A single nuke's impact should be measured by more than megatons

Using publicly available data on 19 types of weapons now held by five major nuclear powers — the United States, Russia, China, the United Kingdom and France — Liska and his colleagues calculated how many nuclear bombs in each category could be used before triggering conditions they describe as “nuclear autumn” or “nuclear drought.” Not as severe as the nuclear winter predicted by scientists in the 1980s, a nuclear autumn nonetheless would significantly impact Earth’s climate.

“The question is not if a nuclear drought can occur, but what factors increase its probability of occurring and what actions can be taken to mitigate the potentially devastating global impacts?” said Liska, who specializes in life-cycle analysis to assess the environmental impacts of products and services.

Other scientists previously have found nuclear blasts sufficient to ignite a developed area roughly the size of Los Angeles — 500 square miles — would throw 5.5 million tons of ash and soot into the stratosphere. Sunlight, temperatures and rainfall would decrease around the world, growing seasons would be significantly reduced for at least five years and global temperatures would be their lowest in 1,000 years. Rainfall could decrease by as much as 80 percent in some areas of the world.

The black ash created by a nuclear blast would cool temperatures at the Earth’s surface, Oglesby said. Because there would be less temperature difference between the lower and upper atmosphere, rainfall would dwindle and cast large areas of the planet into drought.

“If the ash reaches the stratosphere, many months could pass before it dissipates,” Oglesby said.

Physicist Stephen Hawking and former Defense Secretary William Perry are among those who have recently warned about the growing danger of nuclear weapons use.

Liska and colleagues found that the United States, Russia and China each have weapons, including air-dropped, intercontinental ballistic missiles and land-based missiles, that could trigger a nuclear drought with the detonation of fewer than five bombs. Each weapon represents only a fraction of their arsenals. China could cause a nuclear drought with the launch of a single land-based missile. It holds 20 of that type in its arsenal.

UNL notes that the potential climate destruction posed by nuclear weapons is further compounded by climate change related to fossil fuel consumption, Liska added. More nations are turning to nuclear energy to reduce fossil fuel usage, which also creates opportunities for more nations to obtain nuclear weapons. Political instability as a result of people fleeing higher sea levels in the long term could exacerbate global conflict and increase the chance of limited nuclear confrontations.

“We pulled together what is known about nuclear weapons today, to make a case about the magnitude of these impacts,” Liska said. “With that understanding, we can make better choices going forward.”

 Read more in Adam J. Liska et al., “Nuclear Weapons in a Changing Climate: Probability, Increasing Risks, and Perception,” Environment: Science and Policy for Sustainable Development 59, no. 4 (2017) (doi.org/10.1080/00139157.2017.1325300)