Solar geoengineering: a note to inform discussions on physical climate impacts, risks and governance issues

With international efforts on climate action still not on track to limit warming to 1.5°C, technological fixes that aim to intentionally alter the Earth’s climate, such as solar geoengineering, might seem like appealing options for tackling global warming. But they come with questions in terms of feasibility, impacts and risks, governance and geopolitics, and who may or may not benefit.

Crucially, no mature solar geoengineering technology exists today. And even if solar geoengineering was deployed, it would not reverse or halt climate change but create a different, engineered climate future.

Solar geoengineering would result in new and additional impacts on and risks to human and natural systems, mainly driven by changes in temperature, precipitation and extreme events. These would be distributed unequally, with regions already most vulnerable to climate impacts disproportionately affected.

And, as solar geoengineering does not cut emissions, non-temperature related impacts associated with continuing emissions would also continue, including ocean acidification. Also, it would put the world at risk of a sudden rise in global temperatures if solar geoengineering suddenly ends or fails – the "termination shock".

Since solar geoengineering would not affect all regions of the world equally, it could aggravate existing inequalities and regional conflicts, exacerbating the existing divide between those countries contributing most to climate change and those forced to bear the highest physical, societal and economic costs. This also raises questions around how additional adverse impacts from solar geoengineering could require new finance and support systems for adaptation and loss & damage, especially for particularly vulnerable regions.

Motivations for developing and deploying solar geoengineering could meanwhile be driven by geopolitical considerations rather than the actual risks of the climate crisis. Even the hypothetical prospect of solar geoengineering could “green light” the continued burning of fossil fuels, posing a threat to net zero commitments and other mitigation ambitions. And only major world powers have the capacity and capability to deploy solar geoengineering at scale, posing the risk of unilateral solar geoengineering deployment controlling regional and global temperatures and associated impacts and risks.

Rather than promoting potentially dangerous real-world experiments, both climate policy and action must follow the best available science, which is clear on the need for urgent and strong cuts to greenhouse gas emissions if we are to meet the Paris Agreement objectives.