No evangelist for climate intervention, atmospheric chemist Frank Keutsch instead stakes out a pragmatic middle ground: Don’t rush to deploy projects that might cool the planet – but do investigate the possibility carefully so society understands what’s at stake.

On a new episode of Entanglements, a podcast from Undark Magazine, Keutsch, Harvard’s Stonington Professor of Engineering and Atmospheric Science, describes why fundamental science research into solar geoengineering – often known as solar radiation modification, or SRM – is important in this era of accelerating climate change. He debates the topic with planetary physicist Raymond Pierrehumbert of Oxford University.

Keutsch recounts entering the field about a decade ago after realizing that few atmospheric chemists were probing its biggest unknowns, even as the climate crisis deepens.

Yet he is clear-eyed about technology’s pitfalls. Solar radiation modification, he says, is a “painkiller.” It eases the symptoms without treating the disease – continued greenhouse-gas emissions – and it risks moral hazard by tempting policymakers to delay decarbonization. Termination shock (a rapid rebound in warming if injections stop) worries him, a point on which he and geoengineering skeptic Pierrehumbert agree.

Keutsch’s ill-fated SCoPEx proposal exemplifies his approach. The plan was modest: release roughly a kilogram of particles to study how a narrow plume spreads in the stratosphere – essentially a turbulence experiment to map how particles up there mix, not a rehearsal for planet-cooling. He likens it to watching a drop of ink diffuse across an Olympic swimming pool.

Keutsch’s contribution to the conversation emphasizes that “yes to research, no to rush” isn’t fence-sitting; it’s an argument for better evidence, clearer governance, and fewer illusions about silver bullets. If society ever needs a plan B, it will want real data – and a sober understanding of technology’s limits – before touching the planet’s thermostat