Early last year, entrepreneur Luke Iseman says, he released a pair of sulfur dioxide–filled weather balloons from Mexico’s Baja California peninsula, in the hope that they’d burst miles above Earth. 

It was a trivial act in itself, involving far less of the gas than a commercial airliner releases. But the launch was imbued with meaning, and it pushed the simmering debate over extreme climate interventions into a new realm. 

In effect, Iseman attempted to carry out a tiny, DIY act of solar geoengineering, the controversial concept that the world could counteract global warming by releasing particles that reflect more sunlight back into space. By aiming for the stratosphere, he crossed a line where most (though perhaps not all) researchers had stopped short. That’s largely because earlier proposals to carry out even small-scale research efforts in that layer of the atmosphere encountered fierce public pushback. 

Iseman, who went on to cofound the company Make Sunsets to sell “cooling credits” for carrying out such launches, avoided the debate by just doing it, without disclosing his plans or asking anyone’s permission.

“Why,” I asked during a Zoom interview in late December, “did you decide to move forward with these launches without public engagement, without scientific review?”

Iseman stressed the growing dangers of climate change, the link between emissions and deaths, and the increasingly narrow paths available to prevent 2 ˚C of worldwide warming over preindustrial levels without resorting to geoengineering.

“It’s not an abstract thing,” he said. “I would feel uncomfortable—having researched this—to, you know, tell my nieces and nephews that we didn’t pursue this as hard as we could.”

“I don’t think waiting for an [institutional review board] is acceptable in this situation,” he added, referring to the expert committees that customarily review proposed medical research involving human subjects. 

The response is a variation on a theme I’ve increasingly heard in recent months while reporting on climate solutions that lie beyond merely cutting emissions. On the growing list are technologies that could cast more sunlight back into space, suck greenhouse gas out of the atmosphere, or preserve crucial ecosystems through radical forms of climate adaptation. 

Entrepreneurs in these areas increasingly invoke the stark dangers of climate change, and the world’s sluggish response, to explain why they’re ready to forge ahead even when the effectiveness of such interventions or the magnitude of the environmental side effects is unclear. Or, for that matter, when the public they claim to be acting on behalf of isn’t nearly so comfortable with the ideas—or even yet aware of them.

When the fate of humanity or all manner of species or entire ecosystems is at stake, one can rationalize any intervention that promises to reduce suffering and destruction and plant a flag deep in the moral high ground, while waving away any talk of side effects or trade-offs. 

The world does need to do much more and move far faster to combat climate change, and the evidence is increasingly clear that cutting emissions alone won’t be enough to keep the rising dangers in check. But a number of academics and researchers I spoke with in recent weeks warn that none of that urgency creates a social license to leapfrog the scientific process, ignore dangerous side effects, or override people’s right to have a say in the use of technologies that will directly affect the public.

Moreover, they warn that moving too fast can actually undermine support for research into tools that could help and that we may well someday need.

So why is it happening anyway?

Growing dangers

A growing sense of climate danger—and, for many, climate doom—has accelerated humanity’s responses in numerous ways: driving increasingly strict or generous public policies, encouraging more investment into clean technologies, and pushing corporations to take more meaningful steps to address emissions.

It’s also forcing a public debate over what actions are appropriate or permissible in the face of such an ominous looming threat: Is it now okay to throw soup at Van Goghs? To shut down fossil-fuel plants before we’ve replaced them? To demand that poor countries halt their economic progress? To mine the oceans for battery materials, or to coat seabeds with biomatter? 

One area where activity has particularly picked up in recent months, and where the attendant questions are especially vexing, is solar geoengineering.

In addition to Iseman’s efforts, a UK researcher also quietly released a pair of balloons, at least one of which seems to have released sulfur dioxide into the stratosphere, in tests of a low-cost, recoverable craft. Dismaying some in the field, he named it the Stratospheric Aerosol Transport and Nucleation system, or SATAN.

Scientists in a growing number of nations are starting to research a widening variety of potential solar geoengineering methods, which also include breaking up heat-trapping cirrus clouds, brightening reflective coastal ones, or even launching moon dust into space.

