A Large, Sustained El Niño-Like Response To Nuclear Conflict

A large-scale nuclear war would be horrific, and the smoke injected into the upper atmosphere from the firestorms generated by burning cities would result in a shock to the climate through rapid global cooling. We demonstrate for the first time that a global nuclear conflict is also likely to generate a large, sustained El Niño-like change to the tropical Pacific for nearly 7 years. Using the Community Earth System Model-Whole Atmosphere Community Climate Model version 4 (CESM-WACCM4) we conducted six nuclear war simulations, injecting between 5 Tg and 150 Tg of black carbon into the 300 hPa to 150 hPa layer of the atmosphere to simulate several nuclear war scenarios. In each, El Niño-like circulation changes develop within two months. The strength of the response scales nearly linearly with the total mass of black carbon for injections up to 40 Tg, where a saturation effect begins. This “Nuclear Niño” is driven by anomalous westerly trade winds in the equatorial Pacific Ocean. The winds are generated through similar mechanisms which have been used to explain the tendency for an El Niño response to large volcanic eruptions, largely involving the land surface cooling more rapidly than the ocean, setting up anomalous wind patterns around the globe as the Intertopical Convergence Zone shifts southward and the Hadley cell dramatically weakens. A very large radiative forcing allows us to more readily identify the forced response and the mechanisms driving it. These mechanisms involve the evolution of winds in the equatorial Pacific in the 60 days after the soot injections, a sensitive period where the Southern Oscillation Index drops by 5 standard deviations. The sustained Nuclear Niño is an extreme event that stops upwelling along the equatorial Pacific for years and exacerbates drought conditions in southeast Asia, compounding the stress of a sudden change to the climate, including implications for food production.