Unexplainable - The G-word

Episode Date: January 7, 2026

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! ⁠⁠⁠⁠⁠[e-mail]⁠⁠⁠⁠⁠ We read every email. Support Unexplainable (and get ad-free episodes) by becoming a Vox Member today: ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠vox.com/members⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ Thank you! Learn more about your ad choices. Visit podcastchoices.com/adchoices

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Start by imagining a slightly different sky. 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. 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. 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 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. 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. The article says that they spent years in what is known as stealth mode. I spoke to the author, veteran climate reporter Robinson Meyer. If I say the word geoengineering, what is your first thought? Well, my first thought's a little bit different

than it was, maybe a year or two ago. Tell me more. 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. It's unexplainable. I'm Sally Hohm.

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

And I think some people would be like it's dangerous even to have this conversation. We shouldn't be talking about that. Yeah. I mean, air that out for me a little bit. 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, you know, unmitigated release of greenhouse gases and carbon dioxide into the atmosphere.

I think people say, look, we're running one open-ended experiment and irreversible experiment on the Earth's climate system. And it's climate change. You know, it's global warming. We should not compound that experiment by running two. Why are some people pro-geoengineering? I think the pro-case is that, look, climate change is going to be awful. It's going to cause awful heat waves. 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? 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, okay, great, we'll just admit as much carbon as we want. 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. 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. 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. 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 system, which means that even though the Earth will be trapping 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 system, and that will either stabilize temperatures or reduce.

them across the planet. Does it work? 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. 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. 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 one degree Celsius. Climate changes caused by volcanoes can persist for a long time. And we can be looking at much more severe winters than the years that come. And within the next few years, it rains out and goes away in the underlying.

and 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. 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? 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. 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? Well, first, I want to say that no one's done this successfully yet. 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 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.

Sure. 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. And if they were to go away, if we were to stop releasing them, we'd just get all the warming from the carbonates already there. The warming would come back over the course of time that you would have stopped, you know, injecting air.

ourselves into the stratosphere. And maybe like scary fast, right? 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.

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. Yes. Hopefully, any country or person or entity

that did this would have some kind of global mandate that they should do this. 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. It's all about you. And when you fly with Virgin Atlantic in their upper class cabin, they take the VIP treatment to the next level.

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I'm in Washington, D.C. this week to interview Ruben Gallego. He's a Democratic senator from Arizona, and he's been thinking openly about running for higher office. But he's recently run into some hot water because of his connection to Congressman Eric Swalwell. I have to learn from this, and I will learn from this. But for me, it's not a 2028 question. It's about what it means to be a better first boss in my office and also a better senator to my constituents. This week on America, actually, we asked Gallego about predatory behavior in Washington, his plans for immigration reform, and more.

Okay, 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. Stardis says this will be ready by the beginning of the next decade. And not everyone is thrilled.

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, 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. And that's what I think people are most worried about. 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? That's right. So I was able to talk to the two founders, this guy, Yanayadvab, 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 Stardis talks about it, they see that particle as the 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. And they think that they've done all three. I mean, what do scientists that you talk to say about this? They are skeptical. They're skeptical of, I would say, the entire company.

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, like, 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 and 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 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 Stardis 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. Yeah, I mean, you're gesturing at this massive 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? Like, what do people think is the ideal way to decide something like this in theory? 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. The Montreal Protocol signed today aims at stopping the deterioration of the ozone layer in the atmosphere. Robinson told me everyone points to this global group project that we managed to pull off in the 1980s. Chemicals called chloroflora carbons were destroying the ozone layer. CFCs are used in automobile air conditioners, home insulation, and in plastic cups. 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. I think what people fear is that this company is going to do something that we've seen other companies do, which is, you know, 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. 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, Robinson told me the perception people have could be its own problem.

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, U.S.-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 a lot of our weather forecasting technology, or a research.

the atomic bomb, by the way. In some ways, I think it is a little bit like a nuclear weapon in that, you know, 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 precedents 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, 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. 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.

This episode was produced by me, Sally Helm. It was edited by Joanna Solitara, mixing and a lot of. 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 Hodnott runs the show.

Amy Padula is a bright marine cloud, and Noam Hassanfeld is Diamond Dust. Jorge Just and Julia Longoria are our editorial directors, and Bert Pinkerton kept listening to Plotty's story. I wrote a song to remember the code, but without my guitar, I'll never remember it. Bird, my guitar. Somehow you need to fix it. 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 Unexplanable at Vox.com. 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 slash members to sign up. Unexplanable is part of the Vox Media Podcast Network, and we'll see you next time.