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BBC Inside Science

Can we engineer ourselves out of a heatwave?

25 Jun 2026

Transcription

Transcript generated automatically by AI and may contain errors.

Chapter 1: How can solar geoengineering help combat extreme heat?

0.031 - 38.931

This BBC podcast is supported by ads outside the UK. Once upon a time, pessimist, optimist and saletist were grilling. And so it happened that saletist succeeded. Saletist succeeds!

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42.91 - 62.505 Tom Whipple

Hello, I'm Tom Whipple and welcome to Inside Science from the BBC World Service. Are you sitting comfortably? Then we shall... Look, of course you're not sitting comfortably. At least, not if you're listening live in parts of Europe. You're clammy, you're hot, you're wondering if you'll sleep tonight.

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62.485 - 83.658 Tom Whipple

But I'll begin anyway, because this week on Inside Science, as we adjust our sweaty gussets in the heatwave, we are going to consider, is it time to do something a bit more extreme on climate? Is it time to block out the sun? What will the effects of heat stress be in the near future? But there's lightness too.

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84.239 - 98.449 Tom Whipple

Lizzie Gibney, reporter at Nature, has been looking through everything else in science to bring us what's important, what's interesting, and even what is tangentially related to football for our World Cup science section. Lizzie, what have you got?

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98.429 - 107.317 Lizzie Gibney

Well, we have something very exciting in clock news for all those metrology fans and some fantastic effects of football that you might not have thought about.

107.677 - 137.149 Tom Whipple

Fabulous. But let's begin with the heat. It has been, shall we say, an ironic week to hold London Climate Action Week, one of the world's largest independent climate gatherings. On Wednesday, the organisers scheduled an event looking at climate policies titled Extreme Heat. it was cancelled. Due to extreme heat. Due to, in fact, the most extreme heat parts of Europe have ever seen in June.

137.79 - 160.678 Tom Whipple

Are we doing enough then when it comes to climate action? Something scientists have been tentatively, increasingly, hesitantly mooting in public is, what if we tried to reflect more of the sun? Is it mad? Perhaps. Is it extreme? Certainly. But is it possible? Just maybe.

161.378 - 184.982 Tom Whipple

Professor Mark Maslin from UCL sits on the Nuthild Bioethics Working Group on the ethics of what is called solar radiation management. Mark, it's the middle of the week. It's really hot where I am. I suspect it's really hot where you are. Climate change, we've been trying to deal with this for 30 years. We're used to the idea of reducing CO2 and the idea that that's what we have to do.

185.062 - 202.197 Tom Whipple

But as a short-term sticking plaster, I'm increasingly hearing scientists saying that it might be worth considering blocking the sun. Can you explain maybe in a slightly more scientific way what these ideas are and what they might involve

Chapter 2: What are the potential effects of blocking sunlight on climate?

264.759 - 285.422 Mark Maslin

The cost of that is astronomical, but the idea is you'd have mirrors reflecting sunlight from there. So the idea is that you dim the sun slightly, and therefore the temperature of the Earth cools down, so therefore buys us time to decarbonize. So this isn't a fix.

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285.963 - 309.618 Mark Maslin

It is literally my colleague saying, how can we buy us time so the transition away from fossil fuels occurs, and we can buy time to deal and suck out those emissions from the atmosphere, and so we can try to protect the Earth. That sounds like quite a sensible idea to me. The problem is that only deals with temperature. It doesn't deal with things like ocean acidification.

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309.738 - 334.918 Mark Maslin

It doesn't deal with sea level rise. It's just a fix for temperature. And it's also really science at its naissance. We really don't know whether we can do it at scale. We don't know what the consequences are of perhaps chucking all these chemicals into the atmosphere to reflect the sunlight. And we don't know how long we'd have to do it for because...

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334.898 - 354.24 Mark Maslin

The problem with this technology is if you start doing it and you start dimming the sun, you have to keep doing it. And if you stop, that dimming goes away. It's like having a parasol up against the sun. If you close the parasol and you stop chucking chemicals into the atmosphere, the sun comes back and we get heating.

