A new study published in Scientific Reports says that smoke from bushfires in South-Eastern Australia in 2019 and 2020 got into the Earth’s upper atmosphere that ended up helping make the lower stratosphere’s temperature the highest since the eruption of the volcano Pinatubo in 1991.

Millions of tons of smoke aerosols were discharged into the Earth’s atmosphere as a result of the Australian bushfires.

Unusually, a substantial amount of the smoke reached altitudes as high as the lower stratosphere, which begins roughly 15 kilometers above Australia.

Around this time, the lower stratosphere also experienced very high temperatures for several months—the highest since 1992–1993.

Researchers Lilly Damany-Pearce and colleagues looked at whether the Australian bushfires’ smoke aerosols were to blame for the elevated stratospheric temperatures.

The authors tracked the volume of aerosols in the stratosphere across the southern hemisphere between December 2019 and 2020 using information from the CALIPSO and Suomi National Polar-orbiting Partnership satellites.

They also looked into aerosol levels observed by the same satellites between June 2012 and December 2018 for comparison.

The authors say that the first smoke plume reached heights of 16 km on December 31, 2019, and that a similar plume was seen on January 12, 2020. Aerosols of smoke eventually got to heights of 25 to 35 kilometers and were seen all through 2020.

To calculate the effect of these plumes on lower stratospheric temperatures, the authors used the United Kingdom Earth System Model version 1 (UKESM1) climate model.

The authors compared their models to control simulations of the current climate to see how smoke aerosol, ozone layer alterations, or a combination of these factors affected stratospheric temperatures.

The scientists simulated much higher temperatures in the lower stratosphere from January to June 2020 in comparison to the current climate in the smoke aerosol and ozone simulation.

From November 2019 to March 2020, the modelled temperature rise was about 0.65 degrees Celsius, which is about the same as the real temperature rise of 0.7 degrees Celsius during this time.

This shows that wildfire smoke aerosols were responsible for the elevated stratospheric temperatures in the model, according to the authors.

They claim that the observed temperature increase is the biggest since the eruption of the volcano Pinatubo in 1991, which caused the stratosphere to be filled with sulfate smoke aerosols.

The authors conclude that because climate change is anticipated to increase the frequency and intensity of future wildfires, this may raise the likelihood of more instances of stratospheric warming and ozone depletion due to smoke aerosols.

Image Credit: Getty

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