Earth system scientist Jin-Yi Yu says 2026-27 El Niño could be the strongest ever
There is a super El Niño brewing in the tropical Pacific Ocean. That means the sea surface temperature in this region is much higher than normal, a condition that has, in the past, led to heavy rainfall in the Southwestern United States during the winter months. Will this year’s El Niño bring torrential rainfall to Southern California in the coming months, and will that and other El Niño-driven weather cause flooding and erosion on our sensitive coastline? UC Irvine researchers from a variety of disciplines are working to understand El Niño outcomes for 2026 and 2026.
This episode of the UC Irvine Podcast is part of a special, multi-part series on El Niño. It features Jin-Yi Yu, UC Irvine professor of Earth system science, who is one of the world’s leading authorities on El Niño, Earth’s atmosphere, oceans and climate. What causes El Niño, and will it bring more rain to Southern California this year? You can find answers to these questions and more in this episode of the UC Irvine Podcast.
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“To Weather a Storm,” the music for this episode, was provided by Dan Lebowitz via the audio library in YouTube Studio.
TRANSCRIPT:
Brian Bell:
From the University of California Irvine, this is the UC Irvine Podcast. I’m Brian Bell.
News about El Niño seems inescapable these days, but what exactly is El Niño? It stems from abnormally high sea surface temperatures in the tropical Pacific Ocean that can sometimes lead to increased rainfall in the Southwestern United States. We don’t normally see impacts until the winter rainy season here, but this year’s very strong El Niño is already being blamed for high surf and tides that have caused catastrophic erosion along the Southern California coastline.
UC Irvine is home to numerous experts on El Niño. We’ve got Earth system scientists who are running computer simulations to try to predict outcomes and environmental engineers who are getting ready to monitor the impact of El Niño on infrastructure, beaches, and flood-prone inland regions. UC Irvine public health researchers are offering advice on how Southern California residents can protect themselves and their loved ones. Others are exploring the climate phenomenon from economic, cultural, and humanitarian standpoints.
Because El Niño is so big and multifaceted, we decided to produce a special series here on the UC Irvine Podcast. In this episode, you’ll hear from Earth System Science Professor Jin-Yi Yu, who is one of the world’s leading researchers on our planet’s atmosphere, oceans, and climate. He’s gotten a lot of attention in recent years for explaining how the character of El Niño has changed in the 21st century.
Our conversation with Professor Jin-Yi Yu is up next.
Bell:
Professor Jin-Yi Yu, thank you for joining the UC Irvine Podcast.
Jin-Yi Yu:
Thanks, Brian, for having me here to talk about El Niño.
Bell:
So, you can’t turn on the news these days without hearing about El Niño and seeing people’s predictions about what’s going to happen. Can you give us some basic information? What is El Niño?
Yu:
Yeah, El Niño is a climate phenomenon that relates to the warming of surface temperature in the tropical Pacific Ocean. And typically, this phenomenon happens right outside the South American coast in the the Eastern Pacific region. When it happens, the sea surface temperature can warm to more than normal for 0.5 degree Celsius, one degree Celsius or even larger over a very large area of the tropical Pacific Ocean. That warming can cover up to two thirds of the tropical Pacific Ocean region. That’s a huge area in the ocean. And they can warm up one to two degrees C. That’s a huge amount of energy that is going to show up on the upper part of tropical Pacific Ocean. And usually, it first shows up in the springtime of the year and then become very obvious as become strong and grow very quickly in the summertime and autumn season and eventually reach its strongest intensity in the wintertime.
And that’s why the Peruvian fishermen realize this phenomenon usually around the Christmastime. That’s why they refer this ocean warming phenomena as El Niño. I think most of the audience probably know this story already.
Bell:
So, we are in an El Niño phase now, but we have not reached the peak of the El Niño.
Yu:
Yeah, it’s still growing and what makes this event amazing is that even before it reaches the peak intensity, which we anticipate to happen in maybe November or December, but the ocean warming associated or brought up by this event to the Pacific Ocean is already huge. And that’s why the scientifical community is paying a lot of attention to this amazing climate warming phenomenon in the Pacific Ocean this year. So, most of computer models so far already tell, project that this 2026 El Niño is very likely to be stronger, even stronger than the previous 2015-16 El Niño. That is the strongest El Niño so far in the modern observation era. So, I think computer model already projects that the ocean temperature in the Pacific region over the area that we monitor the El Niño strength is going to be over three degrees to five degrees warmer than normal.
