The Infinite Monkey Cage - Head in the Clouds - Owain Wyn Evans, Gavin Pretor-Pinney, Amanda Maycock

Episode Date: December 10, 2025

Robin Ince and Brian Cox look up to the heavens as they try to ‘de-mistify’ the foggy science of clouds. They’re joined by Cloud Appreciation Society founder Gavin Pretor-Pinney, climate scientist Amanda Maycock, and former weather presenter and drummer Owain Wyn Evans, for a whirlwind tour of our too often-overlooked aerial realm.The panel explores how clouds form, why they take such extraordinary shapes, and how satellites and weather balloons help us keep track of them. They discover why low clouds cool the planet but high clouds warm it and why a cloud that weighs as much as a jumbo jet manages to stay up in the sky. From the physics of a crisp packet balancing on a cumulonimbus to the shimmering beauty of noctilucent clouds, tune in for this cirrus-ly fascinating episode.Series Producer: Mel Brown Researcher: Alex Rodway Executive Producer: Alexandra Feachem A BBC Studios Production

This BBC podcast is supported by ads outside the UK. Hello, I'm Brian Cox. I'm Robert Inns, and this is the Infinite Monkey Cage. Now, all of you, and I imagine there's been a few daydreamers here, when you stare out of the window at school, that's what they say, concentrate, what are you doing, staring out of the window? Well, for some people, it wasn't just daydreaming. It was practicing to become a meteorologist or a cloud expert.

Or an astronomer, I suppose. Or an astronomer. What time did you go to school? I'm from Oldham. It was only dark 24 hours a day. I remember the sky was always dark, dark with industrial plumes. You've not bought your clogs again, have you? Because they made a right racket last time.

I couldn't wear him standing on those volcanoes looking enigmatic, could I? Because the clicking would spoil the atmosphere. Oh, they're not made for going over cooled lava, are they? No. They made it wood. It's the worst possible thing to wear, to be honest, walking through lava, isn't it? Isn't it? There must be something, well, paper, I suppose.

Oh, no, because we only had paper shoes in Oldham. Yeah, whatever. Anyway, today we're looking to the sky, but not as far as Brian likes to look. It's kind of parochial level of looking to the sky. We're going to go, well, really the level of clouds, the clouds that, of course, so often hindered your series stargazing. Why were there always clouds there?

Was it Dar O'Brien's head? Because I think because of the roundness of the head, they might have attracted clouds closer. Today we're asking How do clouds help in maintaining I can't say maintaining I'll do it if you want You do it

You do it Today we're asking How do clouds help in maintaining a healthy atmosphere What can clouds Which is so beautiful And so wonderful And sometimes they shine with ice crystals What can they teach us about the climate

Now you've got to do my line doing me To guide us through That's perfect To guide you're joined by a climate scientist. Don't worry, it's all right. The show's going to be okay. To guide us three, we're joined by a climate scientist, a cloud appreciator, and a drummer. Oh, but so much more than a drummer.

And they are. My name's Gavin Preetipini. I'm member number one, and the founder of the Cloud Appreciation Society, which I started 20 years ago, and it brings people together from all around the world, to any countries we've got members in, all united in the belief that, well, clouds aren't something to complain about. They're actually one of the most evocative and dynamic and maybe you can say poetic aspects of nature. And the most wonderful thing I've seen in a morning sky is a morning glory, which you'll be relieved. No. It is a cloud formation that forms in

a remote part of northern Queensland, Australia. It's a cloud that glider pilots surf, just like surfers on an ocean wave. It travels across the Gulf of Carpenteria through the night, and it arrives first thing in the morning on the Queensland coast. And I went there, and I watched this cloud arrive, I rushed up into a plane with all the other gliders and watched them as they surfed up and down this cloud

as the sunrise was breaking over the top of it. It was an absolute glorious and beautiful sight. Hello, I'm Amanda Maycock. I'm an atmospheric scientist and a professor from the University of Leeds. I use computer models to simulate the movement of the air within the Earth's atmosphere, including clouds and how it affects the Earth's climate. The most wonderful thing I saw in this morning's sky, there weren't many clouds around up in Leeds today, was actually Venus, which is visible at the moment. and Venus is another beautiful, cloudy planet but a bit less hospitable than Earth

because the clouds are made of sulfuric acid and they've contributed to a runaway greenhouse effect that means the surface temperature is more than 450 degrees Celsius so that was the beautiful thing I saw this morning. Don't worry, you'll have those sulfuric acids before you know it. They're working really hard in the US and also... I'm Owenwyn Evans.

