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Which materials are dispersed into clouds during cloud seeding?

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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.

Cloud seeding involves the deliberate introduction of substances into clouds to act as condensation nuclei or ice nuclei to induce precipitation. The materials used depend on the temperature and type of the cloud:1

Supercooled clouds: These are most commonly seeded with silver iodide, which is often dispersed as minute particles via aircraft, ground generators, or pyrotechnic devices. Dry ice (solid carbon dioxide) was historically used to trigger ice crystal formation but is less common today. Additionally, lead iodide has been employed in some experimental programs.21
Warm clouds: To encourage the growth of giant cloud droplets, these clouds are seeded with sodium chloride (salt) or calcium chloride particles, or sometimes a water spray.21
Electrical modification: In experiments aimed at altering the electrical structure of clouds to mitigate lightning, researchers have utilized large numbers of short metal strips.2