Smoke from nuclear war would devastate ozone layer, alter climate
Atmospheric impacts of global nuclear war would be more severe than
previously thought

Date:
October 13, 2021
Source:
National Center for Atmospheric Research/University Corporation
for Atmospheric Research
Summary:
The massive columns of smoke generated by a nuclear war would
alter the world's climate for years and devastate the ozone layer,
endangering both human health and food supplies, new research
shows. The international study draws on newly developed computer
climate modeling techniques to paint an even grimmer picture of
a global nuclear war's aftermath than previous analyses.



FULL STORY ==========================================================================
The massive columns of smoke generated by a nuclear war would alter the
world's climate for years and devastate the ozone layer, endangering
both human health and food supplies, new research shows.


==========================================================================
The international study paints an even grimmer picture of a global nuclear war's aftermath than previous analyses. The research team used newly
developed computer climate modeling techniques to learn more about the
effects of a hypothetical nuclear exchange, including complex chemistry interactions in the stratosphere that influence the amounts of ultraviolet
(UV) radiation that reach the planet's surface.

"In addition to all the fatalities that would happen almost immediately,
the climate effects and the UV effects would be widespread," said lead
author Charles Bardeen, a scientist at the National Center for Atmospheric Research (NCAR). "These aren't local to where the war occurs. They're
global, so they would affect all of us." Bardeen and his co-authors
found that smoke from a global nuclear war would destroy much of the
ozone layer over a 15-year period, with the ozone loss peaking at an
average of about 75% worldwide. Even a regional nuclear war would lead
to a peak ozone loss of 25% globally, with recovery taking about 12 years.

Since the ozone layer protects Earth's surface from harmful UV radiation,
such impacts would be devastating to humans and the environment. High
levels of UV radiation have been linked to certain types of skin cancer, cataracts, and immunological disorders. The ozone layer also protects terrestrial and aquatic ecosystems, as well as agriculture.

"Although we suspected that ozone would be destroyed after nuclear war and
that would result in enhanced ultraviolet light at the Earth's surface,
if there was too much smoke, it would block out the ultraviolet light,"
said study co-author Alan Robock, a professor of climate science at
Rutgers University. "Now, for the first time, we have calculated how this
would work and quantified how it would depend on the amount of smoke."
The study was funded by the Open Philanthropy Project with computational support from the National Science Foundation, which is NCAR's sponsor,
as well as from the University of Colorado Boulder and Colorado State University. It was published in the Journal of Geophysical Research-- Atmospheres, a publication of the American Geophysical Union.



========================================================================== Shifting atmospheric response to global war Scientists in the 1980s
found that the enormous amounts of smoke from a nuclear war would cool
the planet by blocking incoming sunlight, an outcome known as a "nuclear winter." They also found that a nuclear war would destroy ozone because
of chemical reactions involving nitrogen oxides produced from the fireball created by a nuclear weapon explosion.

Subsequent research, however, suggested that the smoke would also cause
ozone loss by heating the stratosphere, which changes chemical reaction
rates, and by reducing photochemistry (chemical reactions caused by
sunlight).

In the new study, the authors explored how much the reduced photochemistry would affect ozone destruction, as well as the extent to which the
smoke would protect the surface from UV radiation. They calculated, for
the first time, the combined effects of nitrogen oxides, stratospheric
heating, and reduced photochemistry on stratospheric ozone chemistry
and surface UV resulting from a global nuclear war.

The research team combined four advanced NCAR-based computer models: the Community Earth System Model, which simulates global climate; the Whole Atmosphere Community Climate Model, which simulates higher regions of the atmosphere; the Tropospheric Ultraviolet and Visible Radiation Model,
which calculates the light available for photolysis and the amount of
UV radiation that reaches the surface; and the Community Aerosol and
Radiation Model for Atmospheres, which provides an advanced treatment
of smoke particles.



==========================================================================
They used this modeling approach to study two scenarios. In one, a
regional nuclear war between India and Pakistan produces 5 megatons of
smoke. In the other, a global nuclear war between the United States and
Russia produces 150 megatons of smoke.

The results highlighted the importance of using sophisticated modeling techniques to flesh out the complexities of the atmosphere. In the case
of the global nuclear war, for example, the simulations showed that
massive injection of smoke into the stratosphere would initially cool
surface temperatures by blocking sunlight, alter precipitation patterns,
shield the planet from incoming UV radiation, while also destroying the protective ozone layer. Within a few years, however, the smoke would
begin to dissipate and far more UV radiation would reach the surface
through the diminished ozone layer.

"Conditions would switch dramatically, and adaptations that may work at
first won't help as temperatures warm back up and UV radiation increases," Bardeen said. "Just as the smoke is clearing up, you would get this blast
of UV with completely different impacts on human health and agriculture."
In contrast, a regional nuclear war that generated less smoke would
result in a more straightforward pattern, with UV increasing right away
while surface temperatures are decreasing and the ozone layer gradually recovering as the smoke dissipates.

========================================================================== Story Source: Materials provided by National_Center_for_Atmospheric_Research/University Corporation_for_Atmospheric_Research. Original written by David
Hosansky. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Charles G. Bardeen, Douglas E. Kinnison, Owen B. Toon, Michael
J. Mills,
Francis Vitt, Lili Xia, Jonas Ja"germeyr, Nicole S. Lovenduski,
Kim J. N.

Scherrer, Margot Clyne, Alan Robock. Extreme Ozone Loss
Following Nuclear War Results in Enhanced Surface Ultraviolet
Radiation. Journal of Geophysical Research: Atmospheres, 2021;
126 (18) DOI: 10.1029/ 2021JD035079 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211013174023.htm

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