As a climate scientist working on solar geoengineering, I was struck by Raymond Pierrehumbert and Michael Mann’s call to defund the UK’s Advanced Research and Invention Agency (Aria) research programme (The UK’s gamble on solar geoengineering is like using aspirin for cancer, 12 March).
Given current emission projections, it is likely that the world will reach 2C of warming. The only potential tool we have to reduce temperatures on a short timescale is solar geoengineering. It is necessary to reduce emissions, but once we reach net zero, global temperatures only stabilise, and the melting of glaciers and sea level rise will continue. While it is possible to remove carbon from the atmosphere, it remains slow and expensive for now.
Solar geoengineering research is important because it is possible that the climate will react more strongly to greenhouse gases than expected, and even 2C of warming might have devastating impacts.
It is undeniable that solar geoengineering has physical and political risks, and I share many of the concerns the authors raise. However, a warmer world that would increasingly become uninhabitable is also risky. Hence the risks of solar geoengineering must be balanced with the risks from the warming that would be attenuated.
Climate model evidence suggests that some important hazards linked to climate change could be limited with a judicious deployment of solar geoengineering. However, climate models contain many uncertainties that well‑governed, small-scale outdoor experiments may enable us to reduce. While more research and higher‑quality information on solar geoengineering are not sufficient to guarantee good decision-making about it in the future, they are certainly a prerequisite. I welcome the UK government’s investment in solar geoengineering research.
Dr Matthew Henry
Postdoctoral Research Fellow at the University of Exeter
• Your article is misjudged. Yes we must transform fossil fuel use and deploy carbon capture. But humans are losing the battle and we can’t afford an either/or argument. Just as low-dose aspirin use may protect against cancer, low-dose prevention of heat using sulphur, manufactured clouds, Arctic refreezing or aiding flow of crucial ocean currents may be able to aid climate control. In fact, it might be the only chance we have. So please, UK, spend £57m and more on geoengineering research now.
Prof Stuart Haszeldine
School of GeoSciences, University of Edinburgh
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