Should We Cool Earth?

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


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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