Season 3

Episodes 9 and 10 – Clouds, Atmosphere, and Climate Change Misconceptions – ft. Prof. Dr. Bjorn Stevens

Episode 8	Episodes list	Episode 11

In this episode, Bea talks to Prof. Dr. Bjorn Stevens, managing director at Max Planck für Meteorologie and a director of The Atmosphere in the Earth System, about clouds and water vapour, and the effect they have on climate change.
In the first part, Bjorn talks about the reason why he decided to switch from electrical engineering to studying clouds and explains why clouds are relevant for climate change. He talks about greenhouse gases and describes what role different types of clouds play in the greenhouse effect and in controlling the temperature, as well as how the temperature, in turn, impacts cloud formation. Bjorn explains absolute and relative humidity, the double-sided effects of air pollution, and factors that influence the amount of water vapour in the atmosphere. Bjorn and Bea also discuss approaches to modelling climate change and the reliability of climate change models.
In the second part, they focus on climate change and discuss in great detail some of the most common misconceptions surrounding the topic. They talk about extreme effects of the weather, the difference between 1.5 and 2 degree increase in global temperature, the current state and future prospects of nuclear power, using solar and wind power to create energy, and more. Bjorn also talks about his view on the way climate change is treated by the media and politicians and shares his outlook for the future.

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Bea: Hello and welcome back to the Offspring Magazine the podcast! It’s Bea and I will be hosting today’s podcast. Today, we will be talking to professor Bjorn Stevens who is a director for the department of the Atmosphere in the Earth System at the Max Planck Institute for Meteorology in Hamburg. Today’s conversation is about climate change and what a climate science expert thinks about this topic. We start by talking specifically about Bjorn’s research on how clouds and pollutants affect climate change. This part gets pretty complicated so just hang in there. A good idea is sometimes to pause the episode or re-listen to parts. We do have a video available so that might also be a good way or a good option to understand this part a bit better. We then talk about climate change in more general terms, such as how to approach studying climate change, how reliable climate models are, what are some of the biggest misconceptions, how much do we really know about climate change, and also what are some of the best ways forward. I really enjoyed this conversation and I hope you will too! 


B: Hello! Thank you so much for joining us today. Why don’t you start by introducing yourself to the audience?

Bjorn Stevens: Hi! My name is Bjorn Stevens. I’m here at the Max Planck Institute for meteorology and…

B: You can just look at me, it doesn’t matter, you don’t need to look at it.

BS: Anyway, so I’m Bjorn Stevens. I’m at the Max Planck Institute for Meteorology and I lead a department which is called Atmosphere in the Earth System. How much do you want to know about me?

B: Well, as much as you really want to tell us.

BS: You probably don’t want to know that much. So I’m an atmospheric scientist. I did my undergraduate studies in engineering, electrical engineering. I’m American by nationality but have a, sort of, complicated history and connection to Germany so it’s not too strange to be in Germany. I’ve been here since 2008. Before that I was at UCLA, I just got back.

B: Oh yeah, the merch.

BS: So I was at UCLA for about 10 years after I finished my PhD. I got the offer to come here and I’ve been here since 2008. Yeah, I study clouds, Earth’s atmosphere, how it affects climate. Mostly that has to do things with how water distributes itself in the atmosphere. 

B: So climate change is a really complex topic, why did you choose to study clouds in particular?

BS: Yeah. Yeah, so there’s two things: climate change and clouds. So I chose to study clouds because, I don’t know, I had been studying electrical engineering and I realized I didn’t want to keep studying engineering. And I knew that I didn’t want to spend my life earning money but rather pursuing something what I considered creative. And so after my Master’s, I started a PhD. And I just realized that wasn’t what I wanted to do. And so I went and I worked for about a half year, but it was in the united states, and once you stop your studies you have to pay your student loans. Yeah. And so it was either go to school or start paying loans, which wasn’t a big problem but I thought to take a year off but you only had a six months grace period. And so then I started applying the places and I couldn’t be a chooser because I wanted to start after six months, sort of, mid-year. And I got an interesting offer to work on something. And I thought it was something else. And I went there and it wasn’t something else. It was a person who worked on meso, what we call in the atmosphere mesoscale, intermediate scales.

B: Can you explain that?

BS: Things that happen on two hundred to two thousand kilometer scales, in the atmosphere, we have large scale, small scale, and these middle scales. But in the atmosphere, we often use the word “meso” – it means “middle” – also for the mesosphere, the atmosphere. And at first I thought I would be working in the mesosphere and doing something with radiation. But really it was about intermediate scale clouds. So I got a project with clouds and I thought it was fun. And so then I kept working on clouds. And then climate kind of became important. And clouds are relatively, they’re important, relevant for climate. So yeah, so now I study clouds and climate.

B: So how are clouds relevant for climate change? Why is it so important to study clouds? I guess we keep on saying “clouds”, what is it they exactly study? Cloud formation, cloud… rainfall?

BS: I just gave a talk in Utrecht, a public lecture, and it was about clouds. And the way I posed the talk was, I said, “clouds: object or absence?” so, you know, when you actually think of what is a cloud? It’s a long discussion.

B: Yeah.

BS: But when you think about climate: climate is really just about balancing energy budget. So the Earth gets a energy from the sun and it will accumulate that energy unless it gets rid of it. And so you have to, kind of, work out the balance of energy. And temperature plays a role in that. So a hotter planet will give off more energy than a colder planet. And so one way the Earth can get rid of energy easier is to heat up and a way to get rid of less energy is to cool down. And so the Earth is always trying to balance its energy budget. And clouds play a big role in that because they affect the ability of the Earth to get rid of its energy and they affect how much energy is accumulated. So if clouds depend on temperature, then they kind of are intertwined with that energy budget. So it’s really hard to understand its energy budget without understanding the clouds.

B: You did mention that like clouds can help give off some of the heat that’s coming in? Do you want to just explain the greenhouse effect because I think that’s important to understand how clouds can also then reflect some of the incoming radiation?

BS: Yeah, so how to explain the greenhouse effect in a few words…

B: It can be as long as you want, I’d say just keep it simple so that everyone follows. Because I think you need to know understand that to understand the rest of the discussion.

BS: So a greenhouse atmosphere is one that loses energy – it’s cooling. So on the Earth, we have an atmosphere which has, what we call, greenhouse gases and greenhouse gases are opaque in the infrared. So it means that they absorb and emit thermal infrared radiation. And, I don’t know, one way you can think about the greenhouse effect is to imagine yourself on the moon looking at the Earth. And when you look down into the Earth, if you had infrared goggles and you were seeing not visible light but thermal radiation, so that’s hard for people to understand, that’s what the Earth is giving off to balance the incoming sunlight. So that energy budget for the Earth is this attempt by the Earth to warm up enough that it radiates thermal radiation to balance the visible radiation that it’s getting. So that’s the exchange of energy that’s taking place. Now, if you look at those wavelengths where the Earth is trying to lose its energy, the atmosphere is fairly opaque, which means that the surface of the Earth isn’t emitting that energy in space, it’s emitting it to the atmosphere. And the atmosphere is absorbing it and re-emitting it at its own temperature. And this has a way of shielding the Earth from… shielding the Earth emission so that the atmosphere is emitting at a colder temperature than the surface of the Earth. So it works a little bit like a greenhouse, in the sense that in a greenhouse, it traps heat, but it traps a different type of heat, a convective heat. If you have a greenhouse, and the sunlight goes in and it warms up the surface, the plants kind of get warm up, they evaporate, whatever, but that heat is trapped there, it’s not lost to space. But mostly it’s because the glass stops the warm air from escaping. Some of it is radiant energy transfer but mostly mostly it’s convective energy transfer. So in a simple way, the greenhouse is just about trapping or making it hard for the Earth to emit as much energy it would if it was at that surface temperature. So if we had no atmosphere, the Earth is, so the average temperature on the Earth is, what, 288 Kelvin. And you can calculate how much energy that would radiate. And that would lose far more energy to space than we get from the sun so the Earth would be cooling off. But that energy doesn’t go to space it gets absorbed by the atmosphere, and the atmosphere is colder than the Earth because it’s a greenhouse atmosphere it’s cooling all the time, and that atmosphere then re-emits it to space at a much colder temperature. So it’s a bit of an insulation blanket. I mean, there’s ways in which you can understand the greenhouse effect much easier but then you have to start talking about the spectroscopy. So we can I mean but…

B: You’ll probably lose me as well so…

BS: So I don’t know, if somebody from outside, there’s so many videos on that. But I think for the greenhouse effect, you can really just think about it as the wavelengths that the Earth is trying to give back the energy of space that it’s getting from the sun. The atmosphere’s opaque and that hinders the ability of the surface to lose as much energy as it would like to because it’s the atmosphere is intervening, it’s absorbing that infrared energy, and it’s radiating it again. But it doesn’t radiate at all onward some of it gets back. So you kind of think of it like somebody’s throwing the balls… I’m throwing you things, I wish I had things to throw… so here’s something, right, so I throw these things, you transfer them and throw them back. 

B: Yeah.

BS: Now, the atmosphere sits in between. Yeah, I have two. And so I throw that to you and you throw it back to me. Okay, there that’s energy going back and forth. But the things you throw back to me are a bit different and the atmosphere sits here in between. And every time you throw something an atmosphere catches it. And it doesn’t just pass it on to me, it gives some to you back. So every time you’re trying to get rid of stuff the atmosphere is saying, “no, no, here you have to take some more back”, so you could think of it as cookies: like, if you’re trying to get rid of cookies. You pass them onto me, an atmosphere says, “no, no, here’s one back”, so every time you try to give me a cookie, the atmosphere intervenes and gives you half the cookie back. 

B: Yeah.

BS: So you’re not as good a getting rid of your cookies or your energy. That’s what the atmosphere is doing: it’s just impeding your ability to get rid of energy.

B: But then… yeah, exactly, but then clouds help give off a lot more energy or help reflect some of the incoming radiation.

BS: Yeah, so they play two roles. So the fact that the energy is absorbing that infrared energy that you’re trying to get rid of is due to the greenhouse gases. And clouds are opaque in infrared. So that means that, basically, every infrared photon that you try to send out to space, if there’s a cloud above it, the cloud will absorb it. So clouds are really effective greenhouse agent, they’re not a gas because they’re liquid, but they have a strong greenhouse effect, so they warm the surface.

