The Doomsday clock, which symbolically measures how close the world is to nuclear war, is currently at 89 seconds until midnight – the closest it’s ever been.

Over the past few years, we’ve also heard two presidents discuss the “nuclear option.” This is all to say that the world is surprisingly close to nuclear war. We’ve just become numb to that reality. But what happens after the nuclear bombs go off? A team led by researchers at Penn State have modelled precisely how various nuclear winter scenarios could affect global production of corn, the most widely planted grain crop in the world. They also recommended preparing ‘agricultural resilience kits’ with seeds for faster-growing varieties better adapted to colder temperatures that could potentially help offset the effects of nuclear winter, as well as natural disasters such as volcanic eruptions. In findings recently published in Environmental Research Letters, the team reported that the level of corn crop decline would vary, depending on the scale of the conflict. A regional nuclear war, which would send about 5.5 tonnes of soot into the atmosphere, could reduce worldwide annual corn production by seven per cent. A large-scale global war, injecting 165 tonnes of soot into the atmosphere, could lead to an 80 per cent drop in annual corn yields. In all, the study simulated six nuclear war scenarios with varying soot injections.

Because of the crop’s global significance, the researchers chose to model corn’s collapse in a nuclear winter to represent the expected fate of agriculture overall, according to study first author Yuning Shi, associate research professor in Penn State’s Department of Plant Science. He noted that an 80 per cent drop in global crop production would have catastrophic consequences, leading to a widespread global food crisis. Even a seven per cent drop in global crop production would have a severe effect on the global food system and economy, likely resulting in increased food insecurity and hunger. The simulations were possible thanks to the Cycles agroecosystem model, created a few years ago by scientists in Penn State’s College of Agricultural Sciences, including lead developer Armen Kemanian, professor of production systems and modelling and corresponding author on this study. Using high-performance computing and considering atmospheric conditions, Cycles enables large-scale, high-resolution, multi-year simulations of crop growth by meticulously tracking the carbon and nitrogen cycles within the soil-plant-atmosphere system.