Episode 529 Clouds and Climate

The Pugwash inquiry is concerned here with a proposal to brighten clouds over Hudson Bay, retaining some ice year round. The experts here are Alan Gadian, Stephen Salter, Michael Diamond, Paul Beckwith, Peter Wadhams. The consider the challenging problem of estimating the effectiveness of this intervention. Much of the complexity results from the dynamics of the multiple factors — the way the clouds of different altitudes react differently, the impact of water vapor, altitude, temperature, the changing amount of light in different seasons, etc. Although the mathematical modeling gives a specific prediction, it may be necessary to check it with a real-life experiment, and we have to decide whether Hudson Bay is the best place to carry out such an experiment. For the video, audio podcast, transcript, and comments: https://tosavetheworld.ca/episode-529-clouds-and-climate.


Alan Gadian

Michael Diamond

Stephen Salter

Paul Beckwith


clouds, aerosol, Stephen, ship, big, warming, particles, effect, Hudson Bay, water vapor, spray, people, atmosphere, ice, brightening, reflect, planet, regions, arctic, radiation


Michael Diamond, Stephen Salter, Metta Spencer, Paul Beckwith, Alan Gadian


Metta Spencer says the plan is to discuss the refreezing of the Arctic Ocean. The Pugwash discussion is about refreezing part of Hudson Bay. Michael Diamond is present to answer some questions arising from a video by climatiologist, Jennifer Francis, who remarked in a talk that clouds have an overall effect of warming the climate. This troubled Metta, who decided that the group should make sure we’re not contradicting ourselves.


Stephen Salter credits John Latham and Sean Twomey for originating the idea of marine cloud brightening (MCB). Salter explains that clouds can have both cooling and warming effects, depending on their height, size, and the aerosols present.

Citing a Norwegian study, he notes: If you have a small aerosol, that warms, and if you have aerosol that’s too big, that warms as well. The reason that big drops might be cooling is that they fall fast enough to gobble up other big drops, and that can make rain, which can clear clouds. The second possibility for very small aerosol is that if you’ve got very large numbers of a very small aerosol, they aren’t big enough to do proper nucleation; they don’t grow a big drop. But they can still take out quite a lot of water vapor, which is transparent, and that will let more sunlight come through. So fortunately, the sizes that we would like to make are very neatly in between the two regions that the Norwegians say will warm.

High-altitude clouds such as cirrus clouds, reflect solar energy back to the earth, which causes heating. Low-level clouds reflect incoming solar radiation, resulting in cooling during the day, but they absorb and re-emit infrared radiation, causing a warming effect at night. At night and in wintertime, all clouds have a heating effect. But in the daytime, low-level clouds have a chilling effect.

Paul Beckwith points out that the sunlight is shortwave radiation, which heats the surface of the earth. But when you heat something, it emits long wave radiation. Those longer wavelengths are captured by the greenhouse gases and are reflected back down by the high cirrus clouds in the daytime. The lower clouds are reflecting back outward the shortwave radiation that’s coming down. There also will be some conversion, some heating of the atmosphere, and that long wave radiation is also reflected back up. But it’s mostly the shortwave that’s reflected by the low level clouds. So the cool high level clouds cause the warming during the day. During the night, there’s no incoming shortwave radiation, because it’s dark. So it’s only the long wave radiation, the heat generated radiation that you need to think about at night.

Clouds behave like greenhouse gases, as they absorb and emit infrared radiation. Water vapor is the most significant greenhouse gas; about 30% of the greenhouse effect comes from water vapor. Alan Gadian points out that the increase in water vapor caused by warming the lower atmosphere can create a positive feedback loop, which contributes to increased infrared heating. The Clausius-Clapeyron equation explains that the ability of the atmosphere to hold water increases by 7% for every one-degree Celsius increase in temperature.

If you increase the temperature of the lower atmosphere by two degrees Celsius, you will almost increase the infrared heating by 50 to 60% because of the positive feedback effect. And the clouds can mitigate this. The lower level clouds have a cooling effect, but they are battling against the positive feedback.

However, Paul Beckwith adds that a water vapor source is necessary for this increase to occur. If you’re over a dry area, you’re going to increase the ability of the hot air to hold more water, but it won’t be realized in the atmosphere if there’s not a water vapor source. Hotter air is able to hold much more water. If you cool down the atmosphere, there’s condensation and dew appears on the grass. The air can no longer hold as much water as it held before at a higher temperature. In a desert, it’s dry, so it can go below freezing at night and get extremely warm during the day. But near a body of water, you don’t reach the same highs or lows. But the clouds matter. Notice that in Toronto in winter, if you have a cloudy night, it’s not going to be that cold at night. If the sky is completely clear, it becomes bitterly cold at night.

The group discusses the importance of the sub-tropics in altering the planet’s heat balance due to their higher concentration of sunlight compared to the Arctic region. The group debates the complexity of cloud formation and its various factors that influence their impact on the environment, such as the size and composition of particles. While the importance of Arctic clouds is acknowledged, their overall contribution to the global heat balance is seen as minimal in comparison to other regions.

But Stephen Salter explains that marine cloud brightening with ships releasing spray can help cool the planet. He notes that the average solar input is 340 watts per square meter, but the South Pole gets 550 watts per square meter for a short time. The hope with marine cloud brightening is that it can be used in areas where it is most effective. We do not want to go too close to the ice in the Arctic but want the clouds over the sea instead. Alan Gadian agrees and adds that Danny Rosenfeld believes that any clear area should have aerosols in them to produce the cooling effect.

Paul Beckwith discusses the aerosols from ship tracks, which are different from salt particles, and notes that they can cause both warming and cooling effects on the planet. He adds that spraying aerosols is useless over land as there are already many aerosols in the air, and spraying should be done over the ocean, away from any shoreline, and in areas where the aerosol count is low.

Ellen Judd asks about the dynamic system of clouds, currents, and rainfall and how it will interact with the aerosols. Alan Gadian responds that there are regions, such as the stratocumulus clouds off the coast of South America, where the air is stationary for days, and the aerosols will stay there for days. However, this is not the case in general, and there is a lot of vertical motion in the atmosphere.

There are two different views about cloud brightening in Hudson Bay. One side believes that spraying over Hudson Bay will keep the ice from disappearing in the summer, while the other believes that it is not effective and we should be spraying in equatorial regions or regions less than 60 degrees north.

There are concerns about the aerosol and clouds going over sea ice. Someone could reasonably worry that marine cloud brightening in the Arctic could actually cause warming. Where the ocean is black, if you put a puffy cloud over it, you can reflect a lot of sunlight back into space. But the Greenland ice sheet is white, so it’s already reflecting all of the sunlight. If you put a cloud over that it will still have the greenhouse effect of the clouds, so the only net effect it can have left is warming. (But we will not spray over ice — just over water.)

