In addition to ozone losses of 25 percent to 40 percent at mid-latitudes, the models show a 50 percent to 70 percent ozone loss at northern high latitudes, said Mills. The models show this magnitude of ozone loss would persist for five years, and we would see substantial losses continuing for at least another five years, he said.
The ozone losses predicted in the study are much larger than losses estimated in previous nuclear winter and ultraviolet spring scenario calculations following nuclear conflicts, said Toon, chair of CU-Boulders oceanic and atmospheric sciences department. A 1985 National Research Council Report predicted a global nuclear exchange involving thousands of megatons of explosions, rather than the 1.5 megatons assumed in the PNAS study, would deplete only 17 percent of the Northern Hemispheres stratospheric ozone, which would recover by half in three years.
The missing piece back then was that the models at the time could not account for the rise of the smoke plume and consequent heating of the stratosphere, said Toon. The big surprise is that this study demonstrates that a small-scale, regional nuclear conflict is capable of triggering ozone losses even larger than losses that were predicted following a full-scale nuclear war.
Human health ailments like cataracts and skin cancer, as well as damage to plants, animals and ecosystems at mid-latitudes would likely rise sharply as ozone levels decreased and allowed more harmful UV light to reach Earth, according to the PNAS study. By adopting the Montreal Protocol in 1987, society demonstrated it was unwilling to tolerate a small percentage of ozone loss because of serious health risks, said Toon. But ozone loss from a limited nuclear exchange would be more than an order of magnitude larger than ozone loss from the release of gases like CFCs.
UV radiation has been shown to be particularly damaging to inhabitants of aquatic ecosystems, including amphibi
|Contact: Michael Mills|
University of Colorado at Boulder