Used to be weather presenter. No, I am a TV and radio presenter. and I'm also a drummer. I got the name the drumming weatherman when I played the drums to the BBC news music in lockdown and it went viral and then I went on to play the drums for 24 hours for a children in need drumathon

whilst every so often also doing the weather. And my husband was thrilled to have the drum kit out of the house for 24 hours and I was thrilled to throw the drum kit into a skip after the drumathon. And the most wonderful thing that I've seen in a morning sky is a gigantic pepper pig balloon

stay with me on this one I live in Penarth which is near the water in South Wales and me and Aaron were going for a walk one morning and saw this kind of orb over the water that Aaron what's that Aaron that looks like pepper pig oh is it daddy pig

actually as the balloon approached it was indeed pepper pig And it was drifting up the coast towards Swansea. Stranger things have drifted up the coast towards Swansea. And it turned out to be a child's balloon, which was somehow kind of amplified and expanded by the view across the sea. And Pepper Pig drifted towards us. And off she went.

Last scene off the coast of Barry. As I think a lot of hopes and dreams have. So there we go. And this is our panel. Gavin, we should start with you. Why did you feel a cloud appreciation society was so important? It's because people do like to complain about them a bit. You don't need like a sort of kitten appreciation society

because everyone loves them. You need something that's a society that has a kind of mission to shift people's perspective about the sky. At least that's what I felt. So it's really I just felt someone needed to stand up for clouds. basically. Let's get this out of the way. What's your favourite formation? It's got to be a Pilius. Fair enough. That's a very strong answer.

Amanda, to move back to the science. That's not science. Move back to the science. We had a man talking about a pebber pig balloon at a moment. You've got to bring them gently back to the science. I'm saying, what's your favourite cloud? I said favourite cloud. I said favourite formation, Brian.

technical difference between the have I made a terrible mistake? A formation is just a general term because I mean basically they're all clouds of these random appearances in the sky but humans are amazing at spotting patterns and so when we started to classify

clouds in a scientific way 1802 around then and it was actually a Englishman called Luke Howard Quaker from Tottenham he was spotting patterns and he started to give them Latin names. So he came up with the cumulus and cirrus and stratus. And these names just basically

say what the clouds look like. And you say it in Latin sounds fancy, makes it sound scientific. See, Brian, you've put too much effort in learning physics. Amanda, how do clouds, at the most basic level, how do clouds form? So a cloud forms when a parcel of air become saturated and some of the moisture that it contains condenses. So where does that come from? The moisture in the air? Well, if you imagine standing and drawing a sort of square around your feet that was sort of one metre squared and you weighed all of the water above your head, there's on average about 25 kilograms of water all the way up to the top of the atmosphere, which doesn't sound like a lot, certainly a lot less than the rest of the mass of the air, but it is enough to form these clouds.

So basically the evaporation mainly comes from over the oceans. We've got the vast oceans that provide that source. And the sun heats the surface of the earth. The air warms up, warm air rises, it moves up through the atmosphere, and as it does so, it cools and it expands. And it's that expansion and cooling that can cause the air to become saturated, and that's the point at which the cloud droplets can begin to form. But they don't just form by themselves. They need something to cling onto, as it were, and they tend to form around little things we can't see, specks in the air, there might be bits of dust, bits of pollen, fungal spores from trees, and the water molecules condense around those little particles

and start to grow a droplet. And then where does the structure come from? Because we've heard that there are... Is there a number for how many different types of classified cloud formations? Yeah, well there are 10 basic type, the genera, the main types. And those are the ones you've heard of at school. Cumulus, Ciristratus, cumulonimbus, the superstar,

you know, the storm class. It produces thunder and lightning and hail. But then there are lots of these additional ones, which are sometimes just a feature that looks just like a curl, like a tiny breaking wave, which would be called a Flutus cloud feature. There's a whole bunch of them. I think there's about, when you combine them all, it's probably about 80, something like that. And one of them actually came from the Cloud Appreciation Society.

