Solar geoengineering startups just attracted $60M to cool the sky. Here’s what that means for green technology, climate risk, and responsible climate strategy.
Solar Geoengineering: Why Startups Are Racing To Cool The Sky
Stardust Solutions just raised $60 million to develop solar geoengineering tech. That’s not a grant, a prize, or a think-tank budget. It’s venture capital, betting that someone will pay to dim the sun.
Most climate-focused companies are building solar farms, batteries, or AI for smarter grids. Stardust and a small group of others are aiming higher—literally—by putting reflective particles in the upper atmosphere to bounce sunlight back into space.
This matters for anyone working in green technology, sustainability, or climate strategy. Because if private companies start selling climate control as a service, your risk models, your ESG strategy, and your long-term planning all change.
In this post, I’ll break down what’s actually happening with solar geoengineering startups, why many scientists are alarmed, and how responsible climate leaders should think about this tool alongside renewables, efficiency, and AI-driven decarbonization.
What Solar Geoengineering Actually Is (And Isn’t)
Solar geoengineering is a set of techniques designed to cool the planet by reflecting a small fraction of sunlight back into space. The mainstream version people talk about is stratospheric aerosol injection (SAI): releasing tiny particles high in the atmosphere to mimic the cooling effect of volcanic eruptions.
We know it can work in principle. When Mount Pinatubo erupted in 1991, it blasted around 20 million tons of sulfur dioxide into the stratosphere and cooled the planet by about 0.5°C for a year or two. Geoengineering aims to reproduce that effect in a controlled way, at a much smaller scale and over longer periods.
But here’s the key reality: solar geoengineering doesn’t remove CO₂. It doesn’t fix ocean acidification. It doesn’t replace renewables, electrification, or efficiency. It’s more like a global thermostat tweak on top of all the work we still have to do.
Used badly, it could be incredibly risky. Used carefully, and governed sanely, it might reduce the worst climate impacts while we continue decarbonizing and scaling green technology.
From Fringe Experiments To Funded Startups
Until recently, solar geoengineering was mostly:
- Academic modeling and simulations
- Policy debates and ethical arguments
- A few very small-scale or proposed field tests
Then the private sector arrived.
Make Sunsets: The Rogue Pioneer
Back in 2022, a tiny California startup called Make Sunsets did something that set the tone for public concern. Its CEO reportedly went to Baja California, put a bit of sulfur dioxide in a weather balloon, and launched it.
Technically, the amount was minuscule. It’s not even clear whether it reached the right layer of the atmosphere to reflect meaningful sunlight. But the symbolism was huge: a private company unilaterally experimenting with the global climate, without international agreement or much transparency.
The reaction was swift:
- Mexico announced plans to restrict geoengineering experiments in its territory.
- Scientists criticized both the lack of oversight and the commercialization of “cooling credits.”
- Make Sunsets got attention, a patent, and some customers—but it remained squarely in the “fringe actor” category.
The message from the climate community was clear: the world isn’t okay with startups freelancing the sky.
Stardust Solutions: Serious Money, Serious Anxiety
Stardust Solutions is different. In late 2025, it surfaced with a $60 million funding round, reportedly the largest yet for a geoengineering-focused company. The round was led by well-known climate investors—people who usually put money into renewables, carbon removal, and battery tech.
That single funding event is a signal: solar geoengineering has officially entered the climate tech portfolio.
Stardust positions itself as cautious and aligned with governance. The company says it won’t deploy geoengineering unless commissioned by governments, under clear rules and oversight bodies.
But it’s also a for-profit business. Which means it faces three unavoidable pressures:
- Investor expectations for returns
- Competitive pressure as other firms enter the field
- Incentives to protect IP and move fast
That mix is exactly what’s making many experts uneasy.
Why Scientists Are Worried About For‑Profit Geoengineering
The argument from researchers is blunt: mixing planetary-scale interventions with profit motives is a risky combination.
Two names you’ll see a lot in this debate are David Keith and Daniele Visioni, both leading figures in solar geoengineering research. Their stance is nuanced—they support research, but they strongly criticize a for‑profit race to deploy.
They’ve summed it up in one line that’s worth repeating:
“Research won’t be useful unless it’s trusted, and trust depends on transparency.”
The Trust Problem
Stardust is reportedly developing proprietary particles that it claims will be:
- Safer than sulfur dioxide
- Cheaper to manufacture
- Easier to track and monitor
From a business perspective, keeping the formulation secret until patents are locked makes sense. From a climate governance perspective, it’s a problem.
Because right now:
- External experts can’t evaluate the particles’ safety
- Governments can’t fully assess the risks
- The public can’t see what’s being done in their name
That opacity undermines the very thing geoengineering most depends on: broad, international trust.
