GEOENGINEERTINGWhy Not Use Space Mirrors for Reflecting Sunlight to Cool the Planet?
Given the potential consequences of climate change and a danger of reaching irreversible “tipping points,” there is an argument to be made that all options should be carefully considered. Sending giant mirrors into space to reflect solar radiation away from the Earth is one such option. The problem is that the many such geoengineering approaches have been so taboo that there is not enough information from researchers to definitively decide what options are still viable.
Given the potential consequences of climate change and a danger of reaching irreversible “tipping points,” there is an argument to be made that all options should be carefully considered. Sending giant mirrors into space to reflect solar radiation away from the Earth is one such option.
The problem is that the many such geoengineering approaches have been so taboo that there is not enough information from researchers to definitively decide what options are still viable. A National Academies of Science, Engineering, and Medicine report in 2021 and a report from the Council on Foreign Relations argue for further research and associated governance on solar geoengineering approaches (i.e., stratospheric aerosols, cloud seeding, or cirrus cloud thinning). These reports omit the solar geoengineering approach that utilizes large-scale space mirrors.
Space mirrors would be about the size of Brazil and could be located at Lagrange Point L1 between the Earth and Sun. While they continue to be written off as an infeasible and overly costly idea of science fiction, rigorous analysis given current technological advances in space technology has not been conducted. The other ideas for reflecting sunlight to cool the planet involve putting things into Earth’s atmosphere with potentially global-scale secondary effects on the biosphere, a major concern in terms of public opinion. Placing space mirrors 1.5 million kilometers out in space—though outside of Earth’s biosphere—could present other governance and risk considerations that should be weighed against potential benefits.
RAND recently conducted a review of geoengineering technologies with a discussion of geopolitical risks arising from geoengineering implementation and the existing legal mechanisms that fall short of managing the risks. The review includes space mirrors. However, due to the sparsity of published research, it depends on literature up to 15 years old to determine the cost, technical readiness, and secondary effects. For reference, one feasibility study from 2006 estimated that a fleet of meter-sized spacecraft could be developed and deployed in 25 years, would have a lifetime of 50 years, and cost some trillions of dollars.