B: Okay.

BS: But they also have a strong albedo effect. And that cools the surface. Because they do the same thing to the sun that they’re doing to you. So the sun is… I’m trying to… I’m the sun, you’re the Earth, I’m trying to pitch you energy, right. And you try to give it back to me. And if there’s no atmosphere and no clouds in between, life is easy. I give it to you, you give it back to me. And you just have to decide how agitated, how warm you have to be so that you can throw me the balls back as fast as I give them to you. That’s your temperature. Now, the atmosphere comes in between, forget about clouds, I throw the balls to you, they come to you the same, you, kind of, get agitated, you throw them back to me, but you have to throw back twice as many as you would think, because half of the ones you throw come back to you again, because the atmosphere intervenes. That’s the greenhouse effect. The clouds, when they do that, they make it even worse. However, the clouds start messing with me, the sun, because I throw you the balls and the clouds say, “ah, ha-ha, back!” you know, so they’re doing the same game with me – that’s the albedo effect. So clouds have two effects: they, unlike water vapor, water vapor is primarily just the greenhouse effect, condensed water clouds have an albedo effect, which means that when I’m trying to throw you the ball, they bounce them back to me, so you don’t have to catch as many as you would have had to before. I should have some balls that we could play this game… but yeah, we just need someone in between.

B: Yeah. Oh, so okay, because I always thought of clouds as only having the albedo effect. But interesting that they also… they work as both, which makes everything…

BS: Where are you from, originally?

B: I’m half-Italian, half-Dutch.

BS: Yeah, okay, so in Italy, where in Italy?

B: More in the north. So where the Dolomites are. 

BS: But it can be kind of dry and on a clear night, you know, how cold it gets compared to a cloudy night?

B: Yeah.

BS: And that’s just, and clouds are really effective when you have low clouds of, sort of, trapping the heat.

B: That’s very true, yeah.

BS: And when you have a very clear sky, especially a dry sky because the water vapor is also greenhouse effect… if you’re in the mountains at night, you can have a really sunny day, it cools off really fast at night. Why? 

B: Yeah, because there’s no clouds.

BS: Yeah, there’s no clouds and there’s no water vapor. Because when you’re high in the mountains there’s a very little water vapor above you. So you just lose a lot of energy to space because the atmosphere is in there throwing the balls back, off they go. And so you cool very effectively. And it’s the same with the Earth.

B: Yeah, it makes sense. Because also here, in Germany, sometimes you wake up in the morning in the winter, when you have complete blue skies, it’ll be a lot colder than if you have a cloudy sky. So it makes sense that the clouds are keeping in all the heat. But then they also, I guess, act similarly, I guess, to the way ice does, how ice just reflects radiation.

BS: Yeah, exactly.

B: But then, so are there certain clouds, where the albedo effect is more pronounced than the warming effect and vice versa?

BS: Yeah, yeah. So people, kind of, break down the clouds and what you… there’s a couple things going on. So the short answer is: yeah. And the second short answer is that high clouds tend to have… are better at having a warming effect and low clouds are better at having a cooling effect, so high in the atmosphere and low in the atmosphere. And the reason is you can think of every cloud as being the same at catching my balls, you know, when I’m the sun. Because they just reflect sunlight. But depending on how high the cloud is above the surface, they’re more effective or less effective at intercepting your balls. So if you have a high cloud that means it’s very cold because it’s high in the atmosphere. So the energy it’s giving back to space is very small. So you’re throwing your balls out, that’s caught by the clouds in between. And instead of throwing every second of your ball backwards, it might throw two out of three backwards, and only one forwards because they’re at a much colder temperature. So that the ability, the greenhouse effect of the clouds depends on the difference between their temperature and your temperature. So when they’re high in the atmosphere, they’re at a very cold temperature. And that makes them very good at trapping radiation. Or better put, I’m very bad at passing it onward and more pushing it back downwards. So that’s why the height of the clouds matters a lot for how much of a greenhouse effect they have. And the thickness of the clouds determines how much of an albedo effect they have.

B: Okay, that makes sense.

BS: And so if you have the cloud of the same thickness, if it’s higher, it’s going to be more greenhouse warming maybe the same cooling, and when it’s lower, it’s very little greenhouse effect and a strong albedo or cooling effect. That said, normally, you know, so one way to think of it is the clouds are always warming at night and they tend to be warming in the winter just because there’s not much sunlight to do anything with. But despite that, the clouds have a lot more solar radiation to work with, even if the sunlight comes out during the day, and the sun only is out in the summer. So this cooling effect tends to dominate on average between the two so clouds.

B: So the cooling effect isn’t, like, the albedo effect.

BS: yeah, the albedo effect of the the the clouds, yeah. If we didn’t have clouds, we wouldn’t be here. 

B: So clouds are more of the good guys rather than bad guys. For the climate changes, global warming.

BS: Yeah, they, kind of, mellow our planet. So they make it less hot. In a funny way, they make it less sensitive to CO2. Although a lot of people talk about it clouds making it more sensitive to CO2 but they forget about half their effect when they say that.

B: You lost me there. So you want to explain that a bit?

BS: Yeah, so a lot of people ask so what do clouds do to our planet – they cool it. So that’s a mellowing effect. Then, the question is: what do clouds do when you have global warming? And a lot of people think, “well, if the clouds change, if there’s less of them, then they’ll cool it less, and if they cool it less, then that will amplify the warming”. And so clouds are kind of going to disappear, and we’re going to have more warming than we would if we didn’t have clouds. But if we didn’t have clouds, then, we’d already be way much warmer and, at these warm temperatures, we’d be much more sensitive to CO2. So that’s one thing. Then, you can say, “well, okay, let’s not compare it to not having clouds at all, let’s just compare to the case where the clouds don’t change.” so if we add CO2, the planet warms and the clouds don’t change or clouds do change. And if we do it that way, then we can find a situation in which the change in the clouds make it look like it’s warming more. But there’s a lot of things that clouds do to cool the planet that we’ve taken for granted in that statement, you know. So depending on how you frame the problem, it can look like clouds cause the planet to warm more than it would otherwise. But that has more to do with the framing of the problem than the real impact of clouds. So another example would be: if you have a cloudy planet, when you add CO2, that does less. Because what you do when you add to the CO2 is you make the atmosphere more opaque and that makes it harder for you to get, you know, to throw your balls out of the atmosphere, so to speak, to lose your energy. But that depends on the CO2 being the thing that’s radiating energy to space. When you have clouds the clouds will be dominating that. And so changing the CO2 will happen kind of underneath the clouds and it won’t affect how you see the planet from space. And so changing CO2 would have less of an effect if you have lots of clouds. So clouds, in a way, mask the effect of CO2. And that, you could think of, as a kind of mellowing effect of clouds. So even if clouds change when the planet gets warmer… increases the effect of CO2. So there’s always with clouds, no matter how you look at it, I guess the one thing people should take away from that rant is that there’s two sides to clouds in just about everything you look at.

B: Yeah, that makes it very confusing when you, I think, study also global warming and you have to take into account the impact that clouds has on CO2 or global temperature rise. Because, like, you, I guess, you would have to calculate – well, these specific clouds, they will contribute this much to warming, this much to cooling. And you have to factor that into, like, your studies. And that’s going to be different all around the world.

BS: Yeah, but sometimes when things are complicated, they become easy again. You know, just because so many things are happening, the first thing they mostly do is compensate each other and cancel each other out. So you can often, you know, and with clouds, you can say, “okay, well, clouds are complicated, they have a big negative effect, they have a positive effect, let’s kind of figure out what would happen if we had the planet at about the same temperature without clouds”. 

B: Yeah. 

BS: Then it’s easy to do. And you have a kind of a baseline, you can do that on the board pretty much. Then you kind of know how the climate would change. And then you can say, “okay, clouds are gonna do things, but it’s not…” you know, the thing that makes CO2 so potent and powerful is it does the same thing, all the time, everywhere. And so CO2 is always reducing the emission of radiation to space at night, during the day, at the pole, at the equator. And this little effect adds up all the time. Whereas if every cloud is doing something different, you’re looking at the balance of many effects. Which ends up being smaller to begin with. So it’s more complicated. But it’s also less of a, probably less of an issue. So you can just say, “well, let’s just assume the clouds don’t do anything”, and then you can, kind of, work out, out of this mess of many different things, does one effect, kind of, stand out more strongly than the others? And I think we’ve had a hard time making the case for that.

B: Okay. And so with global temperatures rising right now, how does that impact cloud formation? And I guess the specific types of clouds that are formed? Because it’s the type of clouds that is important, right?

BS: Yeah, so that’s the million-dollar question. Or, actually, much more than a billion-dollar, trillion-dollar question. Because really, if the clouds, if these low clouds that we’re talking about, if they, sort of, diminish then we would expect the planet to warm more rapidly. But if they don’t diminish, then it would warm less rapidly or less, by a lesser amount for a given CO2. And that, kind of, influences our calculation of, you know, if you believe that, somehow, that you want the temperature not to be bigger than a certain value, then you can ask yourself, “well, how much CO2 can you put in the atmosphere before you get to that value that you set as your target or threshold?” and clouds will influence, you know, what that amount of CO2 is. So if clouds are, kind of, really going away, low clouds, then you can put less CO2 in the atmosphere than you would have thought to stay under a certain temperature target. But if clouds are amplifying the warming, then you can’t put as much CO2 into the atmosphere. So people want to know how the clouds will change. And I think, from observations and theory, we’re having a hard time making a strong case for a strong cloud effect, one way or the other. We kind of hope the clouds would save us, right. That suddenly we get lots of clouds… 

B: Yeah. 

BS: But if we had, if it got cloudier, then you would say, “okay, then the temperature won’t rise as much, so maybe this would, kind of, help us out a bit”.

B: Exactly, yeah.

BS: It’s really hard to make the case for that. There’s the danger that the clouds will go away, and we have different hypotheses of how that could happen. But that doesn’t seem to be, on the surface, a real strong effect at the moment either.

