The global food supply would be devastated by nuclear war not only from the direct damage, but through a chain of atmospheric and biological impacts that science only now is trying to measure. New studies indicate that even a small, regional nuclear war would cut world corn production by 7%, while a major nuclear war would drop yields by an astounding 80–87%. These figures, based on high-resolution, multi-decade simulations, highlight the vulnerability of contemporary agriculture in the event of engineered climate disaster.
The research, authored by Yuning Shi at Pennsylvania State University, modeled corn yields at 38,572 locations, under six nuclear war scenarios involving soot injections of 5 million to 165 million tons. The Cycles agroecosystem model, which carefully follows carbon and nitrogen cycling within the soil-plant-atmosphere system, allowed scientists to forecast how black carbon aerosols from nuclear firestorms would reduce sunlight, cool temperatures, and shorten growing seasons for more than a decade. As Shi explained, “An 80 percent reduction in global crop yields would have devastating effects,” and even a 7 percent reduction “would inflict a severe blow to the global food system and economy” in accordance with the team’s results.
And the danger is not just cooling. The atmospheric chemistry initiated by nuclear explosions is just as nefarious. The fireball and shock wave of atomic explosions create nitrogen oxides (NOx) in the stratosphere. With the heat-absorbing soot, they initiate a chain reaction that depletes ozone, the earth’s sunscreen against ultraviolet (UV) radiation. “The presence of both nitrogen oxides and heating from absorptive soot could rapidly destroy ozone, increasing UV-B radiation levels at the Earth’s surface. This would damage plant tissue and further limit global food production,” Shi clarified within the published research.
Sophisticated chemistry and climate models, including the Whole Atmosphere Community Climate Model (WACCM3) and the Community Aerosol and Radiation Model for Atmospheres (CARMA), have shown that smoke from a regional nuclear war might induce column ozone losses exceeding 20% globally, 25–45% at midlatitudes, and 50–70% at northern high latitudes, with such deficits lasting as long as five years according to detailed studies in atmospheric modeling. These losses of ozone would bring a flood of UV-B radiation, hitting its peak six to eight years after the war just when plants are already suffering from cold and lack of light. The biological impact is catastrophic: “A 40% ozone column depletion at 45°N… would increase DNA damage (believed related to carcinogenesis) by 213%, and plant damage (e.g., photoinhibition) by 132% relative to normal conditions,” scientists have warned in peer-reviewed research.
The chemistry of soot and ozone is intricate. Black carbon aerosols warm the stratosphere, speeding catalytic cycles particularly ones with odd-nitrogen-containing compounds that destroy ozone many times faster than before. The consequent “ozone hole” is not confined to the polar regions but extends across much of the globe, with column ozone levels dropping below 220 Dobson units at all latitudes for years. As the smoke slowly dissipates, the world faces a new hazard: just as sunlight returns, the weakened ozone layer allows a “blast of UV with completely different impacts on human health and agriculture,” according to Charles Bardeen of the National Center for Atmospheric Research in his group’s worldwide modeling research.
Photosynthesis, the source of crop power, is threatened twice over first by cold and darkness, then by DNA-destroying UV-B. Maize, selected as a surrogate for global agriculture because of its climate sensitivity and global importance, is especially susceptible. The worst-case estimate of the study is that the combined effects of nuclear winter and UV-B stress potentially reduce corn yields by up to 87% a rate of loss that would cause global famine.
Realizing the magnitude of the danger, the researchers suggest a proactive, science-informed adaptation: “agricultural resilience kits.” The kits would include seeds for crop species that are bred to resist cold and short seasons, providing a lifeline for food production in the unsettled years after a nuclear war or large volcanic eruption. “These kits would help sustain food production during the unstable years following a nuclear war, while supply chains and infrastructure recover,” said Armen Kemanian, lead author and environmental systems specialist. The idea, while difficult to execute worldwide, is based on the premise that “resilience is of the essence” for human-made and natural disasters.
The principles are applied far beyond nuclear war. Volcanic eruptions, as well, can pump enormous quantities of aerosols into the stratosphere, inducing the same cooling and ozone loss. The study highlights a grim fact: global food security is inextricably linked with atmospheric stability, and the buffer zone is alarmingly narrow. As Shi put it, “If we want to survive, we must be prepared, even for unthinkable consequences.”