In the US, the White House is setting up a formal research program, while the National Oceanic and Atmospheric Administration has begun carrying out balloon launches and flights to conduct measurements in the stratosphere (though not to release materials).

Impatient with the pace of public research, Make Sunsets has continued to launch balloons. It even recently invited members of the public to release some near a San Francisco park.

Other private market explorations are underway as well. A Los Angeles–based startup, Ethos Space, says on its website that its mission is to “build a planetary sunshade in space to protect Earth.” The company intends to use the moon as both a source of materials and a launchpad for the space-based sunshade, which would block sunlight from reaching the planet.

Ross Centers, chief executive of the startup, describes the method as the Platonic ideal of solar geoengineering, because it could ease warming without otherwise altering Earth’s atmosphere.

David Keith, who now leads the Climate Systems Engineering initiative at the University of Chicago, says that he’s also heard from several venture capitalists looking for opportunities to invest in solar geoengineering. He tried his best to dissuade them (more on why in a moment).

Meanwhile, in February, I wrote about a handful of companies working to raise funds to move ahead with field trials that would entail spraying iron salt particles above the ocean. This intervention might break down methane in the atmosphere as well as brighten clouds, straddling the line between greenhouse-gas removal and solar geoengineering.

Proposing field trials is very different from launching balloons, but here too some climate scientists warn that we shouldn’t start commercial ventures before it’s clear if the method achieves what’s claimed, or does so in a safe way. But Oswald Petersen, the chief executive of AMR, a Swiss company raising money to carry out such experiments, dismisses those concerns.

“They’re stopping one of the most promising climate technologies with this wariness,” he said, when I asked about the criticisms. “Wariness right now is our biggest problem.” 

He criticized scientists who insist, in the face of grave climate risks, that “we have to do so many lab studies and write many books” before carrying out outdoor experiments.

“No, that won’t help us,” he said, adding that small-scale field efforts pose little environmental risk. “We have to try it and then we’ll know.”

The motivations

Many argue it is critical to explore the potential of more extreme climate responses, including methane destruction and solar geoengineering, because they’re among the few tools that could rapidly reduce warming. They may well be able to alleviate suffering, save species, and preserve ecosystems. 

But there are fine lines between research, mini-deployments, and stunts. There are very difficult questions about what’s appropriate for a research group and what’s okay for a private enterprise. And how work in these areas proceeds, and who carries it out, can have major effects on how the public and policymakers respond to it.

I read the quotes from Iseman and Petersen to Ted Parson, a professor of environmental law at the University of California, Los Angeles, who has been critical of Make Sunsets’ efforts.

He says he sympathizes with the basic argument that rising dangers justify “proceeding expeditiously” because “we are so far behind in taking care of climate change the straightforward way.” 

“But it really sounds like the tech bro mentality has fully made the leap to the climate space,” he says. “‘Move fast, break things, and if it doesn’t work, we’ll try something else.’”

The problem with applying that mindset outside of software and social media is that the stakes are far higher and the potential effects extend well outside the boundaries of any business: We don’t want to break, or even harm, global commons like our oceans and atmosphere. 

We simply don’t know whether some of these proposed interventions will actually work on large scales, or what negative effects they could have on complex and interconnected ecosystems, says David Ho, an oceanography professor at the University of Hawai‘i at Manoa who studies ocean-based carbon removal. 

These are also real dangers that plowing ahead into areas where the public is deeply uncomfortable will stall, not speed up, research in these fields.

He notes that early efforts to commercialize what’s known as iron ocean fertilization, or placing iron in the water to stimulate the growth of carbon-sucking phytoplankton, prompted international bodies to propose restrictions on commercial efforts. He and others say it had a chilling effect on research as well.

Some fear Make Sunsets’ launches have already hardened negative impressions of solar geoengineering. Critics seized on the news as proof that researching the subject puts us on a slippery slope to carrying it out. 

The government of Mexico responded by announcing plans to prohibit solar geoengineering experiments within the country. In addition, the nation is now trying to get other countries “to ban the climate strategy,” according to reporting by Reuters.