Yeah, one of the official types. So what is giving the clouds these different characteristics? broadly speaking? So there's two main sort of types of particle that we can find within clouds as liquid water droplets and then there are ice crystals. And so a lot of the appearance and the differences in appearance come from how much liquid water they contain or how much ice crystals they contain. So the high altitude ice clouds where it's very cold,

they have this kind of wispy appearance. They get sort of stretched out by the winds. So the winds are obviously blowing the clouds around. You can often see that on a windy day. You'll see them being blown along. the lower altitude clouds, which are made from liquid water, the sort of fluffy cumulus type clouds, they're sort of formed because of the liquid water within them.

So, Owen, what about for you? I know technically you'd be called a weather forecaster, but you weren't actually forecasting the weather as you. Yeah, that's right. Yeah. I came from a background of journalism. When I joined BBC Weather, the Met Office were providing the sort of data, if you like.

So I was trained up by them. and then later studied through the Open University, meteorology, through a couple of modules, just because I think we love the weather here in the UK. It's the first point of kind of conversation for a lot of people. You know, if you don't know what to say, it was lovely outside. Oh, it's terrible, isn't it?

Not always that camp, by the way. Terrible weather. But I think that for me, the clouds are the things that a lot of people, you know, it's that thing that you can see and I remember when I was doing the weather in lockdown there was nothing to talk about because people weren't really going out so the producers would give me three minutes

to fill on the weather. I'm like, Hans, like everyone's inside but people would then start to see like you were saying earlier Gavin about the clouds you start to see shapes or faces and I think that's what's amazing about clouds. It almost gives people

a little bit of creativity especially cumulus clouds, the fluffy cotton wool ones. What about Gavin saying about that there's a negative attitude towards clouds? I imagine when you were mainly doing the kind of the presenting the weather, you would get letters of complaint as if you yourself

had created the weather. I mean, did you get that? I still do. I haven't done the weather for three years and people say, oh, didn't forecast this, did you? So if I forecast this three years ago, I'd be monetising this skill somehow. It would happen a lot when we get

we would get bad weather as well if there were really bad storms and we'd get weather warnings the yellow warning is the lowest then it goes up to amber warning which is my drag name as well I do think where the presenters are a bit too apologetic

they sort of seem to feel that and they feel a bit guilty when they say you know there's going to be a lot of cloud around in an apologetic tone I would like to hear a bit more detail about what cloud is going to be a way.

I'd like to know how the formations are going to be changing through the afternoon, what sort of shapes we're going to be seeing. I would like some more detail and a bit more positivity. I'd love that. I'd love that. We could do like a kind of what shapes will we see today in the clouds, like a little bet maybe. Did you used to send to the, because they only used to have one shape of magnet for the cloud, didn't they?

Whatever, whether it was a stormy cloud, whatever. It was a bit of a sad day when they stopped you. using those magnets. But I mean, that is the cumulus cloud, the one that's in the cartoon. And it's like the sort of generic cloud, the cumulus. If you close your eyes and think of a cloud, it's one of these puffy white cumuluses that form on a sunny day. They feel the most solid. The word cloud comes from the old English word clude, which means a rock or a boulder, where we get the clod of earth, that term, from. These feel like solid things, cumulus clouds. Do what I mean? And that's why I think they're kind of iconic for us.

They have very, very distinctive shapes, and the edge of them is very well defined, which seems counterintuitive. It's just this phenomena where water is condensing. So why do they have such a well-defined shape? So it's often because there's a sort of barrier of the air to be mixed from within the cloud to the surrounding clouds. So there's differences in temperature, differences in density between different air masses that are nearby each other. So that's what provides this kind of rather crisp looking shape often. The base of the cloud will be where the kind of layer of the atmosphere starts to

become saturated. I mentioned before the saturation is a sort of necessary condition. So again, that's something that will have a sort of well-defined base to it. And then at the top of the cloud, you'll move into drier air, warmer air above. But they're not sort of stationary things. What's actually happening in reality is that there's constant evaporation and condensation occurring at the base of the cloud. So the base of the cloud, the little drop.

