The fires that devastated Australia in 2019-2020 were the largest, sending smoke into the stratosphere like a massive volcanic eruption, with significant effects on the climate, according to a study published Thursday in the journal Science.
The stratosphere is the second layer that creates the atmosphere (where we live) above the tropics.
“We were very surprised by these results,” one of the two co-authors of the study and a professor at the Weissman Academy of Sciences in Israel told AFP Ilan Coren.
The magnitude of the smoke caused by the 1991 eruption of Pinatubo Mount in the Philippines is comparable to the second largest eruption of the 20th century.
The smoke “left Australia from the east and returned to Australia from the west two weeks later, which is unbelievable,” the researcher said. “I have never seen such a needle (smoke) in the stratosphere.”
According to the study he reached this height due to a combination of three factors. First, the intensity of the fire. Later, some of them were located much farther south, where the boundary between the tropics and the stratosphere is narrower. Finally, as they were located near an area of strong storms, this contributed to the rise in smoke.
It is important that they have reached this height: in low atmospheres, the smoke will only last for a few days or weeks. “But when it reaches the stratosphere, it will be between several months or years,” says Ilan Goran.
In addition, the wind is strong there, which has the effect of spreading the smoke very quickly.
“What you get is a thin blanket that covers the entire southern hemisphere for months,” Goran says.
The researchers were able to prove the existence of this smoke from January to July 2020, i.e. for six months, thanks to satellite observations. Later, it was very difficult to distinguish these fumes from other sources, but according to Ilan Koran, they are still “probably” a part of it today.
The main effect of this layer of smoke is to reflect and reverse a portion of the sun’s radiation: “it has a clear cooling effect,” especially in the oceans below, the researcher says. With serious effects, for example, photosynthetic algae, especially in the southern hemisphere, he adds.
In addition, a portion of the radiation can be absorbed by the smoke, rather than causing local warming, the effects of which are “not yet clear”.