Quirks and Quarks - Coral archives reveal a shift in El Niño strength

Episode Date: September 25, 2026

The El Niño underway in the Pacific Ocean has been called extraordinary, supersized and likely record-breaking. And while El Niño is a natural climate phenomenon, its warming effects are being boosted by climate change. Julia Cole, a paleoclimatologist at the University of Michigan, recently used corals growing around the Galapagos Islands to create a local temperature record of the ocean going back 1,000 years to add to what they've learned from similar studies elsewhere in the Pacific. She said the temperature record in this area of the East Pacific indicates that the El Niños from the last 40 to 50 years are unlike anything the area experienced in the last millennium. Her study was published in the journal Science.

This week on two blocks from the White House. Donald Trump is busy with international diplomacy this week from China to the UN. But he doesn't have too many friends in other countries these days. So we're asking, is Donald Trump even interested in having allies? Find and follow two blocks from the White House wherever you get your podcasts. And watch us on YouTube. New episodes drop every Wednesday. This is a CBC podcast. climate phenomenon is now the strongest on record, according to scientists monitoring Pacific

ocean temperatures. This El Nino is set to be the strongest in records dating back 150 years, and the Met Office says its impact are already being felt. The latest projections for this year's El Nino are being called nothing short of extraordinary. Climate scientists are forecasting the worst El Nino in recorded history that could piece, near 4 degrees Celsius above normal this November. El Niños are a naturally occurring phenomenon that heat the waters of the eastern Pacific Ocean and impact global weather patterns. Many sectors will be affected.

Agriculture, trade, fisheries, health, energy, transport, water resources, disaster management, to name but a few. It is a risk multiplier and we expect to see health impacts across the world. A new report looks at how many deaths it could cause on top of what's already expected, with some of the biggest impacts projected in global South countries already in their hot season. From the start in June of this year through February, we expect 451,000 deaths just from heat. UN Secretary General Antonio Guterres stated that the science leaves no doubt. Climate change has put us into hot uncharted waters

that's supersizing the El Nino before our eyes. I've been tracking El Nino for years, but these numbers, they're off the charts. I've never seen an El Nino this strong hit on top of an ocean that is hotter than we've ever seen it. Teasing apart how climate change is factoring into the intensifying El Nino's we've been seeing isn't easy. But one way we do that is with handy marine record keepers

in the form of corals. Dr. Julia Cole led a study that was recently published in science where she used corals to look back at El Nino's over the past thousand years. She's a paleo-climitologist at the University of Michigan in Ann Arbor. Hello and welcome to our show. Hello, thanks so much for having me. How much of a surprise is it to you that we may be facing the worst El Nino on record this shared? Well, you know, I'm not hugely surprised because our data suggests that strong El Nino's have become more the norm now than they were in the past. So while every really strong event is a little bit of a surprise, I think this is something where it's consistent with the idea that El Ninos are getting stronger in a warmer world. Now, before you started looking at corals to go

back in time, how accurate is our record of El Ninos? Yeah, that's a great. question. You know, El Nino's happened in a really remote part of the tropical Pacific. And so right now we have satellite data that gives us a really clear picture of what's going on across that whole area. But before about the early 1980s, we didn't have that. And so our picture gets blurrier the further back in time we go. So our data on El Nino are pretty good back to about 1950, and then they just get blurrier and blurrier as you go back earlier than that. Well, just give me a little background to hear. What exactly are El Nino's? and what causes them to form and oscillate between warm and cold, like we see?

Sure. El Nino refers to the tendency of the eastern and central tropical Pacific to be a little bit warmer than usual, and it has a counterpart, La Nina, in which that region is cooler than usual. We go back and forth between El Nino and La Nina, naturally, every few years. What happens is during what you might think of as normal conditions, the trade winds blow from east, from South America side, to the Western Pacific, the Australian side, And as they do that, they push warm water across the equator. It gets warmer and warmer under the hot equatorial sun.

That water also piles up in the Western Pacific, forming an actual hill or slope of water that's higher in the west than the east. So when those trade winds fluctuate as they naturally do, that slope can become unstable. And when they weaken, the slope can actually relax down and slosh that water or spread that warmth back towards. it's the eastern and central Pacific. That's what happens when an El Nino develops. Wow. It sounds like water sloshing back and forth in a bathtub. It's going from one side of the Pacific to the other.

