Australia’s Black Summer—as the 2019-2020 bushfire season has been called—charred 13.6 million acres. The intense blazes released vast plumes of smoke that rose an unprecedented 19 miles up into the atmosphere, and created never-before-seen wind patterns high in its upper layers, reports Maria Temming for Science News.
Between December 29, 2019, and January 4, 2020, fires in southeast Australia became so intense that their smoke formed at least 18 massive fire-borne thunderclouds called pyrocumulonimbus (pyroCb) clouds, reports Maddie Stone for the Washington Post.
These anvil-shaped pyroCb clouds can form when an intense blaze creates a strong updraft that sucks a plume of super-heated air and ash high up in the sky where cooler air drops the plume’s temperature. If there’s enough moisture in the air, huge white clouds up to 40,000 feet, or about 7.5 miles, tall can form, capable of hurling bolts of lightning and spewing embers that can cause new fires to erupt, reported Alexandra Witze for Knowable in 2019.
But, according to the Post, these pyroCbs also function like chimneys, delivering blasts of smoke laden with particles called aerosols high into the atmosphere. In Australia, these pyroCb clouds shot somewhere between 300,000 and 900,000 metric tons of smoke into the stratosphere, more than any other fire on record, per Science News. One exceptional plume got launched 19 miles up, circled the entire planet and created novel wind patterns that swirled around it for more than two months, the researchers reported last month in the journal Geophysical Research Letters.
Science News reports that researchers still aren’t sure what caused the stratospheric plume of smoke to become encircled in its own private vortex. Researchers are also waiting to find out if the swirling, ashen cloud did lasting damage to the ozone layer.
As the plume rose into the stratosphere, it displaced the typically ozone-laden air with its high concentrations of water and carbon monoxide, and Pengfei Yu, climate scientist at Jinan University in China who was not involved in the new research, tells Science News that the smoky cloud may also kick off a chain of ozone-destroying chemical reactions.
Unexpectedly, studying these unusual plumes is also helping researchers zero in on what atmospheric havoc to expect from other catastrophes, such as the detonation of a nuclear bomb, according to the Post.
Alan Robock, a climate scientist at Rutgers University who studies the atmospheric ramifications of nuclear blasts, tells the Post that his models of nuclear warfare had predicted that massive plumes of smoke would reach the stratosphere. Now, in light of the unprecedented plumes from the Australian fires, he says, “nature has done the experiment to validate our models.”
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