Twenty-five people working out of offices in the United States and Israel believe they've cracked one of humanity's most contentious problems: how to cool an overheating planet by altering the chemistry of the stratosphere. By April 2026, if all goes to plan, they intend to start outdoor contained experiments from the cabin of a modified aircraft flying at 60,000 feet.
The company is called Stardust Solutions. It's raised $75 million so far—a figure that should give pause to anyone who assumed decisions about planetary-scale climate intervention would remain in the hands of governments and international bodies. The money suggests something different: that there might be a business model in controlling Earth's temperature. Whether there should be, of course, is a question the venture capital community rarely considers its job to answer.
In late October of last year, Stardust closed a $60 million funding round led by Lowercarbon Capital, with participation from Exor (the Agnelli family's investment arm), Matt Cohler, a veteran tech investor, Future Ventures, Starlight Ventures, Never Lift Ventures, Nebular, Lauder Partners, Attestor, Kindred Capital, Orion Global Advisors, and Berlin's Earth.now. It marked the largest single venture investment ever directed toward solar radiation modification—the umbrella term for technologies designed to reflect sunlight away from Earth before it can warm the surface.
The funding also marked something else. A fundamental shift in how climate intervention might actually happen: not through painstaking international consensus or publicly funded university research, but through patent filings, proprietary compounds, and the logic of Silicon Valley.
Following the Money Into the Stratosphere
The numbers, if you track them, tell a story of sudden acceleration.
A March analysis by the Heinrich Böll Stiftung, a German political foundation, found that funding for solar geoengineering research increased dramatically between 2020 and 2025—climbing to more than $128 million, likely three to four times higher in reality. That baseline figure didn't even include Stardust's October round, meaning the startup alone pulled in as much capital as the entire global sector had been receiving in a year.
By December, a POLITICO tally counted at least $115.8 million flowing to nine different startups developing sunlight-limiting technologies. Some of the projects sound almost quaint in their ambition: marine cloud brightening, which aims to make low-altitude clouds more reflective by spraying seawater into them. Others, like Stardust, target the stratosphere itself—the layer of atmosphere between roughly six and thirty miles up, where commercial jets cruise and where volcanic eruptions deposit the sulfur particles that have historically caused temporary global cooling.
Public funding moved even faster in some corners. Between April and May of last year, the United Kingdom's Advanced Research and Invention Agency announced roughly £57 million for stratospheric cooling research, including funds for potential controlled outdoor experiments. The Natural Environment Research Council added another £10.5 to £11 million for five years of modeling and impact assessment.
What explains the rush? Investors quoted by POLITICO acknowledged the starkly binary nature of the wager. Returns could be zero—an expensive dead end if governments balk or the technology proves unworkable. Or Stardust could become, in the words of one backer, "one of the most important companies in the world."
The gap between those two outcomes hinges entirely on a question no one can yet answer: whether governments eventually decide they need what Stardust is selling.
From Theory to Term Sheets
For decades, solar geoengineering lived primarily in computer models and the occasional academic seminar. Researchers understood the basic physics. Inject reflective particles into the stratosphere—sulfur dioxide was the obvious candidate, given that volcanic eruptions do this naturally—and you could bounce a small percentage of incoming sunlight back into space. Global temperatures would drop, at least temporarily.
A 2012 cost analysis by researchers McClellan, Keith, and Apt suggested that delivering millions of tons of material annually might run only a few billion dollars, not counting the thornier expenses of monitoring and governance. Cheap enough, in other words, to be dangerous.
The theoretical elegance masked ferocious complexity. Which particles, exactly? Sulfur dioxide damages the ozone layer and heats the stratosphere itself. Calcium carbonate? Aluminum oxide? Engineered diamond dust? Most alternatives remain untested at any meaningful scale. Regional impacts on rainfall patterns and monsoon systems are poorly understood. And then there's what researchers call "termination shock"—the risk that if deployment stops suddenly, decades of masked warming could arrive all at once.
Recent history has not been kind to outdoor experiments. Harvard's Stratospheric Controlled Perturbation Experiment, known as SCoPEx, was formally canceled in March 2024 after years of planning. A marine cloud brightening test on the deck of a retired aircraft carrier in Alameda, California, was halted by city officials in June 2024—even though consultants later found negligible health risks. Make Sunsets, a startup that launched weather balloons carrying small amounts of sulfur dioxide, faced an EPA information demand in April of last year and had been effectively shut down in Mexico back in January 2023.
Against this backdrop, Stardust chose a different path: build the technology privately, lock down intellectual property, then engage with regulators.
Building in Stealth
The company's CEO and co-founder is Yanai Yedvab, who previously served as deputy chief scientist at Israel's Atomic Energy Commission—a résumé that speaks to both technical credibility and a comfort level with contentious technologies. His co-founders include nuclear physicist Amiad Spector and Eli Waxman, a particle physicist from the Weizmann Institute.