Also, some have suggested that it may be more effective to seed the clouds with ice to thin or remove them in the wintertime, which will thicken the ice below in the hope that it will last through the next summer without melting. We need an experiment that would cost 40 to 50 million dollars to explore these factors, but until then, the effectiveness of cloud brightening in Hudson Bay remains uncertain.


This is a machine-generated transcript that may contain errors. Do not cite it without checking for yourself by watching the video and catching any obvious errors.

Metta Spencer  00:00

Hi, I’m Metta Spencer. Today we’re going to talk again about the Arctic, and about refreezng the Arctic Ocean. And of course, we can’t just immediately run out and refreeze the Arctic Ocean. So we have some people who have some ideas about how we might approach that project and make it at least ascertain whether and how we can go about doing it. And some of my experts are in Europe and some in North America. Stephen Salter is at the University of Edinburgh. And he is one of the great proponents of the notion that we can refreeze the Arctic. The project that Pugwash is going to start with, is the idea of refreezing just a part of Hudson Bay every summer, so that we can keep it, keep some ice there. And year round, not the whole thing, but part of the bay, and then that will be a good experiment to see how well we might be able to use the same principles too on a larger scale, that other countries might want to participate in.  Canada alone can do this project about the Hudson Bay, because we own Hudson Bay. It’s part of us. And so the idea would be to spray sea water or salt water through very fine nozzles, so that tiny particles of of saltwater go up into the clouds and brighten them by making the the overall composition of the clouds of smaller droplets, which are whiter, and these whiter clouds will reflect more of the sunlight coming in, and thereby keep the water below cooler. So that’s the general notion that we’re going to explore again today, because we’ve already talked about this, if you, some of you will have already seen shows that we’ve done discussing this issue before. So this is the thing that Stephen Salter is the guru. And in I’m going to speak to Peter Wadhams as well because Peter is somebody who’s very much in alignment with this. Peter is a great expert on Arctic ice, sea ice. And he’s now in Turin, Italy. And in someplace in the south part of England is Alan Gadian. Alan is a climatologist who does a lot of modeling. So I think he’s a guy that does the number crunching, if I’m maybe simplifying a little bit too much. And in Boulder, Colorado, is Michael Diamond. And Michael Diamond going to be, he is an expert on aerosol and clouds and that sort of thing. Those folks out at the University of Colorado Boulder seem to have a whole institute or something that does that must have dozens of scientists working there who all specialize on clouds. And so he’s, he’s going to answer some questions that basically arose for me as I watched a video by a woman named Jennifer Francis, who’s also a climatologist, and and who remarked something in passing, that the clouds have an overall effect of warming the climate. Therefore my thought was, well, if that’s true, then our whole project may sound a little suspicious, because if we’re going to warm the planet, when we’re trying to cool it, we got to work something out here to make sure we’re not contradicting ourselves. So I wanted to have Jennifer Francis join us today. But she couldn’t. And therefore she recommended a series of people who recommended other people, and which is how I got to Michael Diamond. And the point of this series of inquiry is that we are now conducting an investigation of this whole notion of cloud brightening to cool the planet by Pugwashites, the Canadian Pugwash Group is sending people who  I’m a member, and Ellen Judd is also a member in Manitoba, and so is Michel Duguay, who is a physics professor at Laval University in Quebec, and they are both active in the Pugwash movement.We may be joined by some other Pugwashites. Maybe Stephen, why don’t you begin by correcting any mistakes I have made in this introduction. And then we can ask people to generally comment on whether they think that the the overall project of brightening the clouds over Hudson Bay is a reasonable project that that we might endorse.

Stephen Salter  05:39

Right, Okay, can you hear me?

Metta Spencer  05:42


Stephen Salter  05:42

The first correction is that to acknowledge the work of John Latham, and Sean Twomey.  I’m just an engineer who’s trying to do things that John Latham asked me to do. And really the whole of this, this thing started off with Sean Twomey’s work, and John Latham, who was in Boulder, Colorado, so they’re the guys who you get to blame if it doesn’t work. The second thing is that I’m painfully learning bits of climate physics. And I agree with Jennifer Francis in a lot of respects, that sometimes clouds will cool and sometimes clouds will warm. And it depends on the height that they’re released at they’re forming at. And it depends on the size of the drops in the cloud. And there’s some very interesting work done at the Cicero labs in Norway, by Alterskjær ( I hope I’m pronouncing it correctly) and Christiansen that showed that if you have rather small aerosol that warms, and if you have aerosol, that’s too big, that warms as well. And I was very puzzled about this. Fortunately, the size of drops that I want to make for re engineering reasons is exactly in the right place for what they’re saying. And the reason that big drops might be cooling is that they fall fast enough to go gobble up other big drops, and that can make rain, and that can clear clouds. And if you’ve cleared the clouds by spraying with big aerosols, then they’ll be overwhelming because you cleared the clouds away. The second possibility for very small aerosol is that the, if you’ve got very large numbers of very small aerosol, they aren’t big enough to do proper nucleation, they don’t grow a big drop on them. But they can still take out quite a lot of water vapor, which is transparent. And that will let more sunlight come through, because there’s such a very large number of things that you’re reducing the liquid water content in the cloud. So fortunately, the sizes that we would like to make, for reasons of making filtration, are very neatly in between the two regions that the Norwegians say will warm. We know that if you have very high altitude clouds, cirrus clouds, they will reflect back outgoing energy instead of letting it go to deep space, they’ll reflect it back.

Metta Spencer  08:31

Let me get clear, you’re saying that high altitude clouds…

Stephen Salter  08:36

High altitude clouds could reflect outgoing solar energy back down to ground. And that’s why we don’t want that to happen.

Metta Spencer  08:46

And that it’s going to reflect it downwards. So that’s going to be heating effects.

Stephen Salter  08:51

They heat things up. But also, if you have

Metta Spencer  08:52

Lower level clouds reflected upward and cools therefore a cooling effect, right?

Stephen Salter  09:00

We also know that at nighttime, and in wintertime, any clouds will reflect back energy. So it depends on the height and time of year, time of day even and the size of aerosols. It’s a very complicated issue. And fortunately,

Metta Spencer  09:17

Let me make sure I get you. At night all clouds do what?

Stephen Salter  09:23

Yep, they will reflect back.

Metta Spencer  09:25

Oh, at night, all clouds have a heating effect. And in the daytime the low level clouds have a chilling effect.

Paul Beckwith  09:36

Okay, to complete the picture, Metta, the sunlight coming down is shortwave, called shortwave radiation and that heats the surface of the earth. Now when you heat something, it emits long wave radiation, longer wavelengths, and those longer wavelengths are what’s captured by the greenhouse gases. Those longer wavelengths are what are what are reflected back by the high cirrus clouds in the daytime, the short, the lower clouds are reflecting back the shortwave radiation that’s coming down. There also will be some conversion, some heating of the atmosphere, and that long wave radiation is also reflected back up. But it’s mostly the shortwave that’s reflected by the low level clouds. So they cool high level clouds, you know, they cause the warming. This is during the day. During the night, of course, there’s no incoming shortwave radiation, it’s dark. Right? So it’s only the long wave radiation, the heat, the heat generated radiation that you need to think about.

