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Which two broad approaches have been proposed for geoengineering the climate?

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Illustration of various geoengineering techniques to address climate change, including carbon capture and storage methods like artificial trees, industrial scrubbers, and deep ocean CO2 storage, as well as solar reflectance strategies such as sulfur aerosols, reflective crops, cloud whitening, and orbital mirrors. The scene shows these interventions applied to land, sea, and atmosphere, with labeled features explaining each process. — Geoengineering Various geoengineering proposals designed to increase solar reflectance or capture and store carbon.

To address global climate change, scientists have proposed two fundamentally different geoengineering approaches:

Increasing Solar Reflectance: This approach involves technologies designed to increase the reflectance of incoming solar radiation. By reflecting more sunlight back into space, these methods aim to reduce the heating effect on Earth’s surface and lower atmosphere. Proposed techniques include injecting sulfur particles into the stratosphere, whitening marine clouds, raising ground-level albedo, or deploying orbital mirrors.21
Carbon Removal: This approach focuses on extracting carbon dioxide (CO₂) from the atmosphere and storing it in locations where it cannot interact with the climate system. This method is considered particularly significant because it has the potential to address both rising temperatures and ocean acidification. Schemes include carbon sequestration, ocean fertilization, biochar production, and the use of scrubbing towers or artificial trees.23

While these proposals are discussed as potential options to mitigate climate change, they remain highly controversial due to significant risks, unknown consequences, and the lack of large-scale testing.21