Regional nuclear war would create near-global ozone hole

human health and on terrestrial, aquatic and marine
 ecosystems.”

A paper on the subject,
titled “Massive Global Ozone Loss Predicted Following A Regional Nuclear
Conflict,” appeared the week of 7 April in the Proceedings of the National
Academy of Sciences. Co-authors on the study include CU-Boulder Professor
Brian Toon, UCLA professor Richard Turco, and National Center for Atmospheric Research
scientists Douglas Kinnison and Rolando Garcia. According to the computer simulations,
fires ignited in large cities by nuclear explosions would send several million
metric tons of soot into the upper stratosphere, which would be heated by
massive smoke injections. Higher temperatures would accelerate catalytic
reaction cycles in the stratosphere, particularly reactions of nitrogen oxide
gases known collectively as NOx that destroy ozone, Mills said. 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-Boulder’s
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 Hemisphere’s 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 amphibians, shrimp, fish and
phytoplankton, said Mills. “Most organisms can do little to avoid UV exposure,
so one of the big unanswered questions is how the biota would respond to these
big UV increases triggered by a nuclear exchange.” The team used a cluster of
computer processors at LASP to run three separate 10-year simulations — each
more than 300 hours long — linking the urban fire nuclear scenario to climate
and atmospheric chemistry processes. The team coupled NCAR’s Whole Atmosphere
Community Climate Model 3 with the Community Aerosol and Radiation Model for
Atmospheres developed by CU-Boulder and NASA Ames. Two 2006 studies led by Toon
and involving UCLA and Rutgers University showed that such a small-scale regional
nuclear war could produce as many fatalities as all of the Second World War and
disrupt global climate for a decade or more. Of the eight nations known to
possess nuclear weapons, even those with the smallest nuclear arsenals, like Pakistan and India, are believed to have fifty or
more Hiroshima-sized weapons.

In addition, about 40
countries possess enough plutonium, uranium, or a combination of both to
construct substantial nuclear arsenals, said Toon. A nuclear exchange involving
100 15-kiloton, Hiroshima-type weapons is only 0.03 percent of the total
explosive power of the world’s nuclear arsenal, he said. “We hope other
research groups repeat our calculations and undertake their own scientific
studies on this issue,” said Toon. “The world has become a far more dangerous
place when the actions of two countries on the other side of the world could
have such a drastic impact on the planet.” The study was funded by CU-Boulder.