Solar radiation modification technologies cannot fully address climate change

9 December 2024

With the Paris climate targets looking increasingly difficult to achieve, technologies are being proposed to reduce warming by reflecting sunlight away from the Earth. Known as “solar radiation modification”, these technologies are gaining traction in some circles, and modelling suggests that some of them may have the potential to prevent further global warming and reduce some of its effects, such as extreme weather events and rising sea levels.

But these technologies are not ready, and in any case, they are no substitute for emissions reductions, according to experts from the Scientific Advice Mechanism (SAM) and European Group on Ethics (EGE). Both groups warn the Commission that Europe must maintain the primary goals of its climate policy – bringing down emissions and adapting to inevitable changes. They recommend further research and in the meantime an EU-wide moratorium on the use of solar radiation technologies.

An in-depth study of the available technologies led both Chief Scientific Advisors (GCSA) - informed by the evidence review report by SAPEA (Science Advice for Policy by European Academies) - and the European Group on Ethics to conclude that none of technologies in question are ready to be deployed. They could have negative impacts on ecosystems, change rainfall patterns, and hamper food production. Moreover, they would not address the direct impacts of greenhouse gases, such as ocean acidification or changes in vegetation patterns. Both groups underline that presenting these technologies as available solutions could damage efforts that are already underway to reduce greenhouse gas emissions and adapt to climate change. Furthermore, any large-scale intervention in our common planetary environment would have systemic consequences.

Ekaterina Zaharieva, Commissioner for Startups, Research and Innovation said:

“These technologies do show some promise, but they are far from mature. Research must continue, but the opinion of the European Group on Ethics shows research must be rigorous and ethical, and it must take full account of the possible range of direct and indirect effects. It is also important that the scientific evidence on risks and opportunities of solar radiation modification research and deployment is periodically assessed.”

Based on the evidence, the Group of Chief Scientific Advisors and the European Group on Ethics made the following recommendations to the European Commission:

Continue to focus on reducing greenhouse gas emissions and adapting to climate change as the highest priorities.
Announce a Europe-wide moratorium on using solar radiation modification technologies.
Negotiate a global governance system for future decisions about deploying solar radiation modification technologies, ensuring it is aligned with fundamental rights and values. Given the current state of knowledge, the EU’s position in global negotiations should be to not deploy the technologies.
Hold broad and inclusive public deliberations about fighting climate change, allowing citizens to learn about and debate a range of approaches.
Ensure that research into solar radiation technologies is rigorous, ethical and explicit about uncertainties – and includes critical reflection on the full range of direct and indirect effects, governance and justice issues.
Reassess the evidence on risks and potential opportunities every five to ten years.

The advice comes as non-binding policy recommendations, in form of a Scientific Opinion from the GCSA, a detailed Opinion from the EGE, and an Evidence Review Report prepared by SAPEA. The findings were presented to Wopke Hoekstra, Commissioner for Climate, Net Zero and Clean Growth, and to Commissioner Ekaterina Zaharieva.