Should We Cool the Planet on Purpose? The Solar Geoengineering Debate
Key points
- Solar geoengineering masks the symptom, not the cause: it can cool the planet, but ocean acidification continues
- A 2025 Royal Society briefing: coordinated deployment could cut global mean temperature, but reduces rainfall more than equivalent emissions cuts, and temperatures rebound within 1–2 decades of stopping
- The biggest risk is 'termination shock': stop, and the hidden warming arrives fast
- The research camp argues ignorance is itself a risk, and a rushed crisis deployment would be far more dangerous
- Opponents warn research erodes mitigation pressure and that cross-border effects make governance nearly impossible; hundreds of scholars have called for a 'non-use agreement'
The core dispute
In 1991, the Mount Pinatubo eruption sent sulfate aerosols into the stratosphere and cooled the planet by about 0.5°C for over a year — nature has already demonstrated the principle. Solar radiation management (SRM) proposes copying it deliberately. The dispute is not whether it can cool — models broadly agree it can — but whether it should be done, who gets to decide, and who pays when something goes wrong.
The case for research
Most of this camp does not advocate deploying now, but researching now: if warming approaches a tipping point and one country acts in panic one day, ignorance is more dangerous than knowledge. The US National Academies have recommended a systematic interdisciplinary research programme with governance attached; the UK's ARIA has put £56.8 million into 22 climate-cooling teams, including small controlled outdoor experiments. A 2026 US Government Accountability Office assessment likewise found that more research and field trials would improve understanding.
The case against
Opponents count three costs. First, SRM does nothing about CO2: ocean acidification continues, and rainfall shifts unevenly, with winners and losers falling along national borders. Second, termination shock: if deployment stops — war, a coup, funding collapse — the suppressed warming arrives within one or two decades, faster than ecosystems can adapt. Third, moral hazard: a 'cooling backup plan' dilutes the political pressure to cut emissions. On governance there is no precedent at all: effects cross borders, yet no global body has the authority to approve or halt deployment. Hundreds of scholars have signed an open call for an international 'non-use agreement', arguing even research should be restricted.
Why there is still no answer
Because this is simultaneously a scientific question, a distributive question and a power question. Science can compute global mean temperature; it cannot compute who should pay for a shifted monsoon. And no trial can verify global-scale consequences without actually deploying. The two camps even judge 'research' itself in opposite directions — one sees risk reduction, the other sees a fait accompli in the making.
Where things stand
The 2026 reality is a middle path: no large-scale deployment, no abandonment of research, small trials plus governance talks. But when the next climate tipping point is confirmed crossed, the pressure on this argument only grows.