The scorching destruction of Australia’s Black Summer forest fires between 2019 and 2020 has given an ominous look at the fire’s reach in our warmer, drier world, and the impact of the unprecedented inferno is still being measured.
Only a few weeks ago, scientists noticed that the amount of smoke emitted from the flame into the atmosphere contradicted that of a large volcanic eruption. Now, according to researchers, the giant cloud of smoke was so huge that it heated up the stratosphere.
In a new study led by the first author and climate model Pengfei Yu of Chinese Jinan University, scientists have simulated the rise and evolution of the plume, showing that the worst documented wildfires in Australian history have a lasting impact on the air late in the region.
“Extreme wildfires can smoke in the upper troposphere and even in the stratosphere under favorable meteorological conditions,” the researchers write in their paper. “The higher the smoke is injected, the longer it will last and the greater its extent.”
In the case of the Black Summer fires, the flames sent nearly a trillion grams (about 0.9 teragrams) of smoke particles to the stratosphere, which according to the researchers is the largest amount still documented in the satellite era.
This smoke mass consists of different types of smoke particles, including organic carbon (OC, which includes brown carbon, also known as BrC) and black carbon (BC).
Each of these has different heat-trapping effects in the atmosphere, with BC as the heat-catching result due to the way it warms ambient air after absorbing sunlight.
According to the researchers’ calculations, the Black Summer plume was composed of about 2.5 percent black carbon, which helped produce a warming effect in the stratosphere that lasted the rest of the year.
“Simulations indicate that the smoke remained in the stratosphere throughout 2020 and that it heated the stratosphere by approximately 1-2 K. [Kelvin, equivalent here to 1-2 degrees Celsius] for more than six months, ”the team explains.
“Our study highlights that record-breaking veldfire smoke can persistently affect stratospheric dynamics and chemistry.”
In addition to warming the stratosphere, the researchers say the record-breaking smoking event would also have had a diminishing effect on ozone levels in the stratosphere, destroying ozone molecules in the mid-high latitudes of the Southern Hemisphere and likely making the ozone hole temporarily larger.
While the researchers acknowledge that there have been previous observations of aerosols producing stratospheric warming, this is the first time that scientists have measured the phenomenon to such an extent, given the record yields of the Black Summer fires.
The findings are presented in Geophysical research letters.