Instant Genius - Why the most extreme El Niño event for a century is on its way

Episode Date: August 27, 2026

Every several years, the surface temperatures of the Pacific Ocean rise, triggering a climate event that has a domino effect on weather patterns across the globe. This is known as El Niño – and this year, meteorologists predict we’re in for a big one. But how exactly do these events occur, how big an effect is climate change having on their frequency and impact, and what can we expect to see in the future? In this episode, we’re joined by Prof Adam Scaife, head of long-range prediction at the Met Office in the UK. He tells us how El Niño events arise in the Pacific Ocean and spread across the globe, how they’ve been occurring cyclically for thousands of years, and why the event this year is forecasted to be the most extreme in decades. Take your curiosity further with a subscription to BBC Science Focus magazine. Every issue is packed with fascinating insights into the science behind everyday life, the latest breakthroughs and expert analysis, delivered straight to your door. Receive an extra £5 when you subscribe using the code SF5OFF, (minimum spend £20, see full terms and conditions on our website). https://www.ourmediashop.com/bbc-science-focus-magazine-pod30 Learn more about your ad choices. Visit podcastchoices.com/adchoices

Hello and welcome to Instant Genius, a bite-sized masterclass in podcast form. Every Monday and Friday, you'll hear world-leading scientists and experts talking about the most fascinating ideas in science and technology today. I'm Jason Bidger, commissioning editor of BBC Science Focus. Every several years, the surface temperatures of the Pacific Ocean rise, triggering a climate event that has a domino effect on weather patterns across the globe. This is known as Al-Ninio. And this year, meteorologists predict we're in for a big one.

But how exactly do these events occur? How big in effect is climate change having on their frequency and impact? And what can we expect to see in the future? In this episode, we're joined by Professor Adam Schaith, head of long-range predictions at the Met Office in the UK. He tells us how Al-Nino events arise in the Pacific Ocean and spread across the globe, how they've been occurring secretly for thousands of years, and why the event this year is forecasted to be the most extreme in decades.

So welcome to the podcast. Thanks so much for joining us. Thank you very much. Thanks for having me on. So today's topic is Al-Nino. So there's been lots of talk about this recently. Everyone listening is likely to have heard about it. But first off, what exactly is it? That's a very good question to open with. It's a natural climate phenomenon. So that's the first thing. To a good approximation, El Nino is independent of climate change. So it's been going on for thousands of years. Even though we had no thermometers or people measuring at that time, of course, we know from things like proxy records like corals and other natural recorders that El Nino events have been going on for a very long time, many thousands of years. So that's the first point. It's a natural event. Another key point is that it's actually a coupled phenomenon that actually occurs because of interaction between the

atmosphere and the ocean. It requires both of those things. So it's not like weather systems that come trundling across the Atlantic, for example, which are mainly atmospheric things. El Nino is actually a coupled phenomenon. It's the ocean and the atmosphere working together that generate the phenomenon. And it's actually coupling between those two things that's really important. So when El Nino happens, the tropical Pacific will warm rapidly in the central and east Pacific, so just to the west of South America. And that region will then become the center for rainfall. And rainfall will migrate from the West Pacific into the central and east Pacific where it's warmest. As you can imagine, the rising motion that gives rise to the rain is going to sit over the

warmer water there. That's what's happening at the moment in the 2026 El Niño. We see that in all the other events and there's a particular pattern that develops, which we've named El Niño. We can go into the history of the naming and so on later on. When that first happens, though, it changes the atmosphere. So this rising motion creates flow in from the west. Obviously, the air that goes up has to be replaced by air and it tends to flow in from the west. This means it's going against the sense of the normal winds, which are the trade winds, which come from the east. So they get cancelled out and we end up with kind of a pretty bland situation in terms of wind in the tropical Pacific.