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354.22 - 375.045 Tom Whipple

OK, look, I sense a certain scepticism before you get to telling us why you think we shouldn't be doing this. It's a hot day. I'm putting on sunscreen and I'm using a parasol. I'm not claiming that that's some sort of global solution, but it's a sensible thing to do. So, you know, what are the sort of things we could do? You say it's unproven, but that's only in the sense humans haven't done it.

375.065 - 381.713 Tom Whipple

This is very proven from things like, you know, volcanic eruptions and stuff. We can actually do this, can't we?

381.693 - 402.553 Mark Maslin

So the key thing is that it's about geoengineering. And geoengineering covers this multitude of sins. And there are two things that I think are important. The first is that we can remove carbon dioxide. So we can either remove it from power plants, from coal manufacturing, from steel manufacturing, stopping it going into the atmosphere.

402.533 - 426.347 Mark Maslin

Or what is more likely and what we need to do in the future is suck CO2 out of the atmosphere and put it into deep geological reservoirs to trap it. And we're going to need to do that if we're going to try to keep the world to 1.5. We can also reforest vast areas of the world to suck CO2 out of the atmosphere. We can rewild.

426.327 - 454.719 Mark Maslin

And then, and you heard my skepticism, then there's the whole, perhaps we can do the sunshade approach. And yes, you're absolutely right. When incredibly large volcanoes go off, they do this and put huge amounts of sulfur dioxide and dust into the atmosphere that reflects the sunlight. But they have an effect of a year. So the huge volcanoes exploding has an effect for one year.

Chapter 3: What is the 'Salah effect' and how does it relate to tolerance?

551.215 - 558.225 Mark Maslin

And what are the ethical considerations? But of course, the underlying science has to be there so people can choose.

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558.205 - 567.056 Tom Whipple

You've made a really, really compelling case for reducing our CO2 emissions and controlling climate change, but we haven't done that.

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567.076 - 593.1 Mark Maslin

Oh, so Tom, I would slightly disagree because a couple of weeks ago, scientists retired the RCP 8.5. So 15 years ago, we had stories or scenarios about emissions into the future. One of them was, hey, we're going to do everything we can. We'll keep it to 1.5. Brilliant. And then there was one that said, look, China and India and other developing countries are using a lot of coal.

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593.541 - 619.385 Mark Maslin

This could double or triple into the future. We had that scenario, the RCP 8.5. What we did last year was have a workshop where everybody sat down from the experts around the world and went, do you know what? This is now so unlikely we can retire it. And that meant that the 4 to 6 degrees warming that I was talking about and you were talking about, say, 10 years ago, is off the cards.

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619.946 - 644.375 Mark Maslin

However, we're now still looking at 3 degrees warming, which is a lot hotter than we have today. But... The international negotiations, the global economy, the huge price drop in renewables is already having effect. The problem is, as you and I know, we need to do all of this faster, five times faster if we are going to have any hope of keeping to 1.5.

645.556 - 651.342 Tom Whipple

Well, look, thank you very much for ending with a little bit of hope there, Mark. And I hope you get some ice cream.

Chapter 4: How does exposure to celebrities influence societal attitudes?

651.44 - 661.231 Mark Maslin

oh, I'm going to go and stand by the air conditioning now because it is way too hot, Tom. Hey, but at least I can show that during London Climate Action Week, climate change is actually happening.

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661.491 - 678.19 Tom Whipple

Lizzie, look, Mark represents what I think a lot of scientists think about this, which is it's, this is extreme and quite mad. But the conversation about solar radiation management has changed. You know, the Royal Society has a report out on it. How has this changed in your career?

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678.423 - 695.475 Lizzie Gibney

It's become so much more mainstream. I remember maybe a decade ago, it was something quite risky for a researcher even to propose as a study to look at geoengineering because it was seen as just so radical. I mean, the side effects is just so hard to predict when you're literally altering the atmosphere. But I really think that's changed.

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695.515 - 714.161 Lizzie Gibney

We're now seeing all of these ideas being taken really seriously, which probably tells us something about the dire situation that... We are in. There was a survey done by a new scientist last year that found that two thirds of climate scientists thought humans would, by the end of the century, do some form of large scale geoengineering, even if they don't think it's a good idea.

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714.422 - 732.863 Tom Whipple

When you sort of look at cost estimates, it's tens of billions a year. It's a degree of cooling. But of course, the sort of all the moral hazards and the termination shock, if you stop this, suddenly you get a degree of warming. It's... it will remain quite contentious.

