Nuclear winter theory gets new lease of life

Press, 6 September 1989, Page 21

Nuclear winter theory gets new lease of life

By

ROBIN McKIE

Nuclear winter, the predicted cataclysm that would engulf Earth in the wake of a nuclear war, has reared its controversial head again. The notion was originally outlined by a group of scientists, led by Carl Sagan. It was briefly popular among scientists, and also among nuclear disarmament campaigners.

Both groups backed the idea that plumes of smoke from burning cities and forests, incinerated by nuclear bombs, would blot out the sun for long enough to trigger a devastating “winter.” Robbed of light or heat, humans would be eradicated from the planet. There would simply be no survivors from even a small nuclear war, it was said. But the nuclear winter idea has since been thoroughly debunked. Other researchers argued that there were simply too many variables in the computer simulations created by the theory’s adherents. You could not reliably predict that a nuclear theory would occur. Although plumes of debris would be thrown up, not enough would be generated to cause global catastrophe, nor would the debris clouds stay aloft long enough to cause significant damage.

New evidence, published in “Nature” suggests that the winter theory may still not yet be dead and buried.

As author Dr Jenny Nelson points out, the sooty smoke generated in a nuclear exchange is “a critical factor in determining climatic effects.” Until now, scientists have assumed that the smoke would be made up of tiny spheres of soot. This is an inaccurate assumption, says Dr Nelson. The smoke should, instead, be considered as aggregates of particles with many facets. Such clusters absorb and scatter light in a very different way from spheres. In her computer simulations, Dr Nelson found that sooty smoke would form much darker clouds then previously anticipated. Her research revealed that smoke clouds would depress world temperatures by 5 deg C more than was assumed. It would also double or treble the opacity of debris clouds, increasing significantly the likelihood of a nuclear winter and global catastrophe. Copyright London Observer