Entrepreneurs want to reflect sunlight to cool the planet. There are big risks. : Up First From brightening ocean clouds to launching sulfur dioxide into the stratosphere, some entrepreneurs and scientists are testing technology that could reflect sunlight back into space to combat global warming. There's evidence some types of solar geoengineering could lower global temperatures a lot. But along with potential benefits come huge potential risks. Experts say the science isn't settled and regulations aren't keeping up. Today on The Sunday Story, a journey into the world of solar geoengineering.

The Sunday Story: Startups want to cool Earth by reflecting sunlight

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I'm Ayesha Rascoe, and this is the Sunday Story.


RASCOE: Last year was the hottest year on record for the Earth - another sign that global warming is here. People are desperately searching for solutions. Many are trying to stop the burning of fossil fuels, but some believe we also could engineer our way out of the climate crisis. Joining us now is Julia Simon, NPR's climate solutions reporter. Welcome to the podcast, Julia.

JULIA SIMON, BYLINE: Thank you for having me, Ayesha.

RASCOE: So I understand you're going to introduce us to two guys in California who say they have a simple but effective way to cool the planet.

SIMON: Yeah. A few months ago, I went to this parking lot on the outskirts of Silicon Valley.


SIMON: I walked up to this gray RV where I see this guy in a beanie and a puffy jacket.

Nice to meet you.

His name's Andrew Song.

How are you doing?

ANDREW SONG: Good, good, good.

SIMON: And then I meet Luke Iseman - messy mohawk hairstyle, orange T-shirt that reads, cool Earth.

I'm Julia.


SIMON: Nice to meet you, Luke. How are you?


SIMON: They show me inside the RV - these big metal tanks full of helium and sulfur dioxide gas. Luke takes a wrench and opens them. The gases flow into this long tube. Andrew - he's outside the RV holding the tube to inflate this big, white weather balloon.


SIMON: I join Andrew outside. And as he's filling the balloon...

Oof. Jeez. Oof. (Coughing). You can smell that.

...Sulfur dioxide begins to leak out.

(Coughing). I don't think SO2 is good for you.

RASCOE: Yeah. I mean, when you said sulfur dioxide leaking out, I automatically started frowning up. You don't want to smell that. That's like, rotten eggs, right?

SIMON: Yeah. There was a lot of coughing. I actually called poison control later that evening.

RASCOE: Oh, no.

SIMON: I was OK. I was OK. But, yeah, in high concentrations - not good for your health.

RASCOE: OK. So what are these guys up to?

SIMON: So we know that when greenhouse gases are released in the atmosphere, they trap energy from the sun, right? They heat the planet. But if you put certain particles way up in the stratosphere - think about 6 to 30 miles above Earth's surface - those particles can reflect sunlight, which can cool the planet.


SIMON: Luke and Andrew - they take the balloon, which is now about 6 feet wide, tie it with a rubber band and then a zip tie.

ISEMAN: Do you want to let it go?

SIMON: I'll let you do it.

ISEMAN: Andrew?

SONG: It's pretty straightforward.

ISEMAN: Well, here. I'll hold the parachute and...


ISEMAN: Oh. Go for it.

SONG: OK. Three, two, one.

SIMON: There she goes.

The balloons sail towards the sun, into the stratosphere. They release two more balloons. And when they get up there, those balloons will pop. The sulfur dioxide turns from gas into particles that reflect sunlight. All told, the company says those three balloons are enough to offset the heating of about 175 cars for a year.

RASCOE: OK. That's not a lot 'cause we're dealing with a whole lot of global warming here.

SIMON: Not a lot, but these balloons signal something bigger - the growing realm of solar geoengineering and a growing number of startups, research projects and billionaire-backed nonprofits getting this tech ready to possibly use it to cool Earth on a massive scale.

RASCOE: It seems to me, though, playing with the stratosphere like that could have some really risky, unforeseen consequences.


SIMON: Yes. This tech could change much of our planet. And experts tell me regulations aren't keeping up.

SHUCHI TALATI: It can be done in an effective, globally governed way, or it could be done by two crazy people in California, and it can look horrible for a lot of people.


RASCOE: The world of solar geoengineering when we come back.


RASCOE: We're back with NPR climate solutions reporter Julia Simon, talking about solar geoengineering as a possible way to cool the planet. Before we get back to weather balloons, Julia, can you give us a sense of the ideas out there for ways to do solar geoengineering?

SIMON: Yeah. Solar geoengineering - it's this umbrella term for increasing the sunlight reflected back into space. There's this thing that involves brightening clouds over the ocean. We'll witness a test for that a bit later. There's also an idea to put giant mirrors into space - space mirrors to reflect sunlight. But then there's what Luke and Andrew are doing with balloons and sulfur dioxide in the stratosphere. That's called stratospheric aerosol injection.

