Nuclear war doesn’t have to be big to devastate the world, inducing years of famine and climate catastrophe alongside all that death and radiation.

Stipulated: A nuclear war would be real bad. But, like, how bad, exactly? What if it wasn’t all-out, the United States and Russia throwing thousands of warheads at each other, but instead something more limited? Longtime adversaries India and Pakistan have a couple hundred bombs each, tops, according to the best intelligence. Obviously it’d still be a localized nightmare—radiation, flattened cities, death. But whether a regional, so-called limited exchange could have global ecological consequences is a question on which nuclear strategy is disconcertingly quiet.

Climate science, though, is not. “I don’t like the term exchange,” says Alan Robock, a climate resesarcher at Rutgers who’s been studying nukes for three decades. “It’s jargon that nuclear war planners use to not think about the horror they’re planning.” Robock and a few colleagues have, for years, been running the numbers on what scientists in the 1980s called “nuclear winter,” the idea that multiple nuclear detonations would send enough dust, soot, and smoke into the atmosphere to literally block out the sun.

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