B: So are we seeing more cloud formation or less cloud formation? Because that’s also no one knows.

BS: I think that’s hard for the data… I don’t think a real consensus has emerged if we’re seeing more or less. I think you can find examples…

B: I just thought that maybe, like, because the oceans are warming you’re getting more evaporation and so then you’ll increase the formation of clouds, right?

BS: Yeah. Yeah, kind of the way to think about the ocean evaporation is… so you can think about it that way but the ocean accumulates the heat from the sun and it loses the atmosphere. And the atmosphere is as green out as the atmosphere so it’s losing radiation, you know, throwing the balls back to you and me, it’s kind of getting rid of its energy. And so energy has to be put back in the atmosphere so that it doesn’t get too cold relative to the surface of the Earth. And the way that energy is put back into the atmosphere is through convection, through making clouds. And so the amount of rain we get on the planet, it’s about a meter a year over the whole Earth averaged. So that amount of rain is the amount of rain we need to transfer the energy from the surface into the atmosphere to balance the greenhouse effect. So the greenhouse effect actually determines the global average rainfall. And clouds form, in large part, not only, but in large part to make rain. So from that point of view, you would say, “well, we need more rain and then maybe we would have more clouds because we have more evaporation”. But there’s lots of other arguments which, kind of, show that as you get warmer the difference between an unsaturated atmosphere and a saturated atmosphere is larger. Just, kind of, like, you know, how you always kind of feel damp in cold weather and you can feel really dried out in hot weather, not always, you can feel humid hot weather too, but the humidity, absolute humidity differences are much larger as a function of temperature, increase as a function of temperature. Which makes cloud formation, in a way, a more special situation at a high temperature. So again, with clouds, there’s always a good argument for one way one effect or the other.

B: Okay. So you also said that you study water vapor?

BS: Yeah.

B: So what about water vapor?

BS: Yeah, what about water, is pretty cool.

B: Yeah, I know.

BS: The water molecules are pretty fascinating thing. And so if you look at the water molecule, it’s this two little h’s and the big o. And it’s a real tumbling molecule. It turns out that oxygen, which you probably know better than me, is really good at keeping its electrons. And so water vapor has, what you call, a big dipole moment. So it separates charge really well. And that means when you turn it, you’re, you know, accelerating a dipole, you know, by turning it. And so tumbling motions of the water molecule are really good at radiating energy or absorbing energy. And so the water, I like to think of the water molecule as a really happy molecule: it’s just taking all sorts of energy in and giving all sorts of energy out. And this means that, in the atmosphere, the water sort of dominates the greenhouse effect. So in the infrared, you have these rotational bands of water vapor. And then, the a rotational band is just a coupling, and then, the water molecule will vibrate. So these would be, the two my fists would be the two hydrogens, my head the oxygen, and it vibrates and tumbles. And this creates a really really rich absorption spectrum, which makes our atmosphere only able to radiate energy to space in a fairly narrow range of wavelengths between this viral vibrational band and this rotational band, in a range of about 10 microns wavelength, 800 to 1200 inverse centimeters. Yeah, so water vapor imprints itself completely on our atmosphere. And it’s a wonderful thing because the atmosphere, it’s an expansional atmosphere, you know, all atmospheres on planets are expansional. That means that the pressure of the atmosphere depends on the weight of the atmosphere above you. So as you go up, the atmosphere is less pressure, less weight above you. And it expands. And when you take a gas and expand it cools. So as you go up in the air, the atmosphere cools. But that means the saturation vapor pressure of water is less. So it acts like a filter as you evaporate water at the surface, as it’s transported upwards, then you will find air that was subsaturated, the surface rapidly become saturated. So clouds are often associated with upward motion. And that forms the, you know, water vapor saturates, it forms condensate, the condensate coagulates and falls down as precipitation. And when you get to the top of the atmosphere, you have a much drier, absolutely, atmosphere because a lot of that water has been sort of quenched from the air through this, sort of, you can think of it as a sort of cold drying process, you know. So you can dry air out by cooling, condensing the water out, and then… so the atmosphere is this, sort of, what would you call it, kind of a humidifier or dehumidifier. So as you move air up, you take the moisture out form rain, and when it comes back down again, it’s very dry. So water vapor is very interesting because it traces the motion of the air. Air that has been very lifted very high and then comes back down is very dry. That’s why, when you’re kind of in mountainous regions, as you have kind of flow on the upslope part of the mountains, tends to be cloudy. Like, if you think in the united states, you think of Oregon, or if you think on the, I don’t know, if you look across the Pyrenees, if you have the westerly winds or something like this, then it would tend to be or is often cloudier, and then, on the Mediterranean side, it’s drier. The alps… did you say? 

B: Yeah, near the dolomites. 

BS: Yeah, and then you’re kind of, you know, as the flow goes over the alps, one way or the other, you have the Fön or the downslope winds, I don’t know what you would call it. If you had northerly flow from Europe going over the alps and then it descends over, say, Milan, then that tends to be very dry because it’s been dehumidified. So water vapor is kind of neat because it has this really big effect on the atmosphere. And it’s such a wonderful tracer of air’s motion. So, you know, you can kind of tell where the air has been by how moist it is. And so the water vapor is a nice… so it’s a very dynamic variable. So that makes it interesting to study, you know, what are the circulations on Earth, how does that determine the amount of water vapor and so on.

B: Yeah. And so how does… an increased amount of water vapor, how does that affect global warming, for example?

BS: Yeah, so that’s…

B: That also another complicated thing, kind of, like the clouds?

BS: Yeah, there’s… we think… you know, so the difference between CO2 and water vapor is what we call a long-lived greenhouse gas and a short-lived one. And the short-lived ones have a real strong thermostat, they’re temperature controlled. Because with water vapor, if it gets too cold, it saturates, it forms a liquid. And so, if we think of water vapor being controlled by temperature, then what happens is that it narrows the range of wavelengths where we can emit more energy to balance the greenhouse warming from CO2. And if the water vapor would increase even more than you would expect based on this temperature control, so if the relativity humidity would increase, then this would be a strong, what we’d call, a positive feedback or a weakening of the negative feedback, which would mean that for a given amount of CO2, the Earth would warm much more. So I mean, these are complicated things to talk about at a coffee table because they work better with lectures and diagrams. But if the relative humidity were to increase, that would strongly increase the sensitivity of Earth’s surface temperature to, what we call, forcing CO2 increase in sun whatever. And if the relative humidity were to decrease if, for some reason, the atmosphere would dry out in a relative sense, in terms of relative humidity, then that would reduce the sensibility of surface temperatures. But the working hypothesis, and there’s good reason to take it, is that the relative humidity is relatively invariant as a function. Of temperature and you can kind of see that if you look in the summer and winter. It might feel more humid or something like that in the winter. But if you just made a graph of relative humidity, you would see the absolute humidity changes a lot and the relative humidity changes quite little. And if we look over the climate record, what we also see is that there’s not strong evidence of big changes in the relative humidity, even though the absolute humidity would be changing a lot.

B: Okay.

BS: So I don’t know if people are familiar with the difference between relative and absolute humidity?

B: Yeah, I think maybe it’s beneficial to just explain the difference.

BS: So absolute humidity is just the total number of water molecules, you know, if I capture some air, how many water molecules do I have? And relative humidity measures: how many do I have relative to how many I would need for the air to be saturated? And how many you would need for there to be saturated depends on how warm it is, you know. And you can think about those water molecules, they’re saturated, when they’re more likely to condense or as likely to condense as to evaporate. And that depends on how quickly they’re moving, you know, you can, kind of, catch them. So if you warm them up, they’re moving a lot more so the pressure the number of molecules you have to have before they become saturated increases, and it increases exponentially with temperature. So this is… so for a given air parcel, if you warm it a lot and keep the relative humidity the same, that means, since the saturation humidity increases with temperature, also the absolute humidity had to increase with temperature if you keep the relative humidity the same. If you keep the absolute humidity the same, then the relative humidity will drop as you increase with capture. So anyone listening to this, if they’re still listening to this, they can just hit rewind and then they can hear me say that again.

B: Yeah, yeah, okay. So we’ve talked about water and clouds. Are there any other air pollutants that you study? Like molecules in the atmosphere?

BS: Not too much, I tend to focus on water. I mean, there’s several other minor and not so minor greenhouse gases that people… I mean, there’s CO2, which I study just from how it works in terms of the radiative transfer of the atmosphere. And a lot of the other greenhouse gases behave roughly similarly, like nitrous oxide or methane or ozone. But I think it would be a bit of an exaggeration to say I study them.

B: Yeah, have you ever looked at acid rain? I mean acid rain was a problem in, like, the 1980s, it’s not really an issue now, but I was just wondering whether you also studied that? Since, I guess, it’s kind of related.

BS: So I’ve studied, you know, particulate matter in the atmosphere. So when you think, “what is the atmosphere?” what is the atmosphere?

B: Well, it’s oxygen and nitrogen, right?

BS: Yeah, so gases, you think of gases. But there’s also loads of particulates.

B: Well yeah, like aerosol.

BS: Yeah, exactly. So there’s a little particulate. And there’s condensate, which is clouds. And there’s things, sort of, in between. And then there’s sort of biological matter viruses, mostly the viruses are attached to other things, but, you know, fragments of biological matter, dust particles. So there’s a host of smoke, these are all different forms of particulate in the atmosphere. The aerosol, you know, the word “aerosol” is just the word for a dispersion of one phase and another phase. So you can think of, bubbles in your glass of water are an aerosol because they’re a dispersion of gas in liquid if the water is constantly flowing.

B: It’s kind of like sprays as well, right?

BS: Yeah. Yeah, so sprays are called “aerosols” because they’re the dispersion of some condensate thing that’s coming out of the spray in the gas. So I study… an acid rain was about the emission of SO2 from burning fossil fuels. And that led to an increase in a certain type of particulate in the atmosphere, which would then be rained out. And so you would emitting a lot of SO2, and then it would be formed into an acidic form that would then be rained out and collected in the soils. So basically, the atmosphere was acting like this wonderful, “wonderful” filter, right, because you’re letting go all of this SO2 from fossil fuels. And you don’t want to accumulate that in the atmosphere, that would be nasty. But the way to get rid of it, it led to the formation of more cloud particles, and these would coagulate rain, and the rain would be more acidic, and that gets deposited in the soil. So what I’ve studied, not so much on acid rain, is how these, what we would call “anthropogenic”, particulate matter aerosols influence cloud properties. So there’s thinking that if you have more… clouds tend to form on pre-existing particulate. And when a cloud forms, if there’s more particulate, then the cloud will distribute its water in a more fine-grained way. So if you have lots of particulate, then you’ll have maybe the same amount of cloud water but it will form on more particulate matter, making smaller droplets.

