop things like El Niño exacerbating climate changes that we are seeing as a result of anthropogenic warming.

"If we use our imagination, we could create a better society that is better prepared for these extreme weather events and lives more sustainably, which we do see occurring in local community groups and through local community action around the world right now.

"Those sorts of initiatives need to be scaled up and taken on board by international organizations and governments."