Their pitch rests on three integrated pieces: a proprietary aerosol particle the company claims is inert and safe for the ozone layer; dispersion hardware designed to be carried by high-altitude aircraft; and a suite of monitoring and modeling systems meant to track where particles go and what they do.
The chemical composition of Stardust's particle remains a closely held secret, pending patent publication. Yedvab has described it publicly as trackable and safer than sulfates, but no independent scientists have verified the claims. The company raised roughly $15 million in seed funding in early 2024 from AWZ Ventures and SolarEdge before last fall's much larger round.
In conversations with POLITICO, Stardust indicated it plans to begin what it calls "outdoor contained experiments" as soon as April 2026—releasing particles inside a sealed compartment aboard a modified aircraft flying at roughly 18 kilometers altitude. The distinction matters, at least to Stardust: particles would be released into the stratosphere's environment, but not dispersed into the open air. Whether such tests require formal regulatory approval or advance international notification remains an open question—one complicated by the company's planned use of confined experimental conditions.
Then there's the lobbying. In November, E&E News reported that the Washington firm Holland & Knight had failed to properly disclose its relationship with Stardust under federal lobbying rules. Stardust's explanation, when it came, framed the outreach as an effort to encourage "appropriate and robust oversight" of sunlight reflection research—governance advocacy, in other words, rather than an attempt to preempt regulation. The distinction, to skeptics, may seem thinner than the stratosphere itself.
The Governance Problem No One Knows How to Solve
Janos Pasztor, a former United Nations climate advisor, produced an independent governance report for Stardust in September 2024. The document urged maximum transparency, adherence to a code of conduct, and serious consideration of making any intellectual property publicly available rather than privately held.
Three months later, Pasztor co-authored an opinion piece in Le Monde warning that private control of solar geoengineering technologies fundamentally shifts incentives—away from the public interest and toward the capital requirements of venture-backed companies.
Perhaps he'd seen something that gave him pause.
The tension Pasztor identified reflects broader unease about applying startup logic to planetary-scale interventions. Gernot Wagner, an economist at Columbia's business school who studies climate risk, warned investors in October that the business case for privately held solar radiation modification intellectual property remains uncertain at best. The nonprofit Reflective, which conducts its own geoengineering research, has pointedly contrasted its transparency-first approach with Stardust's proprietary model.
No binding international framework governs solar geoengineering. The Convention on Biological Diversity maintains what amounts to a de facto moratorium on outdoor deployment, reaffirmed at COP16 in November 2024, though it carves out an exception for small-scale scientific research. Whether a for-profit company conducting contained aircraft tests fits that exception is, to put it mildly, debatable.
A February 2024 discussion at the UN Environment Assembly produced no consensus whatsoever. African nations called for an outright Non-Use treaty. Others pushed for controlled research frameworks. The meeting ended without agreement.
In the United States, a federal research plan published in June 2023 emphasized the need for governance alongside scientific inquiry—but provided no actual regulatory pathway. Several states moved in the opposite direction. Tennessee enacted a geoengineering ban that took effect in July 2024. Florida's Senate advanced similar legislation in April last year. Meanwhile, NOAA has been quietly developing detection systems to identify unauthorized deployment, a development that highlights an uncomfortable reality: monitoring infrastructure may arrive before the rules do.
The European Union's Scientific Advice Mechanism weighed in last December with a carefully worded conclusion: solar radiation modification cannot fully address climate change, and any research into it must be responsible, transparent, and focused on understanding impacts rather than rushing toward deployment. The subtext was clear. Study it carefully, if at all. But don't pretend it's a solution.
What Happens Now
Stardust's planned April 2026 aircraft tests—assuming they proceed—will face scrutiny from multiple directions. Environmental groups flagged the experiments within hours of learning about them last October. The Center for International Environmental Law called the plans "reckless" given the absence of international oversight. Whether the contained nature of the tests—particles released inside an aircraft cabin rather than into open air—constitutes outdoor deployment or merely laboratory work will likely be contested in both regulatory interpretations and public perception.
Broader industry momentum suggests the next year or two will bring increased activity. UK-funded projects may reach small controlled outdoor trials in later program phases, assuming political will holds. NOAA continues developing early-warning detection systems. Academic modeling efforts proliferate, exploring everything from alternative reflective materials to potential impacts on monsoon patterns.
In February, the Bulletin of the Atomic Scientists argued that the technical fixation on solar geoengineering sidesteps the actual problem—which isn't whether we can cool the planet artificially, but whether humans can cooperate on planetary-scale decisions without making catastrophic mistakes. Stardust's investors appear willing to bet that particular problem becomes someone else's to solve. Preferably a government buyer's.
The question at this point isn't whether someone can build stratospheric cooling technology. Clearly they can—or believe they can.
The question is whether they should. And who, exactly, gets to decide.
Stardust is proceeding as though the answer to the first question is yes, and the answer to the second is: whoever moves fastest.
