'Nuclear winter' may kill more than a nuclear war
Pastor Dale Morgan
Mar 6th, 2007 11:58 AM
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'Nuclear winter' may kill more than a nuclear war
*Rev:6:12: And I beheld when he had opened the sixth seal, and, lo,
there was a great earthquake; and the sun became black as sackcloth of
hair, and the moon became as blood;
New Scientist Mag.
Debora MacKenzie
A regional exchange of relatively small nuclear weapons could plunge the
world into a decade-long "nuclear winter", destroying agriculture and
killing millions, according to a new study.
Weapons experts to consider that small-scale nuclear exchanges are now
more likely than the massive US-Soviet exchanges feared during the Cold War.
In the 1980s, scientists calculated that such exchanges would put enough
smoke, dust and debris into the atmosphere to black out the Sun and turn
the moon blood red, thus causing a nuclear winter.
Now scientists have re-calculated the likelihood of nuclear winter using
modern, vastly improved climate models and a more likely modern scenario
for small-scale nuclear war. Brian Toon, head of atmospheric and oceanic
sciences at the University of Colorado at Boulder, and Alan Robock of
Rutgers University in New Jersey, both in the US, predict less cooling
than the 1980s modellers. However, they predict the cooling would last
longer, with potentially devastating consequences.
Different targets
The pair modelled the impact of 100 explosions in subtropical
megacities. They modelled 15-kilotonne explosions, like the Hiroshima
bomb. This is also the size of the bombs now possessed by India and
Pakistan, among others.
The immediate blast and radiation from the exchange of 100 small nuclear
bombs killed between three million and 16 million people, depending on
the targets. But the global effect of the resulting one-to-five million
tonnes of smoke was much worse. “It is very surprising how few weapons
are needed to do so much damage,” says Toon.
This is partly because modern scenarios aim at different targets. Toon
says most of the huge US and Russian nuclear warheads are aimed, in a
first strike, at missile silos in wilderness or suburban military
installations. There is not much to burn, and after the first warhead
hits, subsequent explosions do not release much additional smoke.
Urban firestorm
By contrast, a regional exchange where adversaries target each others’
megacities would ignite huge urban firestorms. Toon calculates the smoke
released per kilotonne of explosive yield would be 100 times greater
than in the Cold War scenarios.
Moreover, it lasts longer. The 1980s models, says Toon, did not extend
into the upper atmosphere far enough, and could not be run long enough
to discover this.
“Soot from fires is black and absorbs solar radiation,” Robock told New
Scientist. “As it begins to fall it is constantly being heated and
lofted.” Such particles, they calculate, rise to the upper atmosphere
and stay for more than six years.
Global chill
In comparison, Robock says, particulates from a volcanic eruption, which
stay in the lower atmosphere and last only about a year, have
nevertheless cooled the planet enough to cause famine.
Even taking global warming into account, the models predict that the
cooling of the planet for a decade following the exchange would be
nearly twice as great as the global warming of the past century, causing
colder temperatures than Europe’s "Little Ice Age" of the 16th to 18th
centuries.
Although this might look perversely like a welcome counter-balance to
global warming, the researchers say it would cause equally devastating
changes in weather patterns and rainfall. That, plus reduced sunlight,
would shorten growing seasons and destroy crops worldwide, to the
detriment of all.
Journal reference: Science (vol 315 p 1224)