SONG: This does sound like science fiction. Like, (laughter) you know, this sounds like something you would see in a movie. Like - but this is real life.

SIMON: Yeah. In the case of Luke's experiments, it's literally a science fiction novel come to life. He's this serial entrepreneur, Luke. He had a bicycle taxi company. He was riding tourists around Austin, Texas. He made tiny homes from shipping containers in Oakland. Then he moved to Baja California in Mexico.

ISEMAN: I guess semi-retired, and I figured I'd eventually get tired of spearfishing for 20 to 30 hours a week.

SIMON: So one day he turns on his audiobook. It's called "Termination Shock" - this science fiction novel by Neal Stephenson about this Texas billionaire named T.R. Schmidt. And T.R. makes this plan to shoot sulfur up into the stratosphere to cool the Earth.


UNIDENTIFIED PERSON: (Reading) Two elements, T.R. said, alike in dignity.

SIMON: Sulfur and carbon. Here's a bit of the audiobook.


UNIDENTIFIED PERSON: (Reading) Both alter the climate. Carbon makes it get warmer by trapping the sun's rays. Sulfur cools it by bouncing them back into space. We've been over this...

SIMON: And in the novel, it does cool much of the planet. So when Luke finishes this audiobook, he starts Googling.

ISEMAN: When I started researching, I was like, what the hell am I missing here? Like, there's high consensus among scientists that this alone could drop global temperatures by at least half a degree Celsius.

RASCOE: So is that true? Like, is there really a consensus around this?

SIMON: Many scientists do say that large releases of sulfur dioxide could drop global temperatures a lot. And a lot of what we know about this is from volcano eruptions. When this volcano in the Philippines erupted in 1991, sulfur dioxide from the eruption spread across the global stratosphere. And scientists found the particles cooled the Earth's surface by about a half a degree Celsius over the next year or so. So about a year and a half ago, Luke gets together with Andrew, who he met years ago. They start a company called Make Sunsets. So far, they've raised more than $1.2 million from Silicon Valley venture capital companies.

RASCOE: And this is for two guys with balloons. And to be clear, these are two guys who are not scientists. And they got their inspiration from a sci-fi novel. And they got a million-plus dollars. I guess that speaks to how desperate this situation is?

SIMON: Right. And now there's another startup called Stardust Solutions. It's also working on this tech. It's gotten $15 million in investment. Stardust notes their focus is research, and they see a future for getting big government contracts for this work.

RASCOE: I mean, so it sounds like there are some big investors who want to get involved in this.

SIMON: Yeah. And I should say, when it comes to climate solutions that meaningfully cool the planet, this kind of solar geoengineering is a relatively cheap investment. Buying sulfur dioxide, building special planes to spread in the stratosphere - it costs money, but it's a lot less than a lot of the other climate tech. Again, we're at this moment where people are desperate for solutions. We're coming out of the warmest year on record, but emissions from coal, gas, oil - they're rising. Not a lot, but wrong direction. Governments aren't meeting their climate targets.

So this idea of geoengineering the planet to avoid the worst impacts of climate change is capturing the imagination of lots of people, especially in Silicon Valley. Gernot Wagner is a climate economist at Columbia Business School.

GERNOT WAGNER: Climate tech is sexy - right? - because it's the lure of the techno-fix. Look to D.C., and, you know, things are messy. Politics is messy. Wouldn't it be nice if we could cut through all of this with the ultimate techno-fix that will solve this thing once and for all?

SIMON: And politicians, Ayesha, are also starting to think differently about this tech. Here's scientist David Keith at the University of Chicago.

DAVID KEITH: Things are changing very fast. Suddenly, we're getting conversations with senior political leaders in a way that just wasn't happening five years ago.

SIMON: As far as Luke Iseman's concerned, why wouldn't they do this? We're seeing more catastrophic heat waves, melting ice. Luke says we need to be taking action now.

ISEMAN: It's everything and, in my opinion, on climate now. There are that clear and immediate of harms occurring.

SIMON: But, Ayesha, this tech - there are potential benefits, but there are a lot of potential risks and, as of now, very little regulation.


RASCOE: When we come back, we know it could reduce global temperatures. We don't know much else. Stay with us.


RASCOE: We're back with NPR's Julia Simon, discussing solar geoengineering. So, Julia, there's evidence that putting particles into the stratosphere can reduce global temperatures. Let's talk about the risks.

