Cloud seeding in drought areas to “create” rain

Dear Tom,

We occasionally hear about cloud seeding in drought areas to “create” rain, but I have always been skeptical of the process. What are your thoughts?

Jeffrey Atacommer,
Chicago

Dear Jeffrey,
Cloud seeding is, and always has been, controversial. It involves adding certain particles to clouds with the purpose of altering cloud development. In Russia, clouds are seeded to suppress hail formation. Cloud seeding does not create rain. Instead, it encourages a cloud of the verge of producing rain to produce more rain than it might otherwise produce. Some atmospheric scientists feel evidence that seeding works is very thin. Besides, in a drought, the clouds that produce rain usually are not around to seed in the first place. In addition thorny legal issues arise with cloud seeding that has led many states to ban the process.

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