Even a limited nuclear war would kill billions, study finds

As escalating tensions between the United States, Russia and China revive old fears of nuclear war, some researchers warn that even a small-scale exchange between countries like India and Pakistan could have catastrophic consequences for the global food supply and cause massive deaths worldwide.

A nuclear conflict involving less than 3% of world supplies could kill a third of the world’s population within two years, according to a new international study led by scientists at Rutgers University. A larger nuclear conflict between Russia and the United States could kill three-quarters of the world’s population in the same time frame, according to research published Monday in Nature Food.

“It’s really a cautionary tale that any use of nuclear weapons could spell disaster for the world,” said climate scientist and study author Alan Robock, a distinguished professor in Rutgers’ Department of Environmental Sciences.

The findings come at a time when — 30 years after the end of the Cold War — the threat of a nuclear holocaust may now be greater than ever.

Recently, Britain’s national security adviser Stephen Lovegrove argued that the collapse of inter-nation dialogue, as well as the loss of safeguards created decades ago between nuclear superpowers, has plunged the world into “a dangerous new era.” United Nations Secretary-General Antonio Guterres has also warned that “the prospect of a nuclear conflict, once unimaginable, is now once again within the realm of possibility”.

While Robock and others have previously predicted that nuclear war would result in massive disruption to the climate and food supplies, the recent study marks the first time researchers have assessed the potential magnitude of the famine that would result and how many people would die. , have calculated.

The detonation of even a small fraction of the world’s nuclear weapons would trigger massive firestorms that would quickly inject sun-blocking soot into the atmosphere, causing a sudden cooling of the climate, the researchers reasoned.

Researchers used climate models to calculate how much smoke would reach the stratosphere — where no precipitation falls to wash it away — and how this would change temperature, precipitation and sunlight. They then calculated how these changes would affect the production of different crops, and how fish would respond to changes in the ocean.

As a result, they predicted that tens of millions of direct deaths in the war zone would be followed by hundreds of millions of famines around the world.

That’s without taking into account the effects of increased ultraviolet radiation on crops due to the destruction of the ozone layer caused by the heating of the stratosphere, Robock said. Such an effect, which researchers hope to quantify in future studies, would likely worsen the results, he said.

“In my view, our work is an existential threat to nuclear weapons — it shows that you can’t use nuclear weapons,” Robock said. “If you use them, you’re like a suicide bomber. You try to attack someone else, but you starve to death.”

The data is being released on the heels of a growing consensus among experts that the threat of nuclear war is greater than ever, said Ira Helfand, immediate former president of International Physicians for the Prevention of Nuclear War.

“The general public needs to understand the enormity of the danger we face, the immediacy of the threat and the urgency to eliminate these weapons before they eliminate us,” he said.

Most of the scenarios the researchers considered involved a hypothetical nuclear conflict between India and Pakistan, which they believe is the most likely region where such a conflict could break out, Robock said. The two countries have fought in four wars and still have frequent border battles.

If India and Pakistan each attacked the other country’s urban centers with 250-100-kiloton of nuclear weapons, which they possess, about 127 million people in South Asia would be killed by explosions, fires and radiation, the study found. According to previous research by Robock and others, an estimated 37 million tons of soot would be injected into the atmosphere, causing temperatures across the planet to drop by more than 5 degrees Celsius, a range last experienced during the Ice Age. As a result, food production would collapse, with calories available from key crops and fisheries falling by as much as 42% and the ensuing famine that would kill more than 2 billion people worldwide, according to the most recent study.

In the event of a larger war between the US and Russia, which together are believed to contain more than 90% of the world’s nuclear stock, an estimated 5 billion of the 6.7 billion people worldwide would die, according to the research.

But each of the nine nuclear-armed countries, including China, North Korea, France, Israel and the United Kingdom, have enough firepower at their fingertips to cause massive global suffering and death, with soot in the air and a domino effect. from catastrophic cooling and starvation, the study suggests.

While it’s not possible to test the theory directly, there are real-world analogs, Robock said. Massive wildfires in British Columbia in 2017 and in Australia in 2019 and 2020 pumped smoke into the stratosphere, a finding confirmed by satellite observations. The sun then heated the smoke particles, lifting them five to 25 miles into the atmosphere, he said.

“By lifting them higher, it extends their lifespan and blows them around the world before they fall out,” Robock said. “It’s the same process we modeled in our nuclear winter simulation, with a lot more smoke.”

The researchers’ modeling was able to predict the effects of these fires, giving them greater confidence that the models would also be accurate when it came to predicting the effects of nuclear detonation, he said.

Edward Geist, a policy researcher at Rand Corp., said the relatively recent discovery that wildfires can spread smoke into the stratosphere supports the researchers’ theory. They are doing the world a favor by drawing attention to the potential consequences of nuclear war, he said.

Still, there’s some debate about the extent to which solar lofting would occur in nuclear detonation, Geist said. While it’s certainly possible it would happen in a city under attack by nuclear weapons, that doesn’t necessarily mean it would happen simultaneously in every city under attack, as the paper assumed, he said.

“The big question is, you have a nuclear war of a certain magnitude, how much of this smoke gets into the upper atmosphere?” said Geist. “You can make plausible for both – very little will end up there, all the way up to, we have to assume it actually all ends there, and that’s what [these] types of paper do.”

He pointed out that a 2018 paper by researchers at Los Alamos National Laboratory also modeled a hypothetical conflict between India and Pakistan, concluding that previous research by Robock and others had overestimated how much soot would be produced, how high the smoke would get and how dramatic. the climate would change as a result.

Robock disputes these findings, however. The Los Alamos researchers chose an area in the suburbs of Atlanta to represent a densely populated city in India or Pakistan and did not take into account atmospheric processes such as cloud formation that would carry air upwards, he argued. Robock said they also assumed wind blowing too strongly and running their simulation too short.

“They had some assumptions, which made the effects much less,” he said.

A 2020 paper by researchers at Lawrence Livermore National Laboratory also considered the India-Pakistan scenario and concluded that there were uncertainties. Although the team predicted that an exchange of 100 15-kiloton nuclear weapons would cool the climate if dense urban areas ignited, they predicted that there would be little to no effect on the climate if fires were confined to suburban areas.

By contrast, the Rutgers-led study assumes the countries would target each other’s cities, where fuel concentrations are densest and climatic effects would be most dramatic, Geist said. But Pakistan has said that if it used nuclear weapons against India, it would use tactical nuclear weapons to stop a conventional invasion, not attack cities on a large scale, he said.

“It really comes down to how much stuff you burn, how much of it becomes smoke and how much of that smoke gets into the upper atmosphere, and how much real nuclear war plausibility translates into that,” Geist said. “We really don’t know, and hopefully we won’t find out.”

While there’s a popular idea that nuclear weapons will never be used because they’re so powerful that their destructiveness is a deterrent, that’s wishful thinking, Helfand said. That they haven’t been deployed yet is purely coincidental.

“We know what’s going to happen if these weapons stay around,” he said. “Sooner or later our luck will run out.”

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