The G-word

Is geoengineering the answer to the climate crisis? Or is it too dangerous to even discuss? It’s been theoretical so far, but now, one startup says their technology could soon shield the Earth from the sun. Guest: Robinson Meyer, climate journalist and founding executive editor of Heatmap News. For show transcripts, go to ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/unxtranscripts⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ For more, go to ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/unexplainable⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ And please email us! ⁠⁠⁠⁠⁠[email protected]⁠⁠⁠⁠⁠ We read every email. Support Unexplainable (and get ad-free episodes) by becoming a Vox Member today: ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/members⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ Thank you! Learn more about your ad choices. Visit podcastchoices.com/adchoices

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:01Noam Hassenfeld?

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• 0:37Speaker 01

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• 1:22Speaker 02

  Start by imagining a slightly different sky.

• 1:29Speaker 02

  It's the year 2076 and the sky is almost our sky. A lot of people glance up at it and barely notice anything different. But actually, the sky is just a little bit changed from the year 2026. It's a little bit less blue.

• 1:52Speaker 02

  In this imagined future, the world has made a major decision. Climate change got so bad, floods, droughts, fires, that we needed to do something drastic. So we decided to send aircraft up into the stratosphere to essentially spray particles into the sky and reflect sunlight away from the Earth, creating like a worldwide shade umbrella to keep temperatures down. It's a real idea. It's been discussed since at least the 1950s. These particles would cool the Earth and, incidentally, make sunsets a little bit redder. They might make the sun appear a little bit bigger.

• 2:36Speaker 02

  And they'd make the blue sky ever so slightly whiter. They could also save us from some of the effects of global warming, but it would be like this giant, high-stakes experiment. And, you know, things could go wrong. Some scientists worry that if we did this badly, we'd disrupt global rainfall or trigger droughts. And even if things went well, an experiment this big could cause human drama. One researcher I talked to was like, "Okay, imagine India decides to start doing solar geoengineering, and the next year, just by chance, Pakistan has some of its worst flooding in decades."

• 3:20Speaker 02

  Maybe the geoengineering, in fact, has nothing to do with it, but maybe not everyone believes that. You can imagine things getting ugly. All of this sounds a little sci-fi to me. And to be clear, this technology doesn't currently exist like sitting on a shelf somewhere. But I recently read an article in the climate outlet Heat Map News about a startup that says they are close to making it real. They have a very startup kind of name. They are called Stardust Solutions. And, as sometimes happens with startups, there's a lot about what they've been up to that still isn't public.

• 4:04Speaker 02

  The article says that they spent years in what is known as stealth mode. I spoke to the author, veteran climate reporter Robinson Meyer.

• 4:17Speaker 02

  If I say the word geoengineering, what is your first thought?

• 4:22Speaker 03

  Well, my first thought's a little bit different than it was maybe a year or two ago.

• 4:27Speaker 02

  Tell me more.

• 4:28Speaker 03

  My first thought, I think, a year or two ago, was kind of interesting thought experiment unlikely to happen. But the more we go forward, the more likely I think it might wind up actually occurring.

• 4:43Speaker 02

  It's unexplainable. I'm Sally Helm. And are we doing this? How close are we to a world where some company or country, or even a single unruly billionaire, makes a world-changing decision on behalf of all of us? I talked to Robinson Meyer to answer that question and to find out, if this might happen, what should we all know about it now?

• 5:25Speaker 02

  All right, Robinson. If I were to walk into a room full of climate scientists and say that word, geoengineering, what do you think would happen?

• 5:33Speaker 03

  I think it would be quite divisive. Some people would be like, yeah, let's talk about it. Why do you just walk in and say that word? And I think some people would be like, it's dangerous even to have this conversation. We shouldn't be talking about that.

• 5:47Speaker 02

  Yeah, I mean, air that out for me a little bit.

• 5:49Speaker 03

  Well, there's a lot of reasons. I mean, I think, first of all, we're talking about tinkering with Earth's atmosphere at the planetary scale, which, of course, we're already doing through climate change, through the unmitigated release of greenhouse gases and carbon dioxide into the atmosphere. I think people say, look, we're running one open-ended experiment, an irreversible experiment on the Earth's climate system and its climate change. You know, it's global warming.

• 6:18Speaker 03

  We should not compound that experiment by running two.

• 6:22Speaker 02

  Why are some people pro geoengineering?