Metta Spencer  10:43

Oh, that’s helpful. Okay. I didn’t realize you were here. Paul, I should have introduced you. This is Paul Beckwith. And and Michael Diamond has raised his hand as if he’s a polite man, but we don’t have to be polite here. You can just speak up. Yes, Michael.

Michael Diamond  10:59

Yeah, just gonna echo exactly what Stephen and Paul said really well, and just maybe add a little bit of a caveat that it helps us to think both at what we consider the top of the atmosphere, so kind of where the earth is exchanging energy with space, and at the surface. So all clouds are going to interact with both of those types of energy we just talked about, so they’re going to interact with sunlight or shortwave radiation. And they’re going to interact with this heat radiation or infrared radiation or long wave radiation, all those kind of mean the same, the same thing. Taking the perspective from the top of the atmosphere, right now we’re exchanging energy with space. These low clouds that are our main target for marine cloud brightening, they are very reflective, so they, at least in the daytime, are going to reflect a lot of that sunlight back to space. So that’s their cooling effect. And at the same time, this, clouds act very similarly to greenhouse gases, actually. So they absorb the infrared radiation that gets to them, and then they re emit it at a new temperature. So these clouds that are near the surface, they are relatively warm, which means that their ability to trap the radiation in the Earth system is relatively low, so they have a very small warming effect overall. These high clouds, especially let’s think about those been cirrus, you’ve probably seen these, maybe an airplane comes by and you see this thin contrail after, and you can still see the blue sky through it. They’re not that reflective, right, you can actually see totally through them. So they have a weak cooling effect. But they are very high up in the atmosphere, which means they absorb that radiation, and then they remit it, but they remit it at a very cold temperature and cold things emit less than warm things. It’s kind of the fundamental physics there. So they basically act to trap that radiation in the Earth system. Same way that greenhouse gases do, and they cause a warming. So that’s why from the earth to space perspective, you have a big difference between these low clouds, which mainly cool the climate and these thin high clouds, which mainly act to warm the climate. Overall, clouds, if you take all the clouds everywhere on Earth, day and night, averaged them all together, it’s a pretty strong cooling effect. But regionally, you get some areas of warming. And this is might be what Jennifer was referring to in the video. I should just put an asterisk here. I did not see her video, unfortunately. So um, apologies for anything I get wrong. I don’t want to put any words in her mouth.

Alan Gadian  13:34

Can I?  Can I, there’s a complication here. And that is the biggest greenhouse gas in the atmosphere is water vapor. And this is governed by a thing called the Clapeyron–Clausius equation, which is covered in high school physics. And essentially, about 30% of the greenhouse effect comes from water vapor. So the complication is that if you increase the temperature of the lower atmosphere that’s below three, four kilometers by one degree Celsius, you increase the effective warming by 7%. So there’s a positive feedback here. That I mean, clouds have a role. A very low level clouds have a very important role, specially in the strata cumulus clouds, layer clouds. But the most important role is the fact that water vapor exists in the lower atmosphere. It is far more important than methane, far more important than carbon dioxide. So you’ll have a feedback effect. So when one talks about the infrared absorption and re-emission downwards of clouds. The complication is that water vapor does this incredibly efficiently. So you’ve got this positive feedback. And if you increase, effectively if you increase the  temperature of the lower atmosphere by two degrees Celsius, which is what we’re all talking about now, and I believe it’s gone beyond two degrees – anyway, you essentially will almost increase the infrared heating by 50 to 60%. So you’re getting feedback effect. And the clouds can mitigate this. One of the arguments is the more water vapor in the lower clouds layer, the more lower level clouds you’re getting. But you’re battling against, battling against this positive feedback that you get. So the the the issue with low level clouds and high level clowds is very important and critical. But the other background issue that people ignore, is the fact that if you warm up the lower atmosphere, you’re likely to get–  not as high as Venus — but you’re going to get more and more positive feedback. People keep forgetting that critical fact.

Michael Diamond  14:28

But, Oh, yeah,

Alan Gadian  16:26

Yeah, that’s right.

Paul Beckwith  16:26

So you have to have a source of evaporation for that water vapor to go up in the atmosphere, that 7%. If you’re over a dry area, you know, you’re going to increase the ability of the hot air to hold more water. You’re going to increase the ability of the hot air to hold the water but it won’t necessarily be be realized in the atmosphere because there’s not not a water vapor source. Right and I just want to add that the Clausius-Clapeyron equation, you know, if you increase temperature one degree Celsius, that actually increases the ability of the atmosphere to hold water by that 7%.

Alan Gadian  17:05

Yeah but most of the Earth is covered with water.

Paul Beckwith  17:08

 Yeah, yeah.

Alan Gadian  17:09

Living in the northern hemisphere, one forgets this fact, but in reality, the earth is totally an aquaplanet essentially.

Metta Spencer  17:17

I wonder if somebody can help me here, because Iive gotten, your above my head and  my job as a journalist, is to try to make sure that whatever we put out there for the public, is something the public can grasp, and I’ve gotten lost. So I’m not sure where I got lost, or what I need to do to get back onto the level of intelligibility.

Paul Beckwith  17:47

Like the hotter air, hotter air is able to hold much more water. So if you cool down the atmosphere, you can get dew appearing on the grass and condensation. Like any cold surfaces, you get water condensation, because it’s the air can no longer hold as much water as it held before at a higher temperature. So that’s all. When you increase the temperature a degree Celsius, the air can hold about 7% more water vapor. That’s from this equation, which is called the Clausius-Clapeyron equation. You can just go on Wikipedia and look at it.

Metta Spencer  18:25


Alan Gadian  18:26

Can I give you another example, another example. If you go and camp on the Great Divide 12,000 feet, right, there is very little water vapor above you. High temperatures during the day, you have high temperatures of perhaps 30 degrees Celsius or 100 degrees Fahrenheit. And then at night, it gets very cold, it goes down to 32 Fahrenheit. And the reason for this is there is little water vapor above 12,000 feet, and therefore the radiation goes straight out to space. So if you went down to sea level, at that latitude, night might go down to 80 Fahrenheit — 25 degrees Celsius — but it certainly wouldn’t go down to almost freezing. And this is the effect of the water vapor in the cloud.

Paul Beckwith  19:34

Yeah. I was just gonna say the exact same thing happens in a desert.

