Should We Cool Earth?

Amid climate inaction, scientists confront an idea that scares them.

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Mount Pinatubo erupted in the Philippines in 1991, spewing millions of tons of ash and chemicals into the atmosphere. Over the next year, large parts of Earth cooled by almost a full degree Fahrenheit.

Volcanoes historically have caused some of the planet’s sharpest temperature drops. In addition to ash and fire, they belch sulfur dioxide that lingers as a fine particle spray called an aerosol. These aerosols help Earth’s atmosphere reflect incoming light, creating a cooling effect.

Some scientists speculate that seeding such sulfur aerosols — absent fiery eruptions — could someday be a Hail Mary to counteract climate change. The idea is called geoengineering. Picture fleets of aircraft ferrying sulfur across the stratosphere year-round.

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