will be continuously evaporating, and then at the top of the cloud, they'll be condensing and reforming. So they're very sort of dynamic structures. So is that, because I sometimes, I do find it fascinating, when you're looking on a day where the wind is moving a cloud, and you look at that cloud, and you think it has remained in that shape, and yet, so actually within what appears to be that kind of, you know, the stationary nature of the shape itself, there is still all manner of movement going on there? Yeah, absolutely. There's a lot of motion that's happening within the clouds. In fact, that's one of the reasons why a cloud doesn't just fall out of the sky. So a typical cumulus cloud, the ones we're talking about, might weigh somewhere between

about 250 or 400 tonnes, something like a sort of typical 747 aircraft, something like that. There's a lovely gasp over there. People have got slightly more scared of clouds than they used to. What if they fall? What if they fall? Chicken licking. How big would that be? So a 400-ton cumulus cloud? Yeah. So that would be of the order of a sort of cubic kilometre or something like that, one and a half kilometres cubic. That's a sort of typical size of a cumulus cloud. But, you know, of course, the gravity isn't acting on the cloud as a whole. It's acting on the individual tiny little droplets, which are of the order of a few thousandth of a millimeter across within the cloud. And so actually they only fall very, very slowly, perhaps, you know, a centimetre per second or something like that.

And you actually have motion within the cloud, upward motion, which sort of basically sustains the altitude of those droplets. So they don't just drop out and fall down. They collide and coalesce with each other they join up and become bigger droplets and eventually once they're heavy enough they can actually fall out and and become precipitation this is the the magic of clouds comes from the special nature of water that's naturally found in the three states of solid liquid and gas and that is really the secret of this kind of poetic and beautiful quality of clouds because they can appear and disappear at will because one of those states, the gas one, is invisible.

And so we're at the triple point of these three states on Earth in the atmosphere of Earth. And so the clouds are revealing the changes, revealing the invisible movements of the air. These movements of the winds are happening the whole time. We only see them when they just nudge that water to shift state from the gas. form we can't see to the liquid or the solid.

That's a very beautiful thought, actually, is that they make the atmosphere visible. They're the face of the atmosphere. They're expressions on the face of the atmosphere. And so they can reveal the moods, the shifting, ever-shifting moods of the atmosphere. And we just intrinsically know how to read those moods. Ask a child when they see a cloud that is dark with a base that's low. And they know what's going to happen. They know that that's very likely to produce rain.

You know, we've always known that. Right back to, I imagine, you know, when we were living in caves. Now we know the science of it. We know why. But they've always been this shifting expression on the atmosphere that, you know, I think we need to be more in tune with. I think it is good for the mental health and your well-being to be engaged with the sky personally. What's the physics of that?

So why are rain clouds dark? First of all, I mean, clouds look white, most of them. liquid clouds look white because they're scattering the incoming radiation that's coming from the sun and they scatter that radiation quite equally across different wavelengths of light and that's why they look they look white often if you see a kind of grey cloud it's sometimes a shadowing effect so it's kind of the cloud's own shadow so if it's a very large kind of low cloud as you said it's it's basically kind of shadowing and you can't see that scattering effect as as well how bright they look is sort of dependent on how they're made so if you have lots of small

little droplets within the cloud, then it is very good at scattering that light. It'll look very bright and very white. As the droplets grow and become larger, then it sort of becomes less effective at the scattering. And it's the tallness of the cloud that's super important when it comes to a dark base because a cloud that's tall has a dark base because it just, the light doesn't really get through. And a cloud that's tall is much more likely to produce precipitation. because it often starts with the droplets starting to freeze at the top. It starts as snow, melts on the way down, maybe lands as rain. But that tallness is crucial to a lot of precipitation.

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because the sky isn't physically blue because at night time you can see through it up to the stars right and then in the morning when the sun is lower in the sky and the light is sort of grazing the atmosphere of the earth those wavelengths are scattered again and you get more of the reds coming through

because the red wavelength is kind of could we describe it a bit like a wibbly wobbly wave Is that right? Has that ever been said before? Just a wave, Brian, yeah. I didn't need to unnecessarily I'd wibbly wobbly wobbly then. There's no un-wibbly wobbly wobbly wave.

To be fair, I think O'Wine was saying that this one was wiblier and wobblier, and I think the wibblier wabbliness of this. Does he mean the amplitude or the frequency? No, I mean the wibbley wobbliness. I think it's a longer wave, yeah. It's a longer wave, there we go. So it is more.

Wibbley and less wobbly? Well, yes. No, was it more wobbly? Oh, I can't remember. Brian, I know you've got a question for O'1 because, as usual, last Tuesday, you were with Gloria Estefan and the Miami sound machine. And so...

