New research indicates that a “regional”, limited nuclear war would have even more devastating global consequences than previously expected.

In addition to creating a global “nuclear haze” effect that would lead to global famine, a nuclear war involving as few as 100 Hiroshima-size nuclear bombs could cause serious depletion of the world’s ozone layer, leading to dangerous levels of ultraviolet radiation that would affect plants and animals around the world. (There are approximately 23,000 nuclear weapons, equivalent to more than 400,000 Hiroshima bombs, in the global arsenal.)

Even a nuclear war between India and Pakistan, which have much smaller arsenals than the United States and Russia, might be large enough to cause the predicted effects (“Nuclear War and Ultraviolet Radiation,” Staff Notes, National Center for Atmospheric Research, 2 March 2011):

New research indicates that a regional nuclear war would deplete Earth’s protective ozone layer so profoundly that levels of ultraviolet radiation (UV) across the world would exceed levels now considered extreme. NCAR scientist Michael Mills, who conducted the research with colleague Julia Lee-Taylor, presented the preliminary results in February at the annual conference of the American Association for the Advancement of Science….

To study the impact of the ozone loss on UV radiation, Mills and Lee-Taylor used a specialized computer model developed at NCAR. At present, UV levels typically range from 0 (none) to 11+ (extreme), according to a scale established by the World Health Organization and the World Meteorological Organization. However, the computer model results indicated that the United States and other midlatitude countries could face UV levels of up to 20 on cloud-free days in June, when sunshine is strongest in the Northern Hemisphere, with especially high levels in the Mountain West. The Southern Hemisphere, in turn, would face comparable UV levels in December.

Prolonged human exposure to high levels of UV radiation can result in vision loss and skin cancer. The radiation can have far-reaching impacts on animals and plants, as well as on agricultural productivity.

“The phrase ‘regional nuclear exchange’ is misleading because such an event would have global implications,” Mills says. “Even after such a war ended, it would affect the planet for at least a decade.”