B: Okay. 

BS: And so, if you take a cloud, it’s many little droplets. And if you have a certain amount of water and you have lots of droplets or fewer droplets, then that water will be spread over many fine droplets or a few big droplets. And it turns out the clouds are better at scattering radiation if you distribute their mass over many fine droplets rather than fewer thicker.

B: So it’s good to have aerosols?

BS: Yeah, they’re kind of cool. They’re kind of cool.

B: They are kind of cool, yeah. They cool. Okay, so air pollution is great.

BS: Well, that led to some people, you know, so… we’ve managed to turn that into a threat because the thought is that: had it not been for the concomitant rise in aerosol over the last 50 years, I mean, say, between 1950 and 1980, that we’re emitting a lot of aerosol, which was cooling the planet, a lot of CO2 which was warming the planet – the thought was that if we clean up the air, you know, we have to be afraid of clean air – because we clean up the air, then that was masking a bunch of CO2 warming, and that would go away, and then we’d get the shock, and the planet would be a lot warmer so yeah…

B: So that makes sense to me. And actually, that’s why I’m also here to talk to you about that. Because it’s just very intuitive for me to think that, “well, if we make the air cleaner now, we’re just going to see a rise in temperatures”. But that’s also, like, a really strange way of thinking about it because everyone would be like, “no, we don’t want air pollution!”.

BS: Yeah, I don’t think we have to be afraid of air. I think the argument that… it’s been really hard to show that the strong effect of the aerosol on the clouds has led to substantial cooling. And it’s also hard to think that, you know, what we’ve seen is: we’ve cleaned up, I mean, if you look at the sulfur emissions or the emissions in the Atlantic seaboard, so Europe and the united states, they’ve just gone down drastically since the 1980s. Other places are more…

B: You mean like acid rain?

BS: Yeah, acid rain has gone way down. But also just the particulate matter, so the essential emissions have gone way down. Because people scrub the power plants and they take the SO2 out, source, so it’s not going into the atmosphere, it’s not forming particles, the particles aren’t changing the properties of the… aren’t there to change the property of the clouds, they’re not there to rain out and poison the soils or acidify the soils. And so that’s been enormous changes but overall, there’s many other ways in which the humans make particulate, not all of it… I mean we went from a few very, like, if you look in the late 1800s, I think London was responsible for 5% or 10% of all the pollution in the world, so we had these very concentrated limited sources. And if you live there, it’s pretty nasty. And if you spread London over the whole world, it’s less nasty, it’s much cleaner on average. Everyone’s a little bit influenced. But the total aerosol load hasn’t changed because you’re just putting just as much in. So this idea that somehow the world is going to be super clean like it was before people were here seems hard to fathom. You know, so this idea that somehow we’re going to clean up our air, we need to clean it up locally, because people are going to find other ways to pollute non-locally, right. Because people are spreading around to more and more places. So we should clean our air, that’s for sure. But somehow the idea that we’re going to get it so clean, it seems far-fetched. And so that’s one reason I don’t think, you know, cleaning locally doesn’t mean cleaning globally. Because, in a way, you’re just compensating for someone else’s mess. You can say, “well, that’s not so great”, but that’s the reality. So we won’t change the amount of aerosol in the atmosphere as much as maybe we once fantasized. And the effect of the aerosol in the clouds, it has been more difficult to show a real strong effect. You know, at the beginning we had all these ideas that can, you know, have this huge effect. But they haven’t really panned out that well. I mean, there is an effect, that’s for sure, but it’s not as overwhelming.

B: What about in places like India or Nepal, for example? There’s, like, a lot of air pollution there, so, I would assume, a lot of particulates in the atmosphere that surely then contribute to cooling?

BS: Yeah, if you have clouds. It also contributes to warming because the aerosol can absorb…

B: Exactly, actually, I said that, I was, like, “wait, does it lead to cooling? No it also leads to warming”. Okay, so I guess, because my question would be, like, can we look at the global temperature rise in certain regions and then, based on how many clouds there are and how much air pollution there is, see, like, how this correlates?

BS: Those are kind of the games people play. But it’s difficult also because it’s hard to, sort of, separate one region from the rest.

B: Oh yeah, that’s true. So then, how do you study everything? Is  everything based on climate models?

BS: No, no. No, god forbid. People use climate models in different ways, there’s a whole another discussion about how science works there. The way I tend to use models as ways to kind of help me work through my dumb ideas. So you kind of have an idea of something how something might work, and you could put it in a climate model, and then you realize, “oh yeah, that was stupid”, because something really obvious happens. It’s just a way of logically progressing through your ideas. And once you’ve got your ideas to the point where they’re not obviously stupid, then you can ask if they’re right. You know, just because they’re not stupid doesn’t mean they’re right. So you want to catch the dumb errors. And then use the models and they say, “well, this looks like it could work like this”. But it’s just an idea factory because then, if you have an idea of how the world works, you should be able to measure it in some way. So often we use the models to, kind of, help us generate hypotheses, which we then could measure. So in climate sensors, at least my work, there’s a fairly good mix of simple theory, which you can do on the board, like, the greenhouse effect, working through the absorption spectrum of water vapor, you can do a lot of that pretty analytically. Simple models of how clouds interact, you know, in one column with another column, you can do, you can create kind of toy models or conceptual models, which would be kind of pencil and paper work. There’s simulation, where we try to simulate fluids, you know, and try to be true to the physics. There’s modeling, where we’re not actually using the right equations but we’re using things that seem like they’re plausible. So the difference between simulation and modeling: they’re both, you know, computer calculations, but sometimes you can use a computer to solve equations, which you know are the right ones, and you just can’t solve them by hand, and sometimes you can use computers to solve equations that you made up and you, kind of, hope that they’re the right ones. So simulation, modeling, you can use the computer to kind of work through your ideas. And then we fly around, and make ground stations, and measure clouds and aerosols and water vapor .So we have a lot of measurements. And then we use data that comes from satellites and observational networks and so on and so forth.

B: Yeah, and so do you use then all this data to, like, also predict what’s going to happen in the future? Or do you think that’s just too challenging to do? And I guess, this isn’t just in your field, this can also be a general question. Because a lot of this study of climate change and global warming and all that, I think a lot of people try to use data to then predict what can happen in the future. What are your opinions on that?

BS: Yeah, “predicts”, it’s kind of a big word, you know. It depends what people mean by “predict”. So if you mean by “predict” answering that thought experiment: what if I put twice as much CO2 in the atmosphere, how much warmer would it be – then I could, kind of, predict how much warmer it would be. And that, in that broad sense, it’s predict or anticipate. There’s also the predict in a more specific sense. But they’re more like… it’s really hard to predict what Hamburg would look like in 100 years because you have to know many, many things, not just how the climate system works but how people evolve and how CO2 will be emitted. But you can play these thought games: you can say, “well, if we have twice as much CO2…” I mean, these conditional predictions: if this and this and this and this happens – what will be the world look like? In that sense, of course, we predict… so we try to predict, we say, “well, there’s twice as much CO2”. But the conditionals are normally fairly general. So we say, “well, it’s a world, in which we have more aerosol and more CO2, or less aerosol, less CO2, or we have changing vegetation at the surface. So we, kind of, make these conditional statements about what the future could look like. But the prediction should really be a reasoned prediction, you know. So if I predict something, I should be able to explain it to you. And you should have the idea that you could eventually understand what I’m saying, even if when I explain it to you the first time you don’t get it. But it should be reasoned. There’s a lot of prediction, when it goes to models or things like that, that isn’t reason, it’s just “trust my model, and if you trust my model, this is what the model says”…

B: Yeah, so that’s, generally, what I find so hard with models. Because then, like, they’re not explained very well. Because they’re just extremely complicated and complex. And then I just have to, like, look at them and believe them. It’s like, well, how are you factoring everything in? For example, like, I don’t know, if you maybe use a model or something to predict how precipitation might change in the following years, I don’t know if that’s something that you guys do?

BS: Yeah, but I would do it a different way. You know, so people do that, you know, I would say, “well, let’s see how the precipitation change”, and then you try to figure out why the model does that. And if you understand why the model does, you should have the aspiration to understand what the model, why the model does something. And it should be explainable or reasonable. Reason-able: I mean that you can use reason to untangle why that happens. And if you can’t, then you’re not really… you might as well just go to church…

B: Yeah, but who designs the models?

BS: We build them.

B: Okay, so you build them. So then you can build them the way that you want?

BS: Yeah, we do that too. You know, when I first came here, I tried to build a model that wouldn’t work just for fun. I said, “what do we have to do to make a model that doesn’t…” 

B: Yeah, that’s really cool! That’s awesome!

BS: Yeah, right. Because can you do it? And then what we found out, there was this idea that somehow the atmosphere would dry out and that would allow it to let a lot of heat out. And we couldn’t make our model do it naturally so we said, “let’s just cheat”, you know, “let’s just put a fudge factor in the model that makes it dry out”. Just to see how it works. Not because we think that’s real but we’ll, say, pretend this person x, who thought this, this guy’s name is Diglins and he was an MIT professor, who’s a bit of an honorary intellectual, who doesn’t believe in climate change, and he came up with this hypothesis that “no, what’s going to happen is that the tropics will get wetter in the deep tropics, but the broader subtropics will get drier, and then we’ll lose a lot more heat to space, and that will keep us cool”. So we said, “okay, he’s a smart guy, let’s just pretend he’s right and we’re wrong. And we can’t make our model do that, but let’s fudge it. So we’ll put in that effect.” and what we found out, which we hadn’t thought of before, was that if we tried to dry out the atmosphere, the clouds went away, you know. And that kind of worked in the opposite way. So that’s kind of a way, where you try to create these counterfactuals, you don’t have to believe everything you put in the model, but you have to say, “well, if he’s right and it works like this”, and then you suddenly realize something that you didn’t realize before, which we hadn’t been thinking about before – that it’s hard to dry out the atmosphere and keep the same amount of clouds at the same time. And so to keep the planet cool you need to dry the atmosphere. But if you dry the atmosphere, then you just make less clouds and the planet warms. So these things are in tension with each other. And so that’s why it’s good to be able to, kind of play, with the models to help you again, you know, work through your thoughts and reason your way to ideas.

