Massive wildfire cloud sheds light on nuclear war’s impact

In August 2017, extreme wildfires in British Columbia, Canada pumped so much smoke into the upper atmosphere that an enormous cloud circled most of the Northern Hemisphere, according to new research.

The new finding will help scientists model the climate impacts of nuclear war.

The pyrocumulonimbus (pyroCb) cloud—the largest of its kind ever observed—was quickly dubbed “the mother of all pyroCbs.” When the smoke reached the lower stratosphere, it was heated by sunlight and “self-lofted” from 7 to 14 miles up within two months.

The pivotal ingredient was black carbon (soot), which absorbed solar radiation, heating the air and fueling the smoke’s rapid rise. The smoke lasted more than eight months because the stratosphere has no rain to wash it out.

A mosaic image of several satellite overpasses capture the global scope of the wildfire smoke cloud.
An enormous cloud of smoke from intense wildfires drifted over northern Canada on August 15, 2017. The image is a mosaic composed from several satellite overpasses because the affected area was so large. (Credit: NASA Earth Observatory)

“This process of injecting soot into the stratosphere and seeing it extend its lifetime by self-lofting, was previously modeled as a consequence of nuclear winter in the case of an all-out war between the United States and Russia, in which smoke from burning cities would change the global climate,” says coauthor Alan Robock, a professor in the environmental sciences department at Rutgers University-New Brunswick.

“Even a relatively small nuclear war between India and Pakistan could cause climate change unprecedented in recorded human history and global food crises,” he says.

For the study in the journal Science, researchers used a state-of-the art climate model from the National Center for Atmospheric Research to model the lofting and movement of the colossal Canadian wildfire smoke cloud.

The modeling considered smoke characteristics such as the ratio of soot to other ingredients and the rate at which ozone in the upper atmosphere broke down the smoke.

The smoke cloud contained only about 0.3 million tons of soot, while a nuclear war between India and Pakistan could produce 15 million tons and a US vs. Russia war could generate 150 million tons. Still, the study validated the scientists’ previous theories and the climate model they’re using for ongoing research on nuclear war impacts by studying the wildfire, according to Robock.

The observed rapid rise of the smoke plume, its spread, and photochemical reactions in the ozone layer provide new insights into the potential global climate impacts from nuclear war, the study finds.

For the next steps of a nuclear conflict climate modeling project, researchers will use refined nuclear war scenarios to determine the potential effect on the climate and food production on land and in the ocean, along with the potential for global famine. The scientists say their work on wildfire modeling will make the new work more accurate and credible.

Additional coauthors are from Rutgers; the University of Colorado, Boulder; the National Oceanic and Atmospheric Administration; the National Center for Atmospheric Research; and the Naval Research Laboratory.

Source: Rutgers University