Shading the planet doesn’t have to come with rainfall side-effects

Enlarge (credit: Caetano Candal Sato)

It sounds like a drastic course of action: inject stuff high into Earth's atmosphere to reflect a little sunlight and help counteract global warming. Then again, injecting a bunch of greenhouse gas into the atmosphere and warming the planet was pretty drastic, too.

The key to thinking sensibly about this "solar geoengineering" is to avoid the extremes and consider the most plausible use scenarios. That means we can ignore things like using solar geoengineering to cancel out all warming while still emitting as much CO₂ as we please-it simply isn't plausible.

There are a number of reasons to take it off the table. There's the fact that the cooling influence of atmospheric injections is only temporary-quitting quickly reveals the full force of the warming you're offsetting. There's also the fact that this scheme only counteracts warming-the acidification of the oceans would continue apace. And for another example, the mismatch in physics between solar-geoengineering-driven cooling and greenhouse warming means that precipitation can decline even if temperature stays the same.

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