I have joined more than 60 senior climate scientists and governance scholars from around the world who have launched a global initiative today calling for an International Non-Use Agreement on Solar Geoengineering. We argue that solar geoengineering deployment cannot be fairly governed globally and poses unacceptable risk if implemented as a future climate policy option. The group therefore calls on fellow academics, civil society organizations and concerned individuals to sign an open letter to governments, the United Nations and other actors to stop development and potential use of planetary-scale solar geoengineering technologies. The initiative draws on an academic journal article published today in WIREs Climate Change, co-authored by 16 scientists and initiators of this group.

The initiative for a non-use agreement mobilizes especially against the most widely debated speculative technology: the massive spraying of aerosols in the stratosphere to block a part of incoming sunlight to cool the planet. We argue that such dangerous planetary-scale interventions cannot be governed in a globally inclusive, fair and effective manner and must therefore be banned.

The Open Letter also highlights that betting on solar geoengineering as a potential future solution threatens “commitments to mitigation and can disincentivize governments, businesses, and societies to do their utmost to achieve decarbonization or carbon neutrality as soon as possible. The speculative possibility of future solar geoengineering risks becoming a powerful argument for industry lobbyists, climate denialists, and some governments to delay decarbonization policies”.

In early 2021, this was one of the reasons presented by the indigenous Saami Council and environmental NGOs to stop a balloon test for a Harvard University solar geoengineering research programme. Planned for June 2021 above indigenous territory in Sweden, the test was halted after strong civil society opposition. We argue that such tests should be banned worldwide.

The 60 leading climate scientists and governance experts also fear that without an international ban or restrictions, a few powerful countries with support from major corporations and philanthropists could engage in solar geoengineering unilaterally or in small coalitions, even when the rest of the world opposes such deployment ? or has not yet had the time to assess it and its potential dangers. This threat, the group argues, requires immediate action by governments and the United Nations for an International Non-Use Agreement on Solar Geoengineering.

More precisely, the Open Letter calls upon governments to support five core prohibitions and measures to:

• Prohibit their national funding agencies from supporting the development of technologies for solar geoengineering, domestically and through international institutions.
• Ban outdoor experiments of solar geoengineering technologies in areas under their jurisdiction.
• Refuse patent rights for technologies for solar geoengineering, including supporting technologies such as for the retrofitting of airplanes for aerosol injections.
• Not deploy technologies for solar geoengineering if developed by third parties.
• Object to future institutionalization of planetary solar geoengineering as a policy option in relevant international institutions, including within assessments by the Inter-governmental Panel on Climate Change.

Our initiative’s website offers updated scientific information on various risks posed by solar geoengineering and its hypothetical technologies.

Mike Hulme, 17 January 2022