When are small-scale field experiments in solar geoengineering worth pursuing?

We propose a set of heuristics—scientific rigor, safety, usefulness, engagement, and transparency—for assessing the pursuitworthiness of small-scale field experiments in solar geoengineering research. Rather than offering a fixed logic of pursuit, we emphasize that these heuristics should operate as part of a dynamic and iterative evaluative process within the solar geoengineering research community, responsive to changing modeling priorities, new data, and shifting ethical and political landscapes. We argue that such experiments must be understood within the broader context of climate modeling research, where their primary role is to improve model components and identify further uncertainties. Our analysis assumes, rather than argues for, the pursuitworthiness of solar geoengineering research as a whole. However, we conclude this work by revisiting the overarching question of whether solar geoengineering research itself is worth pursuing; we argue that accounts that focus on how research governance can reduce bias and build stable scientific norms offer a more promising route than appeals to urgency or “moonshot” missions. Overall, we provide a structured framework, situated within scientific practice, that can help determine which field experiments are worth undertaking and why.