Dear EarthTalk:

What are the environmental implications of “blueskying”—that is, seeding clouds to affect the weather—like China did in preparation for hosting the Olympics back in 2008?

William S., Raleigh, NC

Cloud seeding—also called "blueskying"—involves releasing chemicals such as silver iodide, potassium iodide or calcium chloride into the atmosphere to stimulate cloud formation, enhance clouds' precipitation or suppress rain where blue skies are desired. China used cloud seeding to ensure dry weather for the 2008 Beijing Olympics, one of the most recent and significant examples of the technique being used on a large scale. China has also used cloud seeding to stimulate precipitation to help replenish its shrinking Yangtze River watershed.

But at what price to the environment, you might ask? Cloud seeding can theoretically go well, but there is always a chance of unintended adverse consequences. Releasing these chemicals into the atmosphere can contaminate water supplies below and affect human and animal health. Researchers from Spain’s Complutense University found in a 2016 study that silver iodide causes acute toxicity for a range of living organisms both in soil and freshwater.

Another potential environmental implication of cloud seeding is its potential effect on weather patterns. Increased precipitation in one area could lead to droughts in nearby areas, as the rain is diverted away from those regions. Similarly, cloud seeding could cause excessive rainfall, leading to flooding and other weather-related disasters. Cloud seeding could also have an impact on agriculture and natural ecosystems. While increased rainfall may be beneficial for some crops, it could lead to soil erosion and other negative impacts on the environment. Similarly, increased rainfall could alter the ecosystem's balance, leading to the proliferation of certain species and the decline of others.

Cloud seeding can also have an impact on the Earth's ozone layer. Silver iodide can break down ozone molecules in the atmosphere, leading to the depletion of the ozone layer. Ozone depletion can have severe consequences for the environment, including increasing our exposure to harmful ultraviolet radiation and the potential for climate change.

Given all the potential risks, governments should proceed cautiously with any plans to seed clouds. Perhaps with more research and refinement humans can perfect the process in the future, but until then it might be better to just accept whatever weather we have. Of course, what we think here in North America has little impact on what the Chinese or others elsewhere think about this type of geoengineering, so get ready for it to become more and more common around the world.

CONTACTS

• Planned Weather Modification through Cloud Seeding, ametsoc.org/index.cfm/ams/about-ams/ams-statements/archive-statements-of-the-ams/planned-weather-modification-through-cloud-seeding/
• Climate Intervention, ametsoc.org/index.cfm/ams/about-ams/ams-statements/statements-of-the-ams-in-force/climate-intervention/
• Potential risk of acute toxicity induced by AgI cloud seeding on soil and freshwater biota, https://pubmed.ncbi.nlm.nih.gov/27517140.