Highest-ever ocean temperatures recorded as El Niño intensifies

**Benjamin Thompson** (0:04)
Nature Podcast In the experiment, we don't know yet why it's applied so far.

**James Dineen** (0:08)
Like, it sounds so simple.

**Dan Fox** (0:09)
They had no idea.

**Benjamin Thompson** (0:10)
But now the data's...

**SPEAKER_4** (0:12)
I find this not only refreshing, but at some level astounding.

**Benjamin Thompson** (0:23)
Welcome back to the Nature Podcast.

**Nick Patrick Howe** (0:26)
This week, how ocean temperatures have reached a record high and why researchers injected mitochondria into someone's eye. I'm Nick Patrick Howe and I'm Benjamin Thompson.

**Benjamin Thompson** (0:46)
This 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.

**James Dineen** (1:08)
Thanks for having me.

**Benjamin Thompson** (1:09)
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.

**James Dineen** (1:18)
Yeah, 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.

**Benjamin Thompson** (1:45)
And it beats all other records as well, going back to what, the 1970s? Is that right?

**James Dineen** (1:48)
Yes, at least in their satellite records back to the 1979, but almost certainly further than that.

**Benjamin Thompson** (1:53)
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.

**James Dineen** (2:05)
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

**Benjamin Thompson** (2:21)
So 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?

**James Dineen** (2:40)
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 that 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.

**Benjamin Thompson** (3:15)
Right, because in your reporting, you write that we're seeing temperature rises in various oceans, not just the Pacific. And that can't all be to do with El Nino.

**James Dineen** (3:24)
One 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.

**Benjamin Thompson** (3:50)
And this week's event isn't in isolation, right? This heat comes after records fell in 23 and 24 as well, right? There is a pattern developing here.

**James Dineen** (3:59)
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.

**Benjamin Thompson** (4:24)
But of course, it really has only just started, right? In terms of the cycle it's in, what do researchers think might happen in the forthcoming months?