Test launch of an Indian nuclear-capable missile in 2013. Photo: Pallava Bagla/Corbis via Getty Images

A new study argues that a nuclear war between India and Pakistan would cause global cooling and planet-wide food shortages.

Why it matters: Scientists have debated the climatic effects of nuclear war. New computer models show even a comparatively limited nuclear exchange could have global impacts on food production that would eclipse the worst famines in documented history.

Background: In the 1980s, a group of scientists led by Carl Sagan published influential research suggesting the dust and soot created by a global nuclear holocaust would cause such drastic cooling that it would lead to a "nuclear winter," effectively ending human life on Earth.

  • Over the years the nuclear winter theory came under criticism from scientists who saw it as flawed and politically motivated, but it likely helped encourage the U.S. and the Soviet Union to significantly cut back on their nuclear arsenals.

In a study published Monday in the Proceedings of the National Academy of Sciences, researchers led by Jonas Jägermeyr of the NASA Goddard Institute for Space Studies used sophisticated computer models to predict what would happen in a nuclear war that would be both more limited and more likely than a full-scale one: a conflict between the geopolitical rivals India and Pakistan.

  • The team found that even in an exchange of 100 Hiroshima-sized bombs — less than 1% of the current global arsenal — the resulting firestorms would launch about 5 million tons of soot into the stratosphere.
  • From there, the soot would spread around the globe, absorbing sunlight and lowering global mean temperatures by 3.25ºF for at least five years.
  • As a result, production of top cereal crops like rice and wheat would fall by an average of 11% during that period, with tapering effects in the years that follow.

Context: Much of the focus on the threat of nuclear war centers on new players like North Korea, or the possibility of a global conflict between the U.S. and Russia, which possess close to 95% of the world's existing warheads. But India and Pakistan have clashed repeatedly over the past 70 years, and experts have long worried that their next conflict could go nuclear.

  • The study also has important implications for a world groaning under the sudden shock of the coronavirus. "Even though the situation is very different, we're seeing how it would feel if consumers were suddenly not able to buy food," says Jägermeyr.

The bottom line: The world isn't short of things to worry about, but the effects of a nuclear conflict between India and Pakistan are likely even worse than we might have imagined.

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