SIMON: I talked to a lot of scientists in my reporting, and they told me there are a lot of risks. Today, we are focusing on three. And for the science nerds out there, to be clear, I'm focusing on the type of solar geoengineering Luke Iseman works on - stratospheric aerosol injection, just to be clear.

RASCOE: OK. Noted. What's the first big risk?

SIMON: The first risk is that this tech could change weather patterns in really unpredictable ways. It could weaken the summer monsoon, meaning billions of people who depend on that rain could see a lot less of it. And it could shift the population at risk for malaria by nearly a billion people across developing countries.

RASCOE: So more diseases, less rain - that's a huge risk for the people who could be impacted. What's number two?

SIMON: Risk two is this thing called mitigation deterrence.

RASCOE: And when you say mitigation, for climate, that would mean reducing our use of fossil fuels, right?

SIMON: Exactly. Exactly. We know that burning fossil fuels is the leading cause of global warming. Solar geoengineering - it's turning down the thermostat a bit, but it's not dealing with the main issue of rising emissions. Here's Imran Khalid, a climate policy expert in Islamabad.

IMRAN KHALID: It's like putting a Band-Aid on a bullet wound. I mean, it's going to stop the bleeding for a second, but you have to get the victim to the hospital. What this is going to do is essentially going to delay the inevitable. It's going to buy us some time. And then we're going to be talking about the same thing again.

SIMON: So basically, with mitigation deterrence, some people worry that if we think about solar geoengineering as this silver bullet, that could distract governments and companies from actually reducing our emissions from fossil fuels.

RASCOE: And that's the key thing that would actually rein in global warming.

SIMON: One hundred percent.


SIMON: Yeah. If we do solar geoengineering and we don't also reduce our emissions, that means we run into our final risk. Risk three is called termination shock, like the name of the novel that inspired the balloon guys. Termination shock is what it sounds like, the shock of suddenly terminating this huge experiment. When you're doing this type of solar geoengineering, injecting particles into the stratosphere, those particles don't stay there forever. They stay for a year or two, and then they fall back to Earth.

RASCOE: I mean, I would think that in and of itself has risk - those particles just falling to the Earth.

SIMON: Yeah. Depending on the material, those falling particles can sometimes create their own health and environmental risks, even acid rain in cases. But whatever type of particles you use, for this type of solar geoengineering to work, you've got to keep injecting more and more particles to keep that cooling effect. If you suddenly stop and you haven't been simultaneously reducing emissions, you're in trouble. Here's Christopher Trisos, climate scientist at University of Cape Town.

CHRISTOPHER TRISOS: You get a whole rush of global warming and climate change in a very short period of time. And that would be very dangerous for ecosystems, for biodiversity, in many cases, very dangerous for crops and food supplies, as well.

RASCOE: So what is the balloon guy, Luke Iseman from Make Sunsets - what does he think of these concerns?

SIMON: Well, he thinks the risks of global warming outweigh the risks of this tech. And he thinks with emissions still rising, solar geoengineering won't be the thing that gives fossil fuel companies an excuse to let her rip and make more pollution.

ISEMAN: Like, they have way more social permission than they need to put us into a hellishly hot planet already. I think we need to do solar geoengineering hard stop because it - you know, the world is too hot. We need to cool it off. I wouldn't say we should only do that after we start dropping global greenhouse emissions, 'cause, like, frankly, I don't know when we're going to do that.

RASCOE: So it sounds like Luke is ready to do this.

SIMON: Well, Luke is very serious about scaling this if or when a country or a billionaire wants to do this.

ISEMAN: We are ready and awaiting their call (laughter). I'm laughing just because I'm excited about it. I'm 0% kidding.

SIMON: Is he ready ready? Researchers I spoke with say he would need significantly more material. He'd probably need to use special planes. For him or someone like him to have a big impact is likely years away. But I spoke to a lot of people who are very concerned about the relatively near-term risk of this tech - of someone, a private company, a country taking this into their own hands. Here's Tracy Hester at the University of Houston Law School (ph).

TRACY HESTER: I share a concern with a lot of folks. Assume something does start to get worse, and then there's going to be a strong desire by someone somewhere to do something. And they're going to do it now, not after five or 10 years of research. There will be a temptation to grab the throttle and push ahead.

RASCOE: I mean, that's a reasonable point. I mean, given the potential ramifications for the world, do Luke and Andrew have to do anything, follow any regulations?

SIMON: There is not much. I mean, for example, when Luke and Andrew released their balloons in California, Luke called up the Federal Aviation Administration to let them know.

ISEMAN: Like, you call an 800 number, and you talk to a person within, like, 10 seconds. It's crazy.

