Highest-ever ocean temperatures recorded as El Niño intensifies

Record ocean temperatures in August

0:00Welcome back to the Nature Podcast. This week, how ocean temperatures have reached a record high, and why researchers injected mitochondria into someone's eye. I'm Nick

0:35Patricio. And I'm Benjamin Thompson.

0:45This week, the Earth saw an inauspicious record being broken, with the global average sea surface temperatures reaching their highest ever recorded levels, beating a previous high seen in 2024. Here to talk about it and what it might mean is a new voice in the pod, nature reporter James Dineen, who's been covering the story. James, thank you for being with us today. Thanks for having me. So let's talk about the record itself, James, and what this number is, because it's important to remember this is an average. There are some caveats to this.

1:17Yeah, so the average sea surface temperature usually just includes the oceans between 60 degrees latitude in both hemispheres. So excluding the polar oceans. And these numbers come from Copernicus, which is Europe's climate reporting service. And just a few days ago, they described the average sea surface temperatures, they just hit 21.1 degrees Celsius, which beats the March 2024 record. And it beats all other records as well, going back to what, the 1970s? Is that right?

1:48Yes, at least in their satellite records back to the 1979, but almost certainly further than that. And what's striking about this individual record and this high temperature, which was beaten on Saturday, is that it's not just the high number, it was when it happened. So it happened in August, which is unusual in terms of sea surface temperatures. Right. Normally, you would expect the high to come after the southern hemisphere summer, where there's more ocean in the southern hemisphere. But here we see the record high coming in August. And really, that bodes poorly for future records falling as we move into 2027.

2:21So things have shifted then from what, I guess, March is the usual high temperature, right, to August. And a lot of the reasons for this rise have been maybe attributed to El Nino, this climate phenomenon where warm water moves west to east across the Pacific and have all sorts of severe knock-on effects. Is that what's going on here, do we think? I think you could think about two major factors behind the record-breaking sea surface temperatures. First is the background global warming driven by human greenhouse gas emissions. But then on top of

2:53that background rise in temperature, you have the development of an El Nino pattern, which, as you described, sees anomalously hot temperatures in the tropical Pacific. And when that happens, it sort of pours heat into the atmosphere and raises the overall ocean average sea surface temperatures. So it's really the combination of an El Nino on top of the background rise in global warming. Right. Because in your reporting, you write that, you know, we're seeing temperature rises in various oceans, not just the Pacific. And that can't all be to do with El Nino.

3:24One researcher put it to me that basically everywhere you look, the ocean is above average. But where that above average anomaly is most extreme at the moment is in the tropical Pacific. And that is because of El Nino pattern that has developed there. Other places that are notably warm include the Northwest Pacific, like the Sea of Japan, and then also the North Atlantic, the Mediterranean Sea are also especially hot at the moment. And this week's event isn't in isolation, right? This heat comes after records fell in 23 and 24

3:56as well, right? There is a pattern developing here. In some ways, this is sort of a deja vu moment from 2023, 2024, which also saw a El Nino pattern develop again on top of the background rise in global warming. But this time, one, there's been a few more years of global warming. And also this El Nino is shaping up to be a record smashingly big one, much more powerful than the 2023, 2024 event. But of course, it really has only just started, right? In terms of the cycle it's in. What do

4:31researchers think might happen in the forthcoming months?

El Nino effects and ocean carbon

4:33That's again, what's so surprising about this record following just in August. El Nino only emerged officially in June, but it has rapidly strengthened since then. As far as consequences of what a ridiculously strong El Nino means, the first one is higher temperatures, especially in 2027. Normally, the year after the emergence of an El Nino, you see a spike in temperatures. There have been some forecasts that suggest 2027 could reach 1.76 degrees Celsius above the pre-industrial

5:05average, which would make it far and away the hottest year on record. It's even possible that 2026 average temperatures hit record levels given how rapidly the El Nino is developing. But then separate from the effects on global average temperatures, El Nino also has a fingerprint of effects in different parts of the world on precipitation and heat. So Australia, Indonesia, for instance, can expect much drier, hotter conditions. Same thing with the Amazon. There's a lot of concern about

5:37fire and drought there and how that will affect the Amazon forest. Conversely, in places like the western part of North America, you might expect more precipitation under El Nino conditions, which could cause flooding, but also may do something to relieve the longstanding drought there. So a variety of effects are really depending on where you may be living in the world. But in terms of the oceans, James, what do researchers think this might mean in real terms for the state of the seas and oceans around the world? Similarly to effects on land, El Nino has a sort of fingerprint of

