Unexplainable - Cloud atlas

Episode Date: February 2, 2026

It’s surprisingly hard to predict how clouds form, move, and change, but it’s essential to try. Because how clouds react to a warming world helps determine how hot our future will be. (Originally aired in 2021) Guests: Vox contributor Umair Irfan, scientists Scott M. Collis, Angeline Pendergrass, and author Gavin Pretor-Pinney For show transcripts, go to ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/unxtranscripts⁠⁠⁠ ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠For more, go to ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/unexplainable⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ And please email us! ⁠⁠⁠⁠⁠⁠⁠[e-mail]⁠⁠⁠⁠⁠⁠⁠ We read every email. Support Unexplainable (and get ad-free episodes) by becoming a Vox Member today: ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/members⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ Thank you! Learn more about your ad choices. Visit podcastchoices.com/adchoices

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Countertop wipes and fly traps Hey fruit flies your baby boom ends here Save the Everyday with Amazon Hi, I'm Chris I'm a question Ayala, and I'm the sound designer for Unexplanable. This episode is one of the first ones that I worked on when I joined the team. Imagine showing up to a new job and someone asking you to figure out what a cloud sounds like.

And not just a cloud, lots of clouds, fluffy clouds, stormy clouds, all kinds of clouds. People kept comparing the clouds to the ocean, so I added the sound of waves. But it didn't quite have the right texture. So after some thinking, I settled on adding some lava bubbles to sell the slow-moving nature of clouds. Look out for this while you listen to the episode. Enjoy. I had flown many different aircraft in planes for the Air Force, but never had the opportunity to fly an aircraft that's kind of in that World War II era, you know, 1949 vintage.

Big old propeller, big old radial engine on the front. Once the storms started to form, we would get notified that storms are starting to build in this area to get ready and so we'd prep the aircraft and when it was time to launch then we'd fire it up and then take off and then you kind of look ahead and see this huge towering cumuline nimbus ahead of you that's i mean to me that's the ultimate cloud the cumulumines nimbus the thunderstorm is capable of so much power and so much beauty at the same time and it can boil you know with the updraft it just looks like it's alive you briefly ask yourself I can't believe I'm going to go fly through this thing.

That is no place for an aircraft to fly. But this aircraft was modified. It was capable. It did it for over 30 years. So to me, it was not about the adrenaline. It was about getting the opportunity to witness the power, the beauty, the strength of severe weather from inside a thunderstorm. And not many people have had that opportunity.

We would aim right for it. It would be sunny and calm on the outside, and then as soon as you hit that wall, the aircraft would start to rise on its own. We could keep climbing at 2,000 feet per minute. This is when you would really find out if you didn't have your straps tighten down. Lots of rain and hail, and that was one thing that was just remarkable to me. It was just how noisy it was, how loud the hail was when you got into the hail shop. And as charge builds up on the aircraft, it starts creating what we call St. Elmo's fire from the communication antenna. And so you start hearing this buzzing sound over the radio, and it increases its intensity and its frequency.

The more charge that it builds up. And turn up, bam. There'd be a bright flash, and when it attaches to the pillar, that plasma flows right over you. It doesn't get inside the aircraft because the aircraft's metal and it acts like a Faraday cage. And it usually didn't do any damage except for just melting a little bit of metal on the trailing edge of the tail or wing or put a little pit on the propeller. So we'd continue out the forward flank of the storm and eventually break out of the storm. Get out of the storm, assess how the engine is doing. And then we'd set up and do a 180-degree turn and go back and do it again.

It's unexplainable. I'm now I'm Hassanfeld. And I'm here with Umair Irfan, Vox Science Reporter. And obviously, my first question after listening to that is, why is this guy flying an old tiny plane straight into a thunderstorm? Well, it turns out that even though clouds are ubiquitous and found everywhere on Earth, there's still a lot we don't know about them. Sometimes the best way to actually understand what's going on is to go straight into the middle of them. So I decided to start talking to a bunch of cloud scientists about this. And, well, one of the first things you'll learn. talking to cloud scientists is they really love clouds. It is amazing how much science you can do just by looking at clouds. I love deep convective clouds. Those are the really puffy and tall and juicy clouds that happen all the time in the tropics. The asperitas cloud, it looks like crazy waves, as if you're beneath the sea snorkeling and you're looking up on a really rough and turbulent day.