Alan Gadian  19:37


Paul Beckwith  19:37

So if you’re in the middle of a desert, it’s dry. It can go below freezing during the nighttime and it can go extremely warm during the day. If you live near a coastline or near a lake or body of water. It’s totally different. The temperature extremes reached are much lower, right? You don’t reach the same highs that you would reach or the same lows that you would reach. The temperature’s more uniform. Take the extreme case, go to the equator, say.  It’s pretty boring to be a weather forecaster because you know…

Alan Gadian  20:09

The big problem for weather forecasters, is at night. Because if you’ve got cloud cover at the ground, then the temperature remains high, if you’ve got no cloud cover, set that the radiation goes out to space and the temperature drops.

Paul Beckwith  20:31

So Metta, I just noticed, in Toronto, you know, if you’re in the winter, if you have a cloudy night, it’s not going to be that cold at night. If the sky is completely clear, it becomes bitterly cold at night.

Metta Spencer  20:44

Oh okay

Paul Beckwith  20:45

for that very reason. It’s exact same thing happening.

Metta Spencer  20:48

Okay, so now in trying to calculate the overall effect of clouds,  you’ve got several variables. One is, one is whether — the fact that the low level clouds have an effect that’s opposite to what high level clouds have. And then in addition to that problem, there’s the amount of water vapor in the atmosphere under, close to the Earth. Is that right? which determines — what?  I mean now we are not talking about, there was a talk about water vapor.

Michael Diamond  21:24

I think maybe we should…

Metta Spencer  21:26

I think clouds, isn’t it. So where am I lost?

Michael Diamond  21:30

I think maybe we should take a little bit of a step back to get back to Jennifer’s question a little bit, I will mention with clouds, the fact that we can see clouds is because the water vapor that’s in the atmosphere has condensed into a liquid droplet or a solid droplet. So what’s in the cloud itself is solid or liquid, but there’s also gaseous water vapor around it and in the atmosphere when there isn’t a cloud. But let’s put that to the side for a second. If we go to, I believe Alan mentioned, these stratacumulus clouds are very important. So if we go to the tropics, so if you think about the California fog, there’s this big deck of stratacumulus clouds off the coast of California. Another one exists off the coast of South America and off the coast of Africa. These tropical decks. I don’t think you’d find anyone who would tell you that you can’t get any kind of aerosol induced brightening in these clouds. So going back to our marine cloud brightening perspective —

Alan Gadian  22:30

No, I disagree with that. This is this is the area where I would say you should concentrate your efforts. Because if you change the mean droplet,  people like Feingold, people like Rosenfield, people like Bjorn Stevens, would agree: You change the mean droplet size by just a small amount, you can change the reflection. And this is what Stephen Salter is trying to do. Now, the problem with that is you have to get the right size of aerosol, because if you make them too big, they’ll precipitate. The United Arab Emirates are spending millions, billions almost, on __(inaudible)__ and if you make them too small, you’ll dissipate the cloud. So this is a whole balance. And for example off Chile, the smelters there, actually produce lots of small particles. And that removes some of the low level clouds. So I would argue the smelters on the side of the Andes actually cause the planet to warm up because of, not marine cloud brightening, but marine cloud dimming. So the situation is really, really quite complex. But the size of the mean _(inaudible)_(that’s the r cube of r squared) but the mean size of these particles in a cloud is critical. And this was done by Slingo, by Twomey, in that all the numerical models in the world rely on trying to estimate what the mean size of these particles is. And to be honest, the numerical weather forecasting models on climate is a load of rubbish when it comes to it. They just don’t get it right. You can go and measure it and it’s nothing to do with what the forecasters say it is. It’s absolutely critical.

Michael Diamond  24:46

That’s a very fair point in terms of some of the complications but I still think if you talk to Graham Finegold who you mentioned or others and Graham Feingold is actually my advisor right now. They would agree that if you — well, take a heroic assumption right now. Assume you have the right size which we kind of know we do in at least some ship tracks. You can get brightening in the effects. We observed that. I mean I have papers looking at that effect and part of that is because from space we often think of Earth as a blue planet right? And blue is actually mostly from the atmosphere if you just look at the ocean from space it is essentially black. So, sunlight that is getting into the ocean is not getting back out. The ocean is going to absorb basically all of the sunlight. So you now put a nice bright puffy cloud over the ocean, and you have a lot of leverage for reflecting that sunlight back to space. Now, let’s move over to Greenland ice sheet, you have a couple of kilometres of ice below you, put a cloud above that, you’re already reflecting all of the sunlight you would have otherwise because the ice is just so reflective itself. The only effect the cloud can have left is warming. So that is why in the Arctic when we are talking about surfaces that aren’t particularly dark but rather are quite bright. So, Greenland is kind of an extreme example, but let’s take the sea ice example. If you have sea ice that is already reflecting 40% of the sunlight, and you put a cloud above it that is reflecting about 40% of the sunlight or something like that. You’re not really getting a strong cooling effect right? At least from the top of the atmosphere persepective. So you are already going to reflect that sunlight anyway, but you still will have the greenhouse effect of the clouds. So that’s why someone could reasonably be concerned about having this cause warming in the Arctic with similar physics. Another difference I will mention is (inaudible) we have mentioned in some of these arguments are true for liquid phase clouds and particularly what we call warm liquid phase clouds. Usually these clouds that are at temperatures above freezing so they are in the, they are liquid droplets. If you start getting into regimes where you have ice formation a lot more complicated processes start happening and there is actually a really good paper from a couple of years ago looking at these ship tracks I think we have brought up looking at these lines of cloud (inaudible) following individual ships that we can trace back to the pollution those ships emit. In the tropics and the subtropics you can see pretty clearly on average the increase of cloud brightness. That effect is a lot weaker at higher lattitudes when you have these clouds that are not just liquid but a mixture of liquid and ice because those ship particles also effect the ice formation, and that could cause these clouds to rain out more etc. So another question when we are talking about Hudson Bay, in the summer are we getting clouds that are…

Metta Spencer  27:38

Let me see if I.  You got me, if there is ice in the clouds, that’s going to do what? It is going to more have a warming effect or, I mean you have to treat me like a child, I really, I really want to understand but it is hard.

