This year’s massive El Niño, coming less than two years after the last one, has already set temperature records. To explain what’s happening and why, the Guardian spoke with Prof Mat Collins, a climate scientist at the University of Exeter. He has authored some of the world’s most important climate reports and is an expert on the dynamics of the El Niño Southern Oscillation.
View image in fullscreen Mat Collins. Photograph: supplied
What is El Niño?
It’s a natural climate pattern that affects large parts of the world, often bringing higher temperatures, more droughts, and floods. It happens when the normally cool, dry eastern Pacific becomes warmer and wetter, shifting rainfall patterns in the tropical Pacific and causing other impacts far beyond that region. It usually occurs every three to seven years, but it’s very unpredictable. The last one was in 2023-24.
What’s the best way to describe how El Niños relate to human-caused global heating?
The simplest way to think about it is that they are two separate things that stack on top of each other. So if you already have drought conditions from global warming, then an El Niño will make that worse. The harder question is how they interact. With our models, we can run hundreds of years of simulations to figure that out, but we don’t have enough data from the observational record to do that, although some palaeoclimate reconstructions suggest the current frequency of El Niño is quite unusual.
How strong is this year’s El Niño? Some are calling it a ‘godzilla’ or ‘super El Niño.’
It has already broken records and could end up being the strongest in a thousand years. The sea surface temperature in the El Niño region of the Pacific has already reached the previous 2015 high of 3C above average, which is almost unbelievable. And it still hasn’t peaked, so we won’t know how much higher it will go until the end of the year.
But comparing its size to previous El Niños is difficult because the baseline of sea surface temperatures in the eastern tropical Pacific is steadily rising due to global warming.
So there are two things happening – human-driven climate change and the natural variability of El Niño – and it’s not easy to say how much each is contributing to the record high ocean temperatures. But together, they make extremes more likely.
Currently, temperatures in the eastern Pacific are on track to be 4C above average, which is far beyond anything seen before. If that trend continues, we could see an incredible El Niño event.
Which areas of the world will be most affected?
Around the peak of the El Niño, there are likely to be more wildfires in Indonesia and drought in the Amazon rainforest. The Indian monsoon has already been weakened because of El Niño. Temperatures are likely to be higher around the Pacific Rim and as far away as the UK. Meteorologists suggest the UK will see a wetter winter and autumn and possibly a drier, colder spring. I’m not certain about that because weather in the UK is just so variable.
View image in fullscreen Burnt trees after a wildfire in Sungai Putri, in West Kalimantan province, Indonesia. Photograph: Willy Kurniawan/Reuters
Were the recent high temperatures in the UK and the wildfires in Europe, Canada, and the US also made worse by El Niño?
I don’t think so, because they came so soon after the El Niño began and there’s normally a lag. Those conditions are more likely a sign of global warming, combined with persistent anticyclonic circulation patterns that cause weather systems to stay settled (or stuck) for long periods. On top of climate change, that makes record heat more likely.
Several scientific papers, including one by you, suggest that human-caused climate change might be making El Niños more frequent and intense. Isn’t it frustrating that there’s still no definitive proof of that with 100% certainty?
