Manchester: The consequences of a nuclear war have been well-explored by science. Beyond immediate death and destruction, a famine and climate disaster beckons. Over the past 30 years, fear of nuclear Armageddon had faded from its peak at the height of the Cold War. The world's nuclear weapon stockpile has shrunk to about one-fifth the size it was in 1990 and while threats have persisted, they have typically been from rogue states (such as Iran and North Korea) in cases where escalation to global conflict was deemed unlikely. Those fears have been re-awakened by Russia's nuclear posturing.
Russian President Vladimir Putin put his nation's nuclear forces on a state of high alert during the invasion of Ukraine, marking a change of direction that risks a return to when the world's nuclear superpowers were on the brink of conflict during the Cold War. In the remote scenario that the conflict in Ukraine escalates to a nuclear exchange, the consequences would be dire and not just because of the enormous and horrific death toll. Even a limited nuclear conflict in Ukraine that sees just one percent of the world's nuclear stockpile exchanged is likely to bring devastation to the climate that would spread suffering and death globally. It has been termed nuclear winter'. Younger generations may think of a scene from the Fallout video games. But those who lived through the 1980s, a decade marked by renewed international tensions and crises, the largest global nuclear stockpile ever recorded in history, and books and films imagining nuclear doomsday, will remember what it was like to be on the cusp of nuclear catastrophe and an environmental disaster.
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The climatic effect expected from a nuclear war was first studied in 1982 by the Dutch atmospheric scientist Paul Crutzen and his British colleague John Birks. They were concerned that a nuclear exchange could produce many fires with smoke so thick that it would produce an atmosphere-engulfing layer that reduced sunlight penetration, a concept they called nuclear twilight' (or nuclear dawn). A year later, five scientists based in the United States including the atmospheric scientist Richard Turco and the astronomer Carl Sagan took to better understanding these predictions through computer modelling. Their conclusions suggested that nuclear-induced climatic effects would last much longer than first expected, resulting in what they dubbed a nuclear winter.
Enough sunlight would not penetrate the dark blanket of smoke to keep temperatures high on the ground, causing a harsh winter in any season. Disruptions from dust and soot would then be followed by longer-term shifts in the atmosphere that were partly unpredictable, and then patterns resulting in global cooling. The concept of nuclear winter shocked many when published for the first time, fuelling the nuclear protest movements that were already sweeping across Europe and the United States. It divided the scientific community too, seeming exaggerated in its predictions to some climatologists. Although at one point labelled Soviet-inspired propaganda, nuclear winter actually propelled scientific collaboration across the Iron Curtain as Russian scientists confirmed and refined the Americans' computer modelling predictions. One, Vladimir Alexandrov, mysteriously disappeared shortly afterwards.
The nuclear disarmament of the 1990s made the concept of nuclear winter fade from the public view, but atmospheric scientists have continued work on computer models, often energised by new, emerging nuclear threats and technology. Turco and two contributors of the early nuclear winter study, Alan Robock and Owen Toon, continued to actively research the potential global consequences of local conflicts fought with nuclear weapons. They focussed especially on the case of India and Pakistan, concluding that even a limited nuclear exchange in which 50 Hiroshima-size nuclear bombs were detonated would have global ramifications. Using volcanic eruptions as a proxy to understand how smoke would spread across the globe, they further refined the early prediction on limited exchange.