I was on the radio with... And it was Gloria Estefan and Bob Mortimer. Just duetting as usual. Yeah, and Bob Mortimer said, I have a question, a question. I said, what is it? And he said, you know if you get a crisp packet and you open it and you eat all the crisps on an aeroplane,

and then open the aeroplane window and drop the crisp packet and it falls onto a cloud. Will it sit there on the top of the cloud? What is this for six questions? Can I just though mention, by the way, if you are an aeroplane, please don't open the window. No, no.

It's just because we're in a session, you'll be alright. But I had to think for a moment. I thought that's quite a nice question. So what was your answer then? Let's find out if Brian's answer is right, and then I'll cut out you are one. Okay.

So, I mean, they look so crisp, especially when you're in a plane and when the cumulus clouds are below you but like you have that kind of boundary in between what cloud is not yeah it looks solid but then when you fly through those you see it's just like you know flying through a cloud of smoke

or like you know Friday night in my house when I've got the dry ice on so I think the which the cat despises the dry eyes is that what it is like put the dry ice on I think it would it would fall through it

Yeah, I came to the conclusion that it would fall through. But it's a good physics question. Yeah. Yeah, the layer right at the top of the cloud is often quite turbulent because the clouds emit radiation. And so that can actually drive motions along the tops of the clouds. So I actually think it would probably get transported around by the air currents rather than being held up by the water droplets of the cloud.

I think the actual turbulent motion, this sort of mixing effect at the top of the clouds, because the clouds are emitting radiation out towards space would probably hold it up. Are you saying it would move in a wibbly wobbly fashion? A wibbley wobbly. He thought he was being... I think he just thought he was being Bob Morton.

But it's actually a really good physics question, isn't it? Because as you said... I didn't think of that, actually, the radiation back out again. Yeah. Is that one of the reasons you feel turbulence when you enter clouds in an aircraft? Yeah, well, that's exactly what you're experiencing. All of those upward motions I described before

that are happening, all of the local currents that are happening within the cloud is basically what causes that turbulence for the aircraft. The top of the cloud in particular, because you've basically got a body which is emitting radiation, emitting thermal radiation, and that's dependent on the temperature at the top of the cloud, basically. So how cold the top of the cloud is, determines how much energy it's going to emit out. Is it always hotter at a higher temperature than the air, the clear air above it? Depends if it's an unstable atmosphere. Because in a stable atmosphere, a thermal might rise from the ground and come back down because it's not warmer than the surrounding atmosphere. And you don't have clouds forming or storms

developing. But in an unstable atmosphere, as we describe it, the air gets more rapidly cold as you go up. And therefore, if you lift some air from near the ground where it's warm, it comes up, some droplets begin to form as it cools. And remember, every time a tiny droplet forms, a little bit of heat is released, the latent heat as it changes state. And those all add up, even though it's a tiny amount from each tiny droplet. And this is like fuel to keep the buoyancy in an unstable atmosphere. So the droplets form, it gets more buoyant. More droplets form, it gets more buoyant.

And you get building, building, building to this enormous cathedral of clouds. That is the cumulonimbus storm cloud. And within that, these currents, vertical clouds. currents arising rapidly in some areas, precipitation's falling, fast in other areas, and sometimes hailstones develop because these particles are going round and round and building up in layers of ice.

So Bob Mortimer's Chris Packett could have ended up in the middle of a hailstone. It couldn't be one of those very famous physics examples that all undergraduates learn in atmospheric physics, isn't it? Mortimer's Chris Packet. That was... But just to pick up on that point, because it's an interesting bit of physics, the fact that water droplets forming release energy. Could you just, maybe Amanda, just speak about that?

Yeah, so going back to Gavin's triple point for water, so any time that water changes phase, so whether it goes from a gas to a liquid or from a liquid to a solid, in that direction, it's, yeah, basically releasing a little bit of energy, which is to do with the organisation of the water molecules, basically, within the structure. So once it condenses and it turns to a liquid, that little bit of energy gets released. And as Gavin said, that contributes to a heating in the atmosphere. It's basically this latent heating effect of the clouds as they're forming. And you get the opposite as well. So you could have ice crystals up at the top of one of these cumulonimbus clouds. They spread out in an anvil, this enormous plume of ice crystals. It spreads out

hundreds and hundreds of miles. And in one area, those ice crystals can melt. and therefore change state in the other way. That makes the air cool a bit. And you can get these sinking pockets that appear as mama clouds on the underside, these pouches of cloud on the underside of one of these cumulonimbus anvil plumes. And they look really distinctive, these pouches of clouds. And they're the result of the cooling, most likely,

it's not totally understand, most likely the result of the cooling that happens with the shift in state the other way. We've all seen those, haven't we, those anvil clouds? Why are they so flat at the top of the cloud? So going back to what Gavin talked about with the stability of the atmosphere. So particularly in the tropics,

we find a lot of these deep cumulonimbus clouds over the warm tropical oceans. There's a huge amount of fuel and moisture which allows these clouds to get up to altitudes of 18 or 19 kilometers. You know, this is sort of almost twice the height of cruise altitudes of typical aircraft. So these are really tall clouds. And what happens is you hit a sort of boundary.

