nuclear-news

While that debate rages, Robock’s group has published results showing a wide variety of impacts from nuclear blasts.

That includes looking at ocean impacts, the first time this has been done, says team member Nicole Lovenduski, an oceanographer at the University of Colorado Boulder. When Toon first approached her to work on the project, she says, “I thought, ‘this sure seems like a bleak topic’.” But she was intrigued by how the research might unfold. She usually studies how oceans change in a gradually warming world, not the rapid cooling in a nuclear winter.

Lovenduski and her colleagues used a leading climate model to test the US–Russia war scenario. “It’s the hammer case, in which you hammer the entire Earth system,” she says. In one to two years after the nuclear war, she found, global cooling would affect the oceans’ ability to absorb carbon, causing their pH to skyrocket. That’s the opposite to what is happening today, as the oceans soak up atmospheric carbon dioxide and waters become more acidic.

She also studied what would happen to aragonite, a mineral in seawater that marine organisms need to build shells around themselves. In two to five years after the nuclear conflict, the cold dark oceans would start to contain less aragonite, putting the organisms at risk, the team has reported2.

In the simulations, some of the biggest changes in aragonite happened in regions that are home to coral reefs, such as the southwestern Pacific Ocean and the Caribbean Sea. That suggests that coral-reef ecosystems, which are already under stress from warming and acidifying waters, could be particularly hard-hit during a nuclear winter. “These are changes in the ocean system that nobody really considered before,” says Lovenduski.

And those aren’t the only ocean effects. Within a few years of a nuclear war, a “Nuclear Niño” would roil the Pacific Ocean, says Joshua Coupe, a graduate student at Rutgers. This is a turbo-charged version of the phenomenon known as El Niño. In the case of a US–Russia nuclear war, the dark skies would cause the trade winds to reverse direction and water to pool in the eastern Pacific Ocean. As during an El Niño, droughts and heavy rains could plague many parts of the world for as long as seven years, Coupe reported last December at a meeting of the American Geophysical Union.

Beyond the oceans, the research team has found big impacts on land crops and food supplies. Jonas Jägermeyr, a food-security researcher at NASA’s Goddard Institute for Space Studies in New York City, used six leading crop models to assess how agriculture would respond to nuclear winter. Even the relatively small India–Pakistan war would have catastrophic effects on the rest of the world, he and his colleagues report this week in the Proceedings of the National Academy of Sciences¹. Over the course of five years, maize (corn) production would drop by 13%, wheat production by 11% and soya-bean production by 17% .

The worst impact would come in the mid-latitudes, including breadbasket areas such as the US Midwest and Ukraine. Grain reserves would be gone in a year or two. Most countries would be unable to import food from other regions because they, too, would be experiencing crop failures, Jägermeyr says. It is the most detailed look ever at how the aftermath of a nuclear war would affect food supplies, he says. The researchers did not explicitly calculate how many people would starve, but say that the ensuing famine would be worse than any in documented history.

Farmers might respond by planting maize, wheat and soya beans in parts of the globe likely to be less affected by a nuclear winter, says Deepak Ray, a food-security researcher at the University of Minnesota in St Paul. Such changes might help to buffer the food shock — but only partly. The bottom line remains that a war involving less than 1% of the world’s nuclear arsenal could shatter the planet’s food supplies.

“The surprising finding”, says Jägermeyr, “is that even a small-war scenario has devastating global repercussions”.