Mamatus is this droopy, undula kind of cloud. And when you get a sunset and those warm red colors of a sunset reflect on the bottom of a mattis cloud, it looks like looking into the mouth of a giant. Clouds are where the rubber meets the road in terms of weather. You know, things like rainfall, things like temperature, wind. A lot of that is mediated and governed by cloud formation, where the clouds are and how quickly they move. So understanding them is to fill in a crucial blank with whether we have enough water available to grow crops. Or if we lose clouds in a given area, will that cause heat to accumulate in that area?

So a lot of our real-world interactions, a lot of the things that we do day to day are affected by clouds in really profound ways. Okay, so clouds are really important. They impact crops and rainfall and temperature. But are they unexplainable? Like, what do we still not know about them? Well, it's really hard to anticipate them. You know, because they are so important, we really want to be able to get ahead of them. And right now, there's still a lot that we're still trying to figure out.

You know, at the molecular scale, you know, we understand basically how cloud particles form. And then at the overall planetary scale, we kind of understand how cloud spread over continents and over the oceans. But connecting those in the middle, that's really difficult. And without being able to connect those dots there, it's really hard to predict how clouds are going to form and the effects that they're going to have on us. Okay, so we've got this small-scale understanding, this very large-scale understanding. We're sort of missing the connective tissue there. Let's start small.

What exactly is a cloud? Like, what's the stuff of a cloud? It's pretty simple. You know, it's just water vapor condensing around a tiny particle. Tiny, tiny little particles we call aerosols. I talked to Scott Collis, who's this atmospheric scientist at Argonne National Laboratory. Aerosols are about one millionth of one meter in diameter. So these things are absolutely tiny, and they act as a surface that water can condense onto and make droplets.

So it can be a piece of dust, it can be salt spray from the ocean, it can be pollen, it can even be pollution, and it can be synthetic chemicals that, you know, people deliberately try to. seed clouds with. That's interesting because I would have thought of a cloud as a gas, and you're basically telling me that a cloud is actually a mixture of solids and liquids, like solids at the core and liquids kind of coalescing around those small solids? Right. That's really weird. I mean, if you think about it, if you look up at a cloud, they look almost weightless. Yeah. But if you were to imagine, say, a cloud that's, you know, a kilometer on each side. say a cubic cloud that's like one kilometer on each side. That's about a million pounds of water right there. Huh. You know, we're talking, you know, ponds and lakes worth of water directly above

your head and the very low density of it helps keep it afloat in the air. We go, I just, I just am kind of astounded at the fact, like, I get why a bunch of gas could, uh, stay above us and not fall down. But if you're telling me that there's a bunch of solids and liquids in the sky that are the amount of water as a pond, and it is not falling on me all the time. Like, how? I mean, it's, it's the amount of water even as, as giant rivers. Like, there's more water in the air about the Amazon than there is in the Amazon River. Yeah. It's a tremendous volume of water. You know, like every tree in the rainforest can move about a bathtub's worth of water into the air every day, and they effectively help generate about half of the rainfall in the rainforest. So the trees are

kind of watering themselves. How does the water, like, stay up there? Think about, like, a spray bottle, right? Like, if you've ever used, like, a mister, that water doesn't necessarily fall out of the air. Now, if you could make those particles that come out of a mist or even smaller, they can stay suspended in the air for a very long time. But, you know, we can have those ingredients and still not get clouds. You know, you can have dust in the air and still have it where the atmospheric conditions won't lead to cloud formation. And it's really hard to tell exactly what that is because it can change from moment to moment from place to place. Okay, so clouds are made up of tiny bits of water that surround particles. And if being able to predict how they move and form is so important,

how do scientists go from this kind of small-scale understanding to larger-scale questions like predictions? Well, I talked to the scientist about just that. You know, this is a scientist named Angie Pendergrass, she's a climate physicist at Cornell University. And she told me that the moment you start talking about more than one droplet, it gets really complicated really quickly. There's just these hard limits to what it is that you can say, especially about the specifics of how things are going to change in the future. Angie describes these as billions of droplets moving together, kind of like a double pendulum.

