Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).
Efficacy assessment of Stratospheric Aerosol Scrubbing as a Counter Climate Intervention strategy
Anthony C. Jones,James M. Haywood,Matthew Henry,and Alistair Duffey
Abstract. Stratospheric Aerosol Injection (SAI) has been proposed to counteract global warming. Countering SAI may prove attractive to actors who oppose deployment and methods have been suggested but not tested for efficacy. Using a global climate model with double moment aerosol microphysics, we investigate the viability of 'Stratospheric Aerosol Scrubbing' (SAS) scenarios where coarse calcite aerosol is deliberately injected to enhance aerosol growth, reduce particle radiative efficiency, and enhance sedimentation thereby reducing SAI impacts. We simulate two equatorial SAI and SAS scenarios: pulse interventions lasting 2 months, and sustained interventions lasting 20 years. We find that SAS reduces the global Stratospheric Aerosol Optical Depth by 30–40 % when the calcite mass is equal to the sulphur dioxide (SO2) mass in the pulse intervention and half of the SO2 mass in the sustained intervention. The global radiative impact in the sustained simulations is reduced from -3.3 Wm-2 to -2.3 Wm-2 under SAS, a counterbalancing of approximately 30 %. Our results suggest that SAS could be effective at offsetting SAI impacts.
Received: 18 Dec 2025 – Discussion started: 05 Jan 2026
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I struggled with this paper. The analysis is done quite well, and I couldn’t really find any technical errors. But my problem is the motivation for the study and the framing. This is just a weird idea.
More specifically, the authors conclude that to scrub SAI, you would need to do an SAI-level effort. So who, exactly, is doing this? Someone who is opposed to SAI and wants to stop SAI is…going to do SAI? I don’t get it.
Related to that, the authors assert that this method is “effective”. That may be true from a purely chemical standpoint (more on that shortly), but that’s a really narrow perspective. If your countermeasure takes as much or more effort than the original activity, I wouldn’t really call that effective. And again, it requires building a huge amount of infrastructure that is, until deployment, indistinguishable from SAI. So it’s hard to justify effectiveness in many senses beyond chemical.
Getting into the chemistry, the choice of calcite is poorly justified. There are also really important processes missing, including aerosol mixing state (it looks like you use a simple assumption for this), chemical interaction (offline oxidants), and aerosol aging. There is strong evidence to suggest that after a while the calcite aerosols just get covered in sulfate and look a lot like sulfate aerosols. And in terms of particle growth, using a modal double-moment scheme probably has some issues. The point being, while this is an interesting idea, you’ve made enough assumptions in your model that your results could be totally wrong.
And finally, I don’t understand the call to include this in GeoMIP. Getting the microphysics and chemistry right for this idea is highly important. Only a small handful of GeoMIP models can do this. If you had proposed it to CCMI I might agree.
Overall, I have trouble with what the authors did, including the justification for doing the study in the first place, how the modeling was done, and the interpretation of the results. I think these issues could ultimately be addressed by reframing the paper, as there’s some good technical work in here. But considering the headlines this idea might generate, overclaiming what you’ve done and the results you’ve found is irresponsible.
Anthony C. Jones,James M. Haywood,Matthew Henry,and Alistair Duffey
Data sets
Data and Scripts to support "Efficacy assessment of Stratospheric Aerosol Scrubbing as a Counter Climate Intervention strategy" by Jones et al.A. C. Jones https://doi.org/10.5281/zenodo.17574992
Anthony C. Jones,James M. Haywood,Matthew Henry,and Alistair Duffey
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Injecting aerosol into the stratosphere has been suggested to rapidly cool the planet and counter climate change. Rival actors who oppose deployment may seek to counter stratospheric aerosol injection. Using a climate model, we investigate whether stratospheric aerosol removal could be hastened by injecting coarse aerosol which promote aerosol growth and gravitational settling. We find that this could be effective, reducing aerosol impacts by 30 % in simulations, and warrants further research.
Injecting aerosol into the stratosphere has been suggested to rapidly cool the planet and...
I struggled with this paper. The analysis is done quite well, and I couldn’t really find any technical errors. But my problem is the motivation for the study and the framing. This is just a weird idea.
More specifically, the authors conclude that to scrub SAI, you would need to do an SAI-level effort. So who, exactly, is doing this? Someone who is opposed to SAI and wants to stop SAI is…going to do SAI? I don’t get it.
Related to that, the authors assert that this method is “effective”. That may be true from a purely chemical standpoint (more on that shortly), but that’s a really narrow perspective. If your countermeasure takes as much or more effort than the original activity, I wouldn’t really call that effective. And again, it requires building a huge amount of infrastructure that is, until deployment, indistinguishable from SAI. So it’s hard to justify effectiveness in many senses beyond chemical.
Getting into the chemistry, the choice of calcite is poorly justified. There are also really important processes missing, including aerosol mixing state (it looks like you use a simple assumption for this), chemical interaction (offline oxidants), and aerosol aging. There is strong evidence to suggest that after a while the calcite aerosols just get covered in sulfate and look a lot like sulfate aerosols. And in terms of particle growth, using a modal double-moment scheme probably has some issues. The point being, while this is an interesting idea, you’ve made enough assumptions in your model that your results could be totally wrong.
And finally, I don’t understand the call to include this in GeoMIP. Getting the microphysics and chemistry right for this idea is highly important. Only a small handful of GeoMIP models can do this. If you had proposed it to CCMI I might agree.
Overall, I have trouble with what the authors did, including the justification for doing the study in the first place, how the modeling was done, and the interpretation of the results. I think these issues could ultimately be addressed by reframing the paper, as there’s some good technical work in here. But considering the headlines this idea might generate, overclaiming what you’ve done and the results you’ve found is irresponsible.