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Abstract

Achieving the Paris Agreement's aim to limit the global temperature increase to at most 2°C above preindustrial levels will require rapid, substantial greenhouse gas emission reductions together with large-scale use of “negative emission” strategies for capturing carbon dioxide (CO2) from the air (1). It remains unclear, however, how or indeed whether large net-negative emissions can be achieved, and neither technology nor sufficient storage capacity for captured carbon are available (2). Limited commitment for sufficient mitigation efforts and the uncertainty related to net-negative emissions have intensified calls for options that may help to reduce the worst climate effects (3). One suggested approach is the artificial reduction of sunlight reaching Earth's surface by increasing the reflectivity of Earth's surface or atmosphere.