But lots of rainfall in the east. We then have rising motion over this warm water, and what goes up must come down. So we end up on neighbouring regions where we have drought, dry regions that suppresses the rainfall. And this whole circulation through the depth of the lower atmosphere

is what we call the southern oscillation. So the El Nino Southern Oscillation is the name we give to the kind of whole phenomenon of this coupled thing, the El Nino in the ocean and the southern oscillation in the atmosphere. How often does it occur? Because, you know, I'm sort of in my mid-40s now, and it's sort of, from memory, seems to come up every few years. Is that right?

Yeah, that's exactly right. There isn't a kind of clockwork mechanism here that makes it appear every five years. It's not that periodic or regular. But it does crop up every few years, as you say. Maybe every 10 or 15 years we get a really big event. And then in between those events, we get the flip side, which is where the Pacific cools into its Lanina phase. And as I say, the kind of regularity to this thing,

there is a bit of flipping and a bit of periodicity. But it's not like solar eclipses, for example, which we can predict many, many years ahead. These things are more chaotic. The atmosphere in the ocean are chaotic systems that small changes can grow into big perturbations at long lead times. And this is the challenge for forecasting, of course, is to try and predict out as long as we can. El Nino is actually one of the best things we can try and forecast. But because it's coupled to the slowly varying ocean and the time scales pretty long, we can usually see at least six months, sometimes a year or more ahead when a big El Nino event is coming. So first off, is it becoming more frequent? You know, is the cycle occurring more frequently? This is an important question, right? People ask, is climate change affecting El Nino?

Is it changing? Is it becoming more frequent or the events becoming stronger? Is it changing in character? And to be completely frank, that is a research topic and we do not really know the answer. It's possible that climate change is affecting the El Nino and is changing the frequency with which we see El Nino and La Nino events. But it's hard to see from the rather irregular climate record

whether that is really happening yet. Furthermore, when we use the very sophisticated computer models that we use to try and predict global climate, including El Nino, then they give rather different answers for what climate change could do to El Nino. So some of them, for example, show a transition to a few big El Nino events with rather low frequency, but very big

amplitude. You might get a big event every decade with small ones in between. Others do show an increasing frequency and others show not much change. So that is really at the edge of our current knowledge and it's really one of the important questions but not something we can easily answer. What we can say though is that for a given El Nino event, so for a For example, let's say we have a two-degree El Nino in today's climate, and we compare the impact of that on places that get either flooding or drought during El Nino, of which there are many around the world, then those impacts are now bigger than they used to be in the older, cooler climate.

And so as we go forwards, the impact of a given El Nino is getting stronger. And we understand the fundamental reasons for that, so we're pretty confident about that. We like to see things in the observations, in our theoretical models, and have understanding. And when those three pillars are in place, that's when we can be really confident about the science. So you mentioned there, a two degree, El Nino. You know, can you just tell us exactly what you mean by that? Yeah, so we use, obviously, we want to talk to our international colleagues, and in like many areas of science, we try to set up standards so that we can all talk from the same baseline.

and the usual measure for El Nino and Leninia is something called the Nino Index. This is based on a box that we plonk over our data on the equator, and then you average the temperature in that box, five south to five north across the Central Pacific. We usually use something called the Nino 3.4 index. It's just a particular box, 120 to 170 West. And then that average temperature and the fluctuations in that are what we use to determine the size of an El Nino or the size of a Lanina. If the temperatures in the box on average or above norm, we say it's El Nino, if it exceeds half a degree, that is.

If it goes below half a degree below normal, we say we're in Lanina conditions. And the reason I mentioned two degrees is that typically an El Nino event might be one to two degrees. same for La Niño, one to two degrees. But occasionally we do get El Ninoes that get bigger than that. So we might have a two degree El Nino. There was one, for example, in 2015. That's a really big event. And so two degrees you might consider is a good kind of threshold to say this is a really large event amongst the biggest we've seen.

Of course, what's coming later this year actually knocks that out of the water. Yeah, so we're going to the sort of. of the current picture in a moment. But so you say that the one in 2015 was a large event. So what sort of impacts and consequences did that have globally? We know from a whole raft of historical observations going right back into the 19th century, at that time, of course, we didn't have satellites and the things we have now. So the record is more sparse back then.

