• The smoke emitted into Earth's atmosphere by the 2019–2020 bushfires in Australia reduced the ozone layer surrounding the Earth.
• The fires caused a 1 per cent loss in ozone concentration.
• The increasing intensity and frequency of wildfires could slow its recovery.

The smoke emitted into Earth's atmosphere by the bushfires of 2019–2020 in Australia has reduced the ozone layer surrounding the Earth. This is explained in a study published by the Massachusetts Institute of Technology (MIT) by an international team of researchers, entitled "On the stratospheric chemistry of midlatitude wildfire smoke". In particular, the smoke from the devastating Australian fires caused a 1 per cent loss of the ozone layer: an amount that could take a decade to regenerate. Furthermore, the study suggests that the increasing intensity and frequency of wildfires due to climate change could slow the recovery of this important gas.

240 days of fires razed 12 million hectares of forest to the ground

The ozone layer – which forms part of the stratosphere, the second layer of Earth's atmosphere – absorbs ultraviolet radiation emitted by the sun and consists of a high concentration of ozone molecules. Using satellite observations, the researchers discovered that smoke from the burning fires reacted with nitrogen in the stratosphere, causing ozone depletion.

Study co-author Kane Stone of the Massachusetts Institute of Technology stated that the reduction occurred between March and August 2020, that is, as soon as the fires died down after 240 consecutive days during which fire had literally devoured the forests of the country's south-east, killing 33 people, destroying more than three thousand homes and razing 12.6 million hectares of forested areas to the ground.

A decade of ozone recovery gone up in smoke

The reduction of ozone in the atmosphere first began to be discussed in the 1980s, when certain scientific studies discovered the phenomenon of the ozone hole: the name given to the reduction in ozone that is concentrated primarily above the Antarctic continent and that "closed" in December 2020. Among the principal causes of the hole's formation, scientists identified the use of substances known as chlorofluorocarbons (CFCs), the gases used in refrigerators and aerosol cans, which were gradually phased out following the signing of the Montreal Protocol in 1987.

Once the dispersal of CFCs into the atmosphere was halted, a progressive improvement in atmospheric ozone levels was observed: sunlight, in fact, continuously reacts with oxygen, creating ozone molecules. In particular, over the last decade a recovery of 1 per cent was recorded. The same amount that the smoke cloud formed during the fires – three times larger than any previously recorded smoke cloud – dissipated within a year and a half.

Collective action to address the climate crisis

The director of the Centre for Atmospheric Chemistry at the Australian University of Wollongong, Clare Murphy, speaking to the Guardian, stated that more intense fires in the future – as projected by current climate models – will slow the recovery of the ozone layer.

Yet the efforts to address the ozone hole over Antarctica have been a successful example of collective environmental action. "There is no reason why humanity cannot come together and solve the climate crisis too," was Murphy's comment.