SIMON: Luke also fills out a yearly report for NOAA - that's the National Oceanic and Atmospheric Administration - listing their weather modification activities. We did have one interaction with law enforcement while I was with them. The parking lot we were in when they released the balloons is at the edge of a county park. A park ranger drove up to us.

COLBY MEENK: What brings you out to the park today?

ISEMAN: Oh, we're just launching some weather balloons.

MEENK: Oh, launching weather balloons.


MEENK: Sure.

SIMON: Ranger Meenk was somewhat curious.

MEENK: So you said you're wrapping up soon?

ISEMAN: Yeah, this is our last one.

MEENK: OK. Well, cool.

ISEMAN: We'll be out of here in 10, 15 minutes.

MEENK: OK, thank you. Have a good day.

ISEMAN: You too.

SONG: Thank you.

SIMON: He drove off after less than three minutes.

ISEMAN: So you're wrapping up soon, right?

SONG: (Laughter).

RASCOE: What about internationally? Are there any rules against these kinds of experiments outside the U.S.?

SIMON: Well, remember how Luke said he moved to Baja California, Mexico? He did some tests in Mexico, and when the Mexican government found out that Luke was doing balloon launches in their sovereign territory, they were not happy.


AGUSTIN AVILA ROMERO: (Speaking Spanish)

SIMON: Here's Agustin Avila Romero, from the Mexican Ministry of Environment and Natural Resources, on Mexican TV. Last year, the Mexican government put out a statement that they were banning solar geoengineering, specifically mentioning Make Sunsets and their experiments in the statement.

RASCOE: OK. Well, then I'm guessing that Make Sunsets is no longer operating in Mexico.

SIMON: They say no. But outside of Mexico, for Make Sunsets and everyone else, the rules are really unclear. Here's Tracy Hester.

HESTER: There is no express international convention that deals with this type of technology.

SIMON: There are a few treaties that could maybe cover solar geoengineering, but the U.S. isn't party to all of them. There is one U.N. treaty with basically a moratorium on geoengineering, but the moratorium is nonbinding. So last month, Tracy and others filed this petition to the U.S. federal agency NOAA, asking them to get companies like Make Sunsets to file more information about what they're doing here in the U.S., maybe even broaden the scope to regulate U.S. citizens doing experiments outside of the U.S. Tracy says they plan to file a similar petition with the FAA soon. But ultimately, a lot of people worry that governments are going to fall too far behind on regulating this. Here's Alia Hassan, who works on solar geoengineering governance from Quito, Ecuador.

ALIA HASSAN: We are in a situation now where there are private entities moving forward. It's happening, whether we like it or not. Do we want the governance process to be ahead of the deployment of these technologies, or do we want to try and run after it once it's too late?

SIMON: And already, other groups are launching particles outdoors, too.

UNIDENTIFIED PERSON #2: All right. Sensor package in position?

UNIDENTIFIED PERSON #3: Sensor package is ready.

SIMON: A few weeks ago, I climbed aboard this old decommissioned aircraft carrier on San Francisco Bay. I was with scientists and some engineers that were doing a very important test. First, an engineer scooped salt into a large plastic container, mixing it with water. They hooked up the saltwater to this machine and then...


SIMON: ...The machine let forth a giant spray of saltwater particles down the aircraft runway.


SIMON: They're doing research for something called marine cloud brightening. It involves reflecting sunlight, not with particles that come from sulfur dioxide, but by brightening ocean clouds.

RASCOE: OK, so no balloons here?

SIMON: No balloons here. And unlike with Make Sunsets, this project is led by scientists from the University of Washington. It's raised $16 million, but it's a nonprofit venture. Because it's a nonprofit, those involved say they can conduct research to better understand risks without the monetary incentive to deploy the tech too soon to make money for their investors.

RASCOE: And that's in contrast to Luke's company, Make Sunsets. They have investors.

SIMON: Right. Make Sunsets also sells what they call cooling credits to customers. Kelly Wanser - she directs the climate nonprofit behind this marine cloud brightening program - she says this is not the time for for-profit companies doing this tech. She says private companies may take risks to make money, even if the science is still uncertain.

KELLY WANSER: They're going to have a first sort of responsibility as a commercial entity to try to figure out how to make money and to do it relatively quickly. What we say to people is, look - there's a lot of science that needs to get done.

SIMON: I emailed Luke about this. And he responded, quote, "All change is scary, and we can't use some day, maybe as an excuse to avoid the bold actions that the climate crisis demands."

RASCOE: OK, so that's his take.