“If I were an activist looking to raise fears and anxiety and doubts about [solar geoengineering] and I was creative enough, I would probably have done what Make Sunsets did,” says Andy Parker, chief executive of the Degrees Initiative, which provides funds to help scientists conduct solar geoengineering research in climate vulnerable nations. “Which is to launch a test that scientists tell me wasn’t really testing anything, without any reputable scientific backing or any sort of engagement, as a for-profit, funded by venture capital.” 

The dangers

Baked into some of the arguments that we must forge ahead now with more extreme solutions is the assumption that we’re on the brink of creating a barely habitable, hothouse planet. This idea, too, requires some scrutiny.

It does look increasingly certain that the world will warm by more than 1.5 ˚C, which—appropriately—has sparked greater concerns about climate change. 

But a prescient 2017 paper, by researchers Jane Flegal and Aarti Gupta, warned that the global goal of preventing temperatures from exceeding that threshold could promote a “tyranny of urgency,” in which solar geoengineering is portrayed “as one of the only ‘realistic’ pathways to moving toward such aspirational goals.” 

To be sure, climate change is incredibly and increasingly dangerous, particularly for people in the hotter, poorer parts of the world. But a few points of context are worth bearing in mind: 1.5 ˚C is a political target, not a scientific threshold for climate collapse. The growing likelihood that the planet will soar past it has fueled doomish views that largely aren’t backed up by climate science. The shift to carbon-free ways of operating is accelerating, making worst-case emissions scenarios from a few years ago look increasingly implausible. Deaths from natural hazards are trending down, not up, as the world invests resources and technical know-how into protective measures. And the world likely still has several decades to drive down emissions enough to hold warming around 2 ˚C.

So yes, we absolutely need to accelerate the buildout of the clean technologies we have, the development of the tools we still need, the funding of adaptation measures in the most climate-vulnerable regions, and the study of extreme measures that may help in a hotter future. 

But observers stress that we’re not at the point where we need to take ill-considered risks, or waste time and resources rolling out things that we haven’t yet demonstrated are effective even at the lab scale.

“You’ve heard people say, ‘This is the deciding decade,’ and I agree with that,” Ho says. “But it’s the decade we decide on which solutions work, which ones are trustworthy, which ones are effective, and which ones can be applied justly. It’s not the decade to apply these things.”

In some cases, the rising dangers are merely providing a way for people to rationalize audacious efforts that they want to pursue for other reasons, says Holly Buck, an assistant professor at the University at Buffalo and author of After Geoengineering: Climate Tragedy, Repair and Restoration. 

“There are plenty of people on the front lines of climate change that are in far more danger than these people in Palo Alto, and they’re not going out and shooting things into the sky,” she says. “So for people who have a certain sense of ego, possibly a savior complex, a certain need to play a role in a great drama that’s unfolding—they have the ability to rationalize the story and their place in the narrative.”

“They’re right that we’re in dangerous times and we need swift action,” she adds. “But we need a whole-of-society transformation, not an individualized response.”

Private vs. public science

The introduction of profit motives into these fields complicates matters all the more.

Certainly companies can and do carry out meaningful scientific work and technological development, and they can bring levels of funding to these efforts that most academics only dream of.

AMR and other firms working on greenhouse-gas removal insist they will proceed carefully by partnering with scientists in these fields, starting with small, controlled field trials, and adjusting their plans as they learn.

In an emailed response to an inquiry from MIT Technology Review, Petersen and a colleague stressed that AMR is a “profit-for-purpose” operation. They added that they would not proceed with releasing iron salt particles in a “disruptive way.” They claim that removing methane from the atmosphere would help restore the climate and that the public would come to praise such interventions, so long as there aren’t adverse side effects.

They added that climate change can drive feedback effects that release large amounts of methane from natural sources, which could cause warming to accelerate abruptly.

“We therefore cannot afford to hesitate in pushing forward with research and development of such an intervention—we need to move from talking and debating to doing the actual work to find out if this could help us,” the statement read.

