During Australia’s Black Summer bushfires, vast tracts of forest and the lives of billions of animals were extinguished in ash and smoke. The resulting haze has rocked major cities, sparked deadly health emergencies, and obscured remote glaciers.
Now researchers have directly traced how some of this burned biomass contributed to the strongest stratospheric warming in three decades and also interfered with the Antarctic ozone hole.
By combining satellite data with surface observations of aerosol behavior in computer models, University of Exeter statistician Lily Damney-Pearce and her colleagues were able to track the smoke as it floated through our planet’s atmosphere.
The fires burned more than 5.8 million hectares and were so furious that they created their own weather system, including smoke-filled thunderstorms (pyrocumulonimbus) that lasted for days.
As the researchers explain, these systems and their vortices carry the smoke significantly higher, with the sun’s rays heating the dark particles and causing them to rise even higher, in a process called self-elevation. say
The first vortex, detected on December 31, 2019, reached an altitude of 16 km (about 10 mi). Then from January 12, 2020 another column was finally detected up to 35 km in the sky, in the stratosphere, and persisted for 2 months.
“Over a time of one month, the spray crest floated across the South Pacific and was obviously distinguished by [NASA’s instrument] CALIOP, as well as by surface lidars and a sun oriented photometer. From South America”. The group composes on their paper.
During this time there was a sudden increase in global average temperature of 0.7 °C (1.8 °F).
The unusual temperature persisted for four months, and the researchers’ climate model showed that the temperature could not be explained without the injection of 0.81 teragrams of smoke particles detected by satellites into the stratosphere.
This was the largest temperature increase in Earth’s stratosphere since the 1991 eruption of the Panatubo volcano, Damany-Pearce and team note.
While the planet’s surface has cooled by about half a degree Celsius thanks to diffuse clouds of sunlight-blocking particles, the absorption of infrared radiation by particles in the stratosphere has caused this layer of the atmosphere to melt.
Volcanic aerosols released into the atmosphere by such eruptions are also known to deplete the ozone layer, and recent studies have shown that particles from wildfires can do the same.
Chemical reactions on the surface of smog particles use ozone molecules. So the researchers mapped the vertical distribution of ozone in the Southern Hemisphere in 2020 and found further evidence of smog-induced ozone depletion.
The smog increased the duration of the ozone hole over Antarctica and disrupted the Antarctic polar vortex, which normally begins to break up in late spring.
“Ozone depletion acts to increase the strength of the polar vortex, by reducing stratospheric heating and the thermal wind balance, giving a positive criticism that postpones the separation of the polar vortex,” Damany-Pearce and partners wrote in their Explained in the article.
“This, thus, added to a drawn out ozone opening during the 2020s.”
The Antarctic ozone hole hit near-record levels in 2020, and now we know why. The new research revealed how these smoke-induced changes also affected temperatures by strengthening the polar vortex. This led to an unusually cool Southern Hemisphere spring of 2020.
Meanwhile, closer to Earth’s surface, more disturbing smoke particles floated above the ocean and fell into the ocean, creating a feeding and breeding frenzy for plankton that created a suffocating bloom of these microorganisms.
Nearly three years and several large fires later, it is more alarming than ever to see what large, varied and far-reaching effects wildfire smoke can have.