733.003 - 744.548 Lizzie Gibney

I think so. It's got to be the final nuclear option. There are many, many more levers that we have to pull, and I think it's just, as Mark said, it's quite disappointing that those aren't necessarily being pulled yet.

744.568 - 753.02 Tom Whipple

Thanks, Lizzie. And in case we need reminding about why this matters, over to Roland Pease, who has been investigating the effect of heat stress.

753.48 - 772.683 Roland Pease

Yes, a study from the European Centre for Medium Range Weather Forecasting says that across the world, an additional billion people are likely to experience extreme heat stress each year these days compared with the 1970s. And it's not just about population growth. The driving factor, as you'd expect, is global warming.

772.903 - 785.076 Roland Pease

And a study lead, Rebecca Emerton, explained to me this isn't about the temperatures as recorded on a thermometer, but as felt by a living person, calculated as the Universal Thermal Climate Index.

Chapter 5: What new insights does research provide about atomic nuclei?

874.696 - 896.569 Rebecca Emerton

Yes, exactly. So we know there's trends in heat waves across the globe becoming more frequent, more intense, lasting longer. And we really wanted to give this kind of global picture of how the heat stress in our climate has changed over recent decades. So we kind of compare the most recent 10 years of the data, so 2015 to 2024, with how things looked in the 1970s.

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896.77 - 898.392 Roland Pease

And the changes are notable?

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898.372 - 914.693 Rebecca Emerton

Yeah, so there's a few different factors that we look at. One is, for example, the maximum UTCI that you might experience on kind of the warmest days of the year. And this has increased across almost all regions of the globe with some of the strongest warming in Europe, Northern Africa, the Arabian Peninsula.

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914.673 - 940.765 Rebecca Emerton

some of those maximum utci values are reaching four or five degrees higher on the hottest days of the year than they did back in the 1970s we're also seeing more days per year with heat stress more of these so-called tropical nights where the temperature doesn't drop below 20 degrees c and we're also seeing that heat stress is becoming more widespread so it's not only affecting the areas that we might traditionally think of as being hot or experiencing heat waves

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940.745 - 945.054 Rebecca Emerton

but it's expanding out into areas that have been previously unaffected by heat stress.

945.355 - 962.508 Roland Pease

And that seems to me quite important because I guess there are parts of the world which are routinely much hotter than other parts. And so I guess the way this is affecting, let's say, people in tropical climates or... subtropical climates is going to be different from those in temperate climates and so on.

962.528 - 975.647 Rebecca Emerton

Yeah, that's exactly right. So we know that across a lot of the tropics, there are places that experience kind of chronic heat stress, some level of heat stress almost all year round. And we're seeing that in those places, that heat stress level is becoming more severe.

976.127 - 984.96 Rebecca Emerton

In a lot of places, there's an increasing duration more of the year that's being affected by heat stress, whereas in other places, it might be that the maximum feels like temperatures

984.94 - 1010.07 Rebecca Emerton

are increasing or they're starting to see levels of strong heat stress where they haven't experienced it before so it's quite relative kind of based on the baseline climate they started with in the 1970s but we're seeing similar trends in terms of more frequent and more severe feels like temperatures on every continent is the seasonality of it changing as well you know when the first heat wave sets in or when the last one sort of peters out at the end of the season

Chapter 6: How can atomic nuclei be used to improve timekeeping?

1102.536 - 1110.915 Tom Whipple

Tell us what science you think we should be investigating. Our email address is insidescience at bbc.co.uk.

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1118.751 - 1120.252

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1130.964 - 1135.128 Rick Edwards

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1135.148 - 1140.193 Max Crocombe

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1140.612 - 1164.645 Tom Whipple

Let's go on to something that's perhaps a bit cheerier, perhaps a bit less complicated and certainly involves some sounds of football commentary.

1169.283 - 1191.949

Well, he's in. It's been brilliant, Lee! It's been absolutely sensational in the second half. What an unbelievable moment. That's a shot in. Guess it's Hattrick. What a story. What a story. It's unbelievable! With practically the worst kick in the ball! Champions of the world's greatest game.

Chapter 7: What role does laughter play in the evolution of language?

