Head in the Clouds - Owain Wyn Evans, Gavin Pretor-Pinney, Amanda Maycock

This BBC podcast is supported by ads outside the UK. and a valuable community. ASR does it. So, now you can listen to your podcast. BBC NL, the place for the best British misdaad series. Just on your Netherlands TV. What time did you go to school? I'm from Oldham. It was dark 24 hours a day. I'm from Oldham. 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 them standing on those volcanoes looking enigmatic, could I? Because the clicking would spoil the atmosphere. They're not made for going over cooled lava, are they? No. No. OK. 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. Oh, of course, we only had paper shoes in Aldham. 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 Dara 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... Maintaining? I can't say maintaining. I'll do it if you want. Here we go. You do it. You do it. Today we're asking, how do clouds help in maintaining a healthy atmosphere? What can clouds, which are 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. LAUGHTER That's better than that. To guide us through, we're joined by a climate scientist. Don't worry, it's all right, the show's going to be OK. To guide us through, 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 Preeti-Pinney, 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 120 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 could 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 Carpentaria 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. 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 Owen Wyn Evans, used to be a weather presenter. Now 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 drum-a-thon, 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 drum-a-thon. And the most wonderful thing that I've seen in the 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. I thought, Aaron, what's that? Aaron, that looks like Peppa Pig. Or was it Daddy Pig, actually? As the balloon approached, it was indeed Peppa 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 Peppa Pig drifted towards us, and off she went. Last seen off the coast of Barrie. 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 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 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 Apilius. 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 Peppa Pig balloon. You've got to bring them gently back to the science. I'm just saying, what's your favourite cloud? Did you say favourite cloud? I said favourite formation, Brian. Is there a technical difference between that? Have I made a terrible mistake? Formation is just a general term. Because, I mean, basically, they're all clouds. They're 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 an Englishman called Luke Howard, a 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 becomes 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. It's 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 on to, as it were, and they tend to form around little things we can't see, specks in the air, they 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'll ever heard of at school, cumulus, cirustratus, cumulonimbus, the superstar, you know, the storm cloud that 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 fluctus cloud feature. There's a whole bunch of them. I think there's about, when you combine them all, there'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. There's 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 see them being blown along The lower altitude clouds which are made from liquid water the sort of fluffy cumulus type clouds they 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 weather. 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 about you know 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 you know 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 I'm like, hon, if I forecast this three years ago, I'd be monetising this skill somehow. It would happen a lot when we would get bad weather as well, you know, 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 weather 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 around. 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 love that. I love that. We could do like a kind of a what shapes will we see today in the clouds, like a little bat maybe. Did you used to send to, 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 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 clud, which means a rock or a boulder. It's wherever we get the clod of earth, that term from. These feel like solid things, cumulus clouds. Do you know 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 phenomenon 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 cloud. 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, you know, at the base of the cloud. So the base of the cloud, the little droplets 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 when you're looking you know on 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 so actually within what appears to be that kind of you know the the stationary nature of the shape itself there is still all manner of movement going on there yeah absolutely there's a lot of 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 you know 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 are slightly more scared of clouds than they used to be. What if they fall? Chicken lick it? How big would that be? So a 400 tonne cumulus cloud. Yeah. What dimensions? 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 centimeter 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 become precipitation. This is 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 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 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 basically kind of shadowing, and you can't see that scattering effect 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 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. I understand that you want to listen to your podcast, so I'll keep it short. Because if you think it's important to make a lot of choices, maybe the ASR can help. Now I hear you think, how then? Well, for example, when it's a duurzaam herstellen of the things that you love are, it's a schade. Will you know more about the insurance where a duurzaam schadeherstel can be? Go to asr.nl slash duurzamekeuzes. This does ASR for you and a duurzame society. ASR does it. So, we can now listen to your podcast. Moord, mystery and an accent where you immediately fall. Your service, why? This is murder. Put your humor on me. Good humor, sluwe misdaden, wonderful unfulmaakte characters and exactly the right dose of sarcasm. Bingo. BBCNL, the place for the best British misdaden series. Just on your Netherlands