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Tomorrow, Professor Brian Toon of the CU-Boulder Department of Atmospheric and Oceanic Sciences will wrap up the 2014 Annual CAS Symposium: "Catastrophic Asia" with his talk entitled "Self-Assured Destruction: The Climate Impacts of Nuclear War." 

Climatic Consequences and Agricultural Impact of Regional Nuclear Conflict - Brian Toon. A nuclear war between India and Pakistan, with each country using 50 Hiroshima-sized atom bombs as airbursts on urban areas, would inject smoke from the resulting fires into the stratosphere. This could produce climate change unprecedented in recorded human history and global-scale ozone depletion, with enhanced ultraviolet (UV) radiation reaching the surface. Simulations with the Whole Atmosphere Community Climate Model (WACCM), show a long stratospheric residence time for smoke and hence a long-lasting climate response, with global average surface air temperatures 1.1 K below normal and global average precipitation 4% below normal even after a decade. The erythemal dose from the enhanced UV radiation would greatly increase, in spite of enhanced absorption by the remaining smoke, with the UV index more than 3 units higher in the summer midlatitudes, even after a decade. Scenarios of changes in temperature, precipitation, and downward shortwave radiation applied to the Decision Support System for Agrotechnology Transfer crop model for winter wheat, rice, soybeans, and maize by perturbing observed time series with anomalies from the regional nuclear war simulations, produce decreases of 10-50% in yield averaged over a decade, with larger decreases in the first several years, over the midlatitudes of the Northern Hemisphere. The impact of the nuclear war simulated here, using much less than 1% of the global nuclear arsenal, would be devastating to world agricultural production and trade, possibly sentencing a billion people now living marginal existences to starvation. The continued environmental threat of the use of even a small number of nuclear weapons must be considered in nuclear policy deliberations in Russia, the U.S., and the rest of the world.

Owen Brian Toon is a Professor in the Department of Atmospheric and Oceanic Sciences for which he was the founding Chair, and a Research Associate in the Laboratory for Atmospheric and Space Physics at the University of Colorado at Boulder. He received an A. B. in physics at the University of California at Berkeley in 1969 and a Ph.D. in physics at Cornell University in 1975. He was a Research Scientist at NASA’s Ames Research Center from 1975 until 1997 when he moved to Colorado. Brian’s research group studies radiative transfer, aerosol and cloud physics, atmospheric chemistry and parallels between the Earth and planets. Brian has helped conceive, develop and lead many NASA airborne field missions aimed at understanding stratospheric volcanic clouds, stratospheric ozone loss, the effects of aircraft on the atmosphere, and the role of convective and cirrus clouds in Earth’s climate system. He has been involved in numerous satellite missions for both Earth and the planets. He has published more than 300 papers in refereed scientific journals, and is one of the most highly cited researchers in Geoscience.