Nuclear conflict may remain unthinkable in terms of the human cost, but research published this week in the journal Science Advances adds focus on the potential climate impacts if the unthinkable were to happen.
The paper, from 10 authors led by Owen B. Toon at the University of Colorado, does so by detailing the results of a hypothetical regional nuclear conflict set in the year 2025. The scripted conflict between India and Pakistan, in the scientists’ model, is designed for scientific purposes rather than political ones and they’re clear about that.
“Although this scenario has Pakistan first launching nuclear weapons, we do not mean to imply that they are more likely to do this than India,” the authors are careful to note. In fact, neither country is likely to act without extreme provocation, they said. And 93 percent of the nuclear weapons on the planet are believed to belong to Russia or the United States in the first place. Other countries are nuclear capable as well, but current affairs and the history of saber-rattling between Pakistan and India informed the research.
“Because large numbers of weapons are assumed to be used by both sides, we would expect our results to be similar no matter how the war started,” the authors add. Those results are sobering beyond the tens of millions of lives lost in urban centers, and the global economic and diplomatic disruptions.
Toon and the research team warn that in this India-Pakistan model of a regional nuclear conflict, the resulting explosions and fires would release up to 36 teragrams of black carbon into the atmosphere. The scientists’ calculations account for the kinds of fire too: construction materials, furnishings, clothing, asphalt roofs, plastics, fuels, all of it in homes, places of work, schools, stores, gas stations. That’s such an astonishing amount of carbon that it would block between 20 to 35 percent of the sunshine.
As a result, the earth would cool by 2 to 5 degrees Celsius, and rainfall would decrease by up to a third. (If it were a war between U.S. and Russia instead, the precipitation could dry up as much as 60 percent.)
There’s no positive in the cooling though. “The global average surface temperature drops between 1.25° and 6.5°C over several years for our scenario,” the authors note. “These perturbations reach their peak about three years after the conflict and are near the peak value for about four years. It takes more than a decade for temperatures and precipitation to return to normal.”
The scenario shows significant climate impacts to both ocean and land resources. Net primary productivity (NPP) is expected to drop but not all losses will be felt equally on all continents.
“Major crop-growing regions of North America and Eurasia experience declines of NPP averaging 25 to 50 percent over this time,” the authors note, referring to the three-year peak. “Very large reductions in NPP occur in India, China, Southeast Asia, and Indonesia, as well as in tropical South America and Africa. Ocean reductions in NPP are highest in the Arctic, where production is almost entirely extinguished.”
In other words, any such regional conflict threatens food security and has global reach. “Compounding the devastation brought upon their own countries,” the authors conclude, “decisions by Indian and Pakistani military leaders and politicians to use nuclear weapons could severely affect every other nation on Earth.