Michael Diamond  27:43

Yeah. Yeah, so the ice in the cloud just makes more complicated processes start happening. So in the case of these ships this might be different from what you are proposing in the Arctic. But let’s just take the case of ships for right now; becaue that is what we already have observations of. The particles there can form new ice particles, not just new liquid particles. And if you form new ice particles, one way of thinking about this in kind of a simplified way is: ice is a lot greedier for water vapor than the liquid is. So if you start forming some of those new ice particles that actually starts stealing the liquid from other places, and creates big ice crystals and snowflakes, and starts causing precipitation, which causes those clouds to start going away. Well, so if you create more ice in the cloud, you can dissipate or–

Alan Gadian  29:13

Michael you look at the geometry of the Earth, and you look north of 60 degrees and south of 60 degrees. That represents 5% of the cross sectional area of the planet: 5%. It might represent from 60 degrees north it might represent 25% of the surface but it represents 5% of the cross sectional area of sunlight coming into the planet. So we’ve now got 90 to 95% of sunlight coming into the planet. And what you do in that? 5% might help in the middle of the summer, but in the average over the year it’s irrelevant. And I know it’s very important if you live in the pole or near the poles. But in terms of the heat balance of the planet, anything north of 60 degrees north is (I know Stephens going to disagree with me) is almost irrelevant for the whole heat balance of the planet. It’s what’s happening to __________. And that’s why I like to focus this reflection on the sub tropics, because the sunlight is coming in perpendicular. You yourself, Michael said, in the sub tropics, the strata cumulus clouds, the ship tracks, reflect radiation and during most of the year, in the sub tropics, you get a bigger bang for your buck. You got more sunlight coming in, changing the reflectance a little bit, or sending more back. In the Arctic, it might be important in specific regions, like the Hudson Bay, but in terms of the global heat balance, Arctic clouds to me are interesting (because I study clouds) but heat balance of the planet. I mean, I just don’t think they’re very important.

Stephen Salter  31:26

The average solar input is 340 watts per square meter, that’s over 24 hours over the whole year. For a short time, the South Pole gets 550 watts per square meter, because it’s coming in for 24 hours. So, provided you are able to pick and choose the latitude you want to work at, you’ll find it’s a whole lot better than if you just took the average. If you if you could be at more than 340 watts by being being able to move around very fast. And the hope with the marine cloud brightening with ships releasing spray is that they can be where you want to have them during the year. And we don’t want to go too close to the ice in the Arctic, partly because the seawater is absorbing so much. And so we want to get clouds over the sea rather than over the ice. But we also don’t want to have our ships bumping into the ice. We want to be well clear of the ice so we can work anywhere where your friends choose us to be. And this will certainly vary through the year. And we want to be migrating with the seasons.

Alan Gadian  32:41

Rosenfeld would say we should in any clear area, we should spray our salt. Now he goes even further than we do. He says any clear area put aerosol in.  I don’t quite agree with that. But he would go even further than Stephen.

Stephen Salter  33:01

Yeah, he’s predicting about double effect that we’re hoping for. I just wanted people to see these two jars. Okay. Those are glass balls that are four millimeters in diameter. And these are glass balls that are 40 microns in diameter, 100 times smaller. And this is very nice pocket demonstration of the Twomey effect. Okay. And the optics of this is really, really robust. This is what we’re wanting to do.

Alan Gadian  33:28

There’s same mass of glass isn’t there in each one Stephen? The same mass of glass and a completely different reflectance.

Stephen Salter  33:37

Yep. Yep.

Alan Gadian  33:38

That’s the key point. Big ones look dark, absorb that the solar radiation. The little ones…

Paul Beckwith  33:46

The mass can’t be the same, the packing density is quite different. There’s going to be air gaps between the bigger spheres, smaller than smaller spheres. So No show the same ratio of glass to gap. Yeah. But before I forget, a quick question to Michael and Alan. Those ship tracks that you were talking about.  The paper, most recent paper said that there actually might be a much larger effect than we thought because at first we were just looking at visible ship tracks and now we’re looking at all of the ship tracks and then projecting them to where the wind would blow them and see and cooling over that area. So there’s a lot of invisible ship tracks and therefore, the global dimming effect. You know, if we shut off all aerosol production from industry, instead of being about half a degree Celsius, warming from the removal of aerosols, it’s more like one degree. So it means it’s much more sensitive effect than we thought and this is also confirmed, I think from the 911 when there was no aerosol is being produced by aircraft. The aircraft were shut down over the US and Europe, you know, for several days.

Metta Spencer  35:07

Help me again, I think I could almost understand you, but

Paul Beckwith  35:17

We’re talking about clouds. But we need to also be aware of the effect of the aerosols, not just the the indirect effect of clouds.

Metta Spencer  35:28

We’re talking about the effect of the ship sending these trails, or aerosols that have been produced. Is that what you are referring to?

Paul Beckwith  35:38

Well, it’s, it’s basically incomplete combustion particles from the bunker diesel, you know, so there’s black carbon, there is aerosol.

Metta Spencer  35:48

This is not saltwater, this is aerosol, which is different. But aerosol has the same effect as the saltwater particles or, or not? That’s where I’m confused is. I’m not sure what the connection is, or whether they’re even the same thing. Aerosols and cloud particles.

Paul Beckwith  36:13

Yeah, well the aerosol is anything non water.

Alan Gadian  36:18

Let me give you an example of this. When Barack Obama signed the contract to de-sulfurize fuel, the emissions from the ships changed. You got smaller, you got different particle size. So the advantage of burning heavy sulfurous fuel might kill off millions of people in the air with air pollution. Because there’s increased air pollution in places like India. The fuel cleaner actually warms up the planet. Because if you pump lots of sulfur, or these aerosols into the atmosphere, then you’re actually cooling the planet down. If you clean up fuel oil from ships, which is a major source, because ships usually use old (and there’s a paper in Nature, I think about this, saying Barack Obama cleaning up the fuel oil will actually increase the warming at the surface of the planet.) Because there’s less reflected back to space by these aerosols. This is what Danny Rosenfeld says, we should be spraying (inaudible).

Metta Spencer  37:40

Hold on. Now, let me let me struggle. Because I’m doing this for the sake of my listeners. Other people are stupid as I am, so I’m going to help them.  Now, so these aerosols are not salt particles, we know that the salt particles which go up to the clouds will brighten the clouds. But these aerosols are dark things which will have the effect of warming, but that doesn’t figure into it.

Alan Gadian  38:14

No, cooling the planet.

Metta Spencer  38:16

Why we cooling– dark things? Why would they be cooling the planet? They would be warming the planet.

Alan Gadian  38:23

No, because they’re not dark. Essentially, it is to do with the wavelength of. And so if you put lots of sulfuric particles, they have names like PM 2.5, PM 10, which relates to their size. So if you put, it’s like making the droplets in your clouds a little bit bigger or a little bit smaller, you could either warm up the planet or cool the planet. And it’s only because if you get these droplets of a little bit small rain droplets, not cloud droplets a bit smaller than they are now. They will reflect radiation. But if you pump out a lot of sulfuric particles of a certain size, then it warms up the planet.

Metta Spencer  39:15

So, the bigger the size, the more it’s going to warm the planet?  Yeah, no!  No? Maybe that’s where I’m lost. Because I don’t understand the logic of what the size has to do. It sounds like it’s it’s opposite from what we’re arguing about when you put smaller salt particles into the clouds.