So if you have a pendulum hanging from another pendulum, and you start spinning one of them, you stop being able to predict what it's going to do. You've got these layers and layers of complexity that keep building up. And you can't know what it's going to do because small differences grow really quickly and dominate the system. So when you have these layers of complexity building on each other, it becomes harder and harder to model and predict what's going to happen next.

When you have a really small effect, it grows. So then these tiny, subtle change, that happen at the microscopic level suddenly become really, really difficult to scale up. And they have huge effects as they ripple out from the microscopic level to meters and kilometers and then over entire continents. The atmosphere is chaotic. And when you make one tiny change, that can grow exponentially and change everything. So you're saying basically we can't necessarily predict what kind of effect pumping a certain gas into the atmosphere in one place might have on rainfall or weather in a different place? It's really difficult, and right now it's beyond a lot of our capabilities. I mean, I'll give you an example. Think about the boundaries of a cloud.

So like when you're underneath a cloud and you see its bottom, it looks pretty solid and it looks pretty flat a lot of times. But really, it's a lot more complicated than it looks. You know, it's not as though there's a sudden line where you go from cloud to not cloud. You know, the atmosphere is filled with water vapor. And so it's this constant churn of, you know, evaporation, condensation, movement, freezing, thawing, all happening at the boundaries and within these clouds. It's not quite always clear what even you mean by a cloud, and it's not always what it looks like it might be.

I wonder if this is an appropriate analogy, but it almost makes me think of like a wave in an ocean, thinking of a wave as like a thing, but it's almost the rest of the ocean may be coming into a certain shape, but there's not necessarily a moment where the wave becomes the rest of the ocean. That's right. You know, scientists kind of describe these things as emergent phenomenon.

And this is this idea that the whole is greater than the sum of its parts or it behaves in a different way. So if you were to look at an individual water droplet, you would expect some very predictable behaviors, you know, how it would roll or how it would move around in space if it was like a suspended aerosol.

But when they're all aggregated together, in clouds, those properties begin to shift and change. Then they began to behave as an aggregate. Clouds then move together. They fuse and they create layers in the sky, or they form columns where they move up and down, or they condense and that water then precipitates out of the sky as rain and snow. So it has all these other properties that you wouldn't necessarily be able to extrapolate from just its constituent parts. And that's why you have to look at clouds both at a very tiny scale, but then also at this massive scale over kilometers and even over continents to fully grasp the influence that they're having on the planet.

And clouds, you know, while they have important effects in the near term over the course of days and weeks in our lives, they also have an even bigger effect over the long term. And that's where the picture gets even more complicated, particularly if you're concerned about climate change. Clouds might mitigate climate change, but they also have the potential to make it worse. we just don't really know which outcome we're going to get.

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Wednesday morning cloudy with a chance of unexplainable. Umair, we're back. In the first half, you were talking about how clouds are this sort of hard to explain emergent phenomenon. I mean, we know what they are in a very, very granular level, but it's very hard to really explain how they move and change and behave. And you left off on this note of how difficult it is to predict the future and what impact that could have on climate change. So what are we talking about here?

Like, what is the potential impact of clouds on climate change? So there's a lot of far-reaching effects that are going to change depending on how the clouds change as the climate warms up. You know, if you look at climate models, one of the biggest sources of uncertainty is what humans will do, whether we will actually get our act together and curb greenhouse gas emissions or just keep doing what we're doing. But after that, clouds are almost always the largest source of uncertainty in those models. So where could this cloud uncertainty take us? Well, it can go in two directions. You know, you can see clouds that make climate change worse and enhance warming,

or you can see clouds that sort of offset it and mitigate some of those effects. Oh, so clouds could actually, like, help us out on global warming? That's right. Scott call us the atmospheric scientist we heard from earlier. Explain this pretty well. So the basic way our climate works and climate, climate change works is visible light comes in, heats the surface of the planet, and some of that radiation gets radiated back to space.

