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This review aims to assess past Solar Radiation Modification field experiments and extract implications for governance.

May 25, 2026Earth s Future1 citationsOpen Access

Past Field Experiments of Solar Radiation Modification: A Review of the Scientific and Technical Aspects for Governance

IHI. Hernandez‐GalindoCentre National de la Recherche Scientifique AMA. MäättänenCentre National de la Recherche Scientifique BRB. H. Redmond RocheUniversity College London

Key Points

This review aims to assess past Solar Radiation Modification field experiments and extract implications for governance.
Categorized past experiments into techniques: SAI, MCB, CCT/MCT.
Analyzed experiments based on six parameters: justification, feasibility, monitorability, uncertainties, reversibility, exit ramps.
Highlighted notable experiments such as SPICE and SCoPEx for their contributions and governance challenges.
Past small-scale experiments showed feasibility and the need for effective monitoring and reversibility.
Governance challenges like public opposition and ethical concerns led to the cancellation of several projects.
Inconsistent application of governance parameters across experiments suggests a need for robust frameworks for future SRM trials.

Abstract

Abstract As global warming intensifies, Solar Radiation Modification (SRM) has drawn increasing scientific and policy interest as a potential means to temporarily offset climate impacts. This review examines past SRM (or SRM‐like) field experiments, categorized into three primary techniques: Tropospheric and Stratospheric Aerosol Injection (SAI), Marine Cloud Brightening (MCB), and Cirrus/Mixed‐Phase Cloud Thinning (CCT/MCT). While many of these experiments were originally atmospheric science studies rather than deliberate SRM trials, they offer valuable empirical insights into SRM‐relevant processes. Notable experiments such as the Russian tropospheric aerosol trials, SPICE, SCoPEx, E‐PEACE, the Great Barrier Reef MCB trials, the University of Washington MCB trials, and the CLOUDLAB project are assessed for their contributions and limitations. The paper analyses experiments through six key parameters: scientific justification, feasibility and achievability, monitorability, uncertainties, reversibility, and exit ramps. Past small‐scale trials demonstrated technical feasibility and the importance of monitorability and reversibility in their experimental design. The implementation of the six parameters was applied inconsistently across past experiments. Meanwhile, distinct governance challenges, notably public opposition, ethical concerns, and insufficient transparency, directly caused the cancellation of multiple projects (SPICE, SCoPEx, UoW). This points to a need for robust governance of potential future SRM field trials, incorporating the aforementioned parameters and integrating ethical standards, legal compliance, and community engagement, alongside rigorous scientific design.

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