Two years ago, British Columbia suffered one of the worst wildfires in the Canadian province’s history, which consumed 1.2 million hectares and displaced 65,000 people. The 2017 blaze was so intense that scientists are using it to model the climate conditions that might be created in the fallout of nuclear war, according to a study published on Thursday in Science.
The study suggests that the smoky aftermath of a modern nuclear blast will likely persist for longer than current models predict.
A team led by Pengfei Yu at the Institute for Environment and Climate Research at Jinan University in Guangzhou, China, examined the wildfire using data from ground stations, balloons, and satellites.
In particular, they focused on the formation of a huge vertical smoke plume, made from pyrocumulonibus clouds, which rose more than 14 miles into the stratosphere and remained active for eight months.
The plume offered a real-world example of the climate effects expected from a major nuclear conflict, the team said. In that scenario, known as nuclear winter, firestorms lead to a long-term darkening of the skies and global cooling due to the accumulation of aerosols into the atmosphere.
“One of the important predictions of numerous models of nuclear winter is that smoke injected into the upper troposphere from urban fires will self-loft high into the stratosphere,” the authors wrote in the study. “The 2017 fires studied here represent the first observational evidence that such a rise actually occurs.”
Because data from the plume had been collected by so many different observation platforms—in space, in the air, and on the ground—Yu and his colleagues were able to probe the dynamics behind the plume in precise detail.
Black carbon, or soot, was found to be the main driver of its stratospheric ascent. This thick air pollutant only made up about 2% of the 0.3 teragrams of smoke from the wildfire, but it had an outsized effect on the plume because it absorbs so much solar radiation. As a result, the black carbon became heated, which in turn propelled smoke higher into the atmosphere.
In the event of a nuclear war, cities would likely burn alongside forests, and that could fuel even larger aerosol-rich plumes. The researchers estimated that about 0.05 teragrams of black carbon could be released from an urban area ravaged by a nuclear weapon, leading to sootier plumes and lower concentrations of transparent organic smoke.
“If there were a lot of organics it would make the nuclear winter last less long,” said study co-author Brian Toon, a physicist at the University of Colorado Boulder, in an email. “However, smoke from cities does not contain as much organics as smoke from a forest. Burning plastic produces smoke that is almost all black carbon, for instance.”
In other words, nuclear winter simulations may be too optimistic about the rate at which wildfire smoke will dissipate. The fact that the 2017 plume persisted for two-thirds of a year revealed that the smoky aftereffects of a nuclear war would likely last longer than originally projected in models.
“We are currently working on some new simulations of nuclear conflicts, and we will consider the impacts of the organics in this new work,” Toon said.
Nuclear warfare could lead to even worse outcomes for humanity than originally expected, and it’s not as if it was looking very positive before this research anyway. Wildfires exacerbated by human-driven climate change are bad enough without our species escalating them with weapons of mass destruction.
Update: This article has been updated to include comments from co-author Brian Toon.