And in the 2015-16 is only 2.7 degrees Celsius warmer than normal. So, if computer model is correct, then this 2026 El Niño, when it comes to its peak time, which is usually November or December time, it’s going to show us that this event is even stronger than the previous strongest 2015 and ’16. So after that, I think the community’s pretty much very confident that we are going to have this event stronger than 2015-16. So, the next more interesting question is can it even stronger than the 1877 El Niño event? Yeah, that’s the one we are looking to see, yeah.
Bell:
And it remains to be seen if that’s going to be the case.
Yu:
Yeah, because the El Niño typically is the peak intensity should show up in the wintertime. So I think somewhere in the November, December, January time. So, all the El Niño that we know, we observed so far, they always grow with certain seasonality. So, usually, El Niño will begin to show up in the springtime and begin to show its strengths of growing in the summertime and autumn. And that’s the time usually the weather agency in the world will announce officially saying El Niño has arrived, because it’s intensity already grow very quickly in the summer and autumn season. But its peak intensity usually shows up in the wintertime. So we are now hasn’t reached the peak intensity of this 2026 El Niño, but it’s already, it’s, uh, sea surface temperature is about 2 to 3 degrees Celsius warmer than normal.
That’s already very, very strong. Yeah. So for sure, this is very strong El Niño in the scientifical terminology ‘very strong’ means the ocean temperature is warmer than normal by at least two degrees Celsius. So, this is very strong El Niño and it’s still going. Very likely, it’s going to surpass the 2015-16. And the remaining question is, is it going to even stronger than 1877? If that happened, then we are going to witness the strongest El Niño ever.
Bell:
What are some of the weather impacts that people in Southern California will experience as a result of El Niño?
Yu:
So, even though El Niño happens in the tropical Pacific Ocean, and California is away from the tropical region, however, every time when ocean warm up, it’s going to send heat to our atmosphere and therefore displace how the wind move around, the weather move around in our atmosphere. And through some physical process, wave propagation, this ocean warming in the tropical region can impact to California. So, typically, from the past when we have an El Niño event, typical impact on California usually show up in wintertime because that’s the time that El Niño has strongest intensity. Therefore, its impact on California usually is very obvious in our wintertime and to affect our winter temperature and to affect our winter rainfall because for California, our rainfall season is in wintertime. So, typically, when we have El Niño, the California winter temperature will be colder than normal. And at the same time, the El Niño warming in the tropical Pacific Ocean is going to move the jet stream in our atmosphere, the storm track, to move away from Pacific Northwest and southward to California. So it’s going to bring wet, a lot of rainfall to California during the wintertime. And this, so, in brief, Southern California, the El Niño is going to give, typically it’s going to give us cold winter plus a very wet winter season.
Bell:
Now, we have had El Niño conditions in recent years here in California, maybe just a couple of years ago and then 2015-2016 timeframe. What was the impact of those recent El Niños in California
Yu:
Right, that’s a very good question that Brian mentioned because, because he mentioned 2015 and ’16. So, the typical impact told you just earlier about going to get, El Niño going to make kind of Southern California cold winter plus more rainfall. That was what happened typically in the 20th century. But after we have global warming and then this impact affects the El Niño property in the 21st century, we gradually noticed that the, those typical El Niño impact on Southern California become different in recent El Niño event, particularly in 2015 and ’16 event. And 2015 and ’16 El Niño is very important and very interesting to Southern California because 2015 and ’16 El Niño is the strongest El Niño we encounter in the past probably 50, 60 years. And at that time, if people remember that in the news, scientists already tell us that we’re going to have a super arena in 2015, ’16.
So Southern California community feel very excited because before that year, we already have a very long drought for several years. So, people, a resident in Southern California was anticipate that this super El Niño is going to bring the typical rainfall to California and solve this drought problem. And, but actually, it didn’t bring a lot of rainfall to Southern California in 2015 and 2016 El Niño event. So, question is, how come such a strongest, uh, one of the strongest El Niño in 2015 and ‘16 didn’t bring rainfall to Southern California One possible reason, as I mentioned many time to the UCI community, that is because our El Niño in the 21st century are not the same El Niño that we experience in the 20th century. So, the important thing about 2015 and ’16 to this year is, so far everything I look at is 2026 El Niño, every aspect I look at, I feel this event look very similar to the 2015 and ’16 super El Niño.
