Why would reflecting more sunlight not reduce the amount of carbon dioxide in the atmosphere?

Reflecting more sunlight—a strategy known as solar radiation management—does not reduce the amount of carbon dioxide in the atmosphere because it addresses a different part of the Earth's energy budget than the greenhouse effect.1

While increasing albedo (reflectance) can reduce the amount of incoming solar radiation absorbed by the Earth's surface, it does nothing to remove the greenhouse gases already present in the atmosphere. These gases, such as carbon dioxide, function by absorbing infrared radiation emitted from the surface and reradiating it back toward Earth, which traps heat regardless of how much sunlight is initially reflected.123

Consequently, while solar geoengineering might theoretically offset rising temperatures, it fails to counter the underlying chemical concentration of carbon dioxide. This distinction is critical because failing to reduce atmospheric carbon dioxide leaves other issues, such as ocean acidification, unaddressed. To mitigate both warming and acidification, geoengineering approaches must specifically focus on carbon sequestration to remove the gas from the air.1