Atom Nuclear Bomb Exploding Over City Illustration

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BOULDER, Colo. — Nuclear war could be the end of mankind, as the smoke from the blasts would destroy the ozone layer and trigger a climate apocalypse, a new study concludes. The harsh winter following a nuclear war would be replaced by a massive UV blast as the ozone-depleted atmosphere lets in sunlight again.

This alarming international study paints an even grimmer picture of what the aftermath of a nuclear war would look like, emphasizing the deterrent of mutually assured destruction. Using newly developed computer climate modeling techniques to learn more about the effects of a hypothetical nuclear exchange, the researchers were able to see how the chemical interactions in the stratosphere would influence the amounts of ultraviolet (UV) radiation that would 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. These aren’t local to where the war occurs. They’re global, so they would affect all of us,” explains lead author Dr. Charles Bardeen, a scientist at the National Center for Atmospheric Research (NCAR), in a statement.

Dr. Bardeen and his colleagues say that the smoke from a global nuclear war would destroy much of the ozone layer over a 15-year period. Ozone loss would likely peak at about 75 percent worldwide. The scientists note that even a regional nuclear war would lead to a peak ozone loss of 25 percent globally, meaning that it would take up to twelve years to recover from such devastation.

Since the ozone layer protects the Earth’s surface from harmful UV radiation, such impacts would decimate humans and the environment. High levels of UV radiation have been linked to causing 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. Now, for the first time, we have calculated how this would work and quantified how it would depend on the amount of smoke,” says Alan Robock, a professor of climate science at Rutgers University who co-authored the study.

Throughout history, there have been many studies conducted by researchers who set out to understand just how damaging a nuclear war would be. During a previous study conducted in the 1980s, scientists found that the enormous amounts of smoke generated by a nuclear war would cool the planet by blocking the incoming sunlight, creating an outcome known as a “nuclear winter.”

They also found that a nuclear war would destroy the ozone layer due to the nitrogen oxides produced from the nuclear fireball explosion. However, subsequent research suggested that the smoke would cause ozone loss by heating the stratosphere, which would change chemical reaction rates and reduce photochemistry — chemical reactions caused by sunlight.

In the new study, the authors explore the ways in which the reduced photochemistry would affect the destruction of the ozone layer and how the smoke would protect the surface from UV radiation. For the first time ever, Professor Robock and his colleagues calculated the combined effects of nitrogen oxides, stratospheric heating, and reduced photochemistry on the ozone chemistry and the surface, in the event of a global nuclear war.

By using four advanced NCAR-based computer models, the team studied two hypothetical scenarios. The first centered around a regional nuclear war between India and Pakistan, which produced five megatons of smoke. The second focused on a global nuclear war between the United States and Russia, which caused 150 megatons of smoke.

The results highlight the importance of using sophisticated modeling techniques to flesh out the complexities of the atmosphere. In the event of a global nuclear war, the simulations showed that a massive injection of smoke into the stratosphere would initially cool surface temperatures by blocking sunlight, altering precipitation patterns, shielding the planet from incoming UV radiation, while also destroying the protective ozone layer. However, within a few years, 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. Just as the smoke is clearing up, you would get this blast of UV with completely different impacts on human health and agriculture,” Dr. Bardeen explains.

The scientists say that in contrast, a regional nuclear war that generated less smoke would result in a more straightforward pattern, with UV radiation increasing right away. While surface temperatures decreased and the smoke would dissipate, the ozone layer would gradually recover.

The study was funded by the Open Philanthropy Project with computational support from the National Science Foundation, the University of Colorado Boulder, and Colorado State University.

It is published in the Journal of Geophysical Research-Atmospheres.

South West News Service writer Georgia Lambert contributed to this report.

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