We call it the chopper pores. It's basically the transition between the lower part of the atmosphere where all of our weather happens and the clouds form and the layer above it, which is called the stratosphere. And it's called stratosphere because it's stratified layer. It's a stable layer. And so the clouds basically get up to this. It's almost like a lid.

They can't move above that because the air above is stable and so they can only spread out. And that's why you get these anvil clouds because they then just spread sideways because they can't travel further upwards anymore. And if you see the photographs from the Space Station where one of the astronauts takes a photo down onto cumulonimbus clouds. It's like they're formed underneath a piece of glass.

It's this temperature profile, this temperature inversion, we call it, because it's the opposite of the normal getting colder as you go up. It starts to get warmer at the top of the troposphere, and that's this invisible lid. And the cloud you can just see spread out, and it just can't go up. It wants to go up higher, but it can't go up any higher because it suddenly gets stable there.

This is another incredible thing about clouds, is how you get so many different kind of shapes and reasons as why things look a certain way or are a certain way, and they've intrigued people forever. And I suppose it's only fairly recently that we, as people, have kind of fully been able to understand what these things are and why they're doing those things. I was going to ask that question, actually, in terms of the physics of the atmosphere, What's the history of the scientific understanding of the physics of the atmosphere? How recently did we begin to get a good picture of what's happening? In terms of the modern understanding of the atmosphere? So in the sort of 17-1800s when people were getting into sort of ballooning in a big way and starting to try and leave the surface of the earth

and with them were taking some instruments to sort of measure temperature and pressure and trying to really understand what the vertical structure of the atmosphere is, That was really the first time that we started to get some of this basic information about temperature decreasing with height as you go through the troposphere, pressure decreasing with height. So that was a sort of, you know, those were really key foundations. I think in the more modern era, you know, the advances in technologies we've had, the ability to measure through things like radars, Lidars, through satellite measurements with radiometers, that's really given us a much more global view. Aircraft measurements, you know, flying through clouds and actually measuring, you know, these droplets. How big are they? How many of them are there? What's sitting in the nucleus of those little droplets and things?

All of those technologies in the last sort of 50 or 60 years probably has really revolutionised our understanding. Oh, and I just wanted to go back to, when you're mentioning ice crystals, I remember the first time of looking up in the sky and seeing the kind of the... I don't know what the... It's like a cloud bow, is it called?

I'm not sure what it's called. Oh, yeah, yes. Kind of the iridescent clouds or the... When you see those gorgeous colours in a cloud, and they are incredible to see because it's like a rainbow but it's more kind of localised I suppose

in the same way as you get sun dogs which is like a kind of a halo which can appear around the sun or a moon or the moon rather it's the sort of prism effect of I think I'm right in saying this of the ice crystals or the water droplets rather which scatters the spectrum

and then you get these amazing patches of colour in the sky and that's one thing that people love taking photos of as well because it just looks that kind of iridescence you know that you see we don't see that every day when we look up at the sky

so whenever you see something like that you want to go wow I want to take a photo of that and if your phones anything like mine the photo will look absolutely rubbish then and you'll just delete it yeah the only one that it works better like if you try and do a rainbow or anything like that it's never as good

but Aurora Borealis you just look at a black sky but you stick it through a camera go it looks like I saw something amazing didn't it the sky's a cheat isn't it Brian but we'll deal with that another day on the subject of sort of beautiful optical effects there's we're talking mainly about clouds forming within this

troposphere the lowest layer of the atmosphere but actually you can get clouds even higher than that so there are types of clouds called noctilucent clouds that form very high up about 80 kilometres above the surface it's very very dry up in the mesosphere but it's very very cold it's about a minus 120 degrees Celsius there so even though it's very dry it gets cold enough that you can still form these very, very thin ice clouds. And you can see those sometimes, if you're lucky,