B: This might be an ignorant question now but like what do you use, how do you make models? Like is this…

BS: So they’re computer models. So that means, they’re algorithms, lines of instruction, which are… you know, at the core of a modern climate model is moving, you know, the atmosphere is a fluid, in the sense, it behaves the laws of fluid mechanics so that means… normally, when people think of fluid, they think of a liquid, but a gas is also a fluid. And that means it moves and flows like a stream of… we just don’t see it so, we don’t see how it has all these currents. So the atmosphere is a fluid so at the core of a climate model is solving how the wind flows, the ocean currents move, how that depends on their temperature, how that leads to pressure gradients. We try to, you know, balance the wind accumulating in one place or another. So these things we have laws for, I mean, we know the equations for so we solve the equations of fluid motion on as many scales as we can fit into the computer. And radiant energy transfer, we kind of understand how that works. So we can write down algorithms that tell us how photons move through matter and if they get absorbed, or scattered, or things like that. There’s other things, where we might understand how they work on a microscopic level but we are not allowed, we don’t have enough computer capacity to solve for them on the microscopic level, so we have to provide a macroscopic description. And we don’t have one. So a tree, you know, what’s the equation for a tree? Maybe you could understand how the water moves through the, you know, different parts of the tree, on that molecular level or something like that you could. But an equation for a tree as a whole, you know, that just doesn’t exist.

B: It’s so funny because, when I had the podcast with Jochem, he said the exact same thing: “we don’t have an equation for the trees”. Like the tree is the perfect example.

BS: Yeah, we sue it a lot. I use the tree because everyone knows what a tree is and everyone can understand, you know.

B: But it makes sense, yeah.

BS: And so the models we use are algorithms. And they’re partly based on laws, fundamental physical laws, which are incomplete in sometimes important ways. And to complete the equations, because we can’t describe everything that we need to make the whole system complete, we have to make things up. And we try to do that in a way that captures the main effect in a reasonable way. And so then you can say, “well, how do you do that?” and that’s why we’re here.

B: Yeah. So going back to how you would study whether there is an increase in precipitation over the next 10 years. And you said, you wouldn’t use climate models?

BS: I would, to get myself ideas. But then I would go on and ask what those ideas are. So you can run the model, see what it does. But that’s only the first step, then you have to ask yourself” does that make sense? Do you see a sign of that in the data? One of the things is that we can’t measure everything. So if you’re clever with the models, or part of the game, is to use them to help you understand what you should measure, since you can’t measure everything. So to be… it’s, kind of, a… or, you know, you have to frame your hypothesis in a way that it’s observable. So that the model should be ways that can lead you to something that’s observable that would be consistent with your reasoning. So you see the model does this, this, and this. And then you say, “well, if I’m right, if that’s really how it works, then I should be able to measure that”. And that’s the game we play. And then we try to go measure it. And we saw, ah, I might be right, you know. But, of course, just one. Then you say, “okay, looks good, what else would I expect to measure?” I can measure that and say, “oh, it’s looking better, I’m happy”, right.

B: So what about these extreme weather events? Can you talk a bit about those? Just because a lot of times in the media you see that there’s like an increase in extreme weather events happening right now, which are because of climate change. So is that also something that you study or can you just give your opinion on that?

BS: Yeah, I wouldn’t say I studied a lot but I do spend not a small amount of time thinking about it because it’s sort of motivation. If you think of it, if you heat the system up, you’re just going to kind of sample a wider range of things in a sort of naive way. But you can think about that as the Earth as a whole – if you’re heating the Earth up it’s just kind of, it has a capacity to maintain more water vapor, everything becomes a bit more exaggerated in a way. So on some, very basic level, it doesn’t come as a surprise that, you know, an example of the only state where nothing happens is, you know, state of absolute zero, if you take that. So the hotter the system is, the kind of more that can happen – you can kind of think of it that way. But that’s a far, far, far away from being able to say, “well, we’re actually seeing more extremes: more tornadoes, more hurricanes, more floods, more heat waves, more droughts”. Some people even say more cold snaps out of, you know, a funny argument. And that’s really hard to say because we’re talking about things that happen fairly rarely. And so how do you test these ideas? So people, of course, will run a model and they’ll show that the model makes more extremes but yeah…

B: Yeah.

BS: But that’s, at most, a first step. And I think being specific with extremes and, in the end, and something that makes extreme an extreme is that it has impact. And impact is this coincidence of something unusual happening somewhere unusual. So if you have a heat wave over the ocean it might affect the biology of the ocean but it’s different than if you had a heat wave over new york city.

B: That’s like this happened like last year or two years ago, where they had that volcano near, close to New Zealand and that volcano, that happened like in the ocean, was just, you know, in the end, didn’t have an effect really.

BS: Right, imagine if that went off in Brooklyn, you know. 

B: Exactly, exactly.

BS: So the extremes are really… and they affect different things, different ways, right. So they’re hard to understand how extremes will change and how that will impact societies. You can even take a step back and you can say, “well, forget about Earth changing”, you know, how susceptible, you know, in China, you see all these cities have kind of risen up out of nothing over the last 20 years. And in Africa, they’re hot at it in terms of making… there’s a lot of urbanization happening in Africa. So some of the biggest growing cities, I mean, most of the biggest growing big cities are in Africa at the moment.

B: Yeah.

BS: And are they vulnerable to extremes? You know, because they’re building these huge urban areas and there’s not a long record of measurement there, you know. So how often when you build a giant city in the north of Nigeria, how often do they have record floods, you know? No one really knows, they weren’t measuring. And so trying to understand the vulnerability of infrastructure investments people to extremes, and then on top of that trying to understand the future vulnerability of people to extremes because the climate’s changes, is a big deal because it has to do with huge investments but it’s also a very challenging problem.

B: Okay.

BS: So I think, in general, you could say, “well, there’s good reasons to expect, as the planet warms, that you would see more extremes”. But that’s not really that helpful. Because if you want to deal with this, you want to know. You can just close your eyes and say “we don’t want it to warm”, that’d be nice.

B: Yeah.

BS: The reality is it’s going to warm and we’d like to be able to scientifically help people adapt to this or to make wise choices about how we invest in infrastructure, you know, so…

B: Yeah.

BS: I work in Barbados a fair amount. And there they have the choice: can they invest their money in protecting them against floods because it’s going to rain too much, or desalination because it will rain too little and they need fresh water. So those are two very different decisions and what do you do? 

B: Yeah, what do you do?

BS: They kind of, they built desalination for a while, people said it was going to get drier. But then it kind of, there’s this one report I found, it was really great, they had to stop work on their desalination plan because it was raining so much in the dry season, right, you know? So…

B: Yeah.

BS: So can you do this more intelligently? Or do you just, kind of, have to iterate your way through.  Maybe that’s it: you just have to prepare for everything and, kind of, let time select, you know. So you try to do both but normally you can’t do both in a lot of places, so yeah…

B: But you do think that, with the global temperatures rising, we should prepare for, potentially, an increase in extreme weather events? Or it’s just so hard to say, in the end, you just have to invest in the science to find new solutions to, kind of, protect you?

BS: Yeah, I probably use that word, “should”, a lot but I always try to avoid that “should”. 

B: Oh yeah. Just because a lot of what you see in the media right now is – there’s more hurricanes, right, or more extremes. 

BS: Oh, it depends what papers you read.

B: Yeah it’s actually, it could be. 

BS: If you read The Guardian, then, you know, The Guardian took it upon the ivory, The Guardian. But they took it on themselves too, they felt like they had a social imperative to warn people about climate change. So a few years ago they made it a point to really keep climate change in the public eye. And other papers kind of feel just as compelled to, kind of, talk down the climate change. So the media is often following an agenda that they have, and so you do read about extremes because people like reading about extremes. It’s fun.

B: Yeah, it’s fun, it’s interesting.

BS: Yeah, and if you can tie the extremes to climate change, then it also fits a point of view that… which makes it really hard for normal people just to figure out what’s really going on.

B: So that was actually my next question, as well. You, as an expert, like, I guess you can read a bunch of news articles and know like, “oh, this is not true” or “this is the right one to read”. Whereas normal people, I mean, you just, you look at everything, you see so many different opinions.

BS: Yeah, it’s very speculative on the extremes. And I think the science is still very speculative.

B: So the science is still speculative? 

BS: Yeah, I think the science isn’t helping us here, you know. I think you can use the principle that, if you don’t know what’s going on, you probably shouldn’t mess with things too much. So I would tend to be conservative, in the sense that, why would you want to heat up the planet two degrees if you don’t really have a good understanding of what that means? You can’t evaluate the trade-offs. So that would lead me, from this point of view, to be saying: “we should reduce emissions”. And I think that’s a perfectly, you know, good argument to make. Other people think that they’re in a public relations situation where they have to convince the public something really bad will happen if they don’t do it, rather than saying something bad could happen. And they think that’s the only way to make sure that, collectively, we as humans behave, in their eyes, responsibly to, you know, guard against the risk. But it’s really a risk calculation. And there’s some things where we have, I mean, in general, there’s things that we do know, you know. So things will happen, but not in a way that we really know where, and when, and how strong. We would expect the, you know, the amount of rainfall you can produce in a storm will increase with temperature. And we know that. I mean you don’t need to be a climate scientist to know that, you just see how hard it rains in winter compared to summer. I mean go to tropics and you’ll just get nailed by a torrential storm, and that’s just basic physics. So there’s some general things we know about extremes, which make you realize that, as you have a warmer world, extremes will change in a certain way. You know, this idea of, like, if you look in the Mediterranean, and imagine that, you know, in the Mediterranean, you tend to have winter rains and summer dry, that’s a, sort of, typical climate pattern. And so if you have a lot of rain in the winter, because the rainier things rain more, and there’s good reason that you can explain that, with that water vapor argument I gave about how much water you can hold in the atmosphere depends on temperature, so the difference between saturation and dry is larger. That means that when you’re saturated it’s got much more water and when you’re dry it’s relatively much more drier. So that means, when it rains in the winter, it rains more. And when it’s dry in the summer, it dries out quicker. And that’s just a wonderful ingredient for making fire. Because you just grow a bunch of fuel in the winter and then you can burn in the summer. So you kind of expect these things to happen and you can, kind of, go out and say, “well, they’ll happen everywhere, all the time”, or you might want to say, “actually, you know, there’s ways in which we can plan for that”. And that’s the scientific challenge is trying to be more specific about extremes. And normally when you read about extremes in the paper, and that’s where I’m maybe coming across a little bit more sceptically, is that they’re often talking about the specific and they’re using the general as the argument. You know, just because in general, this happens doesn’t mean that this storm wouldn’t have happened without this tendency. And we can’t really show that this storm or that storm or three of these storms, it’s very hard to show that these are really due to warming. Some of these things will happen without warming.