Alan Gadian  39:41

Yeah, it depends on the size of the particles you’re putting into space. So if you look at Australia, Australia is a great big open-cast mine as far as I’m concerned. And because there’s huge amounts of coal and iron ore going to China. And if you look at the clouds produced, ______ actually radiating out to space. And if you’ve close down the mines, the planet reflects less to space. So you’ve got aerosols, and you sometimes call it sea salt and aerosol, but it’s different. You’ve got little bits of particles of clay, dust, dirt, whatever, sulfur from fuel. They’re the aerosols. And then you have the cloud droplets. So the aerosols grow, like water condenses on the aerosols to produce cloud droplets. And Stephen is showing the slide there. Those are cloud droplets he’s showing from the book The the water forms on the aerosols. Stephen.

Stephen Salter  41:01

Yeah, I just wanted to show you this set of 20 different gray bars going from black to white. Okay, so there’s 5% difference between each bar. Now, if you look at the group. How many bars do you need to count before you can tell which way the gradient is? It’s three or four bars, okay, which is a 20% difference in contrast. And to see a ship track, you need to get at least at least 20%, maybe 30%, for it to show up against the background. So that’s a tremendous amount more than we need to save the planet, we need to save the planet by about a half a percent contrast change, if we did it everywhere. And if we can only do it in 10% of the area, we need to increase the contrast by 5%, which is one bar. And that means that you won’t be able to see the change in the clouds from a cloud experiment, but you will still be cooling the planet. Right? That’s the gray scale. If anybody wants another gray scale with a different number of bars, it’s very easy for me to produce it. Alright, so 5% per bar, going from white to black 20.

Metta Spencer  42:15

Okay, I’m afraid I’ve interrupted your dispute. Where you were having a what makes sense to you a logical argument and I just stopped you to try to get you to make sure it’s sunk in here. But so I’ll think further about this. Oh, here comes Ellen Judd. She wants to ask a question, too. So maybe we can really discombobulate you between the two of us. Ellen? There’s sort of a niggling thought in the back of my mind that there’s been a great deal of discussion here about how, when to use certain kinds of aerosols at certain altitudes, and so on. But all of this is a dynamic system. So none of this is going to stay put. And I’m not hearing about how is this going to interact with all of the other factors that the currents, the levels of moisture, the rainfall.

Alan Gadian  43:13

Because we did a big experiment called vocals off the coast of South America. And you had these cloud decks, right. ______ stratacumulus, and you flew underneath them for hours, and the wind was almost zero, and this went on for days. So under these regions, what happened was, you got a circulation. So the aerosol went off into these layer clouds. dropped down, went up. And this went on for days, and days and days. So in those regions, the air does really, it moves up and down a little bit. But these clouds are in you can see from one day to the next to the next. They’re stable. And yet, you can see if you look at a mid latitudes storm, that I mean, the air is ____out- it’s completely dissipated. So spraying under the stratocumulus level, it will stay there for days and days and days. It’s like smog, it was could stay there for days. But over sea there’s nothing: the radiation at the top, the solar radiation, the infrared radiation, the dynamics, all balance. And that is what’s so amazing about the stratocumulus clouds, and why the numerical weather forecast just can’t understand them. There’s no way the physics in a numerical weather forecast can actually get them right. And it’s because the air is stationary for days effectively.

Metta Spencer  44:58

It’s interesting. Will that happen in general?

Alan Gadian  45:03

No, no, oh, no, oh no. In general, there’s lots of vertical motion in the atmosphere. And there’s lots of what we call slantwise convection, there’s lots of vertical convection, there’s lots of overturning due to radiation at night. But in these regions, there is so little motion, there’s small eddies that go round and round, maybe two kilometers in size, and they just go round up and down a little bit. And it rains out of the bottom, the aerosol evaporate, they go back in, and people including Graham Feingold and people like that, have spent years looking at the edge of these clouds, to see how they break down. It’s intriguing how this balance works. A lot of cloud physicists are still trying — Graham Feingold included — are still trying to understand how these systems can work.

Metta Spencer  46:05

Are there a lot of places in which you could do this and do it stably –to a degree that it’s going to make a large difference? Or are these sort of anomalous and special circumstances?

Alan Gadian  46:17

Well, we argue that we can do it in these regions, if you’d look at 10% five% of the, five to 10% of the maritime, It is covered with these clouds. And if you did it enough, you could reduce it — if it works, and this is a big challenge, will it work? I don’t know whether it work. But the radiation equations, say, if you do it in these five to 10% region, you can effectively compensate for double carbon dioxide for four watts per meter squared. Very easy if it works. And on one occasion, Richard Branson invited Stephen and I and John Latham for dinner because he wanted to offset the carbon from his aircraft. And he wanted the patent –didin’t he Stephen? — for so he could offset so he could say I’m offsetting this emissions, in my aircraft.

Paul Beckwith  47:21

Did you got to his island or something during the hurricane?

Alan Gadian  47:26

No, we met him in California after his first SpaceX crashed.

Paul Beckwith  47:32

Ok. One key point that, that the public needs to do, the listeners. And I’m sure Metta already knows this. But Stephen often points out that the spraying is absolutely useless over land. Right? There’s loads and loads of aerosols in the air above land.

Alan Gadian  47:51


Paul Beckwith  47:52

It’s when you go over the ocean, especially, you know, away from any shoreline that the aerosol count drops. But there are some places of the ocean where the aerosol count is extremely high, for example, west of Africa, you know, where the winds just blow and pick up the particles in the deserts and blow it off offshore. And that’s where the Hurricanes spin up which then come to North America. So, the spraying you know– if you are wondering, the idea of spraying if you’re spraying on land, you need to have a prevailing wind, like on an island carrying, carrying the stuff over the ocean. So that’s the key point we’re talking about, like how many particles Stephen over the ocean compared to the land,  like a million times difference or something?

Stephen Salter  48:41

Not a million, I think the range over the ocean system by between 10 and 100. And over land.

Paul Beckwith  48:48

100 particles per cubic meter?

Stephen Salter  48:51

Cubic per cubic centimeter.

Paul Beckwith  48:53

Cubic centimeter.

Stephen Salter  48:54

And over land it’s 1000 to 5000. I could maybe, if I am able to share a screen,  find a map of them.

Metta Spencer  49:04

Don’t worry about that. What I’m a little bit apologetic about is diverting the dispute, because we do need to tackle where it is that there’s a controversy, and I wanted simplification for my own edification. So let’s go back to whatever it is that you folks disagree about, because I think there is a significant controversy that is meaningful and important. And it may even determine whether or not the whole idea of cloud brightening in Hudson Bay is a reasonable project. And that is I want you to go back to what it is that you’re disputing and see if we can find out or make any progress with that controversy.

Paul Beckwith  49:54

So the one side is spray over Hudson’s Bay and bring back the ice In the, you know, cool in the summer so that the ice doesn’t all disappear in the summer it stays there. And the other idea is that no, it’s not going to do anything at all. We should be spraying in the equatorial regions or regions less than 60 degrees north.