Now, low clouds that sit very close to the surface of the Earth and look very white and fluffy that are mainly made up of liquid water, they do a really good job of reflecting that incoming solar radiation back out into space. Okay, so the low altitude clouds might be like, I don't know, wearing white on a hot day in the summer, like keeping that. the heat out reflecting it. Right. On the other hand, when you have some of the more high altitude clouds.

You know, above 30,000, 40,000 feet in the Earth's atmosphere are mainly made of ice. And they can actually appear to be kind of translucent. They let some of that sunlight through, but they're very effective at blocking the outgoing infrared radiation, so they act more like a blanket. So you're saying more high altitude clouds, more heat on the planet, right? Yeah. And I guess the issue is here that we don't really know on a large scale whether we're going to get more of these blanket clouds or more of these cooling clouds? It could quite easily go either way.

It can go both ways at the same time. You know, we've only really been measuring clouds and observing them scientifically in an era where we've been also modifying them extensively. Like we've been doing this since the Industrial Revolution when humans have been pumping greenhouse gases into the air as well as pollution. We don't have a good sense of what clouds were like before a human started drastically interfering in the atmosphere. And that's because we don't really have a good record of clouds. There's no fossil record. We have ice cores that we can use to sample the atmosphere

from decades, centuries, and millennia ago. We have tree rings that we can use to look at rainfall patterns. We can look at the geological record. But clouds themselves, they have barely a footprint. Right. And so we don't really know what they looked like. and how they behaved before we started spewing carbon dioxide into the atmosphere, before we started emitting particles of soot and sulfur from our industrial facilities.

It's almost like if scientists are trying to predict how clouds will change over time and how that will impact climate change, they don't really have a before picture. Exactly, and that makes it really hard to get a sense of what we're doing to the planet now. We don't really have something to compare it to. We've only seen it under our influence and the best records we have to go on are just what people told us back in the past. For instance, sailors and navigators for a long time keep very accurate track of weather because, you know, weather and wind is very important for sailing. And so now scientists are really trying to delve back into old handwritten records,

especially from ship's logs to try to understand pre-industrial cloudiness. We have maritime shipping logs going back, centuries that some researchers are working on digitizing so they can actually get a sample of what clouds were like over the ocean hundreds of years ago. You know, like even sailors' legends about like how they look for certain types of clouds as heralds of bad weather or good weather. Red sky and morning, sailors take warning, red sky at night, sailors delight. Exactly. And, you know, there's truth to that.

You're really looking for those high serious clouds usually generated, they're created by Thunder When a thunderstorms, when a thunderstorm happens, the vertical winds in that storm, push up water vapor and cloud droplets and ice. So if you see that serious cloud coming to you in the morning, you know you've probably got a storm coming at you. Another thing that some scientists have suggested we should look at is art and literature. What do you mean? Like how people wrote about clouds? Well, exactly. They have been rich metaphors and rich inspiration for poets.

and artists throughout the ages. This is Gavin Prenderpini. He is the founder of the Cloud Appreciation Society, a group with more than 55,000 members across the world. The Cloud Appreciation Society. Oh, yeah, there's a lot to appreciate about clouds. And one thing that he built my appreciation for is just how profoundly clouds have influenced art and literature and culture.

You can see carvings on stones in Mexico showing cumulonimbus storm clouds with recognizable features to them, you know, thousands of years old. Like, you know, how are clouds depicted in paintings from centuries ago? Does that provide a useful signal? You know, zoom right forward to the romantics of the 19th century. And you have landscape painters like John Constable said that the sky is the chief organ of sentiment in a landscape. Have you heard of that painting The Scream by Edvard Munk? Yeah. The Norwegian painter. Yeah, I love the scream.