particularly at sort of dusk or in the morning when you get that, as Owen was described, you get this sort of horizontal path of the light through the atmosphere, which gives you that more sort of reddy colours. You can sort of see them very like ghost-like clouds almost. Similarly in the stratosphere, we have these mother-of-pearl clouds, they're often called, the necruous clouds, which again form over the polar regions where it's very, very cold. And again, you can get these beautiful effects, light effects, if you're looking at. enough to see those. Gavin, I wondered about, you know, having done, having, you know, CloudSpotter's guides and things like, which is when Amanda was talking earlier on about the importance of, you know,

what we might call imperfections or grey, whatever, if you had written that book and put that together in 1950, for instance, what were the different formations we might have seen? Thinking of the nature of injury, thinking of the nature of the smog in London, all of those things. Well, we wouldn't have seen so many condensation trails that formed behind aircraft. I mean, I guess there were there weren't just weren't so many of those and those are human-made clouds that result from the water vapor in the exhaust of the aircraft cooling as it rapidly expands in the high atmosphere and forming this crisp line of cloud so long as that part of the atmosphere that the plane's flying through has enough moisture in it anyway otherwise it doesn't form it's a bit like when

you start your car on a cold day you can see kind of the plumes of moisture that are in amongst all the other exhaust fumes of your car, but you don't see them on a dry, warm day. But yeah, we would have had far more particulates from all the cold smoke and pollution that was in particulate form, and those have an effect on the fog. You get lots and lots of tiny droplets if you've got lots and lots of these little aerosols for the droplets to get started on. And that's a thick, dense, nasty fog.

The P-Super that London was known for, which is especially nasty because it has pollution at its centre. So clouds would have been different in some ways, but the main formations, I think, have been the same forever. We've talked about weather. Can we now talk about climate? What role do the clouds play in climate modelling? So the clouds have a really important effect.

on the balance of energy of our planet. So they do two main things. We talked earlier on about the scattering by clouds of the incoming radiation from the sun. So that has the effect of cooling the planet, so less of that solar radiation reaches the surface of the earth and causes heating. So that's a cooling effect.

But they also can contribute to warming, particularly the higher altitude clouds, which are colder. We talked about the clouds themselves emitting their own radiation, their own thermal energy. And they therefore have a sort of trapping effect and can contribute to heating of the planet. So the overall effect that they have on the climate is the balance between two opposing effects, this cooling effect and the warming effect.

Now, in the current day, the net of those two things is that the clouds contribute to a cooling of the climate. So if we did a sort of thought experiment and got rid of all the clouds on the planet and thought about what that would mean for our climate, roughly we'd expect the temperature to be about 10 degrees warmer at the surface than without the clouds. So it's quite a significant effect. So the average global temperature? The average temperature, yes, would be a significant.

significantly warmer if we didn't have that cooling effect. So they're absolutely critical for the climate. A really important question is, of course, what's happening to clouds now that the planet is warming and the atmosphere is becoming warmer. And so the big question is, you know, which of those two competing effects will win out in terms of whether the cloud changes might amplify the warming of the planet that's occurring due to greenhouse gas increases or whether they might offset it. So at the moment, basically the science evidence as it is, we think that the clouds will contribute to further warming. So they'll basically amplify the global warming that's coming from the greenhouse gas increases in the atmosphere. And it's a sort of positive feedback effect

in that way. Clouds drive climate scientists crazy, don't they? Because they mess up their computer models. They're so dynamic and the system is so complex that you only need a slight change in the clouds and then fast forward your model 50 years and it's entirely different from the clouds did something else so you've got this really complex role that the clouds play in temperatures down the ground high ones have a warming effect low ones have a cooling effect and then this change in clouds that seems to be emerging you know we've had studies look at how clouds have changed over 24 years of consistent satellite data and you start to see fewer of those low cooling clouds in the cloudier regions

of our planet. And these are sort of worrying signs that, you know, the clouds may be shifting and that shift may have a feedback loop. Of the uncertainties, the major uncertainties in climate models, our understanding of cloud, is that one of the bigger problems that we have in the models? It's the biggest source of uncertainty that we have as climate scientists in being able to kind of quantify how much warmer the planet might be in sort of 50 years from now, for example. So we're very, very confident that as greenhouse gases increase in the atmosphere, the planet will warm, but exactly by how much is more difficult because of these feedback loops that start to kick in as the atmosphere is warming. And clouds are really tricky. As Gavin said, we need to use computer models to make projections and predictions into the future. And so we're solving lots of complicated equations on big supercomputers.