• 6:26Speaker 03

  I think the pro case is that, look, climate change is going to be awful. It's going to cause awful heatwaves. It's going to cause extreme weather, and it's going to hit poor communities and poor places, often the worst of all. Isn't this our responsibility as stewards of the planet? Because, by the way, it's not only going to be bad for people, it's going to be bad for coral reefs. It's going to be bad for animals. And if there was some way to stop that suffering, shouldn't we try it?

• 6:59Speaker 02

  I've also heard the objection, like, the real problem is the carbon, people. Like, don't talk about this way to mitigate global warming. Maybe people are going to then hear that and be like, OK, great. We'll just emit as much carbon as we want.

• 7:13Speaker 03

  That's true. That's really, and in some ways, that's really the main objection, that people's response is not going to be, oh, this is amazing. Well, we've bought ourselves more time to deal with the greenhouse gases, which we understand are still a problem, and really get serious about climate change. They're going to go, oh, great. We don't have to worry about it anymore then. I can burn as much coal or gasoline or natural gas as I want, and there's no consequences. And this idea that as soon as you give people, that there's a moral hazard to talking or researching or conducting geoengineering, I think is one of the biggest drivers of the taboo.

• 7:48Speaker 02

  Robinson told me, mostly when people talk about geoengineering, they're talking about solar geoengineering, this thing where you somehow reflect sunlight away from the earth. And it's kind of a simple idea. Like, you could literally do this with mirrors or with white paint. There's been a kind of wild proposal to spread glass beads over Arctic sea ice. But the form of this that people most often talk about is called stratospheric aerosol injection. It involves spraying some kind of sunlight reflecting particle into the stratosphere. And people usually talk about sulfate aerosols. So sulfate, like sulfur, that smelly mineral, and aerosols, meaning basically little droplets.

• 8:34Speaker 02

  Now, these particular particles do have some known downsides. They can make asthma worse. They can cause acid rain. There's a question about whether they could hurt the ozone layer. But they're relatively well-studied compared to other types of particles that we could use. And they'd probably do the main job we'd be asking them to do. Cooling the Earth.

• 8:55Speaker 03

  So we're talking about reflecting away maybe a single-digit percentage of the sunlight hitting Earth in order to reduce the amount of heat coming into the Earth's system, which means that even though the Earth will be trapping, you know, higher amounts of heat, that's what global warming means, we'll be kind of messing with a different input into that equation. We'll be reducing the amount of heat that comes into the Earth's system, and that will either stabilize temperatures or reduce them across the planet.

• 9:27Speaker 02

  Does it work?

• 9:29Speaker 03

  So we know that the basic chemistry here works because we see nature do it all the time. So the most famous cited example is that in 1991, Mount Pinatubo, this big volcano, erupts in the Philippines.

• 9:45Speaker 04

  Three powerful explosions sent molten rock, mud, and ash more than 10,000 feet into the sky. Within minutes, falling ash turned day into night.

• 9:56Speaker 03

  When it erupts, it hurls this massive cloud of sulfur dioxide into the stratosphere. And over the next few years, that cloud spreads across the Earth in a very thin layer and cools the planet. At its peak, it cools the planet by about 1 degree Celsius.

• 10:14Speaker 05

  Climatic changes caused by volcanoes can persist for a long time.

• 10:18Speaker 06

  And we can be looking at much more severe winters in the years to come.

• 10:21Speaker 03

  And within the next few years, it rains out and goes away, and the underlying global warming effect returns. So we know the mechanism exists. What we don't know is whether we can duplicate that scientific effect with our technology in a way that we can control and harness in a dependable and safe way.

• 10:43Speaker 02

  So there's this question about whether it's technically possible to do this. But I've heard that this is kind of cheap. Is that true?

• 10:53Speaker 03

  It's theoretically cheap. We often talk about climate change as a free rider problem. You know, countries have to collaborate to avoid burning cheap fossil fuels. And that makes dealing with climate change kind of a big, expensive, communal problem. Solar geoengineering, on the other hand, it is theoretically cheap enough that one country could do it alone. And the challenge with solar geoengineering is keeping any country from arriving at this potentially cheap solution that would be quite disruptive to the international system, quite disruptive to the global climate by itself.

• 11:32Speaker 02

  I mean, what's like the bare minimum you need here? Like, is it closer to like, I have a little two-seater plane and a bucket of dust? Or is it closer to like, I have a SpaceX rocket and I have the money to fund like a nice big laboratory?

