It was on again, off again but President Trump did meet with North Korean leader Kim Jung Un, and they agreed to denuclearizing the Korean peninsula. What that means is still unclear, but a new study has some advice for all nuclear nations: limit your arsenal to 100 weapons.
That apparently is the tipping point where the risks of nuclear annihilation outweigh the benefits of nuclear deterrence.
David Denkenberger is an assistant professor at Tennessee State University and director of the Alliance to Feed the Earth in Disasters (ALLFED). He co-authored the study and is interested in the long-term future of the world, and preventing what he calls “catastrophic risks.”
“I’ve done work on backup plans for a disaster that blocked the sunlight, like an asteroid impact or volcanic eruption," Denkenberger said. "But what’s most likely is a nuclear exchange: burning of cities, and smoke going up into the atmosphere.”
The best solution is to prevent such a catastrophe, he said, and complete denuclearization is best scenario. But there is the argument of using nukes as a deterrent.
“If my country has nuclear weapons... other countries would be less likely to attack,” he said. “What we’re interested in is when the diminishing returns of that nuclear deterrence hit."
In other words, the point at which you start endangering your country with your own nuclear weapons.
According to Denkenberger, 100 nuclear weapons could kill a significant percentage of people in another country and the fatalities could be as large as those in World War II.
“It’s also similar to mortality to some of big plagues and pandemics in the past," he said. "We feel that’s sufficient deterrence.”
But firing a weapon on another country can impact the country doing the attack. The smoke that goes into the upper atmosphere can stay there for years, even a decade, and would spread globally.
“It would reduce sunlight and temperature, which is not good for plants,” he said. “And it would reduce rain and it could also disrupt the ozone layer and create more ultraviolet radiation.”
Fewer weapons could also create what’s called nuclear autumn rather than nuclear winter.
"If you reduce the number of nuclear weapons being used, the global temperature might fall by two degrees Fahrenheit,” he said.
The study assumes there is no retaliation, but a basic principle behind nuclear deterrence is mutually assured destruction -- the idea that the other side would fire back.
"It demonstrates how conservative we’re being," he said. "If the firing of your nuclear weapon results in another country firing back, the damage to your country is going to be much larger. So that could be a reason to have even fewer nuclear weapons."
He added that his study supposes a very optimistic scenario. "And still the result is to have many fewer nukes than U.S. and Russia currently have, which is many thousands of weapons,” he said.
Denkenberger also encouraged governments to take into account these secondary effects, noting that governments have generally focused their planning on the initial blast but not on the nuclear winter that follows.
In the case of a global nuclear catastrophe, there would be a lot of dead plants and trees, which would make conventional farming difficult.
"One option is growing mushrooms on that material," he said. "Another option is turning corn stalks into sugar."
He noted that cows, sheep, goats, and rabbits can eat fiber that people cannot, making those animals a possible source of food after an apocalypse.
Or maybe we should just avoid nuclear war.
"I would agree," Denkenberger said.