But the scales of the clouds, as we've been discussing, are absolutely microscopic. You're talking about droplets, you know, of the size of a few thousandths of a millimeter, you know, and you need to then represent that at a global scale. So it's a real challenge. And what we need to do in our models is kind of use physics to enable us to represent those small-scale processes across a larger area. We're in a really exciting time now, I think, where we're able to have enough computer power where we can actually start to resolve finer and finer spatial scales

and we can actually run computer models, you know, with scales of the orders of tens of meters rather than, you know, hundreds of kilometres. And at those scales, you're really then explicitly representing all of that physics in the model. The microphysics and the interactions of the droplets with the little particles and so on is all being simulated by the model. And you start to see really interesting things happening then, like convective organisation, for example, where clouds, little pockets of cloud actually through their own circulations will draw together and become a larger cloud system and turn into a mesoscale convective system, for example, one of these biggest storm clouds by themselves.

We've only got time for one more question. And your favourite question this week, Brian, which we've not got to, but you were very excited by this is balloons. How do they work? Now, this is true, by the way, I'm not making this up. It wasn't my favourite. It was the crisp one, but that's only because it's connected to your celebrity. I read it in the scripts and said that is an absolutely ridiculous question.

Why would that be there? No, you didn't, you went. It's true. How do they work? Have you segwayed from a discussion about the detail of the climate? I'll tell you why, because we've only got a minute left. So we could keep in everything. Or we could just go.

So, O'Ine, I know that balloons have played a major part in your fascination with... Absolutely. I mean, there's the Papa Pig balloon, aforementioned. But also, when I was about four, a weather balloon crashed into our garden in Ammonford which is in South West Wales

where I grew up and I remember this thing my father going out and sort of saying to my older brother oh this thing's in the garden and I was tiny but I can remember this

weather balloon in the garden it looked like a big polystyrene box with some sort of material attached to it and apparently I went up to it and I gave it a good kick and that was my introduction to weather forecasting

I think and that all these years later who'd have thought that I would still be interested at what weather balloons and what weather forecasting systems do after that first kick. Just think, if you'd really had been a little bit smarter,

you could have turned that into the Roswell of South Wales. Oh my gosh. You could have turned that into... Well, you know what? You walk around some parts of that town and it feels like we're in Roswell, 1947. We asked the audience a question.

We always have fabulous minds here. So the question we asked the audience was what's the strangest thing a cloud has reminded you of? This is a good one. It reminded me that I'd forgotten the tent. Oh, one, what have you got? This is from Daniel. I love this one.

The strangest thing a cloud has reminded you of, it's probably time to open my parachute. I think so, Daniel. A heavy dora storm cloud reminded me of John McEnroe because I knew it could not be Cirrus. I'm just like, it's very, I don't know if I can read that. I think it says, but I can't say this, can it? What's the strangest thing, a cloud is reminding you of?

A tiny, fluffy fruit bat growing on a digestive. I think that's what it says. No, it doesn't it? Noring. Noying on a, oh, now it makes sense. This is lovely, this is from Neve. My granddad, not because he was strange, but, because he would get a spoon out on cloudy days to eat them. I believed him.

That's like Cosmicomacus. I love that one. Oh, that's brilliant. Well, thank you very much. Thank you to our panel, who were Professor Amanda Maycock, Gavin Preeto Pini, and O'Wine Wynne Evans. Thank you. Next week, the Infinite Monkey Cage finally goes deep into the darkest recesses of the Monkey Cage, because we are considering the sex life of monkeys. And if you've ever seen monkeys, you don't have to go into the darkest recesses. They do it everywhere.

Thank you very much, everyone. We see again. Bye-bye. Hi. Hi, I'm Phil Wang, and this is a podcast-to-podcast trailer. for a different podcast than this podcast that you've listened to or are going to listen to. But nonetheless, I'm talking about another podcast that you should also definitely listen to. The podcast I'm talking about is Comedy of the Week,

which takes choice episodes from BBC sitcoms, sketch shows, podcasts, and panel shows, including my own show, unspeakable, and puts them all into one podcast. Maybe I'll trail this podcast on that podcast. Who's to say? I'll do what I like. Listen to Comedy of the Week now on BBC Sounds. Podcast.