Leading climate scientists have issued a stark warning against solar geoengineering, arguing that it does not 'buy time' for decarbonisation and poses significant planetary risks. In a recent commentary, Raymond Pierrehumbert, Julia Slingo, Michael Mann, and Valerie Masson-Delmotte—experts with over a century of combined climate research experience—urged caution against techno-optimistic 'quick fixes' for climate change.
Understanding the Risks of Solar Geoengineering
The scientists explain that solar geoengineering proposals, which aim to reduce sunlight reaching Earth, are often seen as a way to offset slow progress in cutting carbon emissions. However, they highlight a critical flaw: while carbon dioxide remains in the atmosphere for millennia, the effects of solar geoengineering decay within years. This creates a dangerous dependency, as it would take up to two decades to build the necessary infrastructure, leaving humanity vulnerable to a 'termination shock' if the system fails.
'Solar geoengineering does not buy time for decarbonisation,' the authors state. They note that other geoengineering schemes, such as damming the Bering Strait, also require centuries of maintenance, while carbon dioxide continues to wreak havoc.
Uncertainty and Lack of Scientific Rigour
The scientists criticise the current push for geoengineering research, which they say focuses on technology development rather than understanding risks. Climate model simulations show wide disagreement on required intervention levels and responses, with global cooling ranging from less than 1°C to as much as 3°C after just ten years of stratospheric aerosol injection. 'We are essentially flying blind,' they warn.
They also dismiss small-scale experiments as naive, arguing that natural climate variability would swamp any effects, providing no reliable data on efficacy or risks.
Governance and Profit Motives
The commentary highlights the lack of governance around geoengineering, with venture-capital-funded startups like Stardust and Reflect Orbital pursuing near-term deployment. Stardust has received over $60 million in venture capital, while Reflect Orbital plans to place giant mirrors in orbit. These companies operate without legal obligations for public scrutiny or climate impact assurances.
'All of this is happening in the total absence of governance,' the authors note, calling it a 'huge diversion of resources' from the real task of cutting fossil fuel use.
Call for Caution
The scientists, who have contributed to IPCC reports and national academy assessments, urge the same level of scientific diligence for geoengineering as for understanding greenhouse gas impacts. They conclude: 'When you're in a climate hole, stop digging... and burning fossil fuels. It really is, at some level, that simple.'
