Unexplainable – “The G-word” (January 7, 2026)
Host: Sally Helm | Guest: Robinson Meyer

Episode Overview

This episode of Unexplainable (“The G-word”) explores the extraordinarily urgent and controversial topic of solar geoengineering—the idea of intentionally manipulating Earth’s climate by reflecting sunlight away from the planet in order to cool it. Host Sally Helm speaks with veteran climate reporter Robinson Meyer, focusing on the emergence of startups like Stardust Solutions, a company claiming to be on the brink of making solar geoengineering a reality. The conversation weaves through the science, societal risks, motivations, technological feasibility, and governance nightmares that surround this potential “global emergency button.”

Key Discussion Points & Insights

1. Introducing Solar Geoengineering: The High-Stakes Climate Experiment

• Sally opens by painting a speculative picture of Earth’s sky in 2076, subtly altered by human intervention—less blue due to particles sprayed high above to cool the planet ([00:35]).
• Geoengineering is described as:
  • Deploying aircraft to spray sunlight-reflecting particles in the stratosphere—a "shade umbrella" for Earth.
  • Both a potentially lifesaving and dangerously unpredictable experiment:
    • Potential benefits: saves from worst global warming effects; “make sunsets redder, the blue sky whiter.”
    • Potential risks: worldwide droughts, disrupted rainfall, and major geopolitical backlash if misattributed to disasters.
• Sally sets the theme: How likely is this “science fiction” to become reality soon? ([03:48])

2. Geoengineering in the Climate Change Debate

• Divisiveness among Scientists
  Robinson: “I think it would be quite divisive... Some people would be like, ‘Yeah, let’s talk about it.’... Some people would be like, ‘It’s dangerous even to have this conversation.’” ([05:07])
• Why Support It?
  Proponents view it as moral responsibility: “Isn’t this our responsibility as stewards of the planet?... If there was some way to stop [suffering], shouldn’t we try it?” – Robinson ([06:00])
• Why Oppose It?
  “We should not compound [climate change] by running two open-ended, irreversible experiments on Earth’s climate system.” – Robinson ([05:23])

3. The “Moral Hazard” & Risk of Distraction

• Solar geoengineering could trigger complacency:
  “They’re gonna go, ‘Oh great, we don’t have to worry about it anymore. Then I can burn as much coal or gasoline or natural gas as I want and there’s no consequences.’” – Robinson ([06:47])
• The concept of “moral hazard”: Technology as an excuse to stall critical emissions reductions.

4. Science and Feasibility: Does It Work and What Does It Take to Do It?

• Sally summarizes basic mechanisms: mirrors, paint, glass beads, but mainly stratospheric aerosol injection—sulfate aerosols sprayed to reflect sunlight ([07:22]).
• Known effects: “They can make asthma worse, cause acid rain... hurt the ozone layer... but they’d probably do the main job we’d be asking them to do: cooling the Earth.” – Sally ([07:40])
• Robinson: “We know that the basic chemistry here works, because we see nature do it all the time...” ([09:03])
  • Mount Pinatubo erupted in 1991, ejecting huge amounts of sulfur dioxide—cooled Earth by 1°C temporarily.
• Big question: Humans have not yet demonstrated control over such effects on demand or at global scale.
• Is it cheap?
  • “It is theoretically cheap enough that one country could do it alone.” – Robinson ([10:26])
  • Raises geopolitical alarms (i.e., “free rider” problem reversed—rogue actors possible)
• Tech requirements: “Somewhere on the scale of a SpaceX operation... need to monitor the cooling and avoid overshoot.” – Robinson ([11:22])

5. The Problem of “Termination Shock”

• If spraying stops, temps rebound dangerously fast:
  “If you were to cease that geoengineering activity, within a year or two we would have what’s sometimes called a termination shock. We would watch all that warming come right back really fast.” – Robinson ([12:32])

