CHRONIC CLIMATIC EFFECTS OF NUCLEAR-WAR

Numerical simulations of the global-scale atmospheric response to large smoke injections from fires following a nuclear war indicate that a significant amount of smoke could be lofted from the troposphere to the stratosphere where aerosol residence times are 6 months or longer. This suggests that interactions with the ocean mixed layer and sea ice are important in the chronic phase. To address these issues, a set of three 18 month simulations, two with smoke and one without, have been performed using a tropospheric general circulation model coupled with a model of the ocean mixed layer. Several aspects of the climatic response support the conclusions of Robock (1984, Nature 310, 667-670) using an energy balance model. The ocean mixed layer cools by 3-6-degrees-C within 2 months following the smoke injection; thereafter the ocean cooling follows the distribution of available insolation, with a lag of some 2 months and an amplitude of about 3-degrees-C. Sea ice expands by up to 10 million km2, or 2% of the global ocean area. Land surface cooling is 10-15-degrees-C for the first few months and 2-degrees-C thereafter. Snow cover expands by more than 40 million km2 (25% of global land area) briefly at high latitudes, but by no more than 10 million km2 thereafter. For an injection of one-third the smoke mass of the large injection, the same cooling patterns result, but with about half the magnitude.