The article spotlights the accelerating interest in solar geoengineering (or solar radiation management/SRM) — large-scale, deliberate efforts to reflect sunlight away from Earth to counteract global warming.

Some scientists, particularly at Cambridge University’s Centre for Climate Repair and backed by UK government funding via the Advanced Research and Innovation Agency (ARIA, ~£50–60 million), are described as “racing” to develop and test these technologies.

Stratospheric Aerosol Injection (SAI): Releasing reflective particles (sulfates, calcium carbonate, or other aerosols) into the upper atmosphere to mimic volcanic cooling (e.g., Mount Pinatubo 1991).

Marine Cloud Brightening (MCB): Spraying fine seawater mist to make low-level clouds more reflective.

Smaller-scale ideas like thickening Arctic ice or cirrus cloud thinning.

Research remains mostly in modeling, lab work, and small-scale studies. No large-scale deployment exists.

A standout quote from Dr. Hugh Hunt (deputy director at Cambridge): “When you run the numbers, there’s just no way to avoid global warming without geoengineering.”

The piece acknowledges risks, skepticism, and governance issues but presents the work as a pragmatic response to stalled progress on mitigation.

The framing is urgent: emissions cuts alone aren’t happening fast enough, so “Plan B” interventions like dimming the sun are moving from fringe theory to active experimentation.

This “race to dim the sun” feels like the flip side of Gary Abernathy’s column on renewables finally standing on their own without subsidies.

Both reflect frustration with decades of policy-heavy approaches that haven’t delivered reliable, scalable results.

Instead of doubling down on market-driven energy (nuclear, natural gas for AI/data centers, advanced storage), some pivot to planetary-scale experiments with unknown side effects and massive governance questions.

Critics argue it’s a symptom of the same mindset: when the preferred “green transition” stalls, reach for bigger interventions rather than pragmatic, dispatchable solutions that already work.

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The climate change scientists racing to dim the sun

Geoengineering schemes may hold the key to reversing global warming, but risks abound and many remain sceptical

Ian McEwan’s recent novel, What We Can Know, is set in a semi-underwater Britain in the year 2119.

A few decades on from a climate catastrophe, things are pretty dire. If you want to get from the Chilterns to the South Downs, you have to travel by boat. The Telegraph has the story.

What saves humanity from total wipeout is, ironically enough, nuclear explosions in the Middle East. Detonations in the desert in the 2040s send gigatons of dust and sand into the upper atmosphere, where they begin to filter out the sun’s harsh light – and reverse global warming.

“Over the graves of millions, the earth began to cool,” our narrator tells us. Over time, the cooling encourages “a new spirit of optimism”.

As sci-fi as all this may sound, the scenario is grounded in scientific fact.

What McEwan is describing is a particularly brutal form of geoengineering – that is, modification on a planetary level – and specifically, “solar radiation modification”, or SRM.

In other words, turning the dimmer switch on the sun. The good news is we don’t need a nuclear apocalypse to do this. It is, theoretically, entirely possible for humans to cool the planet by reflecting more sunlight back into space.

“When you run the numbers, there’s just no way to avoid global warming without geoengineering,” says Dr Hugh Hunt, deputy director of the Centre for Climate Repair at Cambridge University, who has been studying this for the best part of three decades.

“Increasingly, that’s what anyone who really sits down and thinks about it comes to believe. If you stop the sun’s rays from reaching the surface of the Earth, it’s kind of obvious, it’s cooler – as it is on a cloudy day.”

He points to the so-called “napkin” diagram, which charts predicted temperature rises in various scenarios: business-as-usual, mitigation (i.e., the outcome if we switch to renewables), carbon removal and SRM.

The mitigation helps, but it is only with SRM that the temperature actually falls. Again, theoretically.

Proposed techniques vary from the surprisingly lo-fi – painting city rooftops white to reflect more sunlight, say – to the Thunderbirds-esque.

Some have suggested using balloons to send artificial clouds made of aerosols into the sky; others have proposed fleets of planes circling the Earth and spraying sulphur dioxide aerosols into the upper atmosphere.

Last year, a US-Israeli start-up named Stardust, whose co-founder and chief executive, Yanai Yedvab, was once the deputy chief scientist at the Israeli Atomic Energy Commission, announced it had raised $60 million to develop a “full-stack solution” to climate change, promising “a safe, measurable, adjustable, and fully reversible system to stabilise Earth’s temperature” (in other words, the deployment of particles, and bells-and-whistles monitoring).

Another US start-up, Make Sunsets, founded by two Silicon Valley entrepreneurs, is banking on making artificial clouds.

To say that these companies are controversial is an understatement. Indeed, shortly after making its announcement, Stardust was accused by the Center of International Environmental Law of “accelerating a reckless race that threatens to put humanity on a path of no return to perpetual dependency on this extreme technology”. It comes with risks: acid rain, or climate becoming a new vector of warfare.

Read full story here.

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Risks and Challenges

Uneven regional impacts: Cooling might not be uniform. It could alter precipitation patterns (e.g., weaken monsoons in Asia or Africa), shift storm tracks, affect agriculture, or disrupt ecosystems in ways that harm some regions more than others.

Termination shock: If deployment stops suddenly (due to conflict, technical failure, or politics), temperatures could rebound rapidly — potentially faster and more damaging than gradual warming.

Ozone depletion, acid rain, and other side effects: Sulfate aerosols in particular raise concerns about stratospheric chemistry.

Governance and geopolitics: Who controls the “global thermostat”? Unilateral action by one country, company, or actor is theoretically possible, raising risks of international conflict. Attribution of weather events (droughts, floods) to SRM would be scientifically and politically contentious.

Moral hazard: Critics argue it could reduce urgency for emissions reductions, creating a dangerous distraction or “techno-fix” mindset.

Real-world practicality: A 2025 Columbia University study emphasized that SAI is far harder, costlier, and more unpredictable in practice than computer models suggest, due to engineering, delivery systems, maintenance, and atmospheric dynamics.