But any whiff of commercialization when it comes to technologies designed to adjust the entire planet’s thermostat, or significantly perturb natural ecosystems, raises concerns that can exacerbate public distrust. One fear is that investor and financial pressures will compel for-profits to move ahead and scale up even if their interventions don't prove to be as effective, safe, or well received as hoped.

An added question for solar geoengineering is: Should we as a society allow profit motives to dictate how hot or cold we make the planet? 

Keith of the University of Chicago has strongly argued no. He says we simply shouldn’t patent or commercialize core solar geoengineering technologies, given the potential for perverse incentives—and the risk that it will undermine the credibility of the research.

“Commercial development cannot produce the level of transparency and trust the world needs to make sensible decisions about deployment,” he has written. “A company would have an interest in overselling, an interest in concealing risks.”

Centers of Ethos Space agrees that solar geoengineering should only be authorized and funded by governments, and he says the company would launch the planetary sunshade only in response to federal policy.

But the company is developing the technological capacity to meet that government demand now because he believes it is certain to arise.

"Geoengineering is inevitable because governments are making an implicit commitment to it by continuing policies that are going to result in intolerable global warming," he says.

For his part, Iseman previously said that the company’s mission is as much an effort to drive debate and break the taboo around geoengineering research as it is to actually make money. On its site, Make Sunsets laments that earlier academic proposals to conduct stratospheric studies were canceled “due to well-intentioned but misguided activism and patent disputes.”

In an emailed response for this story, Iseman again stressed the dangers of climate change and he rejected any argument that profit motives would drive him to “freeze the world,” referring to it as "ivory tower philosophical bullshit."

“It's unfortunate that many of the esteemed professionals in the nascent field of solar geoengineering are mad that I've sold (and deployed!) several thousand Cooling Credits,” he added. “But I'm just getting started:)"

He also noted that emitting carbon dioxide already amounts to a form of geoengineering.

“I don't poll billions before taking a flight,” he wrote. “I'm not going to ask for permission from every person in the world before I try to do a bit to cool Earth.”

‘Silly stunts’ 

So how should work in these areas proceed?

Plenty of reasonable people say it shouldn’t at all, arguing it pulls focus from the most pressing need: cutting greenhouse-gas emissions as rapidly as possible. 

Critics of solar geoengineering argue that even talking about the possibility extends the social license for oil and gas companies to carry on with business as usual. They also contend there’s no way to equitably govern a technology that could lower the dangers of extreme weather events in some areas but create new dangers in others.

Jennie Stephens, professor of sustainability science and policy at Northeastern University, wasn’t surprised at all by the Make Sunsets balloon launches. 

“It’s exactly why we’ve been calling to not advance these technologies,” she says. “The scientists advocating for advancing the research on these technologies have no control over the science after they’ve done it.”

But strict restrictions on research carry their own risks, Parson argues. The prohibitionist camp “bears responsibility for the silly stunts and dangerously premature attempts to commercialize SRM that we are now seeing,” he wrote in a recent post. “When funders and researchers who want to act responsibly and care about their reputations are scared away but the demand or need is great, what happens?”

“Like other zealous prohibitionists before them, the prohibitionists are creating the conditions for emergence of the bootlegging industry, the dangerous back-alley abortionists,” he added.

The pressure to conduct research in this field will persist for a simple reason: there’s evidence it could ease global warming, which means it may reduce risks and save lives. And since small-scale balloon efforts are currently legal and cheap, it’s likely we’ll continue to see DIY efforts as well, Parson argues.

The best antidote, in his view, is open, responsible, publicly funded, and globally coordinated research programs.

Others say the research that does move forward should be overseen by scientific bodies that can impartially evaluate the risks and the value of proposed experiments. It should be carried out by a wide array of research groups across a wide array of regions, exploring hard questions about local impacts, ethics, equity, and global oversight.

And instead of starting with surprise launches that force solutions on people, the efforts should begin on the ground, with community conversations that strive to understand the concerns these technologies raise and to make the case for why we need to understand them better.