Metta Spencer  50:20

Do we agree that that is the controversy?  Is that the question? That’s what we’re arguing about.

Michael Diamond  50:28

I might add one more thing about how concerned we should be about the aerosol and clouds going over sea ice. And then also, how concerned should we be that maybe the Arctic cloud dynamics, if you spray too many small particles, as we talked before, you can actually thin the clouds instead of thicken them? So add those in Arctic clouds, I think have one more kind of mechanism, I won’t go into the full physics and the subtropical clouds in terms of why they might be even more sensitive to thinning.

Stephen Salter  51:01

Can I show you an experiment done was trying to simulate the release of one spray vessel. If you if you do that and you are looking for the clouds being a bit whiter. You were from, from once, wherever you won’t be able to see it at all, it looks as if it’s just ordinary clouds. But if you take 100 images of different clouds that have been sprayed and add them together, you can see the there is a useful amount of light. And I can show you a computer result if you can let me share a screen. What I have done is taken the algebra from Twomey and I’ve used this to change the brightness of things in the in this pattern. And then what I did was to apply the same algebra to a real cloud image, which is here. And you should be we’re hoping that we’d see some white plumes along here. And it’s very difficult to believe that there is one there, you can actually see some here as well. But this would not be enough to persuade someone to spend $100 million. But if I take this image, and add it to a whole bunch of other images, I can see this brightening coming up. And this isn’t enough to save the planet. This amount of brightness.

Metta Spencer  52:28

Stephen, what’s the background? What is the stuff we do see this swirly thing. What is that?

Stephen Salter  52:35

You can see here ordinary proper clouds. This is South America. And this is the area that Alan Gadian was talking about. And these are the patterns of clouds, right? What I’ve done is I’ve got 100 different images from Robert, and put them together, average them and divided by 100. And I get this thing here where I can see these four blooms, showing you that we have made a difference to the brightness by enough to save the planet, although you can’t see it at all on that one. That 100 different cloud images average up to that.

Alan Gadian  53:17

Yeah, I think that picture there is the average strata cumulus cloud over a period of weeks, it isn’t like that. It’s more distributed. But if you average the number of droplets there at clouds, that is what a numerical model hopefully will produce that sort of thing over maybe a few days. In fact, they don’t do it. It is a real problem for climate models. Climate models do not get these clouds. Beyond Stephens (inaudible).  He laughs at this because the climate models do not get the clouds’ radiative properties. And so we’ve got a real challenge from the numerical modeling you can do, Michael, or you can do Graham’s high resolution studies, and you can see a signal. I’ve shown it, but whether this works in practice, the only way you’re going to do it is actually. An experiment it will only cost 40 or $50 million. I think you get a few research aircraft and measure  the droplet sizes. But until someone does it, we just don’t know.

Metta Spencer  54:39

But well, Alan, would the the Hudson Bay experiment be a good test?

Alan Gadian  54:47

Well, you’ve got to get the right clouds. So the best example is to do it where the clouds exist and try it there. And the sorts of clouds you know exist. They know they’re there every every year, every month or whatever, do it there. And if it works there, then it’s likely to work in other places. But you really do need to operate three or four or five research aircraft, you need spray generators. And you need the ability to measure the drops to see if it will work.

Stephen Salter  55:24

I think we can get it by off satellite images. I don’t know, I don’t think you need to have aircraft. These are all just satellite images.

Alan Gadian  55:36

Well, maybe. I don’t know whether I agree with you or not. Stephen, I think you need both – in my view.

Metta Spencer  55:42

Now. Let’s go back to my big question, which is, what is that controversy? About what do we disagree about ?

Paul Beckwith  55:51

Well let’s go back to Michael talking about, some other differences between Arctic clouds and subtropical clouds. And then Stephen came on, so he didn’t finish what he was going to say.

Metta Spencer  56:04

Right, good.

Michael Diamond  56:07

Yeah, so I think some of the differences that might be controversial for why we have questions about it and Hudson Bay in particular? So those questions of–  if you have the clouds over sea ice, not just over open ocean, you could get a warming effect? Are these clouds maybe more sensitive to drying out, instead of brightening? That might be one? And then I think the question, we didn’t talk about it too much, but of cloud phase. These aren’t just liquid clouds, but they also are other ice clouds. Are there other processes we need to be thinking about? One thing I’ll throw out. We didn’t really have time to talk about it, but there are folks who actually have argued that in the winter, what maybe you want to do is seed the clouds with ice to get rid of them, to thicken the sea ice then then hope it lasts more into the summer. So that’s another kind of question. If you want the sea ice in the summer, does that necessarily mean you want to target the summer? It might not. It might mean you want to thicken ice in the winter and have a longer.

Stephen Salter  57:13

We want to operate in the summer half part of the year. So we’d do the stuff in the summer. We want to see the brighter clouds by averaging them, leave the water a little bit cooler than it would have been so the ice might form a little bit more when the winter comes.

Paul Beckwith  57:31

But what Michael is saying it might be more effective to not do anything in the summer but to reduce, remove clouds in the winter to thicken the ice then.  He’s saying that would need to be looked at too.

Stephen Salter  57:44

The difference in the reflectivity of clouds and ice isn’t very much. I want to have the black water the very very dark water having more clouds over it than without the the spray.

Paul Beckwith  57:59

No, but Stephen in the winter it’s dark. There’s no light so if you remove the clouds in the winter then there can be a lot more radiation out to space which will cool the cool the whole region and thicken the ice so so that might be very effective way of doing it as opposed to looking at the summer.

Stephen Salter  58:16

That’s right I did a little paper about making very small aerosol which does clear clouds.

Alan Gadian  58:28

This is where I disagree slightly with Stephen in saying that look I’m not worried about the poles. They only represent 5% of the cross sectional area, 20% of the globe. So Stephen and I have a slightly different approach  _____ to cool Hudson Bay even more.

Paul Beckwith  58:52

Okay, isn’t the easiest way to get a better handle on what’s going on is to just have an aerosol generator on a ship and you know, just capture run the emissions from a smokestack through water or whatever so it doesn’t go up into the air, you know, just tilt the smokestack and pump stuff into the ocean instead and then have generators, particle generators of all types on the ship. As the ship is transversing its regular route, you can see what’s happening from satellite measurements. How would that cost 50 million?

Alan Gadian  59:27

The problem is that this particle size has to be very mono, it has to be _______ because if you make the particles come up too big, you will maybe cause condensation precipitation. If you make the particles too small, you’ll just remove the clouds as well. This cloud physics is really people don’t appreciate how complex it is because you’ve got infrared radiations, solar radiation dynamics, air going round, you’ve got dynamics of the large scale, dynamics of substance. It’s a hugely complex system. And cloud physicists, I think, only two of us will agree on this is a really overlooked fact, it’s so complicated, and it’s so detailed.

