What is geoengineering?
Climate geoengineering refers to a number of large-scale techniques that are used to try to reduce the impacts of climate change. Some methods focus on the reduction of greenhouse gases in the atmosphere, such as through direct carbon capture or approaches that target methane, a powerful greenhouse gas.
What is cloud seeding, and how commonly is it practiced today?
Cloud seeding to increase precipitation and snowpack has been around since the 1940’s. This is typically referred to as “weather modification”, since the focus is on a short term (on the scale of hours) increase in rainfall or snow. It’s used in a number of Western US states where there are concerns around drought, as well as in many other countries around the world.
Silver iodide is an inorganic compound with the formula AgI, known for its bright yellow color and use in photography and cloud seeding. It can form ice crystals in supercooled clouds, aiding in precipitation processes.
Cloud Seeding
Silver iodide is widely used in cloud seeding to enhance precipitation. It acts as a nucleating agent in supercooled clouds, promoting the formation of ice crystals.
GHS Hazard Statements
H400 (16.7%): Very toxic to aquatic life [WarningHazardous to the aquatic environment, acute hazard]
H410 (95.8%): Very toxic to aquatic life with long lasting effects [Warning Hazardous to the aquatic environment, long-term hazard]
4.1.1 Toxicity Summary
Metallic silver is oxidized and may deposit in the tissues, causing arygria. The silver ion is known to inhibit glutathione peroxidase and NA+,K+-ATPase activity, disrupting selenium-catalyzed sulfhydryl oxidation-reduction reactions and intracellular ion concentrations, respectively. Silver nanoparticles are believed to disrupt the mitochondrial respiratory chain, causing oxidative stress, reduced ATP synthesis, and DNA damage. (L808, A243, A244, A245, A246)
The major hazards encountered in the use and handling of silver iodide stem from its toxicologic properties. Toxic by all routes (ie, inhalation, ingestion, and dermal contact), exposure to this odorless, light yellow, crystalline substance may occur from its use in seeding clouds for rain-making, as a photosensitive agent in photography, as a local antiseptic, and as a chemical intermediate. Effects from exposure may include skin rashes, conjunctivitis, argyria (a permanent ashen-gray discoloration of skin, conjunctiva, and internal organs), headache, fever, hypersensitivity, laryngitis, and bronchitis. Exposure should be minimized by engineering controls (eg, local exhaust ventilation, or process enclosure).
1978 United States Senate Report: Weather modification: programs, problems, policy, and potential by Committee on Commerce, Science, and Transportation Publication
https://archive.org/details/weatificat00unit
https://pubchem.ncbi.nlm.nih.gov/compound/Silver-iodide
https://news.climate.columbia.edu/2025/07/17/geoengineering-cloud-seeding/What is geoengineering?
Climate geoengineering refers to a number of large-scale techniques that are used to try to reduce the impacts of climate change. Some methods focus on the reduction of greenhouse gases in the atmosphere, such as through direct carbon capture or approaches that target methane, a powerful greenhouse gas.
What is cloud seeding, and how commonly is it practiced today?
Cloud seeding to increase precipitation and snowpack has been around since the 1940’s. This is typically referred to as “weather modification”, since the focus is on a short term (on the scale of hours) increase in rainfall or snow. It’s used in a number of Western US states where there are concerns around drought, as well as in many other countries around the world.
Silver iodide is an inorganic compound with the formula AgI, known for its bright yellow color and use in photography and cloud seeding. It can form ice crystals in supercooled clouds, aiding in precipitation processes.
Cloud Seeding
Silver iodide is widely used in cloud seeding to enhance precipitation. It acts as a nucleating agent in supercooled clouds, promoting the formation of ice crystals.
GHS Hazard Statements
H400 (16.7%): Very toxic to aquatic life [WarningHazardous to the aquatic environment, acute hazard]
H410 (95.8%): Very toxic to aquatic life with long lasting effects [Warning Hazardous to the aquatic environment, long-term hazard]
4.1.1 Toxicity Summary
Metallic silver is oxidized and may deposit in the tissues, causing arygria. The silver ion is known to inhibit glutathione peroxidase and NA+,K+-ATPase activity, disrupting selenium-catalyzed sulfhydryl oxidation-reduction reactions and intracellular ion concentrations, respectively. Silver nanoparticles are believed to disrupt the mitochondrial respiratory chain, causing oxidative stress, reduced ATP synthesis, and DNA damage. (L808, A243, A244, A245, A246)
The major hazards encountered in the use and handling of silver iodide stem from its toxicologic properties. Toxic by all routes (ie, inhalation, ingestion, and dermal contact), exposure to this odorless, light yellow, crystalline substance may occur from its use in seeding clouds for rain-making, as a photosensitive agent in photography, as a local antiseptic, and as a chemical intermediate. Effects from exposure may include skin rashes, conjunctivitis, argyria (a permanent ashen-gray discoloration of skin, conjunctiva, and internal organs), headache, fever, hypersensitivity, laryngitis, and bronchitis. Exposure should be minimized by engineering controls (eg, local exhaust ventilation, or process enclosure).
1978 United States Senate Report: Weather modification: programs, problems, policy, and potential by Committee on Commerce, Science, and Transportation Publication
https://archive.org/details/weatificat00unit
https://pubchem.ncbi.nlm.nih.gov/compound/Silver-iodide
https://news.climate.columbia.edu/2025/07/17/geoengineering-cloud-seeding/
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