The Governance Black Hole
Solar geoengineering has another uncomfortable feature: one determined actor could, in theory, act alone. You don’t need a global fleet of power plants; you need aircraft or balloons and the will to use them.
That raises brutal questions:
- Who gets to decide if and when the planet is cooled?
- What counts as “too much” or “too little” cooling?
- What if one region benefits and another suffers from changed rainfall patterns?
Now layer commercial incentives on top of that—contracts, investors, market share—and you see why many researchers want public, transparent, non-profit-driven research to lead the way, not startups racing for first-mover advantage.
Where Solar Geoengineering Fits In The Green Technology Landscape
Here’s the thing about green technology: the backbone of climate action is still emissions reduction. That means:
- Scaling renewable energy (solar, wind, geothermal)
- Electrifying transport and heating
- Deploying storage and demand response, often orchestrated by AI
- Improving industrial efficiency and circularity
- Investing in carbon removal where necessary
Solar geoengineering doesn’t replace any of that. At best, it’s a temporary risk management tool that might:
- Lower peak global temperatures
- Reduce extreme heat waves and some climate damages
- Buy time for decarbonization to catch up
But it also introduces new risks and dependencies:
- Termination shock: If we cool the planet artificially while CO₂ keeps rising, and then stop suddenly, temperatures could spike rapidly.
- Unequal impacts: Regional changes in rainfall or weather patterns could benefit some countries and harm others.
- Moral hazard: Politicians or companies might slow down on decarbonization because “we can always spray the sky later.”
As part of a Green Technology strategy, the only sane stance is this:
Solar geoengineering should never be a substitute for cutting emissions. At most, it’s a last-resort complement, governed at a global level and built on open, trusted science.
What Climate‑Focused Businesses Should Do Right Now
You don’t need to be a geoengineering expert, but ignoring it entirely is a mistake. The conversation has moved from theoretical papers to funded companies, patents, and (so far) small real-world tests.
Here’s how to respond in a practical, non-hype way.
1. Build Solar Geoengineering Into Long‑Term Risk Scenarios
If you work in climate risk, ESG, or strategic planning, start treating solar geoengineering as one of several plausible future pathways, alongside:
- High-mitigation + no geoengineering
- Moderate mitigation + limited, coordinated geoengineering
- Fragmented mitigation + rogue or unilateral geoengineering
For each scenario, ask:
- How could this affect physical climate risks in our regions (heat, storms, water)?
- How might regulation or disclosure requirements evolve?
- What’s the impact on supply chains, especially in climate-sensitive regions?
You don’t need precise probabilities. You need to acknowledge the possibility and avoid being blindsided.
2. Prioritize Transparency and Governance In Any Engagement
If your organization is:
- Funding climate tech
- Partnering with research institutions
- Participating in climate policy forums
…then advocate for three non-negotiables around geoengineering:
- Open data and methods for research projects
- Independent oversight by scientific and public bodies
- Clear separation between early-stage research and commercial deployment
The companies that win long-term trust in green technology are the ones that welcome scrutiny, not hide behind secrecy and patents alone.
3. Use AI To Double Down On The Solutions We Already Trust
Ironically, the rise of solar geoengineering startups is a reminder that we still haven’t fully used the tools we already have.
AI is already helping cut emissions and costs by:
- Optimizing renewable energy dispatch and storage
- Managing smart grids that match demand and supply in real time
- Improving building efficiency with predictive controls
- Optimizing logistics and industrial processes to cut waste
If you’re serious about climate and competitiveness, the rational move is to squeeze every possible gain out of these proven green technologies before even thinking about supporting planetary-scale experiments.
Geoengineering might one day be part of a global emergency toolkit. But your fastest, cleanest ROI—for both climate and business—still comes from smart, AI-enabled decarbonization.
How This Story Fits Into The Bigger Green Tech Picture
Solar geoengineering sits at the sharp edge of climate innovation: high stakes, high uncertainty, and huge ethical questions. The arrival of serious startups like Stardust Solutions is a turning point. We’ve moved from, “Should we even talk about this?” to “Who controls it, and on whose terms?”
For climate-conscious businesses and investors, here’s the stance that makes sense right now:
- Treat solar geoengineering as a research and governance issue, not a near-term solution you can rely on.
- Push for public, transparent, non‑profit research as the foundation for any future decisions.
- Keep your main climate bets firmly on renewables, electrification, efficiency, and AI-driven optimization.
We don’t get a second chance at experimenting with the entire atmosphere. But we do have a real shot, right now, at scaling the green technologies we already know are safe and effective.
If you’re planning climate strategy for 2030 and beyond, the question isn’t just “Will someone try to cool the planet?” It’s “Will we have done enough with the tools we already trust that we never feel forced to?”