Stephen Salter  1:00:28

I want to spray salt water, and I want to spray them with a very controlled size. And I can make all this fit into an ISO sea container. And that can be on land, or it could be on a very small island in the middle  or a few islands in the Hudson Bay, or it could be on the deck of the ship. But when it’s on a deck of a ship, I don’t want the ship to be releasing other materials of sizes that we don’t understand. So this is why I think I’d rather do it from a land point and rotate the images of the clouds that we’re making to make them all be in the direction of the wind. And that will let us see the works from this source by averaging them up.

Paul Beckwith  1:01:21

There’s a prize by the Royal Family, millions of pounds per year, 10 different projects going on until 2030. Or, you know, I’m sure Elon Musk,  if he can spend 44 billion on Twitter and make it down to 6 billion in three weeks. I’m sure he could spare some cash if you just go in. So it’s a matter of getting some funding from somebody to get a device on a ship, like making shipping container-size unit. And then you’re set right?  From there you just, all you..

Metta Spencer  1:01:54

We need to wind this up and I need to ask a couple questions. Simple. Do we agree that doing what Stephen has just proposed, which is not even clear what he’s proposed, but sort of I know what he’s doing. Does everybody think there would be value in doing that? Or is Is there really any doubt that it’s even going to be worthwhile doing?

Alan Gadian  1:02:20

Yes, I think it’s an experiment that needs to be done. And the only way we’re going to find out if marine cloud brightening works is if we actually do it.

Paul Beckwith  1:02:30

We should do it where the chance of success is greatest. And that might not be Hudson’s Bay, then.

Stephen Salter  1:02:36

It might not be, but if

Paul Beckwith  1:02:38

Hudson’s Bay is within Canada, so you don’t need international buy-in. It’s all within Canada. So that’s the one of the big things: push for Hudson’s Bay, right?

Alan Gadian  1:02:48

Do have the clouds, the right clouds, that’s the trigger signal. And I don’t know. That’s Michael. I don’t know.

Metta Spencer  1:02:58

How do we find out whether we have the conditions that are required to make this experiment worthwhile? Like whether the clouds are are right.

Paul Beckwith  1:03:08

Okay, so Michael and Alan can look at some satellite images of Hudson’s Bay clouds. And they can tell us in a week or two, right?

Metta Spencer  1:03:19

We need another session like this, because this has really been hard for me to follow. And I hope our we have some listeners here, an audience that has persisted, but I am happy to come back at it again however often we need to do it in order to get it. Something that we can comprehend, and we have some consensus about what we agree on or don’t agree on.

Stephen Salter  1:03:48

We can do a quick experiment now with a computer package called windy. If you share the screen again, I’ll see if I can do it while you wait. And we want to go to Hudson’s Bay, which is up here. And what we want to do is look at the cloud fraction.This is what’s happening there now. Okay, that’s the three minute here. You can see the direction of the wind going. I’m going to look at clouds here. Right now that’s where the clouds are in Hudson’s where at the moment.

Metta Spencer  1:04:33

Are these these dots the clouds?

Stephen Salter  1:04:37

The white is the cloud fraction. So there’s, there’s there’s no clouds in this area here. But that’s low clouds. That’s medium clouds. And that’s high clouds. And we what we wanted to do is there’s not much in the way of high clouds by the look of it. It looks as if we’ve got medium ones there, and low ones here. And it’s slow runs, we can get out. So the brown is clear sky. Okay, and the

Alan Gadian  1:05:06

The problem, you have to do it at best time of year. And I agree with Stephen, this is not a good time of year to do it. Want to do it in the summer. And how much cloud is in the summer? We don’t know yet.  Yeah, we could run this program in summertime, we’ve got two weeks, either side of the day’s date.

Michael Diamond  1:05:34

Yeah. So I think maybe to summarize in a way that might be a little bit more helpful is,what  we could look at satellite images and find out in the summer, when do you have low clouds that are not obscured by high clouds? Because if there’s a cloud in the way, it doesn’t really matter how it doesn’t matter what that other lower cloud is doing. I’m going to look at that from satellites. And you could also do numerical modeling. So if you have a regional model of this part of Canada that does clouds and sea ice, at least moderately well, or moderately, realistically, you could see how does this proposal work in model world? And that would give us a sense of what kinds of effects can we expect in reality, but I would start with the model experiments before spraying anything in the real world.

Paul Beckwith  1:06:21

Right, and then overlay the clouds with where the sea ice is at that time. So see how many of those clouds are over open water?

Stephen Salter  1:06:28

Yeah, the software should give us this answer very quickly.

Metta Spencer  1:06:35

My question is, do we is there a reason to resume this conversation? And hope that we have some data that will make it possible to move forward a little bit? Because I’m not sure still, whether we’ve made any progress in getting some understanding that’s generalized here that everybody understands? And we agree on? Do we need a follow up?

Paul Beckwith  1:07:04

Well, I think we should, you know, go away and have a look at these things. We’re talking about clouds over Hudson’s Bay, you know, sea ice, SAT, both satellites, and so on, and try to come up with, once we have a bit more info, and then have have another follow up meeting.

Metta Spencer  1:07:23

Now, one of the one of the things that I’m hoping to do in probably the next session on this topic about the Hudson Bay project, is to invite some Indigenous people, or at least one Indigenous leader, because these are the people whose lives will be immediately affected by the project if we do it and we hope that officially so rather than detrimentally. But we need to consult with them,  what do they want? Would they will their lives be improved if they had ice returned and restored throughout the year in their region? And how important is that to them and so on. So we don’t have those contacts yet, but I’m looking out for for contacts with some Indigenous peoples.

Paul Beckwith  1:08:12

The conference on biodiversity COP 15 is starting in a couple of days in Montreal, it runs for two weeks. And, you know, it’s all on biodiversity. There’s gonna be a lot on Canadian biodiversity, including probably the Hudson’s Bay region. I’m attending the conference. So I’ll keep my eyes open on anything that is relevant to Hudson’s Bay.

Metta Spencer  1:08:37

Thank you all. I appreciate it very, very much. And hope to see you again sometime soon. With progress. Thanks. Project save the world produces these shows, this is episode # 529. Watch or listen to them as audio podcasts on our website tosavetheworld.ca. People share information there about six global issues. If you want to find a particular talk show enter it’s title or episode number in the search bar or the name of one of the guest speakers. Project save the world also produces a quarterly online publication, Peace magazine. You can subscribe for $20.00 Canadian per year, just go to pressreader.com on your browser and in the search bar enter peace, you will see buttons to click to subscribe.


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We produce several one-hour-long Zoom conversations each week about various aspects of six issues we address. You can watch them live and send a question to the speakers or watch the edited version later here or on our Youtube channel.