6:11ways that it affects ocean temperatures. A lot of times El Ninos are associated with impacts on fisheries. For instance, off the west coast of South America is an extremely productive fishery. El Ninos are associated with a collapse of the fisheries there, like the anchovy populations decline. One of the biggest concerns among ocean researchers has to do with coral reefs, which are really sensitive to changing temperatures. And the previous big El Ninos over the past few decades have led to what are

6:43called mass bleaching events, where large portions of the world's coral reefs are so stressed by the heat that they reject the symbiotic algae that makes them work. And then the corals bleach and then they can die. And if that's what potentially researchers are expecting to see, I know you've been talking to them as well about what they're not so sure about in terms of the impacts that the warming ocean will have. What have they been telling you there? One issue that I think is interesting has to do with the ocean carbon sink. So the ocean absorbs a

7:16huge amount of carbon dioxide from the atmosphere every year. So without that happening, the climate would be warming even faster. But there's this relationship between the temperature of the ocean and how much carbon dioxide it's able to absorb from the air. And normally during El Nino years, the ocean actually increases as a carbon sink. But in the past El Nino event, there was an interesting pattern where the oceans were so hot, this effect declined because of temperatures

7:47elsewhere. So overall, the ocean carbon sink saw a weakening during the last El Nino relative to what might have been expected. So that's one confusing and concerning aspect of this. Finally, then, obviously, El Nino works in a cyclical fashion, and this cycle will have an ebb and a flow. Does what it's doing now, do you think, give a sense of what might happen in the future? Because you said there is a combination of El Nino and human-associated climate change. Does it give an idea of what the future might look like for the oceans, do you think?

8:19There are two aspects to that question. First is that given El Nino is boosting global average temperatures and will very likely make 2027 a record-breaking year, there's been some discussion that 2027 temperatures will resemble what we might expect in 2037. So it's sort of like a sneak preview of temperatures as they might be a decade from now with another decade of global warming from our greenhouse gas emissions. There's some complexity there because the rise in temperature due to

8:51greenhouse gas emissions is distributed across the planet, whereas El Nino has this very distinctive pattern of how it affects temperature and precipitation. But that is definitely concerning to researchers. Another question is how human-caused climate change itself is influencing these swings between the warm El Nino pattern and the cold La Niña pattern. There's been a lot of debate in the field about whether this swing between cold and warm in the Pacific has been becoming more variable or more

9:25skewed towards stronger El Ninos because of the warming effects of climate change. There's definitely not consensus on that question, but it's an important one because it suggests, if we think about decades into the future, how many more super-strong El Ninos might we expect on top of even more warming with our continued greenhouse gas emissions from burning fossil fuels? That was Nature reporter James Dineen. For more on that story, check out the show notes for some links. Coming up, a trial to

9:58restore vision using mitochondria. Right now, though, it's time for the Research Highlights with Dan Fox.

Radiation vests and thunderquakes

10:05A protective vest could shield astronauts from some of the harmful radiation found in deep space. The region outside of the Earth's protective magnetic field, deep space, is a harsh environment, and protons flung out from the Sun are among the most abundant forms of radiation out there, especially during solar storms. Covering an entire spacecraft in protective coating could block

10:36some of this radiation, but would be impractically heavy. So instead, researchers have developed a lightweight vest to protect astronauts made from a durable plastic rich in particle-blocking hydrogen atoms. The team tested the vest on a model of a human torso aboard Artemis 1. Measurements taken when the spacecraft flew through the high-radiation inner Van Allen belt suggested that the vest, called AstroRad, could block 40 to 60 percent of a solar storm's radiation. You don't have to fly to deep space to find

11:12that research. It's in Science Advances.

11:23A huge thunderclap from a passing storm shakes the ground. Researchers have now found that these thunderquakes can help to map hidden geological structures. Geophysicists have long measured the varying speeds of seismic waves from earthquakes to survey rock underground. Now a team have tested whether they could use thunderquakes as an untapped source of seismic energy. The researchers recorded seismic data on an unused fiber-optic cable that snaked underneath their college campus. This method,

11:58known as distributed acoustic sensing, uses scattered light to measure how vibrations in the ground stretch a cable at discrete points along its length. From 458 thunderquakes over two and a half years, they reconstructed a profile of the 100 meters beneath the cable. The resulting map matched with other geological information, identifying several weak spots in the limestone beneath the campus. According to the researchers, this demonstrates that thunder offers a reliable source to survey

12:30otherwise inactive areas, including on planets where seismic activity is rare but lightning is frequent. If that research has shaken you up, you can read it in full in Science Advances.

