With Ukrainian tensions mounting, the notion that such regional conflicts could morph into something nuclear is now dogging Western leaders in a way not seen in a generation.
Cold War policy was long built on Mutually Assured Destruction (MAD), the idea that a global thermonuclear war would be so horrific that it was deemed unthinkable.
But even a limited regional nuclear conflict would have catastrophic global impact, as detailed in new atmospheric and climate models in a forthcoming paper in the journal Earth’s Future.
The paper notes that a hypothetical exchange of a hundred 15-kiloton warheads between India and Pakistan could cause firestorms that would spew soot high into earth’s atmosphere. An estimated 5 Teragrams of this black carbon would both absorb and block sunlight; heating the stratosphere and at least temporarily destroy much of earth’s protective ozone layer.
A follow-on increase in summertime ultraviolet (UV) surface radiation of as much as 80 percent would be “off the charts” says Michael Mills, an atmospheric scientist at NCAR (the National Center for Atmospheric Research) in Boulder, Colorado, and the study’s lead author. Mills notes that just one such 15-kiloton weapon would represent about the same kilo-tonnage as “Little Boy,” the American atomic bomb dropped on Hiroshima, Japan. .
As a result of such a UV increase, Mills says those susceptible to sunburn after only an hour in a midday summer sun, would burn in about half the time. And more importantly, such large amounts of ultraviolet radiation would destroy both land- and sea-based ecosystems, as well as agricultural food crops, potentially leading to global nuclear famine.
At the same time, largely due to such soot blocking incoming solar insolation, earth’s mean global surface temperature would be expected to cool by 1.5 degrees Celsius (about 2.7 degrees F); its lowest in more than 1,000 years.
Mills says soot from such a regional exchange today would also reduce global precipitation, creating a plethora of wildfires, particularly in regions like the Amazon.
Meanwhile, cooler surface temperatures would mean an expansion of sea ice at both polar regions; which, in turn, would increase earth’s albedo, or surface reflectance. This would only exacerbate the problem of a cooling earth surface, since sea ice acts to reflect incoming sunlight back into space, only cooling the planet further.
The team concluded that null ; while Antarctic sea ice would more than double.
Mills says this is the first study to include interactive effects of atmospheric physics, ozone chemistry, deep-ocean and sea ice response, and land vegetation all in one earth system model.
The team ran seven models using NASA’s Pleiades Supercomputer at the space agency’s Ames Research Center in Silicon Valley.
“[We were] expecting to confirm earlier studies that there would be about a decade of cooler temperatures following such an exchange,” said Mills.
But, instead, he says, the team found that cooling would last longer than 25 years; causing growing seasons worldwide to be reduced by as much as 40 days.
“In the 1980s, we learned that global thermonuclear war could render the planet close to uninhabitable,” said Mills. “Now, we know that even [regional] nuclear war can cause great suffering worldwide, with potential for a lot of people to die from starvation in regions very far from a conflict.”