That’s just science. One paper we pubPublished research suggested the signal will emerge first in rainfall patterns. So I think we may have a clearer picture in the next decade. James Hansen, arguably the world’s most influential climate scientist of the past 50 years, argues that human-driven climate change is likely behind the abnormal strength of this El Niño. What’s your take on that? It’s a plausible hypothesis but hard to prove. Will warmer Pacific ocean surface temperatures guarantee fiercer El Niños? Climate change makes it more likely El Niños will be fiercer, but that is still not certain. That’s because the impact of an El Niño depends on the temperature difference with other oceans, such as the Atlantic and the Indian. The rainfall goes where the warmest water is found. If that warmth is distributed, then so will be the rainfall. If that warmth is concentrated in one ocean, then the rainfall will shift around so it is more intense in that basin. View image in fullscreen Aerial view of the German Channel off the coast of Koror, the capital of Palau, in the western Pacific Ocean. Photograph: Saeed Khan/AFP/Getty Images May this year’s huge El Niño be a sign that the world’s oceans are – to use a non-scientific term – vomiting heat into the atmosphere because they are reaching the limit of their ability to absorb excess energy? Well, that’s kind of what happens during an El Niño, which is a transfer of heat from the ocean to the atmosphere. But it’s just part of a cycle. It’s not as if the ocean has reached some limit and then can’t hold any more. I guess there’s still plenty of cold water in the world that we can heat up so I don’t know if there’s a physical limit. What would be your hunch about whether El Niños are going to get more powerful in the future? I certainly think the impacts are going to be greater and if we are to believe our models, then the rainfall response is also going to be bigger. There will be bigger and more impactful El Niños over the coming decades. How can we reduce the risks? Knowledge can help. If we go back to the 1982-83 El Niño, people really did not know what was happening. Back then, one of my colleagues got a message from someone on a ship in the east Pacific saying the temperature of the water was off the scale. He had never seen anything like that before. Nobody understood then. But now we’ve got a forecast system which can confidently predict these things six to nine months ahead. So you can prepare. You can tell farmers in Latin America to plant different crops. You can warn governments in south-east Asia to think about their infrastructure and to strengthen defences against wildfires. Ultimately, the main response should be to reduce greenhouse gases, but perhaps there are also options to do weird and wonderful geoengineering – for example to change the properties of clouds in the eastern Pacific which may influence the scale and timing of El Niño events. One paper suggests you could terminate a big event by creating lots of clouds, which would cool the surface of the ocean in the east Pacific. Would such geoengineering help or could it make things worse? It is not yet clear because the heat comes from the deep ocean. So even if you manage to prevent an event in one year, it may come back the next. On an emotional level, how do you feel at the prospect of even more impactful El Niños in the future? It’s worrying. El Niño causes huge disruptions to agriculture and the global economy. This is very bad for people, particularly in poorer countries who are already suffering the consequences of climate change and now they get an El Niño event on top of that. Luckily, we have good predictions now and it is important to maintain that capability, for example collecting real-time data from the Pacific Ocean. Then we can be forewarned.
Frequently Asked Questions
FAQs El Niño What It Is What Causes It and Can We Reduce the Risks
Basics
What is El Niño
El Niño is a climate pattern where the surface waters of the central and eastern Pacific Ocean become unusually warm It happens every 27 years and can change weather around the world
Is El Niño the same as El NiñoSouthern Oscillation
Almost ENSO is the full system El Niño La Niña and the neutral phase in between El Niño refers specifically to the warm phase
How long does El Niño last
Usually 912 months It typically develops between June and December and peaks around December then fades the following spring
How do we know when El Niño is happening
Scientists track ocean temperatures winds and atmospheric pressure across the Pacific When sea surface temperatures in a key region stay at least 05C above average for several months its officially an El Niño
Whats the difference between El Niño and La Niña
Theyre opposites El Niño warmerthannormal Pacific waters La Niña coolerthannormal Each shifts global weather in different directions
Causes and Mechanics
What causes El Niño
It starts with changes in the tropical Pacific atmosphere Normally trade winds blow west and pile up warm water near Asia When those winds weaken warm water sloshes back east toward South America and that triggers El Niño
Why do the trade winds weaken in the first place
Scientists dont have one single answer Its linked to natural backandforth patterns in the ocean and atmosphere and possibly influenced by longerterm climate shifts Its a bit like a pendulum that swings on its own
How does El Niño change global weather
By moving huge amounts of heat around the Pacific it shifts where rain falls and where air rises That ripples through the jet streams and affects weather on every continent
Does climate change make El Niño stronger or more frequent
The evidence is still debated Some research suggests stronger more extreme El Niño events in a warming world but scientists arent certain yet Whats clearer is that El Niños impacts now land on top of already hotter more stressed