B: Yeah. Yeah, how do we know, like, how many of the weather events, for example, are due to anthropogenic warming and how many are due to just natural variability?

BS: I can tell you how people calculate that and then you can decide if you believe it or not.

B: Okay.

BS: So they take a model and they try to make a model simulate something, like, was observed. And normally it doesn’t look that much like what was observed, it’s sort of close. Or you just take a model and you take, you know, you had a flood so you take a model and you make it have the same flood. Same flood in a sense that it was, you know, a 10th percentile flood or one of the most extreme floods that we’ve measured. And then you can ask yourself in the model, “well, if we look at this similar sort of thing, how often would this have happened, if we hadn’t had warming, if we do have warming”. So you can play these, sort of, counter-factual games but it all relies on your model being correct. And we know the models are wrong. So the question is: are they wrong in a way that makes that quantification difficult? And I always think, like, when you read that in the paper, you should ask: if they say that the storm was 30% more likely in a warmer climate. 30% plus or minus what? You know, it’s not like they can calculate 30%. But, you know, until you can put an error bar on your estimate, it’s not really an estimate. Because it could be 30% plus or minus 200%, then is it really saying anything? And often it is 30% more likely plus or minus 200%.

B: Yeah.

BS: You know, so really, it could have been, you know, three out of five times, you know, it could very well have been less likely, given the uncertainty of the measurement, you know. So yeah, I don’t know if there’s a good example for people but if I say, you know, I see a person on the street and I say they’re two meters. Or, you know, I say, “can you give this book to, you know, our friend Joe?”, and he said I don’t know Joe, and I say, “well, he looks like this and he’s two meters tall”, then, you kind of, think I know two meters. But if I really meant, you know, well he’s somewhere between 50 centimetres and four meters, then that would be completely useless information to tell you that he was two meters tall. Anyway, so this attribution stuff – people like to hear it, people want to read about it, but I’m, kind of, sceptical about. I think we just like talking about climate change, to be honest.

B: Well, yeah, it’s a hugely politicized topic right now. It’s just everywhere, everyone’s talking about it, so many different opinions.

BS: Because we’re not doing anything about it, you see. I think you talk about things you don’t do things about. So we must prefer talk about it because maybe it makes us feel better about not doing anything about it, I don’t know.

B: So do you not think that we’re doing enough for climate change? And if you, obviously, say “no” to that answer, then what do you think we could do about it? Or what more could we do about it?

BS: So I think climate change is a class, of what’s called, Anthropocene problems. And then you can say, “well, what’s the Anthropocene?” and so we think the Anthropocene is this age where individual actions scale globally. And so most people talk about it as sort of the imprint of humans geologically on the whole Earth, like in terms of pollution. But you also see it in finance, you know. You couldn’t have had the amount of wealth that Jack Bezos has, comes from the fact that he just can’t sell in his town or he just can’t sell in his country but he can sell his products worldwide. So you just increase the scale at which how people can scale their activities globally. And when people individually can imprint themselves on the planet globally, whether it’s in finance, or pollution, or terror, or whatever. And you don’t have a way to regulate that, you create problems. And so a lot of the problems we have are, on one hand, there’s this ability to scale globally. So we emit CO2, and it affects the world globally. If it only affected something locally, then you can deal with that, you know, like, if it’s only in the house and somebody is, you know, I don’t know, not opening the window in the bathroom or something, then you can make a rule that says “you have to open the window in the bathroom”. Or they’re not doing their dishes, you can say “you have to do the dishes”. And then there’s all sorts of procedures for doing that so we can solve those conflicts locally, not perfectly but roughly. We can solve it in communities, you know, if people are behaving poorly in public, or they’re, you know, using unfair business practices, or they’re not you know paying taxes, or whatever. We can solve them in the community, we can solve them nationally. But the problems we have aren’t people. It’s not that people aren’t doing dishes, they’re just not doing everyone’s dishes, globally, right, you know. And we haven’t figured out how to govern ourselves globally. And global governance for most people sounds frightening because, you know, that’s sort of like, “oh my goodness, it’s even worse than…” but, on the other hand, we have these problems, which are global, and I don’t know that we’ve come to terms with that, the fact that we have global problems that we have to solve globally. And we just don’t know how to do it. And we’re just kind of looking away from that. 

B: So it’s like every country is kind of dealing with it but within the country.

BS: Or not dealing with it.

B: Or not dealing with it. But we should rather be, like, all coming together and…

BS: Yeah, but that’s so much easier said than done.

B: I mean, it’s impossible basically. 

BS: Yeah, so that’s why I just don’t know how… so one way that this works itself out is that we find technological remedies. So that’s one hope that people have is if technology comes up with solutions that make it easy to avoid a problem. And there’s lots of examples of that, I guess, in the past, although please don’t ask me to name one.

B: I was just gonna ask you, “give an example”, but no…

BS: You know, maybe with CFCs is the example that people use, you know. Or now we’re seeing with electric cars that we can, they’re really growing, you know. And so when we can do certain things technologically, then we don’t have to solve them socially. And so that’s a way a remedy could happen is that it just becomes more attractive to do things a different way. And we get out of the problem that way. If it really comes push to shove where we have to make rules…

B: Well, it’s not worked so far.

BS: Yeah, it’s hard to imagine that that would work because I don’t see them… yeah…: But then, yeah, so this is where I, kind of, I agree with that, or I’m more of the opinion that we should really be looking for solutions to problems. And this is where we should have to rely on science. And this is where I’m also optimistic that science will be able to find certain solutions. Because if we just go via the “we need to reduce emissions” and, you know, “we need to do this, this, and this”, and people need to follow those things, I just don’t see that being very efficient.

BS: Yeah, I don’t see that happening. And so we can all wish it. But wishing something is very different than getting it. Doesn’t mean that we shouldn’t try. But our focus should be: how can we incentivize good behavior and how can we incentivize good solutions? Rather than how can we attract to… regularly, it might be the wrong word but, you know, it’s hard to be moralistic about it, you know, because we’re, you know, saying people shouldn’t…. Yeah, it’s a lot. I mean how can… it’s hard to tell other people what they should do, you know.

B: Yeah.

BS: You need to present them with better choices. And have faith that they will make the good choices. But trying to make the choice for them, I find, always it’s not a very successful strategy. And so if we build our strategy on a sort of making a choice for people, it doesn’t seem like a winning strategy to me.

B: Yeah. Yeah, the biggest problem that I have with that is that, in the end, it’s the politicians that make the decision for you. Because they’re the ones that make the decision. But then, what influences what the politicians want you to do is, in the end, the public’s opinion. Because politicians will do anything to be in power. So then, in the end, what you want, which might not be the best is, in the end, what they will tell you to do because they want to stay in power.

BS: Yeah, that’s where I think some people. Yeah, who knows if I see this right, but some people kind of, like you said, they think that what politicians do is that they try to tell people what to do or regulate society. But mostly they’re just, the job of a politician mostly is to get reelected. 

B: Yeah. 

BS: That’s what they do. And then it’s so it’s kind of reverse, you know, the politicians are really trying to sense, within their moral comfort zone, you know, but they’re trying to figure out how to get elected. And so there’s a little bit of nudging going on in a positive way. And also the media, you know, a lot of people think that the media exists to inform the public. So there’s this idea in people’s head that the media sells information to the public. But really the media sells consumers, readers, watchers to the advertisers. So what the media sells is not information, they sell readers. And when you realize that, it changes your whole view. Because what they then show people is the thing that allows them to collect the things they can sell the best, right. They want certain types of readers, they want readers which are affluent, which they can then auction the advertisers. They want readers who are open with their data. Because if they auction someone who has lots of linked data to them then, you know, when you read something, I was informed about that the other day, when you go, when you read the web, you’re auctioned immediately. When you click on a newspaper story, you’re sent to an auction.

B: Oh, wow.

BS: They say, “I have this person, with this sort of data, how much will advertiser a, b, c, or d pay me to show them their ad?” and so not all readers are equal and all of us are being auctioned all the time by the media. And we think somehow, you know, the l information media is doing is just, sort of, secondary. It’s the way of auctioning and so they want to get a lot of readers, they want to get a lot of valuable readers, they want readers with lots of data. But in the end, they’re just trying to make as much money as possible. And the politicians are just trying to get elected as much as possible. And that’s the reality. 

B: And l science papers aren’t open access so…

BS: Ah, yeah, but I think access is overrated.

B: Oh, really? How come?

BS: Yeah. Because it, again, it inverts that thing, open access is just a trick of publishers to make more money, you know. Because it used to be that you would sell content to readers, libraries, other scientists. And if you double the amount of content, then it costs you more, and so you had to charge more. But if the readers didn’t want that content, then you couldn’t sell it to them. So there was a really natural filter, a content filter, it had lots of problems, which open access tried to address, but I think in a poor way. So what it did was, it made it, you know, it was a content filter, which made sure that the supply was driven by demand. So, you know, by making it supply-driven, the publishers can publish, its scales infinitely. And that’s why you see publishing exploding. Because if you make the producers pay, if the model is that producers pay or the public pays, which is in the end because it comes from tax dollars, then the publishers just win-win because they can just… there’s no disincentive for publishing more. Because how much money you make depends on how much you publish because you’re charging the public for that. So I think open access went about solving a real problem in a way that actually was more designed to enrich publishers than it was to inform the society.

