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How would stratospheric sulfur injection reduce the amount of sunlight absorbed by Earth?

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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.

Stratospheric sulfur injection is a proposed geoengineering technique that aims to reduce the amount of solar radiation reaching the troposphere by creating an aerosol layer in the stratosphere.12

By dispersing sulfur particles into the stratosphere—using methods such as balloons or aircraft—the technique mimics the atmospheric cooling effects observed after major volcanic eruptions. These aerosols increase the scattering of incoming sunlight back into space. Because more radiation is scattered in the stratosphere, less energy is absorbed by the lower atmosphere, where weather patterns occur.12

This process is inspired by events like the 1991 eruption of Mount Pinatubo, which injected sulfur dioxide into the atmosphere, resulting in a global temperature decrease of approximately 0.5 °C (0.9 °F) for several years. While this method could theoretically lower global temperatures, it remains an untested and complex intervention in Earth's climate system.123