"Beyond their effect on local weather, wildfires are becoming large enough, and intense enough, to have a material effect on climate," said John Fasullo, the lead author of the study. "In this work, we demonstrate their potential to influence climate variability. We are still in the process of understanding other aspects."
Fasullo and his colleagues concluded that the 2019-2020 Australian wildfire season resulted in 0.1 degrees Fahrenheit of cooling by mid-2020. The cooling, however, was tacked atop a continued net warming of the climate and had a negligible effect on slowing the pace of human-induced climate change from fossil fuel burning. [...]
The most intense wildfires produced pyrocumulonimbus clouds, or enormous plumes of smoke, ash and other aerosols, like sulfur dioxide, that towered to heights of up to 19 miles. Those fire-induced mushroom clouds ejected aerosols into the stratosphere, which surfed the jet stream eastward and gradually dispersed. The result was a volcano-like cooling of the global climate.
Smoke from wildfires has a range of effects on the Earth's climate. Black carbon actually absorbs solar radiation and heats the atmosphere, while other organic materials reflect or scatter light, yielding cooling. Smoke occasionally helps seed cloud development, blocking incoming sunlight but also retains outgoing heat. Sulphur dioxide aerosols can be converted into sulfuric acid, blocking incoming sunlight and also contributing to the destruction of ozone. Researchers noticed a "localized stratospheric ozone-hole."
Australian fires had bigger impact on climate than covid-19 lockdowns: the fires had a cooling effect while reduced pollution from lockdowns exerted a slight warming influence.