It's a little more complicated, but yeah, but that's the idea. Boy. So how does this shift in the warm water affect different regions around the Pacific? Yeah. If it only happened in the remote tropical Pacific, we might not know very much about this. But because that warm water changes how the atmosphere circulates. It turns out that El Ninoes and their counterpart, L'Anneas, are the biggest source of

year-to-year climate variability on the planet. The main thing that happens is when that warm water moves to the central and eastern Pacific. It also moves with it the pattern of atmospheric circulation across the Pacific. Over warm water, air tends to rise because the water heats the air, the air is warm, it's lighter, and it rises up. Rising air leads to rainfall. rising air also pulls the trade winds in from both sides, so it kind of keeps those trade winds kind of weak and disorganized across the Pacific. And the rising air stirs up the upper atmosphere circulation as well and shifts the pattern of atmospheric circulation around the Pacific and indeed around the entire tropics.

We even see its impact on the jet stream, which is the storm track that brings storms into North America. Well, how did you use corals to help teetops? apart the role that climate change plays in the development of these powerful El Nino's. Yeah, we're really lucky that corals, as they grow, they record the conditions under which they grow in the chemistry of their skeletons. So a coral can live for decades to centuries, and it grows a centimeter or two every year. We take a core from those corals, and we sample that core at millimeter resolution. So that gives us a sample every month, essentially. We're able to measure the

chemistry of those samples, and we measure them with an eye towards a couple of particular compounds that are sensitive to the temperature of the formation of the skeleton. And so we're able to come up with monthly records of temperature from these coral skeletons. And we put those together using corals that are living and corals that are dead, but we have collected on the beaches of Galapagos and we date them, they date across the last millennium. So we've put these records together for many different corals to come up with a history of Almenio across the last millennium. Where did the corals for this current study come from? This study focused on corals from the Galapagos Islands. The Galapagos lie on the equator,

about 1,000 kilometers offshore South America. And this part of the Eastern Pacific is where the biggest, strongest El Nino events have their biggest impact on ocean temperatures. So this is a really great place to study the history of the Eastern Pacific side of El Nino. So you mentioned that you also study coral fossils. So what's the difference between what you get from living fossils and ancient ones? Yeah, the living corals allow us to determine that our coral thermometer is working, basically. We can take a cord from a coral that is living today, and we can take our monthly samples back through time and compare the chemistry that we get from those samples with temperatures that have been measured, either by satellites or

by local thermometers. So we can ground-truth our records and confirm that the record we're getting from the corals is an accurate reconstruction of local temperature and of the broader-scale El Niño pattern. So then we can look for corals that are dead and older, and we date these using uranium-thorium-thorium methods, radiometric dating methods, that give us ages that are accurate to within about a few years. So we might find a coral washed up on a beach that we can date to, say, 500 years ago, but it may preserve a record of 40 or 50 or 80 or 100 years in it. And so we can then do our monthly reconstruction of temperature and see what El Niño was doing

at that time 500 years ago. Wow, that's amazing. You know, you say that the Galapagos Islands are the most impacted by El Nino. You're lucky you were able to get living corals there at all because we hear about so much bleaching going on. Yeah, absolutely. In fact, my first experience in the Galapagos in 1989 was kind of a bust. You know, we went looking for corals that people had identified as living there prior to the 82, 83 El Nino event. But when we looked for them in 1989, they weren't there. They were gone. So we really struggled to find living corals initially.

But eventually we were able to work on a reef in the far northern archipelago that hadn't been well documented early before the 2000s. And we started working there and found some living corals that had managed to persist. Wow. So what did you see once you put it all together? Yeah, we put together a history of El Nino and La Nina variability going back almost a thousand years. Our record has almost half of those years covered. You know, we're using individual corals, so they're not continuous, but we're getting these windows on the past.

And what we found is that the strong el Niños of the last 40 to 50 years are really unusual. We don't see anything like that in the pre-industrial era in our coral data. The strengthening of the variability in the Galapagos happens in parallel with warming temperatures. And so our interpretation is that the warming of climate is what has generated these stronger events. And we looked hard for natural explanations that could have accounted for this strengthening. But we saw no evidence that natural variability could create this same level of variability that we saw in the last 40 to 50 years. So are you saying human-made climate change is responsible? We understand that very well that the human burning of fossil fuels is what's responsible.

for the warming that we're seeing today. Okay, so now that you have a better understanding of how the past climate worked and how the corals were affected, what can we expect going forward, including this year's El Nino? Yeah, that's a great question. And I have to be a little careful here because our corals provide us a window onto the past, but they don't give us a crystal ball into the future. So what we used to look ahead are climate models, and the majority of climate models actually do say that El Nino is likely to strengthen in the eastern Pacific over the coming century.