So first, they both has very, very strong intensity. They are both classified as a super El Niño. Second, they both have two warming center, one located right outside South America, the other warming center located in the international date line. This two center warming pattern in the El Niño, we do not see that often in the 20th century El Niño until we, we come to 21st century. We publish a paper to explain why 2015, ’16 El Niño didn’t bring, didn’t bring rain fall to California. So in our paper, we run a computer model to prove the reason we didn’t get a lot of rainfall in Southern California in 2015 and ‘16 is because of this double warming center pattern. And I noticed that same pattern also showing up this year for this 2026 super El Niño. That’s why I was thinking there’s a possibility that this 2026 El Niño even is going to be stronger than 2015-16, but it’s impact on California winter rainfall has a possibility may look like 2015-16. I mean, we may not get a lot of rainfall we anticipated from this El Niño intensity alone.
Bell:
We’ll just have to wait and see.
Yu:
Yes, that is case.
Bell:
Have heard you talking about another warm water area in the Pacific Ocean. This is closer to the Gulf of Alaska. Is there something to do with that related to El Niño?
Yu:
That one is what we usually call the marine heat wave, or sometimes in the climate research community, we call it ‘Pacific blob,’ a big piece of warm water in the Gulf of Alaska region. That one is not necessarily related to El Niño. That one actually has an independent physical process to produce that event, meaning that it can happen with El Niño or without El Niño. Those are two separate ocean warming phenomena. So, actually, that one is what we call the marine heat wave in the Gulf of Alaska region. And El Niño actually is another type of marine heat wave, but it happens in the tropical Pacific region. So that warm marine heat wave in the Gulf of Alaska region or in the North Pacific region is another ocean warming phenomenon that can affect the California rainfall because the ocean warming in the Gulf Alaska region, in the North Pacific and El Niño warming in the tropical Pacific region can both affect where the winter storm going to displace away from California or coming close to California.
If we only have El Niño, then we know, typically, the winter storm should be brought closer to California away from Pacific Northwest. But when we have a marine heat wave also showing up in the Gulf of Alaska, another warming in the North Pacific, then the jet stream has to decide whether or not it should move north or south, listen to marine heat wave in the Gulf of Alaska or listen to El Niño in the tropical Pacific. So that phenomena actually also exists this year. That adds another uncertainty for us to decide exactly what may happen to California winter rain for this year because now we have two factors to consider. One is this super El Niño in the tropical Pacific Ocean, at the same time we have a strong warming in the North Pacific region and we have to see whether the atmosphere wants to listen to El Niño or wants to listen to the marine heat wave to decide what kind of winter rainfall we going to have in California.
Bell:
Do you think all of these different marine heat wave areas, El Niño conditions in the tropical Pacific have some connection to global warming, climate change that we’ve experienced in the last 50 years, say?
Yu:
Yeah, actually, global warming is one of the few factors that we identify because my group did a lot of research to try to document and explain why El Niño in the 21st century looks so different from El Niño we encounter in the 20th century. And global warming is one of the factors because it changed the way our climate machine operates. So, because after global warming, whether or not our climate machine should rely a lot on this air moving around in the tropical region or in extra tropical region will change and that will change the El Niño location, El Niño property. But, beside global warming, there’s also other factor that can affect this El Niño property, including like whether or not the Atlantic Ocean temperature warm up or cool down, because in our climate system, Atlantic Ocean usually will warm up, cool down every 60 to 80 years. And now after we enter the 21st century, the Atlantic Ocean warming and cooling cycle happen to enter warming phase. And there’s several climate research already explaining that that warming phase in the Atlantic could be another reason our El Niño property change, either change location or change intensity. So that could be another reason.
And the third reason to make El Niño property change is because we’re cutting trees in the Southeast Asia region, because of deforestation over the South Asia region — the Maritime Continent region — also is the third factor contributing to this El Niño property change. And related to the other side of the question, the marine heat wave, because we don’t hear a marine heat wave a lot in the news or in the research community because also could be related to global warming. Maybe we elevated the background ocean temperature because of global warming and then we trigger physical process that will enable marine heat waves to occur more frequently, to last longer, to reach a higher intensity.
That’s why in recent year we hear and read and notice there are more frequent news report about we have this marine heat wave here and there, including the one outside the Gulf of Alaska. So yes, global warming is one reason to make El Niño become different and marine heat wave to happen more frequent and they both act together to affect how our California weather and climate may look like.
Bell:
Well, Professor Jin-Yi Yu, thank you very much for spending some time explaining this science to us today. I really appreciate it.
Yu:
Yeah, thank you Pride for having me here.
Bell:
You can read more about Professor Jin-Yi Yu’s El Niño research at news.uci.edu. While you’re there, please check out the other episodes of our special El Niño podcast series.
The UC Irvine Podcast is a production of Strategic Communications and Public Affairs at the University of California, Irvine. Please subscribe wherever you get your podcasts.
I’m Brian Bell. Thank you for listening.