Chronic climatic effects of nuclear war

Abstract

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°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°C. Sea ice expands by up to 10 million km 2, or 2% of the global ocean area. Land surface cooling is 10–15°C for the first few months and 2°C thereafter. Snow cover expands by more than 40 million km 2 (25% of global land area) briefly at high latitudes, but by no more than 10 million km 2 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.