Well, how important is it to establish this link between a warming climate and strengthening El Nino's? Well, I think our work has given us one more brick in the wall, if you will, of the idea that, you know, we're building a story and an understanding of El Nino, and part of that story is understanding whether the conditions that we're seeing right now are unusual. And our data says, yes, they are unusual. And we're able to say that with some confidence, given the amount of data that we've collected in the past. So that tells us that there is a trend happening now. And I think that was an important gap that we didn't know quite as clearly, especially in the eastern Pacific.

We had a little bit of a hint that this was happening in the Central Pacific, but we didn't really have a clear picture in the Eastern Pacific until this study. And so now that we've got that, you know, better understood, I think it helps us rule out some other possibilities, like that these strong El Nino's we're seeing are just part of El Nino being its natural self. That's not what our data say. Now, we've been talking about El Nino in the Pacific,

but how far reaching are its effects around the world? El Nino creates impacts all around the world, all through the tropics, all around the Pacific basin, and it does things like it rearranges where we find tropical storms, you know, the warm waters over the Pacific. generate more and stronger tropical storms during strong El Ninoes, and we're seeing that already this year, right? Conversely, an El Nino tends to suppress tropical storms in the Atlantic, so that's helpful, but, you know, ramps them up in the Pacific. Another thing it does is it

rearranges where droughts and floods are formed. So we may see floods in places that are usually dry and droughts in places that usually have a lot of moisture. An example of that might be in South America where right now we're seeing lots of rainfall along the equatorial coast near Peru and Ecuador. At the same time, up in Central America and Panama, they're experiencing a drought that is slowing down shipping in the Panama Canal. Even further afield in the Indian Ocean, we tend to see warmer conditions across much of the Indian Ocean during an Al-Nino, and we find that we see increased rainfall along eastern Africa and coast in Kenya and Tanzania, at the same time that we see reduced rainfall in southern Africa and in the Horn of Africa.

Wow. So El Nino really mixes things up all around the world. So what kind of effects are we looking at here in North America? Well, during an Al Nino, we expect to see more rainfall coming into the southwest, where we would normally have dry conditions. So in some ways, that is welcomed, although it can take the form of tropical storms that come in with great intensity, and it can overwhelm systems that aren't used to a lot of rain. We tend to see more rainfall across the southeast as well.

And then we'll see less rainfall in the northwestern part of the U.S. and in southwestern Canada where we would normally see rain. Because what El Nino does is it shifts the path of those storms southwards. So what can countries do at this point to protect their populations from the worst effects of the super El Nino? Yeah, the ability to prepare for El Nino's impacts really takes some resources, right? And it's a challenge to prepare. But I would say that one benefit we can point to is that we understand a lot about what the typical pattern of extremes that an El Nino event will cause. So I've just listed some of those.

And these are going to be different in different areas. But we can expect, for example, that areas that are prone to flooding during El Nino can prepare in ways that minimize the damage and risks to the population. there. For example, clearing out culverts so that they don't get clogged easily. In the case of drought, one can think about stockpiling food or think about planting different kinds of crops if you have enough warning. So there are ways to prepare, but each of these ways is very dependent on the particular impacts in a particular location. Just one last thing. What kind of emotional toll does this take on you to be the bearer of bad news that our actions will likely have such extreme effects on the weather?

Oh, boy. I mean, I think you hit the nail on the head there. It's really difficult to be talking about these things in this dispassionate scientific language and at the same time thinking about the impacts that El Mino can have on people, on ecosystems, on places that we care about, and not see a way to solve this problem that's immediate. I think by pointing to the connection between Alinio and global warming, it may give us one additional push to think and do more about reducing our dependence on fossil fuels

and getting off of the greenhouse gas producing fossil fuels that we depend on now. I mean, pushing us towards renewable energy. We know renewable energy is cheaper, and we know that most of the, new electrical capacity that we've put into place in the last few years has been in renewables. So that's something we really need to accelerate to get out of this. And I hope that this is one additional kick that gets us down that road. Dr. Cole, thank you so much for your time. Thank you for your interest. I appreciate it.

Dr. Julia Cole is a professor and chair of the Department of Earth and Environmental Sciences at the University of Michigan. For more CBC podcasts, go to cBC.ca slash podcasts.