Solar radiation modification (Scientific Opinion)

For decades, technologies have been proposed that would reduce or counteract global warming by reflecting sunlight away from the Earth. These proposals, known as Solar Radiation Modification technologies, include stratospheric aerosol injection, cloud brightening, and others.

However, none of these technologies is mature and deploying them could have many effects, both intended and unintended. 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. Even if some of these proposals could address the symptoms of climate change, they do not address the cause, and presenting them as solutions could damage the efforts that are already underway to reduce greenhouse gas emissions and to adapt to climate change.

The benefits and risks of these proposals are also highly uncertain. Deploying them could have effects on the climate in different parts of the world that would be difficult to predict and difficult to manage in practice.

Furthermore, any large-scale intervention in our common planetary environment would have systemic consequences. Some SRM applications would need to run for generations-long timescales and have impacts across the entire planet. A strong global governance framework would be needed for this, with adequate representation for all affected parties, and with compensation mechanisms for those potentially harmed. No such framework exists, and it is not clear how one could be created.

Therefore, based on the available scientific evidence, much of which is uncertain and contested, the Group of Chief Scientific Advisors and the European Group on Ethics in Science and New Technologies recommend the following:

• Continue to focus on reducing greenhouse gas emissions and adapting to climate change as the highest priorities;
• Announce a Europe-wide moratorium on using SRM technologies;
• Negotiate a global governance system for future decisions about deploying SRM 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 SRM 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.

Edition / Volume: Scientific Opinion, 17
Standard identifier: ISBN 978-92-68-19568-0 / doi 10.2777/391614