1261.512 - 1270.382 Lizzie Gibney

So what happened after that? He's Muslim. He's very upfront about his religion. His religion was really a part even of the chants that the supporters would sing.

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1271.103 - 1274.046 Tom Whipple

Lizzie, do you have any examples of that?

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1274.515 - 1297.9 Lizzie Gibney

So there actually are some examples in the paper. I'm having to infer what the tune is from the words. But for instance, if he's good enough for you, he's good enough for me. Sitting in a mosque, that's where I want to be. So... All about Mo Salah. So they really took him to heart and embraced his religion as well. And so the researchers wanted to see what the effect of this was.

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1298.02 - 1318.931 Lizzie Gibney

They collected data on hate crimes, on tweets, and then surveyed a bunch of Liverpool fans as well. And they felt that the effect was pretty big. So after Salah joined Liverpool, hate crimes there dropped by 16% compared to what you'd expect. And fans of Liverpool posted about half as many anti-Muslim tweets as other fans.

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1319.291 - 1320.934 Tom Whipple

That's a huge effect.

1321.214 - 1342.851 Lizzie Gibney

It's pretty big, isn't it? And then there was a subtle but significant effect from the surveys as well. When the fans were asked to think about Mo Salah, the fact that he's Muslim, that made them more likely to say that they saw Islam as compatible with British values. I mean, there are limitations to this. It's very hard to say how much of this effect was Mo Salah.

1343.593 - 1355.757 Lizzie Gibney

And also hate crimes are by far not the only way in which racism manifests. So there are limitations to this. But the takeaway, which I think is quite interesting, is that having these role models can have an impact.

1355.817 - 1374.993 Lizzie Gibney

And you might have seen previous studies where they found that when people actually know someone who's from a minority religion, a trans person, any kind of minority that can face prejudice, they're much more likely to have positive views towards them just if they know them, if they have people in their lives from those groups. And this shows that that can happen with a celebrity.

1375.073 - 1387.406 Lizzie Gibney

It can be a parasocial, one-sided effect. You don't actually have to personally know them. They just have to be this kind of positive role model. So Yeah, maybe it's something we can bear in mind when trying to foster more tolerance in society.

Chapter 8: What are the broader implications of the discussed scientific findings?

1436.29 - 1451.831 Lizzie Gibney

It comes from the oscillations of the light wave that would bump an electron up in energy level around an atom. So electrons live in these orbits at different energy levels. You've got to tune a laser to be at exactly the right energy to trigger this jump between those levels.

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1452.132 - 1460.886 Lizzie Gibney

And you lock your laser to this natural timekeeper and then use that laser's frequency, its oscillations, in order to keep time, just like a pendulum.

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1460.866 - 1474.555 Tom Whipple

So you know that if the laser is bouncing up this thing, you've got exactly the right amount of energy. And then you know that it must have a very precise frequency. So you define time according to the frequency of light in the laser.

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1474.94 - 1497.024 Lizzie Gibney

Exactly. And we use this really precise time for all kinds of things, for GPS to work, to synchronise mobile phone networks, computing systems. It's really, really important, even if we don't always notice it across society. So at the moment, we have these optical atomic clocks. But now what we have, which was new earlier this month, is a completely different way of doing this.

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1497.064 - 1506.634 Lizzie Gibney

So rather than getting your tick from the energy levels of electrons, this plot gets them from the energy levels of nuclei. So the nucleus of thorium-229.

1507.375 - 1510.458 Tom Whipple

So it might surprise... I didn't even know they had energy levels.

1510.478 - 1527.523 Lizzie Gibney

Exactly. So nuclei have energy levels, and that comes from the different configurations that you can have of their protons and neutrons. And thorium is very unusual in it that it has these two energy levels that are very close together. So with a laser, you can actually nudge that in the lab. And two teams have now done that.

1527.543 - 1536.233 Tom Whipple

So why do we need even more? Presumably we're losing a second in the lifetime of the universe or less. Why do we need clocks this accurate?

1536.567 - 1555.774 Lizzie Gibney

So for scientific reasons is a big one. So what's quite exciting about this particular clock is that the way that it's made, the fact that you're using these nuclear energy levels, lots of different kinds of dark matter predicted that they would mess with the forces that bind the nucleus.

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