“ Here’s the thing about the stratosphere, the region between six and 31 miles up in the sky: If you really wanted to, you could turn it pink. Or green. Or what have you. If you sprayed some colorant up there, stratospheric winds would blow the material until it wrapped around the globe. After a year or two, it would fade, and the sky would go back to being blue. Neat little prank.”
In "The Ministry for the Future", India reacts to a megadeath wet-bulb event by dumping sulfates into the upper atmosphere. It's generally considered a bad idea, and in effect an act of war to do unilaterally, but they still do it, no one retaliates, and the consequences are mostly positive, if not terribly significant.
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