Nuclear Winter: Global Consequences of Multiple Nuclear Explosions

Abstract

The potential global atmospheric and climatic consequences of nuclear war are investigated using models previously developed to study the effects of volcanic eruptions. Although the results are necessarily imprecise due to wide range of possible scenaros and uncertainty in physical parameters, the most probable first-order effects are serious. Significant hemispherical attenuation of the solar radiation flux and subfreezing land temperatures may be caused by fine dust raised in high-yield nuclear surface bursts and by smoke from city and forest fires ignited by airbursts of all yields. For many simulated exchanges of several thousand megatons, in which dust and smoke are generated and encircle the earth within 1 to 2 weeks, average light levels can be reduced to a few percent of ambient and land temperatures can reach -15 degrees to -25 degrees C. The yield threshold for major optical and climatic consequences may be very low: only about 100 megatons detonated over major urban centers can create average hemispheric smoke optical depths greater than 2 for weeks and, even in summer, subfreezing land temperatures for months. In a 5000-megaton war, at northern mid-latitude sites remote from targets, radioactive fallout on time scales of days to weeks can lead to chronic mean doses of up to 50 rads from external whole-body gamma-ray exposure, with a likely equal or greater internal dose from biologically active radionuclides. Large horizontal and vertical temperature gradients caused by absorption of sunlight in smoke and dust clouds may greatly accelerate transport of particles and radioactivity from the Northern Hemisphere to the Southern Hemisphere. When combined with the prompt destruction from nuclear blast, fires, and fallout and the later enhancement of solar ultraviolet radiation due to ozone depletion, long-term exposure to cold, dark, and radioactivity could pose a serious threat to human survivors and to other species.

Climate effects of a hypothetical regional nuclear war: Sensitivity to emission duration and particle composition

“…These particles are assumed to be immediately lifted by the fires to the upper troposphere/lower stratosphere region where they will reflect and absorb solar radiation, locally heating the atmosphere and cooling the surface. The first studies using global climate models (GCMs) to examine the impact of the particles [e.g., Turco et al, 1983] showed catastrophic climatic consequences of a nuclear war between superpowers, with subfreezing land temperatures even during summer. More recent studies, using state-of-the-art GCMs, have assessed the damage that might result from a more restrictive use of nuclear weapons [Robock et al, 2007;Toon et al, 2007aToon et al, , 2007bMills et al, 2008;Stenke et al, 2013].…”

Smoke Emission Factors from Medium-Scale Fires: Part 1

“…The concept of nuclear winter was reviewed by a committee of the National Research Council (NRC, 1985). In general, the case put forward by Turco et al (1983Turco et al ( , 1984 was supported with the strong recommendation that the uncertainties be reduced by further research directed toward achieving an understanding of the basic processes that are important to the problem.…”

“…The concept of "nuclear winter" has been posutlated with a number of assumptions regarding the smoke produced by postnuclear-exchange fires (Turco et al, 1983(Turco et al, , 1984. The general premise is: after the use of nuclear weapons, sufficient smoke would be generated from fires and deposited in the atmosphere to cause a decrease in the incident solar energy reaching the Earth's surface.…”

“…Two general fire types, urban and wildland, are considered with respect to representative fuels and their smolung characteristics (Turco et al, 1983(Turco et al, , 1984NRC, 1985). Urban fires are composed of fuels derived from many types of materials found in the built environment, including primarily wood-based products and polymeric materials.…”

“…Turco et al (1983Turco et al ( , 1984 used data from small-scale fire experiments (Tewarson, 1982) to estimate the smoke emission factors (i.e., the mass of smoke produced by the burning of a unit mass of a fuel). Penner (1986Penner ( ,1987 has reviewed many of the uncertainties in the smoke "source term" in which she considered the estimated fuel loading, smoke emission factors, the optical properties of the smoke, injection height of smoke, and the fraction of smoke scavenged by precipitation.…”