6. The Startup Moment: Stardust Solutions

• Stardust, led by Israeli scientists, has raised $60 million aiming to develop “the technological building blocks of solar geoengineering” ([15:33])
• Unique because:
  • Private, for-profit, not government-led.
  • Claimed development of a proprietary sunlight-reflecting particle (not sulfates), but details are mostly secret ([17:09])
• Scientific skepticism:
  • Lack of transparency, secrecy (“stealth mode”), pursuit of patents, and not publishing key research is seen as violating field norms ([17:55])
  • “They are skeptical… even before you get to their concerns about the particle...” – Robinson

7. Governance: Who Gets to Make This Decision?

• “All of that is up in the air. Ideally this would be a consensus decision that everyone had bought into to some degree.” – Robinson ([19:53])
• Reference to the Montreal Protocol: “We got together and stopped it... They may have saved the world.” – Sally & Robinson ([20:19])
• Fears for transparency, tech control, and “public interest vs. investors’ interests” ([16:02]; [21:02])
• Even “perception” of private control could undermine global trust, regardless of the science.

8. Stardust’s Response & Ongoing Questions

• Stardust claims it will publish safety results soon, peer-reviewed, and eventually will be transparent—even as it patents tech ([21:36]).
• But the problem remains:
  • “A for-profit... US-Israeli technology company founded by people whose background is in national security or nuclear science is maybe not the right vessel to convince the rest of the world that... this is a really good technology.” – Robinson ([22:22])
• Analogy to nuclear weapons: governments, not companies, control such global technologies.

9. Big Picture Reflections: Playing God With the Planet

• “We are as gods, and so we might as well get good at it.” – Robinson, quoting biologist Stuart Brand ([24:32])
• “If I’m Prometheus, do I steal fire, give us cooked food... but also unleash the potential for massive destruction? I don’t know. It doesn’t actually seem like a decision that Prometheus or anyone should be making alone.” – Sally ([24:32])

Memorable Quotes & Moments

• On risks of complacency:
  “[Geoengineering]... there’s a moral hazard to talking or researching or conducting geoengineering. I think is one of the biggest drivers of the taboo.” – Robinson Meyer ([07:09])
• On feasibility:
  “It is theoretically cheap enough that one country could do it alone.” – Robinson Meyer ([10:26])
• On the stakes:
  “If you were to cease that geoengineering activity, then within a year or two we would have what’s sometimes called a termination shock.” – Robinson Meyer ([12:32])
• On governance horror:
  “Historically, we haven’t allowed the private development of nuclear weapons... When I asked the founders of Stardust what this technology reminded them of, they said AI.” – Robinson Meyer ([22:22])
• The Prometheus dilemma:
  “If I’m Prometheus, do I steal fire, give us cooked food and... unleash the potential for massive destruction? I don’t know. It doesn’t actually seem like a decision that Prometheus or anyone should be making alone.” – Sally Helm ([24:32])

Important Segment Timestamps

• [00:35] – Imagining a geoengineered sky in 2076; setting up urgency
• [05:07] – How scientists react to “geoengineering” in a room
• [07:22] – What solar geoengineering actually is and main methods
• [09:03] – Mt. Pinatubo as real-world proof it can work
• [10:26] – Why geoengineering is “theoretically cheap” and that’s a problem
• [12:32] – The dangers of termination shock
• [15:33] – Stardust Solutions: the first big startup (and its secrecy)
• [17:55] – Scientists’ deep skepticism and field norms
• [20:19] – Montreal Protocol as the model of how to do it right, in theory
• [22:22] – Robinson’s reflections on the risks of private tech and global trust
• [24:32] – “We are as gods…” and Sally’s reflection on the Prometheus myth

Tone & Style

The conversation is accessible, curious, and often strikingly candid about the unknowns and ethical quicksand of geoengineering. Sally brings a narrative energy and sense of awe and unease, while Robinson blends expertise with analytical caution—raising, rather than resolving, the big question: Who, if anyone, gets to pull the Earth’s ultimate emergency lever?