What role could sunshades play in stabilizing the climate? This is the most is the most comprehensive look at this topic yet.

We set out to analyze six different sunshade architectures, and evaluate their impacts with climate modeling. The results include several papers making their way through the peer-review process, a multi-disciplinary network of leaders, and a much higher fidelity map of the sunshade landscape. Our report pulls together these findings. It’s written for the smart non-expert, and it puts the technical results in context with heuristics that can anchor future sunshade policy discussions in what the physics actually allows.

Our work has identified the following key findings:

• A sunshade is buildable with no new physics, but is realistically 20–40 years away. The largest factors influencing that timeline are a) the cadence of heavy lift launch vehicles, and b) the development of large-scale lunar resource extraction to reduce the total mass launched from Earth.
• A sunshade is unique among climate interventions in that its shading levels can be ‘adjusted’ in a matter of days, while also durable over a span of many decades.
• Spectrally-selective shading is possible, and may address solar radiation modification (SRM)’s hydrological side effects, although this result is extremely preliminary.
• A novel concept for controlling a cloud of dust particles promises a 600x mass advantage over the commonly studied sail-based concepts, with the potential for reversible deployment and removal. Note that engineering to verify the controllability of a dust cloud is in the early stages.
• We affirm the field’s overwhelming preference for a location near the Sun-Earth Lagrange 1 point. Our associated report on Earth Orbit concludes that it is not a relevant location for sunshades.