TV. You mentioned there about how they appear white because they scatter the wavelengths of colour. But ray-ly scattering, which is what makes the sky blue, 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? Just a wave. Has that ever been said before? Just a wave. Just a wave, Brian, yeah. I didn't need to unnecessarily add wibbly-wobbly then. There's no un-wibbly-wobbly wave. To be fair, I think Owen was saying that this one was wibblier and wobblier, and I think the wibbly-wobbliness of this... Does he mean the amplitude or the frequency? No, I mean the wibbly wobbliness. I think it's a longer wave, yeah. It's a longer wave. There we go. So it is more wibbly and less wobbly? Well yes Is it more wobbly and less wobbly Oh I can remember Brian I know you got a question for everyone 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? That was a specific question. Can I just, though, mention, by the way, if you are an aeroplane, please don't open the window. No, no. It's just that we won't get letters otherwise. If you're an assessor, you'll be all right. But I had to think for a moment. 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 cover it to you, Owen. OK. 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's cloud and 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. I love that, the dry ice. Is that what it is? Like, put the dry ice on. I think it would fall through it. Yeah, I came to the conclusion that it would fall through. But it's a good physics question. 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 wibbly-wobbly fashion. 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. 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 currents, are rising 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 crisp packet could have ended up in the middle of a hailstone. It's going to be one of those very famous physics examples that all undergraduates learn in atmospheric physics, isn't it? Mortimer's crisp packet. That was the infinite monkey cage. 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 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. 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 understood, 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 on 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 kilometres. 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 pause. 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 a 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've formed underneath a piece of glass, because 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 any. 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 about the, 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, we're 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 revolutionized 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 oh yeah yes your kind of the iridescent clouds or the when you see those gorgeous colors in a cloud and they are incredible to see because it's it's like a rainbow but it's more kind of localized 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 color 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 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 phone's anything like mine, the photo will look absolutely rubbish then and you'll just delete it. Yeah, the only one that 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 and 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, 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 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 describing, you get this sort of horizontal path of the light through the atmosphere, which gives you that more sort of ready 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 Nacreous 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 lucky enough to see those Gavin I wondered about you know having done you know Cloud Spotters guides and things like which is when Amanda was talking earlier on about the importance of you know what we might call imperfections or grain or 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 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 There just weren't so many of those. And those are human-made clouds that result from the water vapour 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 pea 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, but 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 sun, 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, the 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 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 if 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. it 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 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 kilometers 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 organization 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 bigger 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. Well, your favourite one was the crisp one, but that's because it's connected to your celebrity age. I read it in the script 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 segued from a discussion about the detail of the climate? So balloons, what's that all about? I'll tell you why, because we've only got a minute left. So we could continue to see, or we could just go. So, Owen, I know that balloons have played a major part in your fascination with... Absolutely. I mean, there's the Peppa Pig balloon, aforementioned. But also, when I was about four, a weather balloon crashed into our garden in Armonford, 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 all these years later, who'd have thought that I would, you know, still be interested in 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... Yeah. Well, you know what? You walk round 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. All right, 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 Stormcloud 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 it 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. Is that what I was saying? I think that's what it says. No, it doesn't. Ignoring. Gnawing on a... Oh, now it makes sense. This is lovely. This is from Niamh. My grandad, 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 Cosmic Comicus. I love that one. Oh, that's brilliant. Well, thank you very much. Thanks to our panel, who were Professor Amanda Maycock, Gavin Pretor-Pinney and Owain 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'll see you again. Bye-bye. APPLAUSE Donkey Cage. Till now, nice again. 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. ...to the dark streets of Belfast. Put your humor on me. Good humor, serious misdades... ...hearly unfulfilled characters... ...and precisely the same dose of sarcasm. Bingo. BBCNL, the place for the best British misdades series. Just on your Netherlands TV.