Australian bushfire smoke made its way around the globe

Researchers at the Weizmann Institute of Science have revealed that Australian bushfire smoke traveled around the world. The experts report that the fires injected vast amounts of smoke into the stratosphere, which led to high levels of atmospheric aerosols over the Southern Hemisphere in 2020. 

According to the study, the impact of the atmospheric aerosols was comparable to what would be produced by a volcanic eruption, and caused marked cooling over cloud-free ocean regions. 

From 2019 to 2020, the Australian bushfires released millions of tons of smoke particles into the atmosphere. Most of those particles settled to the ground in a matter of days. However, the researchers found that particles from fires in one corner of the country managed to blanket the entire Southern hemisphere for months. The persistent effects of these particles is similar to what is observed following explosive volcanic eruptions, which blast aerosols high into the upper atmosphere.

In early 2020, scientists observed record-breaking levels of aerosols over the Southern Hemisphere. The aerosol concentration even  exceeded what was measured after the eruption of Mount Pinatubo, the second-largest eruption of the 20th century. 

Using data from two satellite missions, study co-authors Eitan Hirsch and Ilan Koren traced the aerosols to particularly intense bushfires in southeast Australia.

The experts report that the enormous levels of wildfire smoke in the stratosphere were made possible by the intensity of the fires combined with their location within the mid-latitude cyclone belt. Here, energetic convection lifted the bushfire smoke into the stratosphere.

Once the particles were in the stratosphere, a strong current moved them eastward over the ocean to South America and back over the Indian Ocean toward Australia, explained the researchers. The particles ultimately settled around the entire hemisphere. 

“People in Chile were breathing particles from the Australian fires,” said Hirsch. “By sailing on an endless air current, these particles remained airborne for much longer than lower atmosphere smoke particles.”

Koren noted that for people on the ground, the air may have just seemed a bit hazier or the sunsets a bit redder. “But such a high aerosol optical depth – much, much higher than normal – means sunlight was getting blocked, just as it does after volcanic eruptions.” 

“So the ultimate effect of that smoke on the atmosphere was cooling, though we still do not know how much influence that cooling and dimming may have had on the marine environment or weather patterns.”

“There are always fires burning in California, in Australia and in the tropics. We might not be able to stop all of the burning, but we do need an understanding that the precise locations of those fires may grant them very different effects on our atmosphere.”

The study is published in the journal Science.

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By Chrissy Sexton, Earth.com Staff Writer