• 11:48Speaker 03

  Well, first, I want to say that no one's done this successfully. And we're still talking about a technology that's only, in theory, feasible. And lots of people will tell you that this problem is actually going to be harder than we think it will be to solve. But I would say it's somewhere in between. I think this is classically understood to require somewhere but an engineering operation, actually, probably somewhere on the scale of a SpaceX. You would need a confidence in your particle and whatever you were using to reflect away sunlight. You'd need some way to get it up into the stratosphere. And then you'd need some way to like, understand what was happening so that you could monitor the cooling effect, not accidentally send the Earth into a new ice age.

• 12:32Speaker 02

  Sure.

• 12:33Speaker 03

  And Also understand when you would need to add more sulfate aerosol into the high stratosphere because it just falls out over time as part of a natural process.

• 12:44Speaker 02

  And if they were to go away, if we were to stop releasing them, we'd just get all the warming from the carbon that was already there.

• 12:48Speaker 03

  The warming would come back over the course of time that you would had stopped, injecting aerosols into the stratosphere.

• 12:56Speaker 02

  And maybe like scary fast, right?

• 12:58Speaker 03

  I think it depends on how much warming you're trying to avoid, right? So if you tried to solar geoengineer us back to our pre-industrial average, first of all, it would get colder, you know, a lot of places. But then if you were to cease that geoengineering activity, then within a year or two, we would have what's sometimes called a termination shock. We would watch all that warming come right back really fast.

• 13:19Speaker 02

  Scary. I mean, you'd also presumably need to believe that like, the world is going to hell and you're the person to save it, right? Like, people would be doing this because they think it would help either the world or them?

• 13:34Speaker 03

  Yes. Hopefully, any country or person or entity that did this would have some kind of global mandate that they should do this.

• 13:48Speaker 02

  But that is what is scary about all of this. Like, if we are talking about something on the scale of SpaceX, theoretically, maybe someone like Elon Musk could just do this on their own. Or some nation being hit really hard by climate change could just do it on their own. And that one company that Robinson has been reporting on, they might be bringing us closer to that world. That is after the break.

• 14:20Noam Hassenfeld?

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• 14:26Noam Hassenfeld?

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• 14:51Noam Hassenfeld?

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• 15:09Noam Hassenfeld?

  And yeah, I didn't miss a second. And I can make each speaker louder or softer in the Sonos app, or if I'm using AirPlay, so I can make it louder in the kitchen without blasting whoever is still in the living room. It's all just easy and it sounds amazing. These speakers are crisp, they've got great bass, and I'm especially impressed with the new Sonos Play. It packs this like truly awesome sound in a much smaller size. So, I don't know, if I want to head outside for a minute. It's super easy and yeah, pretty

• 15:48Noam Hassenfeld?

  nice out. Visit sonos.com and build your system. Sonos, love the sound, feel the system.

• 16:00Speaker 07

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• 17:25Speaker 01

  Support for the show comes from Engine. Running a small business means every dollar has to work hard. But if your team is still booking travel the old way, it's costing you more than you think. Engine is the fastest growing travel and spend platform in the country, built specifically for businesses like yours. Book a trip in as little as two and a half minutes. Earn up to 10% back on hotels. And in 2025, Engine customers save more than $300 million on travel with zero booking fees, no contracts, and no BS. More than 1,000 businesses join Engine every month. Join them and get $500 when your business signs up and starts traveling at engine.com/box.

• 18:13Speaker 08

  No, I must, I must have, I must have this sun. She must have this sun.

• 18:20Speaker 02

  OK, this company, Stardust Solutions. They're led by a team of Israeli scientists and physicists, and they have raised $60 million, which is, you guessed it, a lot of money. They're going to use that money to develop what they call the technological building blocks of solar geoengineering. Stardust says this will be ready by the beginning of the next decade. And not everyone is thrilled.

• 18:48Speaker 03

  How, how would I put this? They are perhaps not the most controversial startup in the space, but that's because every startup in the space is fairly controversial. And because the idea that there are even solar geoengineering startups now, you know, private companies, private for-profit companies that are researching this technology is not what researchers and... Folks who've been studying this technology for a long time expected. The idea was that it would always happen because governments or academics or nonprofits led the way. But Stardust is a for-profit company and that could mean that it eventually gets into a position where the interests of the public and the interests of its investors lie at cross purposes.

• 19:33Speaker 03

  And that's what I think people are most worried about.

