The prospect of global thermonuclear war haunted humanity for 50 years during the Cold War. And while the fall of the Soviet Union in the early 1990s largely relegated such a comprehensive scenario to the relics of a bygone era, the threat never went away. Today, the most likely scenarios include a skirmish along the India-Pakistan border raging out of control, or a nuclear mistake — a computer hack, unstable leader or miscommunication that causes a missile launch. Or as some have disputed in a grim scenarioCould the US and Russian militaries, pushed to the brink by a war like the one currently underway in Ukraine, reach their nuclear stockpiles? A simulation 2019 from Princeton’s Science and Global Security Program modeled how such a conflict could take place. With more than 12,000 nuclear weapons combined, researchers looked at how such a war would escalate. Based on the two countries’ current nuclear strategies, the team looked at how long it would take to go from a conventional to a nuclear war and how many people would die. Starting with a nuclear warning shot from the Russian enclave of Kaliningrad, NATO retaliates, with a single tactical nuclear strike. Within three hours, Europe, the United States and Russia are plunged into an all-out nuclear conflict as hundreds of short-range missiles and airstrikes are launched at each other’s bases. With Europe in ruins, the US launches 600 warheads from silos and submarines at Russian nuclear forces. Russia responds. To prevent the other side from recovering, both NATO and Russia are targeting dozens of cities and financial centers with five to 10 warheads each. In the end, the modeling found that more than 34 million people would die immediately, with nearly 60 million more injured. But it is the deaths that come after that that would be truly debilitating for the survival of humanity and the nearly nine million others species believed to exist on Earth.
Nuclear fallout at sea
Last week, a new study published in the American Geophysical Union journal AGU Advances replicated old models of a global nuclear winter dating back to the 1980s — this time plugging the numbers into a modern climate circulation model. What were they looking to answer: how would a nuclear war affect the planet’s oceans, and in turn, the life that springs in and from them? Using it Community Earth System Modelresearchers determined the short- and long-term effects of nuclear storms after the missiles landed. This meant measuring how the debris from this disaster would disperse into the atmosphere as black carbon or soot and how it would affect the oceans. In the worst-case scenario, nuclear war between the US and Russia breaks out on May 15. With most of their arsenals spent bombing each other’s cities, 150 million tons of soot are spewed into the atmosphere. This would block 70 percent of the sun’s shortwave radiation and reduce the average global surface temperature by seven degrees Celsius in the first few months. “It comes from burning cities,” said Cheryl S. Harrison, an oceanographer at Louisiana State University and lead author of the study. “You have all these different military objectives. Many of them are located near cities. And so you have great fires of burning cities.” In the Northern Hemisphere, and especially in places like Canada, those temperatures would drop even further, leading Arctic ice to clog ice-free areas. This, in turn, would decimate several species of fish important to coastal fisheries. Harrison said the drop in temperature will immediately affect many bottom-dwelling fish. Unlike tuna, species such as halibut would likely struggle to swim in warmer waters and suffer as a result. Salmon, meanwhile, would likely struggle to make it up and down BC’s waterways as they freeze more. But even species in the sea would struggle to survive. In the first years after the nuclear war, the sky would be darkened by the soot of hundreds of cities. With the sun largely gone, phytoplankton would die, erasing the base of the ocean food chain across much of the world. “There will be no food for them,” said Harrison. Those people who survived, mostly in tropical areas, would inevitably have to turn to wild-caught and farmed algae, the study notes.
Small skirmishes lead to a devastating nuclear winter
Harrison and her colleagues looked at various scenarios, from the detonation of a few hundred warheads in a limited conflict between India and Pakistan, to thousands of warheads in an all-out war between Russia and the United States. Even in the smallest (and most likely) nuclear skirmishes between India and Pakistan, aerosols released into the upper atmosphere reached levels seen in the 1815 eruption of Mount Tambora in Indonesia, the largest volcanic event in recorded history. “We have it year without summersaid Harrison, referring to 1816. “Aerosols from the volcano [go] in the upper atmosphere, they are distributed globally and cool the planet – and cause famine.’ The summer of 1816 saw everything from widespread crop failures to red sunsets. On the shores of Lake Geneva, 18-year-old Mary Shelley was kept indoors due to bad weather. When his friend Lord Byron proposed a competition to write the scariest story, he wrote the famous novel, Frankenstein. A nuclear war, however, would be far more terrifying – and deadly. Unlike a volcanic eruption, scientists believe that the aerosols in a nuclear war would be much thinner, and therefore, stay high in the atmosphere for much longer. Harrison said a medium-sized regional nuclear conflict involving 4,400 100-megaton weapons would result in a 10-degree celsius crash in average global temperatures – colder than the last ice age. In some northern latitudes, it would be twice as much. At this scale, modern climate modeling found that ocean temperatures would plummet by 30C in some parts of the globe, leading to massive increases in sea ice formation in the seas of the Korean Peninsula and Japan. The sea around Canada’s Maritimes would drop more than 15 degrees Celsius, while on the West Coast, sea temperatures would drop closer to 10 degrees Celsius. “The shallower parts of the ocean near land would become even colder,” Harrison said. “You could have sea ice everywhere … the land is even colder than the ocean.” Global ocean temperature changes during and after a nuclear war between the US and Russia spew 150 million tons of soot into the atmosphere. Ocean temperature drops are greatest near coastal areas of the Northern Hemisphere. Harrison et al (2022)
Modeling refined through wildfires, large earthquakes
Modeling a hypothetical nuclear war presents great uncertainty, mainly due to the fact that we do not have many precedents surrounding such a conflict. To refine their calculations, the researchers turned to reports from the 1908 San Francisco earthquake, where eyewitness accounts of the storm’s aftermath speak of huge plumes of dark soot rising into the sky. As dark clouds absorb radiation, they heat up and continue to gain altitude. “There’s these eyewitness accounts of that wind from all over going into the city as that wind was coming up,” he said. “And we have some observations from recent large wildfires about how smoke works.” Harrison added: “It’s a model, so it’s imperfect, and you can always do more. But the whole point is that even if that’s possible … these very small nuclear wars have a very big impact.”
A possible climate recovery effect
After a ‘Nuclear Little Ice Age’, recovery from low temperatures would likely take decades at the sea surface and hundreds of years in deep ocean habitats. In the Arctic, Harrison and her colleagues concluded that a recovery to current temperatures would take thousands of years. In their study, the researchers found that human-induced climate change, although not simulated in their model, could moderate some of the nuclear-induced cooling and resulting ice expansion. But Harrison warned that after a cooling period, global warming could return. It shows a 2017 study looking at the effects of a large volcanic eruption. Looking at volcanic activity in the past, the study found that intense cooling associated with the spewing of volcanic soot was quickly followed by another period of warming. In other words, in the long run, there are no guarantees that a nuclear winter will offset human-caused global warming—and it could deliver a one-two punch to many species around the world. Even with the sun out, the planet’s oceans would still be acidified by the existing carbon in the atmosphere, “and you’re still breaking up the shells of creatures on the West Coast, which affects the food chain,” Harrison said. “From a cold you will like heat again, and then it really affects animals like us and others… Billions of people would die.”
Call for a ban on nuclear weapons
Harrison and her colleagues are working to get their data into the hands of social scientists, policymakers and the public. They are now in the process of creating a database detailing the effects nuclear war could have on ocean life, sea ice expansion and, in an upcoming study, how crop failures will affect countries’ ability to feed themselves . According to a preprint version of the studywhich is run by a colleague and has not yet…
