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Regional
Nuclear Conflict Would Create Near-Global Ozone Hole, Says CU-Boulder
Study
A new computer
modeling study led by CU-Boulder scientists Brian Toon, left, and Michael
Mills, right, indicates a limited nuclear weapons exchange in the Middle
East would create a near-global ozone hole, impacting human and ecosystem
health for a decade or more.
April 7, 2008
A new computer modeling study led by CU-Boulder scientists Brian Toon,
left, and Michael Mills, right, indicates a limited nuclear weapons
exchange in the Middle East would create a near-global ozone hole,
impacting human and ecosystem health for a decade or more.
A limited nuclear weapons exchange between Pakistan and India using their
current arsenals could create a near-global ozone hole, triggering human
health problems and wreaking environmental havoc for at least a decade,
according to a study led by the University of Colorado at Boulder.
The
computer-modeling study showed a nuclear war between the two countries
involving 50 Hiroshima-sized nuclear devices on each side would cause
massive urban fires and loft as much as 5 million metric tons of soot
about 50 miles into the stratosphere, said CU-Boulder Research Associate
Michael Mills, chief study author. The soot would absorb enough solar
radiation to heat surrounding gases, setting in motion a series of
chemical reactions that would break down the stratospheric ozone layer
protecting Earth from harmful ultraviolet radiation, said Mills.
"We would
see a dramatic drop in ozone levels that would persist for many
years," said Mills of CU-Boulder's Laboratory for Atmospheric and
Space Physics. "At mid- latitudes the ozone decrease would be up to
40 percent, which could have huge effects on 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 April 7 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 World War II 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
50 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.
A podcast with
Mills is on the Web at: www.colorado.edu/news/podcasts/.
Contact
Michael Mills,
(303) 492-7767
Mills@colorado.edu
Brian Toon, (303) 492-1534
btoon@lasp.colorado.edu
Jim Scott, (303) 492-3114
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