• 19:36Speaker 02

  So this company is pretty controversial. They've raised a good chunk of money and they say that they have this technically feasible solution that might be ready pretty soon. But my understanding is like, we know very little about all this, right?

• 19:55Speaker 03

  That's right. So I was able to talk to the two founders, this guy, Yenay Yedvab, who's their CEO. But there are some things they haven't yet revealed to the public. And one of them is that they believe that they have developed a type of sunlight reflecting particle that is not a sulfate aerosol. We don't know a lot about it, but they basically have developed a proprietary particle that they say does the job just as well, that eventually, of course, they hope to spray all over the world. The way Stardust talks about it, they see that particle as centerpiece of their whole kind of technological building block idea. So they say, you know, it's not just enough to have a particle. You need a way to get that specific particle into the atmosphere and then you need a way to measure that particle across the whole planet.

• 20:39Speaker 03

  And they think that they've done all three.

• 20:42Speaker 02

  I mean, what do scientists that you talk to say about this?

• 20:45Speaker 03

  They are skeptical. They're skeptical of, I would say, the entire company.

• 20:53Speaker 03

  I mean, at one point that I've seen scientists make and heard scientists make is like, look, the thing about sulfate aerosols is we know they break down and they might break down into harmful things, but we kind of know what that process of their destruction in the atmosphere is like. Whatever this particle is, either we have to know how it breaks down and where it goes, or if it doesn't break down, then it's going to accumulate. In natural systems, including presumably in our bodies. And so there's some skepticism around that. I think the other concern you hear from scientists is actually almost pre-scientific in that they have concerns about the entire way Stardust has gone about its approach. There's a set of norms about solar geoengineering and how you would research it, that you should

• 21:38Speaker 03

  be open about your research, that you should publish as you go, that you should be open about the kind of particle you're using, and that you shouldn't pursue intellectual property protections for your technology. And they say Stardust isn't open about its research. It was in stealth mode earlier this year. It hasn't been straightforward about what kind of particle it's using. And that's because it's trying to patent the particle. And then also, by the way, it's trying to patent the particle. You're not supposed to do that. And so there's a lot of concerns from scientists, even before you get to their concerns about the particle, which they feel like they can't answer yet because the particle isn't public yet, that Stardust has not gone about its research in the way that you would hope a company developing such an important and weighty technology would do so.

• 22:23Speaker 02

  Yeah, I mean, you're gesturing at this mess of issues that gets called governance in this conversation. That's like, how do we make this decision as a globe? I mean, how should we? What do people think is the ideal way to decide something like this in theory?

• 22:41Speaker 03

  The question of who would deploy this, who controls what gets distributed, all of that is up in the air. I think ideally, this would be a consensus decision that everyone had bought into to some degree. And so we've actually, the world has arrived at a similar consensus to this before.

• 22:59Speaker 09

  The Montreal Protocol, signed today, aims at stopping the deterioration of the ozone layer in the atmosphere.

• 23:05Speaker 02

  Robinson told me, everyone points to this global group project that we managed to pull off in the 1980s. Chemicals called chlorofluorocarbons were destroying the ozone layer.

• 23:18Speaker 10

  CFCs are used in automobile air conditioners, home insulation, and in plastic cups.

• 23:24Speaker 02

  We got together and stopped it. If enough of them ratify the protocol, it is probably not too dramatic to say they may have saved the world. That's the kind of global collaboration that a lot of people are hoping for here. And Robinson said Stardust says that they are hoping for that, too. They're kind of like, we're just developing this tech so that the world has the option to use it.

• 23:48Speaker 03

  I think what people fear is that this company is going to do something that we've seen other companies do, which is advertise its good results and suppress its bad results and make its technology look safer or less risky than it might actually be. And as solar geoengineering then becomes an option that policymakers can pursue, they won't have the full slate of information they need about to make that decision. And of course, as the technology becomes more feasible, they'll become more likely to make that decision.

• 24:22Speaker 02

  I reached out to Stardust about these concerns and got a detailed response from their CEO. He said, "The company agrees that scientists and regulators will need to be convinced that the new particle is safe. The company plans to start publishing the results of their safety testing early this year, and he said those results will go through peer review and be vetted by independent experts." He also said that patents are a standard way to prompt innovation and that they don't mean that the company won't ultimately be transparent with their work. In fact, he says they plan to ultimately publish all the results of their research, whether those results are favorable or not. But even if the research on Stardust's particle and their whole plan ultimately holds up,

• 25:03Speaker 02

  Robinson told me, the perception people have could be its own problem.

