Agriculture Responses To Nuclear Winter

A nuclear war between U.S. and Russia could inject 150 Tg of soot into the upper troposphere, which would absorb sunlight, self-loft into the stratosphere, decrease global averaged surface temperature by 9 K for more than 5 years and have major impacts on precipitation and solar radiation reaching Earth's surface. Over agriculture regions, the temperature reduction would reach 25 K in the Northern Hemisphere midlatitudes in the first summer after the soot injection. The nuclear winter (summer temperatures below freezing) would last for at least two years, and only gradually warm, making agriculture virtually impossible for at least five years. We use the crop model in the Community Land Model version 5 to study the global response of six crops to nuclear winter: maize, soybean, rice, spring wheat, cotton, and sugarcane. While traditional midlatitude agricultural regions would certainly not be able to grow any crops for at least two years, we investigate whether under these extreme conditions there could be new potential areas for major crops to grow. In general, all six crops show over 70% reduction in global averaged production over the first 5 years, and gradually return to the control level after 10 years. In midlatitude regions, agriculture activities are terminated with a 100% yield reduction. The only possible area for crop growth would be in the tropics, such as in India, Central Africa and South America. But large-scale agriculture would only be possible if there were regions with the proper soil, available seeds, agricultural know-how, agricultural equipment, and fuel for the equipment. And it would only be useful if the food or remaining survivors could be transported to the same location. In addition, as the smoke would clear out after several years of the simulated nuclear war, ultraviolet radiation in the tropics may be a problem due to stratospheric ozone depletion. Therefore agriculture in the tropics would face another challenge, even if the surface temperature and precipitation began to return to normal. Temperature reduction is the most important factor in these crop production changes, based on sensitivity simulations of individual climate forcings.