But we still have some observations, for example, from ship records. So over the last hundred years or so, we can collect together all of the El Nino events, look at what happened in those cases, and then we can get this kind of composite picture of what the real impacts are. You can look at individual cases like 2015, but of course that will be the addition of the El Nino effect with other things that happened that year. So the best way to tell what El Nino does is to do these kind of averages of several events. then we kind of get rid of all the noise, if you like, and see what the El Nino really does. And when we do that, we see very clear pictures where we have more rainfall in the Central Pacific.

We have droughts over the Amazon, for example, and over Central America. And then if you move to the West Pacific, again, where there is this descending motion that suppresses the rainfall, you get drought in the West Pacific. So many of the island nations there. and then further west over India, the monsoon tends to be suppressed as the El Nino builds up towards its peak in the northern winter. And you can see these kind of impacts, you know, pretty much worldwide, actually. There are dozens of these so-called teleconnections, meaning connections across space between one event and another in the weather.

You see them in Australia. You even see them in southern Africa and parts of the northern hemisphere, North America, and even in Europe, as we now understand. So how about the interplay between Al Nino and global temperatures? What can we say about that? There is a very clear impact of El Nino and global temperature. It's not as big as climate change. Climate change, we've now accrued maybe 1.4 degrees of climate change.

So the globe is now 1.4 degrees warmer than it was in the 19th century. But El Nino's can top up that warming. And so it's often the case that the record is broken coinciding with an El Nino year. This tends to happen after the peak of El Nino. El Nino will peak in December. And then it takes some time for the heat that's released during El Nino to spread around the globe and warm the other ocean basins. But a good rule of thumb is that if you have an El Nino of some intensity, then for each degree of warming, of the El Nino in the Pacific, you get about 0.1 degrees on the global temperature the year after.

So if this year, for example, we get a 3 degree El Nino, that means that we can add 0.3 to the global temperature for next year. And that, of course, is enough on top of the 1.4 degrees of so of climate change to tip the balance into the point where we're breaking records again. It's interesting to note that if you look at the current record, which is 2024, that was after a sizable El Nino. And the one before that, which was 2016, is also after an El Nino, the big El Nino of 2015-16. So the recent records have often followed Al-Ninos. And so this leads to the obvious conclusion that after this El Nino in 2026, then we expect 27 to be a new global temperature record.

So there's also something that we have to deal with, which occurs, effects that occur after the initial El Nino event. So could you tell me about the current thinking on that, please? That's a very good question, and it's a really interesting area of research. Because what we've now found is that when the El Nino has peaked in the northern winter, say December time, and then died away in the spring, it leaves behind a signature in the atmosphere of stronger westerly winds circulating around the tropics. Each side of the equator you get these two bands. And then over the following months those bands propagate slowly polewards towards the extra tropics. And this takes months.

So this is really fascinating because of course as soon as I see signatures like that, I'm thinking, oh, there's a potential here to make better long-range forecast if we can understand this process. And we see impacts on, for example, the East Asian monsoon in the summer after the El Nino. So the El Nino has been and gone, as I say. And it tends to energize the East Asian monsoon. So after one of the previous big events in 1998, that happened. And it led to massive flooding across the Yanksy River Valley. And I think there were thousands of casualties from that event.

So that's something we really need to monitor in 2027 and keep our eyes open for. Let's have a look at what's going on now in the present day. You know, you said we've got a real big one on our hands now. So, you know, what do we know about that? What's happening and, you know, how big do we think it's going to be? This is an important question right now because actually what we're seeing in the forecast is truly unprecedented. I have not seen an event like this unfold in anything that we've predicted. before. I guess the story begins last year, in fact, in 2025. At that time, at the Met Office, where I'm based,

we collect together each year a whole suite of decadal predictions going out to the next 10 years. Now, you can't predict individual El Nino events 10 years ahead, but by looking at each year in those forecasts we saw in November 2025 that actually a lot of the models and a lot of the forecasts were starting to warm the El Niño region in 26. So this is now a year ahead of the actual event, but we could see signs of that coming. So that was the first signature really at the end of 2025. Then as we come through into 26, the forecasts start to ramp up even more. And at this point, seasonal forecasts that run out just for a few months also started to pick up on strong signals. And it became very quickly apparent over the spring and into summer 26th that actually something really exceptional was happening.