It's sort of like the predecessor to McCauley Cochon and Home Alone. Exactly. With his hands on his cheeks, kind of looking like a ghost skeleton. Well, if you look past the eerie skull-shaped character in the front and into the background, you can see these vivid red streaks in the sky. And some scientists say that this was actually what the sky looked like in Norway. About a decade before he painted this, this was due to the Krakatoa volcano eruption. that spewed soot into the air all over the world and cause these amazing sunsets.

Now, some scientists dispute that. They say the time gap was too large. Others will say that this is actually another type of cloud that you actually see in the northern latitudes called Nacrius clouds that are actually seen in and around Arctic and polar regions that actually reflect sunlight in these vivid colors. Seriously? So this may have actually been an early depiction of a phenomenon that we've only now begun to appreciate. So some people might be looking at that Munk painting and seeing, oh, wow, this is just some really weird portrayals of clouds with this sort of like red, orange, yellow colors. And then other people might be like, oh, no, he's totally serious.

Like, that's actually what the clouds were like then. Well, maybe in that particular moment or that specific memory that he was evoking. I mean, that's fascinating. But the other thing to caveat is, of course, this is art and there is some artistic license. Paintings and art, they're constructed a lot of the time. You know, they're not photographs of the sky. They don't give you a real indication of how many of them there were, how often they were around, all these quantifiable factors

which are important in understanding how our climate has changed. We get glimpses at the sky throughout history, but that's all we can get from human culture, really. So what have scientists learned from all of these glimpses of cloud history? I think we, I mean, I think it's a process right now, like, especially with like the digitization of nautical records. The impossible to read handwriting of the crew of some whaling ship in the 18th century to try and pick out references to the weather. It's going to take time to actually get enough useful information out of them. Eventually, you know, you could use this to sort of put together a picture, a spotty picture, but a picture nonetheless,

of what the oceans and the skies looked like centuries ago. You know, it strikes me, Muir, that we're talking here about how there's so much we don't know about how clouds might change and behave in the future. There's probably even more we don't know about how clouds behaved in the past. Where does that leave us right now? I think it should leave us here with a little bit of humility to understand that, you know, there's a lot we still don't know and that there's still some things beyond our control. But it should also give us, you know, inspiration and motivation to study this further, that we know that clouds are going to be something that's hugely consequential for us, that these are really important blank spaces that we really need to fill in, and we should, you know, redouble our efforts to try to understand them.

Our relationship with our atmosphere is a crucially important one going forward. And one way to help that is. is to be more connected to the atmosphere, to realize that we don't live beneath the sky, we live within it. And the sky is an ocean that we inhabit. We just happen to live on the bed of that ocean. So once you start appreciating clouds, you start appreciating your role in the world

and your role as both an observer and a participant in the atmosphere. And so what we put into that ocean is not something separate from us. It's not something that happened above us. It is something that happens to us. And that may help you sort of center yourself in the world. When you notice out of the corner of your eye something interesting or beautiful appear above you,

be prepared to stop and look up. Just allow your imagination to drift along with the breeze for a few moments. To do that, to have a few moments with your head in the clouds, helps you keep your feet on the ground. ground. Thanks to all the cloud experts we heard from in today's episode. Tom Warner, our fearless flyer from the beginning, Scott Collis, Angie Pendergrass, and Gavin Prenderpenny. This episode was produced and co-reported by me, Meredith Hodnott, and edited by Brian Resnick, Bird Pinkerton, Gillian Weinberger, and Noam, who also made the music. We had sound design and mixing from Christian Ayala. Mandy Nguyen did the fact check for this episode, and Liz Kelly Nelson is the V-Eyne

of Vox Audio. If you want some juicy, undulating pictures of clouds, video of Tom Warner's plane getting hit by lightning, or more information on the Cloud Appreciation Society, sign up for our newsletter. You can do that at Vox.com slash unexplainable. And send us your thoughts on the show. Email us at Unexplanable.com.

We read every email, and we'd love to hear what you're thinking. And if you like the show, tell a friend. leave us a review or a rating. Do whatever you can to help bring new unexplainable listeners into the fold. Unexplainable is a part of the Vox Media Podcast Network. Thank you for listening.