B: So how would you go about it? 

BS: Oh, you see, for a lot of publications there’s laws, which says the intellectual rights of the articles are open, everyone can publish on the web pre-prints of their things. So there’s nothing in the way of making things open. And if the journals want to select some papers, package them, and sell them to readers, then they can do that and then you can decide, we can decide if we want to buy them as libraries or not. But there’s no, there’s nothing inhibiting open access, you know. So this open access is really, we call it open access but, in more times than not, it’s “pay the publisher”, you know.

B: Yeah, I see. I haven’t really thought about it that way.

BS: So it’s a whole system that seems really that they’re always the worst, the things that seem like a really good idea. Because who could be against open access.

B: Well, yeah, and then if you are against open access, then you’re the bad guy. You can’t say that you’re against it.

BS: Right, but I think open access has gone wrong, you know.

B: Okay, yeah. For me, especially with climate change, it’s sometimes hard to find the right things to read. Just because I can’t… most of the papers are either too complicated to read or I don’t have access to them. And then there’s the media. There’s nothing, kind of like, you know, in between, right. But this is where I guess podcasts, also…

BS: Yeah, yeah, that’s what we are doing here.

B: Yeah, exactly, in the end, you’re talking to the expert and it is open access, it’s available to everyone. So what are some of, kind of, the big misconceptions about climate change that you think are floating around?

BS: That one and a half is really much different than two degrees. 

B: Okay. 

BS: So we know… so here’s a question I ask people: in what way is two degrees different than four-thirds of one and a half degree? Yeah. So yeah, it’s just four-thirds of one and a half. And there’s some things like the water vapor equation I was talking about, that scale exponentially with temperature. So then, it’s four-thirds inside the exponential. But, you know, can we really say that one and a half degrees is sort of, somehow, fundamentally, you know, we’re safe at one and a half degrees and we’re not safe at two degrees? That’s communicated a lot, as if these temperature thresholds have a real scientific meaning. And they are political devices to help focus the debate, you know, because people like a target. So, you know, people who study communication and, you know. But it’s really just a political tool that people use to shape the debate.

B: But don’t we…

BS: There’s nothing really… I mean the warmer it gets, the less we know about the future and with that comes more risk. So, obviously, warmer is worse than colder. But that’s, you know, if we used a different temperature scale: instead of one and a half degrees why don’t we use three degrees Fahrenheit and five degrees Fahrenheit? You could use those, those would be fine. It’s kind of like this Abstand, you know, in Germany, with the virus, one and a half, two meters… clearly, two meters is better than one and a half, but it’s nothing magic that happens at one and a half, you know. If the room is closed and stuff like that so…

B: Yes. 

BS: And so the misconception is that there’s something magic, like, everything’s okay at one and a half. Certainly one and a half’s better than two.

B: But just because we don’t know what’s going to happen at two and, I guess, you increase your risk, right?

BS: Right.

B: So there’s not a specific reason.

BS: Yeah, yeah. So that it’s not like we’re safe at one and a half, you know. They’re often posed in the media as, you know, if we keep temperature at one and a half, we’re safe. It’s just that if we’re at one and a half, we’re better than a two. And two is better than three. But exactly how, you know… and then some people like to, they try to quantify the risk between one and a half and two. And that’s what we’re not very good at. So if you ask, “how much more expensive would a two-degree world be compared to a one-and-a-half-degree world?” of course, people will make models and do calculations but I don’t think there’s really a good scientific basis for it…

B: Yeah, I guess there’s too many unknowns.

BS: Yeah. So misconception, I guess, you asked about misconceptions, so I guess the misconception would really be that there’s something magic about these numbers, you know, that they’re sort of scientific. They’re scientific in the sense that we know that two is four-thirds of one and a half, i. e. bigger, you know. And the bigger it gets, the more risks come with it. But that’s about as far as we go with it it’s not like there’s, you know, some theory that says at two degrees the ice sheets will collapse and at one and a half they won’t. The risk that they’ll collapse is higher at two, obviously, it’s warmer than one and a half. But yeah, so that’s a misconception that somehow, that these temperature targets have a… there’s a popular perception that they have a stronger scientific foundation than what I just explained to you.

B: Okay, yeah.

BS: Yeah, that’s a misconception. There’s lots of misconceptions about science, you know. I always like Greta, I’m a fan of Greta I must say. But, you know, she says, “listen to the science”. It doesn’t mean, so if anyone’s listening to this, it doesn’t mean listen to me the scientist, right. So “listen to science” means somehow being able to digest the stuff that comes from scientists, which is robust.

B: Yeah, so for me, “listen to the science” just means, like, “listen to the data”, right?

BS: Yeah, when it’s clear. But often when we see, like, you know, just, I guess, all of us have tried to follow the covid thing and try to figure out how to… and there’s some things that are clear but there’s many things, where it’s a bit unclear about what to do when you read the study. And you read that study, and we’re arguing about it, and then suddenly you see it from a different light. And so science is really about arguing. And arguments can be more settled or less settled. And once, while we do settle argument, we understand that the planet’s warming and we understand it’s from greenhouse gases, and it’s pretty simple. We know the Earth is going around the sun. I mean there’s things that science can kind of definitively say and you want to be able to sort those out. And there’s other things where we’re in the midst of a hot argument. And sometimes if you translate, “listen to the science” can really quickly be an authoritarian way of interacting with the world. Because, you know, “listen to god”, “listen to your mother”, “listen to the science”. And really, I’d like to understand “listen to the science” as “listen to the reason”, and the reason should be something that makes sense to you. And then you say, “this is how I understand it, and this is why I think this is like this, and I learned to understand it because people who worked at it taught me this and I can follow their reason,” – it can still be wrong but it should be reason-based rather than authority-based. And the beauty of the science is that it’s a system of reasoning. And so we should really lift the reasoning up and not the authority. But that’s a lot to ask of people too. Because people want to spend time thinking about other things, you know, they don’t want to…

B: Yeah, yeah.

BS: So, in the end, we all try to figure out who we can trust and we listen to them.

B: Yeah. So we’ve talked about 1.5 degrees going to two. And so one of the ways to prevent how to do that is to reduce emissions. I guess that’s one of the ways, right? And we live in Germany and nuclear energy is always a topic I like to talk to a lot of people about, particularly in Germany, since we phased out all nuclear power plants. So what do you think is the best way to reduce emissions? And it doesn’t, we don’t need to be looking only at Germany, like we said, we should probably be looking at a global solution to reduce emissions.

BS: Yeah.

B: Would this be nuclear energy, renewable energy?

BS: So it seems like, yeah, I don’t do a lot with energy politics, I always kind of joke that, you know, Germany doesn’t really need nuclear because we have France.

B: Exactly. 

BS: You know, so okay, if they have a big industry that’s their sort of competitive advantage. So just get the nuclear from France and then, I mean, we’re a networked European continent. So if for whatever reason, it doesn’t work to have nuclear in Germany, and then people can argue about the transport effectiveness of having all the nuclear in France or something like that. You know, one of the things I think on energy where, because these problems are intertwined with the other ones I mentioned of inequality and development and just using the full human potential that we have on the planet, I don’t know, I never understood why we couldn’t use climate change as also a development exercise. And my example would be if you go to the Caribbean, I mentioned I’ve worked a lot on Barbados, they have all sorts of, it’s energy wonderland there, right. You have infinite sun, super wind, volcanic islands, you have geothermal, you have hydropower because of the rain and the ions. And most of them, they get their energy from Venezuela, and Trinidad, and they buy oil and they ship it in and they burn it, and that’s because the infrastructure, you can use old infrastructure, it’s cheap, and they get it fairly cheaply. But if we’re serious about climate change, then how can we make Barbados energy-efficient? So I think the rich countries should adopt developing countries and do it in a way that’s sustainable, not just that, you know, you ship in a bunch of danish, you know, wind turbines there, build them up, and then they start falling apart, you know. But really build the wind turbines in the Caribbean and found Caribbean firms that actually developed the technology, if it’s wind turbines or solar cells. But really trying to make a concerted effort to work with the sort of under-resourced part of the world to let them be energy efficient. You could say, “well, you know, they don’t use a lot of energy, so that doesn’t save a lot”…

B: Oh, but they will. That’s the thing, that’s what a lot of people don’t realize. Like, we need a lot of energy because if you want them to develop, they will require loads of them.

BS: Yeah, so I thought for me, a serious approach would be to couple that with a development strategy. And we can talk all about here in Germany – how many wind turbines we want? And we can talk all about, you know, how do we meet our carbon budget? But yeah, why can’t we get two things at once and make it part of a broader development strategy? But then you really have to go back to the question of: how do you do these things too in a way that isn’t just a hidden way of subsidizing, let’s call it, first-world companies? Because a lot of development aid is, as I see it,  is just a way, you know, the way it would work is you’d go to Barbados and say, “oh, let’s make you renewable”, so you need wind turbines and, like I said, then you say, “okay, then buy them from siemens, made in Germany”. And then you create a dependency, and it’s not sustainable, and it’s really just a way of the taxpayer giving siemens money, you know, filtered through Barbados.

B: Yeah.

BS: So you don’t want to do that, you’d like it to be a really organic approach.

B: Which is very difficult.

BS: Yeah, but if we can’t do that, then the rest is all fantasy anyway. So why not begin trying to do that? And that would be… nothing against rethinking how we approach energy in Europe or in Germany. 

B: I mean it makes a lot more sense to put solar panels in Africa, for example, as opposed to Germany – we get no sun here. In Africa, it’s constant.

BS: Yeah, exactly. But you need, you know, the problem there is that you bite into the whole structural problems that we have in the world and development problems. And I don’t think people really have an appetite for taking on these issues. But if we don’t take on these issues, I have a hard time seeing how… you know, maybe the argument is that we just develop in technologies in Europe for renewables. They’ll be so cheap and easy to use, then they’ll filter down, you know, to the developing countries. Maybe there’s an argument to be made there.