• 25:08Speaker 03

  I think a lot of other critics say, "Look, solar geoengineering can be a force for good. It can be a force to make climate change less risky and more survivable for many more people across the world. But a for-profit, you know, US-Israeli technology company founded by people whose background is in national security or nuclear science is maybe not the right vessel to convince the rest of the world that like, this is a really good technology and everyone should go for it." I think most people anticipated that when solar geoengineering happened, the research into it would be led by a government, the same way that, say, government research produces

• 25:49Speaker 03

  a lot of our weather forecasting technology or research the atomic bomb, by the way.

• 25:58Speaker 03

  In some ways, I think it is a little bit like a nuclear weapon in that it has repercussions for everyone on Earth. Historically, we haven't allowed the private development of nuclear weapons. When I asked the founders of Stardust what this technology reminded them of, they said AI. And now AI has big repercussions for the future of humanity, and we do allow its private development. And so maybe there's more precedence here than we want to recognize. You know, honestly, I'm not convinced that Stardust is going to be the company that develops these technologies. But I do trust researchers and scientists when they say, as they've said for decades, that this is, while a technically difficult problem, not a technically impossible one.

• 26:42Speaker 03

  And if Stardust doesn't figure it out, I think someone else will. You know, Stuart Brand, he's a biologist and a writer and a philosopher from the Bay Area, had this quote, which was roughly, I'm going to remember it maybe incorrectly, but he said, "We are as gods, and so we might as well get good at it." I can imagine us going the more Promethean route and saying, "No, we're just going to directly take control of the amount of sunlight entering the Earth's atmosphere." I do wonder if someone's going to start looking for that emergency button to tap.

• 27:18Speaker 02

  It's sort of shockingly easy for me to imagine a world where someone just makes this decision. But like, if I'm Prometheus, do I steal fire, give us cooked food and the ability to turn sand into glass, but also unleash the potential for massive destruction? I don't know. It doesn't actually seem like a decision that Prometheus or anyone should be making alone.

• 27:56Speaker 02

  This episode was produced by me, Sally Helm. It was edited by Joanna Solotaroff. Mixing and sound design from Christian Ayala. Fact checking from Melissa Hirsch. Special thanks today to Pete Irvin and Ansar Lemon for helping me understand geoengineering and what our future sky might look like. Meredith Hoddinott runs the show. Amy Padula is a bright marine cloud and Noam Hassenfeld is diamond dust. Jorge Just and Julia Longoria are our editorial directors. And Bert Pinkerton kept listening to Ploddy's story. I wrote a song to remember the code, but without my guitar, I'll never remember it.

• 28:37Speaker 02

  Bird, my guitar, somehow you need to fix it.

• 28:45Speaker 02

  Thanks, as always, to Brian Resnick for co-creating the show along with Bird and Noam. And if you out there have thoughts about the show, please do send us an email. We are at [email protected]. You can also leave us a review or a rating wherever you listen. That really helps us out. And if you are into supporting the show and all of Vox in general, join our membership program. You can go to vox.com/members to sign up. Unexplainable is part of the Vox Media Podcast Network, and we'll see you next time.

• 29:28Noam Hassenfeld?

  Support for the show comes from Sonos. No matter how much you know about frequency response or harmonic distortion, the thing that's going to make you fall in love with a speaker is how it makes you feel. And Sonos has that it factor, you know? It's this seamless system that makes things sound good in every room. That obviously takes some serious engineering, but it also takes a big-picture understanding of how and why we actually listen to things. The birthday playlist, the new TV show, the exciting new game you just got. And for the nerds out there, Sonos does have amazing frequency response and extremely low harmonic distortion. Visit sonos.com and build your system. Sonos: love the sound, feel the system.

• 30:18Speaker 01

  Support for the show comes from Engine. Running a small business means every dollar has to work hard. But if your team is still booking travel the old way, it's costing you more than you think. Engine is the fastest growing travel and spend platform in the country, built specifically for businesses like yours. Book a trip in as little as two and a half minutes, earn up to 10% back on hotels. And in 2025, Engine customers save more than $300 million on travel with zero booking fees, no contracts, and no BS. More than 1,000 businesses join Engine every month. Join them and get $500 when your business signs up and starts traveling at engine.com/box.