Mitochondria injection for vision

12:45Researchers have injected a woman's own mitochondria into her eyes in an attempt to restore vision. This research, described in a not-yet-peer-reviewed preprint posted on the 10th August, hoped to discover if mitochondria can help restore tissue in the eye and whether such a procedure was safe. Joining me to give us more details is reporter Miriam Nadath, who's been writing about this

13:19work in this week's Nature. Miriam, hi, how's it going? Hello, Nick. Well, thank you so much for coming to talk to me. It's a very interesting story, I think, like putting mitochondria into someone's eyes. Can you tell me a little bit about what is the thinking behind this? Why would you do something like this? Yeah, so mitochondria are these organelles that provide cells with energy, so they are very important for the functioning of cells. And almost every cell in the body needs mitochondria. And there's been an interest in using mitochondria transplant as a treatment for disorders where

13:52the mitochondria is not working properly, but also in disorders where the mitochondria could potentially help restore cell function and survival. So researchers have published studies in animal models with mice. And there were even clinical trials that involved injecting mitochondria into the human heart and the human brain. And so how did we get here? Because this is looking at restoring vision to an extent. So tell me a little bit about the background of this story. Like this was done in a woman. What happened to her?

14:24And why did we get to giving her mitochondria? So this is the story where a woman in February suffered from a brain bleeding and was estimated to have had reduced blood flow to her brain for 18 hours before she was found and admitted to a hospital. And at the hospital, doctors confirmed that there was severe injury to her optic nerves. But the woman still showed some response to light, but that was lost over time. And she continued not to show

14:57any response to light for three months before the treatment. So was the thinking here that by injecting some mitochondria, perhaps they could restore some of this lost function? Exactly. So the hope was that injecting mitochondria directly into the vitreous fluid would deliver fresh mitochondria that are functional and vital into the retinal ganglion cells, which are neurons that sit in the interface of the retina, and they send vision signals into the brain. There have been

15:28some animal studies experimenting with injecting mitochondria into the vitreous fluid, and it has shown some positive results on cell survival and cell function. And so these researchers, as I understand it, they approached the US Food and Drug Administration to get approval to try this out, and then did it. How did it go? Yes, Nick. So this was an emergency approval for an experimental procedure in one person. And the authors of the preprint have told me that they worked day and night. Some of them were based in the east

16:00coast of the US, some of them were in the west coast. So they would take turns in completing the paperwork required to get this emergency approval as quick as possible. On the day of the treatment, the researchers and the doctors had three hours to take a muscle biopsy from the woman's leg, extract mitochondria from these muscle tissues, and we're talking about fresh naked mitochondria, and inject it into the vitreous fluid in the woman's eye. And they waited. So once they did this for

16:34the first eye, they waited 24 hours. And then they repeated the same procedure for the next eye. Now, because this has never been done before, the researchers main concern was safety. So they wanted to know whether such a mitochondrial transplant into the eye could trigger an immune response or inflammation. So they monitored the woman for several weeks, and there were no signs of inflammation and immune response. And they have seen temporary improvement in the woman's response to light.

17:05So she showed response to light. But by day 28, the response has faded. Well, it faded away in one eye and remained higher than it was before for another eye. So maybe not a full restoration of vision, as maybe one might hope, but it seems there were some signs there. What did the other researchers that you spoke to for this story have to say about this? So the researchers that I spoke with, who were not involved with the research, were quite cautious about interpreting these findings, because it is still not very clear whether

17:40the responses that the woman displayed were a result of the mitochondrial transplant itself, or some residual brain function, or even natural recovery. So what are the open questions for them then? One of the questions that researchers hope to have an answer to is what cell types ended up gobbling the mitochondria? And if this treatment did indeed produce some improvement, how exactly did it do so? And the team behind the work, what are they planning to do next?

18:12So the team behind the work is talking with the FDA for potentially approving repeated treatments so they can establish whether a mitochondrial transplant could help at all with restoring or improving vision. Well, early data then on this, but I'm sure there'll be more to come and we'll be keeping an eye on it here at Nature. But for now, I think that's all we've got time for. So thank you, Miriam, so much for joining me. Always a pleasure, Nick. That was Nature reporter Miriam Nadath. For more on that story, check out the show notes for some links. And that's all for this time. If you'd like to stay in touch, you can. We're on social media,

18:46at naturepodcast. Or you can send an email to podcast at nature.com. I'm Benjamin Thompson. And I'm Nick Petri. Ciao.