Nuclear Winter Temperature Patterns Driven By Extreme Stratospheric Circulation Changes

47510">Current nuclear arsenals used in a war between the United States and Russia could inject 150 Tg of soot into the lower 47510">stratosphere47510">. We simulated the climate response to such an injection using the Community Earth System Model-Whole Atmosphere Community Climate Model version 4 (WACCM4), run at 2° horizontal resolution with 66 layers from the surface to 140 km, with full stratospheric chemistry and the Community Aerosol and Radiation Model for Atmospheres47510">, 47510">allowing fractal 47510">soot 47510">particle 47510">aggregation47510">, and compared the results to a simulation with Goddard Institute for Space Studies 47510">ModelE47510"> run at 4°x5° horizontal resolution with 23 levels up to 80 km and constant specified aerosol properties and ozone, conducted in 47510">200747510">. These are the only two comprehensive climate model simulations ever conducted of this scenario. 47510">Both models give similar results indicating a robustness to the climate response47510">. 47510">Nuclear winter, in the sense that below freezing temperatures envelop much of the Northern Hemisphere during summer, would occur due to a significant reduction of solar radiation from the aerosol loading. In addition to cooling the surface, the aerosols alter meridional temperature gradients as they heat the stratosphere. In both GrammarError SCXW35347510">models47510"> stratospheric zonal winds increase by as much as 250%, ending the occurrence of Sudden Stratospheric Warmings and completely disrupting the Quasi-Biennial Oscillation. Stratospheric heating also destroys large amounts of ozone. These responses also have profound climate impacts beyond the first order effect of black carbon aerosols reducing sunlight. The stratospheric circulation changes change the Arctic Oscillation (AO), causing winter surface air temperatures poleward of 60°N, including Scandinavia and northern Eurasia, that are 8°C above the control average for two years, despite the enormous aerosol 47510">loading47510">. Although winter-averaged temperatures are mostly below freezing, sea ice growth is affected. Even after the black carbon aerosols fall out of the stratosphere, the AO remains highly positive for three winters, despite the meridional temperature gradients returning to normal in the stratosphere. 47510">Vertical wave propagation changes are investigated to determine how they maintain this AO pattern47510"> 47510">and what this means for the devastating environmental aftermath of such a confl47510">ic47510">t47510">. "134233279":true,"201341983":0,"335559740":240}"">