As escalating tensions between the United States, Russia and China revive old fears of nuclear war, some researchers warn that even a limited exchange between nations like India and Pakistan could have devastating consequences for global food supplies and cause mass deaths worldwide. A nuclear conflict involving less than 3% of the world’s stockpiles could kill a third of the world’s population within two years, according to a new international study led by Rutgers University scientists. 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 be catastrophic for the world,” said climate scientist and study author Alan Robock, distinguished professor in the 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 be greater now than ever. Recently, UK National Security Adviser Stephen Lovegrove argued that the breakdown of dialogue between nations, as well as the loss of safeguards built up between the nuclear superpowers decades ago, has plunged the world into “a dangerous new era ». UN Secretary-General Antonio Guterres has also warned that “the prospect of a nuclear conflict, once unthinkable, is now back in the realm of possibility.” Although 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 estimated the likely extent of the famine it would cause and how many people would die. . The detonation of even a small fraction of the world’s nuclear weapons would trigger massive storms that would quickly funnel solar soot into the atmosphere, causing a sudden cooling of the climate, researchers believe. The story continues The researchers used climate models to calculate how much smoke would reach the stratosphere – where there is no rain to wash it away – and how that would change temperature, precipitation and sunlight. They then calculated how these changes would affect the production of various crops, as well as how fish would respond to changes in the ocean. As a result, they predicted that tens of millions of immediate deaths in the war zone would be followed by hundreds of millions of starvation deaths worldwide. This is without considering the effects of increased UV radiation on crops due to ozone depletion caused by stratospheric warming, Robock said. Such an effect, which the researchers hope to quantify in future studies, would likely worsen the results, he said. “In my opinion, 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 will starve to death.” The data comes after a growing consensus among experts that the threat of nuclear war is greater than ever, said Ira Helfad, immediate past president of the 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 of eliminating these weapons before they wipe us out,” he said. Most of the scenarios the researchers looked at involved a hypothetical nuclear conflict between India and Pakistan, which they believe is the most likely region where such a conflict could erupt, Robock said. The two countries have fought four wars and still have frequent border skirmishes. If India and Pakistan were to target urban centers in the rival country with 250 of the 100-kiloton nuclear weapons they are believed to possess, about 127 million people in South Asia would be killed by explosions, fires and radiation, the study found. An estimated 37 million metric tons of soot would be injected into the atmosphere, causing global temperatures to drop by more than 5 degrees Celsius, a range last experienced during the Ice Age, according to earlier research by Robock and others. . As a result, food production would collapse, with the number of calories available from large crops and fisheries falling by up to 42%, and the resulting famine killing 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 hold more than 90% of the world’s nuclear stockpile, an estimated 5 billion of the world’s 6.7 billion people would die, according to the research. However, any of the nine nuclear-armed nations, which also include China, North Korea, France, Israel and the United Kingdom, have enough firepower at their disposal to cause massive suffering and death worldwide, with soot rising into the sky and triggering a domino effect of catastrophic cooling and starvation, the study suggests. While it’s not possible to directly test the theory, there are real-world analogs, Robock said. Huge wildfires in British Columbia in 2017 and Australia in 2019 and 2020 pumped smoke into the stratosphere, a finding confirmed by satellite observations. The sun then warmed the smoke particles, carrying them five to 15 miles farther into the atmosphere, he said. “By raising them higher, it increases their lifespan and they blast 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 those fires, giving them more confidence that the models would also be accurate when it came to predicting the effects of a nuclear explosion, he said. Edward Geist, a policy researcher at the Rand Corp., said the relatively recent discovery that wildfires can spew smoke into the stratosphere bolsters the researchers’ theory. They are doing the world a service by drawing attention to the possible effects of nuclear war, he said. However, there is some debate about the extent to which the solar boost will occur with the nuclear explosion, Geist said. While it’s certainly possible for a city under attack by nuclear weapons to happen, that doesn’t necessarily mean it will happen to every city under attack at the same time, as the paper assumed, he said. “The big question is, you have a nuclear war of a certain size, how much of that smoke ends up in the upper atmosphere?” Geist said. “You can make a reasonable case for both — very little will end up there, by the end, we have to assume that basically everything ends up there, and that’s [these] the types of papers do’. He pointed out that a 2018 paper by researchers at Los Alamos National Laboratory also modeled a hypothetical conflict between India and Pakistan and concluded that previous research by Robock and others had overestimated how much soot would be produced, how high the smoke would reach and how the climate would change dramatically as a result. Robock, however, disputes these findings. The Los Alamos researchers chose an area of ​​suburban Atlanta to represent a dense city in India or Pakistan and failed to include in their modeling atmospheric processes such as cloud formation that would transport air aloft, he argued. Robock said they also assumed very strong winds and ran their simulation for a very short time. “They had a number of assumptions, all of which made the results much less,” he said. A 2020 paper by researchers at the Lawrence Livermore National Laboratory also looked at 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 densely populated urban areas ignited, they predicted that it would have little to no effect on the climate if the fires were confined to suburban areas. Instead, the Rutgers-led study assumes that countries will target each other’s cities, where fuel concentrations are densest and climate impacts will be most dramatic, Geist said. But Pakistan said if it were to use nuclear weapons against India, it would use nuclear weapons routinely to stop a conventional invasion and not to attack cities wholesale, he said. “It really depends on how much stuff you’re burning, how much of it ends up as smoke and how much of that smoke ends up in the upper atmosphere and how much actually plausible for nuclear war translates into that,” Geist said. “We really don’t know and we hope we never find out.” While there is a popular perception that nuclear weapons will never be used because they are so powerful that their destructiveness is a deterrent, that is wishful thinking, Helfand said. That they haven’t been developed yet is just a matter of luck. “We know what will happen if these weapons remain,” he said. “Sooner or later our luck will run out.” This story originally appeared in the Los Angeles Times.