Some of these forecasts are going completely off the scale. There's a range of answers, of course, there's still uncertainty. But some of the models, and they're quite reliable, respectable models, are going way beyond anything we've ever seen in the history. historical record and ever seen in our forecasts, we're talking about maybe three or four degree events in these forecasts now. So those are record events. They are way beyond anything we've ever seen. And so on top of climate change, we are now concerned about these global impacts. But just to come back to the amplitude, once again, it's the biggest thing we've seen. And perhaps the only comparable event I know of in the historical record is the 80s.

177 El Niño, which was really intense. And we don't know exactly how big, but may have been similar to this event. And that created worldwide disruption, massive droughts, particularly in the tropics. So this is why we think this is such an important issue. Yeah, so it sounds, that's quite alarming, to be honest. How worried should we be? Well, I think we have to learn from the science and what we know. We know from previous. El Nino's where the impacts are likely to be. We know which areas are likely to experience drought. And we know which areas, there are a few areas which actually are at risk of flooding. So we know those patches around the globe. We know where the hotspots are, if you like, where there is most risk. Each month, actually, we make long-range forecasts as well,

not just of the El Nino, but of the whole globe, showing rainfall and temperature, for example. So we can see in those forecasts patterns now that really do look like these historical impacts of El Nino. You can just see it imprinted on there. It looks like you've taken the globe and overlaid a map of the historical El Nino impacts. They're very similar. There are actually some detailed differences, and so the current forecasts are the best guide. But this means that we have some months of warning, right? So people have been talking about the El Nino of 2026 for some months.

We have some lead time. It's not like a weather forecast where you might only have a day or two of warning. In terms of El Nino and these wider global risks, we do have many months. So we need to use that. Disaster risk reduction, aid organizations, you know, government departments that deal with international aid and so on, now are preparing and are aware of this stuff. It has been well communicated, I think.

It is pretty well known that this event is on the way. Of course, the devil is in the detail, and we need to be careful about the regional impacts and where we think the risk is highest. But that's, I would argue, is what needs to be done next. I'm no expert in some of these things, of course. I just do the science side, but we pass this information.

It's all publicly available, and it's really for governments and society, now to use that and I hope that they heed the warnings and use those forecasts. So one final question for summing up then. Is this a very rare event? You mentioned, I think you said 1877 was the last sort of comparable event that we're seeing. You know, is that if sort of, you know, if we can cope with this one, we've got a lot of time to figure out what to do until the next one comes. or is that just the wrong way of thinking of it

and they're just going to keep coming and coming? We've had other big events, not as big as the one that's on the way now, but we had a big event in 9798. We had a big event in 2015. So we do get two degree el-Ninos, typically every 10, 20 years or so. So we have experienced these things before.

And I think, you know, hopefully, because we now know more about the regions that are going to be affected, and the warnings are much better than they were a few decades ago. I hope that we can adapt to these things, and I hope that governments listen to these forecasts. This is very much an international activity. There are a few global climate centres like the Met Office in the UK, but there are other centres worldwide. There are just a few that issue these forecasts, but they are available publicly. They are available and communicated to governments. So hopefully that, combined with previous knowledge, will help us to adapt well to the coming events.

Whether the fact that we're going to have a big El Nino in 2026 means that we are off the hook for some years afterwards is not so clear. It's not really regular enough to say that, okay, we had a big event here, so we're not going to get a big event three or four years later. It's not that regular, so it's hard to say that. And of course, there is this kind of joker in the pack in the background. We don't know whether climate change is really shifting the frequency of the big events. We don't yet have a really clear answer to that. So it's hard to say, you know, that we will get some kind of respite for some years. I wouldn't like to say that.

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