Climate change: Oceans warmer last month than any May on record
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00:00 is also World Oceans Day, marked every year to raise awareness about the importance of
00:05 the oceans and marine ecosystems. It comes at a time that oceans are warming as well
00:11 at an alarming rate. According to the EU's Climate Monitoring Unit, global oceans were
00:18 warmer last month than in any other May on record, those records stretching back to the
00:24 19th century. To tell us a bit more, in the studio with me now is our Environment Editor
00:29 Valerie de Kamben. Valerie, the warming of the oceans seems to be one of the main threats
00:35 that currently faces our marine ecosystems. Just tell us first of all what the implication
00:40 of that is. Well, according to the data you just mentioned of that report, the average
00:46 temperature of the sea surface has reached 19.7 degrees Celsius. And essentially what's
00:53 happening is that oceans, they act like sponges, absorbing 90% of the excess heat generated
01:00 by climate change, driving up temperatures and cascading effects. So the melting of ice
01:07 sheets, rising sea levels, ocean acidification and also ocean heat waves. And so that list
01:14 of cascading effects in reality goes a lot further than that because oceans are a key
01:21 pillar of the planet's health. They sustain so many functions. They produce, for example,
01:27 more than 50% of the world's oxygen. More than half a billion people on the planet depend
01:34 on marine ecosystems. And yet those resources from the ocean are actually being depleted.
01:40 More than 90% of fish stocks already depleted. 50% of coral reefs destroyed. And the problem
01:48 is that all of this is happening so fast, actually faster than the time needed for oceans
01:56 to recover and adapt to these changes. For example, IPCC scientists have been telling
02:02 us that oceans are warming twice as fast as in the last 30 years. So all of this is accelerating.
02:10 And it's all part of a vicious circle because climate change, global warming is accelerating
02:16 some of these changes. And then that's also making us more vulnerable to the impacts of
02:21 climate change because we know, for example, that ocean coastal ecosystems like wetlands,
02:27 for example, which are suffering from ocean warming and all these issues that I've mentioned
02:33 just now, well, they protect us from coastal erosion. They protect us from rising sea levels.
02:39 And so you see how all of this is very much interconnected and tipping oceans off balance
02:46 can disrupt a very fragile equilibrium we depend on.
02:51 And Valerie, just tell us a bit about your experiences. You're a reporter who has firsthand
02:57 witnessed some of the changes that you've actually just described for us now, including
03:02 severe marine heat waves in the Mediterranean here in France.
03:07 Absolutely. So last summer, the Mediterranean Sea was hit by its worst marine heat wave
03:13 in decades. So temperatures reach 28 degrees Celsius at a depth of 28 meters. So something
03:21 scientists have never seen anything like it. It's unheard of. And marine heat waves have
03:27 been described as underwater wildfires because quite literally they ravage entire ecosystems.
03:34 The weather team at Down to Earth, we reported on this phenomenon, which is pretty much under
03:39 reported and overlooked. And we went to Marseille in southern France and we spoke with two divers
03:47 who were able to see firsthand what was happening underwater as it unfolded. And I want to show
03:52 you a clip of our report and you're going to understand why we call them underwater
03:57 wildfires. Let's take a listen.
03:59 I'm diving for fun in Marseille. I'm a diving monitor, a specialist in deep diving.
04:07 And this year we witnessed an absolutely unprecedented phenomenon, namely that we had
04:13 particularly significant episodes of water heat. We reached peaks of 28 degrees Celsius
04:19 up to 28 meters deep. An increase in this temperature is no longer water, it's a
04:25 stream of lava. And over the first 15, 20 meters, the whole thing is burned. And so we see
04:38 these gorgons. They were blood red, purple red. They turned green. It made me think
04:47 actually of the images we saw of the fires of Gironde after the fire, where we see the
04:53 gorgon that is still standing with its branches. And we see this black trunk full of sweat.
04:58 This is the image we had made with Nicolas of this underwater fire.
05:03 I call it a genocide. The term may be brutal, but when in a given space a population of
05:16 individuals is completely eliminated, stripped of their map, I can't call it anything else.
05:22 The thing with marine heat waves is that they're not as visible as perhaps, you know, heat
05:31 waves happening, terrestrial heat waves. And scientists, though, on the other hand, they
05:36 tell us that from 2015 to 2019, every single area of the Mediterranean was subject to at
05:44 least one marine heat wave per year. 2022 was an historic year because it lasted so
05:51 long. It started in April and it went all the way into October. And that's what makes
05:57 marine heat waves so deadly compared to terrestrial heat waves, because terrestrial heat waves
06:02 never actually last that long. Imagine being in a heat wave from April to October. And
06:08 what you saw in that clip is the consequences of marine heat waves. They can lead to mass
06:15 die-offs of marine life, corals in particular, as we saw just now, and some species will
06:21 inevitably disappear. More than 50 species, according to scientists, have been affected
06:28 in the Mediterranean by marine heat waves. Now, fish, because of their mobility, they
06:34 can, you know, swim into deeper waters and stay cool and avoid the heat wave. But other
06:41 species like corals, for example, they live attached on rocks and so they cannot escape.
06:47 And that's what's causing those mass die-offs in corals. I guess as with anything else related
06:55 to climate change, what's so difficult is that this is going to become a lot more, marine
07:01 heat waves will become a lot more frequent, a lot more intense. And the problem is that
07:06 if they come back every single year, year after year, those ecosystems will not be able
07:12 to recover. And that's what we, when we're entering dangerous territory.
07:16 Valerita Kamp, our Environment Editor, thanks very much indeed for coming in and telling
07:20 us about that really important story. Thank you.