SIMON: Yeah, but there's also some worries about university-led research and the lack of regulation because while some of these solar geoengineering research projects might be transparent about what they're doing - they might be out in the open on San Francisco Bay - there are no rules requiring them to be open. And while this study released a small amount of particles, there are no specific regulations to limit a larger future release. And that's a big concern for people like Imran Khalid. He looks at solar geoengineering now, with most of the funding and people originating in the U.S. and Europe, and it worries him.

KHALID: When we're talking about solar geoengineering, it's important to contextualize it from this perspective, from the point of view of somebody who's sitting here in Pakistan who's recently seen the 2022 floods.

RASCOE: Those were the floods in Pakistan that had almost a third of the whole country underwater at their peak. You know, and scientists have said that global warming increased that extreme rainfall and flooding.

SIMON: Yeah, and just as global warming's impacts are often felt more in developing countries, many fear this could also be the case with solar geoengineering's risks. Here's climate scientist Christopher Trisos in Cape Town.

TRISOS: That's especially concerning because a lot of these developing countries in the tropics, such as in Africa, Asia and parts of Latin America, right now don't have a strong voice in the solar geoengineering conversation.

RASCOE: So some countries could be winners, but some countries could end up as losers. And that's a concern because right now, many countries just don't have enough say in what's going on with this tech.

SIMON: That's a big concern for a lot of people. Here's the way Imran Khalid put it.

KHALID: There might be individuals in the U.S. who are interested in taking this up. Then they'll need to account for concerns in Pakistan because at the end of the day, what happens in one part of the world, as we know vis-a-vis climate change, it has an impact on other parts of the world, and then it makes them a lot more vulnerable.

RASCOE: So are there any solutions here? Like, are there ways to get the countries in the global south to have more power in these questions of, like, research and deployment?

SIMON: There are multiple groups working on this, including a nonprofit that started consultations, workshops in countries like South Africa, Pakistan, educating local scientists and civil society groups. Earlier this year, at the United Nations environment meeting, there was a proposal to basically better understand where we are with solar geoengineering tech and research. It didn't pass, but I spoke to people who are still really optimistic about it because there were all these new countries starting to engage in the conversation. Shuchi Talati, the head of that nonprofit doing the workshops, says while her work towards more inclusive governance can sometimes feel naive...

TALATI: At the same time, I don't really know what other choice we have. Like, if we don't engage in doing this type of work, I do think we'll see a bad version of solar geoengineering. It can be done in an effective, globally governed way, or it can be done by two crazy people in California, and it can look horrible for a lot of people.

RASCOE: So what's Luke have to say about this? I mean, I'm sure he wouldn't consider himself one of the crazy people in California, but what does he have to say about this idea that people in places like Pakistan feel like people like him are disregarding the risks that might leave them more vulnerable?

SIMON: Well, I asked him about this, about how he wants to go full speed ahead with solar geoengineering. And some places in the global south could be particularly vulnerable to risks, and we don't have the regulations yet.

There's some people in the global south who are still like, but you're the ones who are making this decision, still, about when to let go of the balloons. And, like, couldn't you wait so that we can have more of a say?

ISEMAN: I think that it is unfair that I was born as a lower-middle class, white-ish American male. However, you know, I didn't choose that. And I think my obligation is to do what I can with what I have. I have an obligation to do what I can to cool the planet, as does anyone else who actually reads the science.

SIMON: And I played this audio of Luke for Imran Khalid in Pakistan on Zoom. On the one hand, he thanked Luke.

KHALID: Yes, you do have that agency, and thank you for highlighting it. But there are a number of ways in terms of you can utilize that agency.

SIMON: For Imran, a top-down approach to geoengineering the planet - it didn't work with global warming, and it won't work here. What we don't need right now, he says, is a climate cowboy.

KHALID: A cowboy, a John Wayne out there to take things into his or her own hands and try and go alone, we need to avoid that. There needs to be a global discussion around this issue, and we need to have a seat at that table.


RASCOE: Julia, thank you so much for bringing us this really fascinating reporting.

SIMON: Thank you, Ayesha.

RASCOE: That's NPR climate solutions reporter Julia Simon.


RASCOE: This episode was produced by Abby Wendle and edited by Jenny Schmidt. The reporting for this episode was brought to us by NPR's climate desk. Neela Banerjee was the editor. Mastering by Robert Rodriguez. Special thanks to Nell Greenfieldboyce and Dan Girma. The Sunday Story team includes Justine Yan and Andrew Mambo. Our supervising producer is Liana Simstrom. And Irene Noguchi is our executive producer. I'm Ayesha Rascoe. UP FIRST is back tomorrow with all the news you need to start your week. Until then, have a great rest of your weekend.

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