B: I see that because that tends to happen. Like, we developed cell phones, and now they have them as well, but only because we developed them quickly, made them also cheap enough.

BS: Right, yeah. 

B: So I see that argument.

BS: Yeah, so that, you know, that could be an argument. So yeah, in Germany, it’s kind of tough, isn’t it? You know, because I think a lot of people like to talk about nuclear: I have some good friends who are staunch advocates of nuclear.

B: They’re not germans though, right?

BS: No, they’re not germans. But they all talk about fourth generation nuclear and things like this, which is still a bit, seems like a bit of a fantasy. Because it’s yeah, it’s where we could go in. And if south Korea develops this nuclear, then fine, we’ll just end up buying some, you know, if there’s a safe nuclear and people have it. But nuclear is, it’s again, it’s normally a lot of these things are subsidized. There’s a lot of money behind nuclear. And there’s a lot of money to be made so nuclear has very powerful friends. There’s enough countries developing nuclear. If you can come up with safe nuclear, wait till south Korea does it, and then people say, “oh, but then south Korea will do it”. Fine, you know, so I don’t feel like Germany needs to compete with south Korea. We should pick our spots and technology. And if France, I mean France does it, that’s their competitive if they come up with really great nuclear technology. But it’s not like France has been so successful in building, putting new nuclear reactors online. And again just like all the other renewables: if somebody comes up with a way that addresses the problems of nuclear, then maybe it won’t be so hard to convince germans.  And maybe then, you know, the world will be making nuclear energy. And they won’t be german firms doing it, but I guess german firms will make some of the pieces. So I wonder sometimes, why people get so worked up about the fact that Germany’s not doing, among my friends, not doing nuclear. Because why does everyone have to do it, german can do through the wind and other people are doing it. And I have a feeling they just want that investment, you know.

B: I guess nuclear just generates so much more energy than wind and solar, particularly in places like Germany. So I think that’s probably the main argument.

BS: Yeah, but we could… there’s nothing against having nuclear in Germany if there’s a good nuclear solution. But it’s not it’s not like there is one right now. It’s not like anybody’s making cheap reactors, which you don’t have to subsidize, you know. You couldn’t insure a reactor.

B: Yeah, exactly.

BS: You can insure a windmill. So I have another, a good friend who I respect tremendously, but he talks about the number of people who have died from coal. And he’s right, it’s enormous because it’s not insured and there are consequences. But wind turbines, if a wind turbine breaks and kills someone, the state I don’t think, here I’m just talking from guesswork, but I guess the winter runs are insured by the people who put them up. So if the wind turbine breaks down, and the blade goes off and drops into someone’s house and kills their cow, then the person who had the wind turbine will be liable for that, and have to buy a new cow, and roof, and whatever, right. That doesn’t work with nuclear, that the state has to subsidize it. And I think that’s a pretty good measure, you know, if somebody has a technology that they’re able to insure, then, and that’s an argument against coal too because you can’t insure it, and it does kill a lot of people, if coal companies had to be liable for their emissions, we wouldn’t have coal, so they’re also living on a giant subsidy of public subsidy that we’re kind of accommodating their emissions.Yeah, so nuclear would be great but it should be a solution that we believe, you know, in a sense. And “believe it” means that if we require the state to insure it, because no reasonable person would, you know, insure that, that’s to me kind of saying we don’t believe it. So if somebody comes with technology, we can burn the fuel down, and burn, and burn. Like, this fourth generation seems promising, maybe it will. Maybe we’ll do that. But if it doesn’t, then maybe there’ll be a basis for reevaluating of building those plants. But right now it’s not like there’s a plant that we can build in Germany that, you know. And even in the nuclear countries, like I said, they have a hard time building plants in France. And yeah.

B: Speaking about solutions, actually, I just thought about, like, so you know how in Dubai, they like artificially make it rain because they put…

BS: They try, yeah.

B: They try? Does not work so well?

BS: Well, I don’t know, I haven’t looked in enough detail. I know they’re trying, there’s a lot of scepticism about how effective it is, I’m sure they have examples where that works.

B: How does it even work? I think it’s like these…

BS: They have all sorts of different approaches to do that.

B: Okay, but I guess it’s just, you put, like, chemicals or…

BS: Well, the old idea, sometimes you can, the best way is, you know, the rain forms because of the way the air moves. So you need to change the way the air moves. What they try to do, because, basically, you have to bring moisture and condense it, and it has to fall down. And if the air’s not going up and condensing moisture, you know, there’s one way, if the air is going up and making moisture and it’s not falling down, and then you can try to do things that can initiate this process that makes the rain form out of the moisture. But you need this, you need the moisture. And so that’s the bigger problem normally is how to get the convergence of moisture, that then you can do the other things to make it fall down. So if you have a lot of big clouds there and they’re just, you know, not raining soon enough, but they drift off shore and rain, you probably can kind of help them along so that they rain a little more.

B: What about doing the opposite? So it’s like in places where there’s a lot of rainfall, you try to, like, put chemicals or particular matter in the air that prevents the rain from falling. Could that technology be used to prevent certain natural disasters? Maybe even like the flooding that happened in Germany last year?

BS: Yeah, you know for a long time, in the 50s people had this idea that you could, well 50s maybe it’s the wrong year but in the last century say, you know, by putting oil slicks down on the ocean you could stop hurricanes from getting the heat that they wanted, you know. 

B: Oh, I did not hear that.

BS: Yeah, so if you could smooth the ocean, you’re good. There’s been ideas that you can explore a ton. 

B: Well, that seems a lot more difficult. Because one, you need to, in the 1950s, it would have probably been a lot harder to know exactly where the hurricane was, right, and it’s also hurricanes are not very predictable. And two, the ocean’s just so big. 

BS: So my point more was in general that looking for these sort of technological solutions to… so let’s do another one: the geo-engineering, where people have this idea, geoengineering is this idea that you can put particles in the stratosphere, right, and if you have the partiles in the stratosphere, then it would stop the sunlight from coming to the ground. And people debate about whether this will happen, whether it would be good, and whether you could detect it, and whether it would be effective. And all of these things, that’s all fine, then I go to myself, though, and I say, “okay, imagine we could do it, imagine it was effective, we could do it, it was good, all of these things. And we did it. And we did it starting on the first of January 2021. And on the 15th of July we had the floods in our village in the German region…

B: Yeah, that’s where I come from, I have them right there. 

BS: So imagine that happened. And actually, it wasn’t we doing it, Germany, but it was Russia who was doing it. Or something like that. I guess people would say that this flood was because of what they did. Or that, you know, in 2000, I don’t know what year that was these giant floods in Pakistan, but every year there’s these extreme weather that happens – how would you litigate that? You know, because the people would… and there again this difficulty we have in regulating global systems makes it hard. So that the sort of international framework that you would need to have, that would allow you to regulate these sorts of conflicts, is the one that we’re missing to solve the global warming problem. So to me, if you could manage that, then you can manage the simpler problem of reducing emissions. So in your example of “let’s stop this terrible flood” but I meant if you intervene in that way, there’s a chance that something else happens. And so you induce a liability that goes beyond the local control. And then you need the precisely those sorts of international frameworks to resolve conflicts that we are missing to solve the CO2 problem. I don’t know if that makes sense. 

B: It does make sense. I actually didn’t even think about that… that, I don’t know, if you artificially change the way the atmosphere works, that you might do some more damage, that you can’t really predict for…

BS: Yeah, so the collateral. And even if you don’t, you have to be able to show that you don’t, otherwise yeah we will try to hold you liable. And that happens every time you do something on purpose. Where we tend not to hold people liable if we do things inadvertently, like we’re changing the atmosphere all the time when we, you know, change our crop rotation, or build our cities differently, or change our coastlines. So we’re changing, you know, the natural environment is far from natural. It’s every yeah space on the Earth is influenced by humans. But the changes haven’t been, in most cases, directly intended to modify something. I mean here, in Hamburg, we have the Elba and we dredge the Elba, which makes the region more susceptible to floods. And we know that but it doesn’t, you know, that’s still in our local governoral wall.

B: Wait, what did you do to the Elba?

BS: We dredge it so the big ships can go up and down.

B: Oh right, right, yeah, that makes sense. 

BS: And so we take that, and deepen it, and dredge it, and that makes that, it tends to make the channel deeper. And it can affect the high and low watermarks. It affects the local landscape. So it has collateral influences, but they’re local. And when you start doing things on large-scale floods, then maybe you stop the flood, but then it floods in Poland or something like that and yeah. And so how do you protect yourself against something like that? So that’s where I kind of think: these are distractions. Because we talk about like geoengineering or we talk about intervening, but they’re gonna fail for the reasons the more easy things or the more straightforward things fail, which is this lack of inability to build a global consensus about what we should do.

B: Shame, I thought I had a million-dollar idea. No, joking. And so in Dubai, how do they get more moisture?

BS: I don’t know. I’m always asked to, kind of, review those proposals and participate in these programs.

B: Just because it’s so dry there so it’s curious.

BS: Yeah, I don’t know. And I also don’t know the economics of it. Because it’s dry but there’s also a lot of money that they have. So they might be able to trade money for water.

B: That’s funny.

BS: Yeah, and they have a lot of sun so desalination seems like that would win in the end anyway, right.

B: Yeah, that’s actually true.

BS: Desalination is mostly just a question of energy and well, they have sun. So I don’t understand why that’s not a better way to make water. And it is in Israel, I know that the amount of desalination happens in Israel.

B: Does it happen a lot?

BS: Yeah, and it’s become much, in the last 20 or 30 years, I think desalination has become much more cost-effective. And if you’re any energy-rich, I mean solar-rich place, I think there’s lots of potential.

B: Nice. Okay, well, thank you very much for this talk, it was really interesting. I had a lot of fun and yeah, good luck with your research!

BS: Yeah, thanks very much.

B: That’s it. Thank you all so much for listening! If you would like to learn more about professor Stevens and his research then just check out his website. And if you like our podcasts, make sure to follow us on our Twitter, LinkedIn, and Instagram page. Thanks again for listening! Bye!


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