Research shows that wildfires can significantly impact the stratospheric ozone layer by injecting aerosols that alter ozone levels through complex reactions, underscoring the need for continued vigilance in climate change research.

In a discovery that underscores the fragile balance of our planet’s atmosphere, scientists from China, Germany and the US have discovered an unexpected link between large-scale wildfires and the chemistry of the ozone layer. Published today (July 12) in the journal Science Developments This research shows how bushfires like the 2019/20 Australian disaster are affecting the stratosphere in previously unknown ways.

Ozone layer restoration and challenges

The ozone layer, a vital shield that protects life on Earth from harmful ultraviolet (UV) radiation, is on the road to recovery thanks to the Montreal Protocol. Adopted in 1987, this landmark international agreement has successfully halted the production of many substances that deplete the ozone layer. Significant signs of recovery have been seen in the ozone layer in recent years, a testament to global cooperation and environmental policy.

But the stability of this vital layer of the atmosphere now faces a new and unexpected challenge. During the 2019/20 bushfires in Australia, researchers observed a sharp increase in stratospheric aerosols, small particles that can affect climate, health and atmospheric chemistry.

New ideas for wildfire research

Using state-of-the-art satellite data and numerical models, the research team successfully demonstrated the impact of wildfires using a new phenomenon, smoke vortex (SCV).

“The SCV is a powerful smoke vortex that carries forest fire emissions into the stratosphere, reaching heights of up to 35 kilometers,” explained Professor Han Su from the Institute of Atmospheric Physics of the Chinese Academy of Sciences, one of the researchers involved, the authors of the study. “This process led to at least a doubling of the aerosol load in the middle stratosphere of the Southern Hemisphere. Reaching such a high altitude, these aerosols initiated a series of heterogeneous reactions that affected the ozone concentration.”

Consequences of ozone dynamics caused by forest fires

The international team found that these aerosols caused by forest fires promote heterogeneous chemical reactions that paradoxically lead to both the depletion of the ozone layer and the increase of its content in various layers of the atmosphere.

They found that although significant ozone loss occurs in the lower stratosphere, increased chemical reactions on aerosols at higher altitudes, namely the middle stratosphere, lead to increased ozone. In the southern mid-latitudes, this complex interaction prevented about 40% (up to 70%) of the ozone loss observed in the lower stratosphere in the months following large-scale wildfires.

Urgency of current research

Why does it matter?

“Our study demonstrates an unexpected and important mechanism by which the absorption of aerosols such as soot in wildfire smoke can create and sustain huge smoke-laden vortices that spread thousands of kilometres. These vortices can persist for months, transporting aerosols deep into the stratosphere and affecting the ozone layer in different ways at different altitudes. This underscores the need for continued attention and research as climate change progresses,” said Professor Yafang Chen, another corresponding author from the Max Planck Institute for Chemistry.

Future directions for climate change and ozone research

The ozone layer’s role in filtering UV radiation is critical to the protection of all life on Earth. The Montreal Protocol’s success in reducing substances that deplete the ozone layer was a tremendous achievement, but new findings highlight that natural events exacerbated by climate change pose additional risks to this fragile layer. As wildfires increase in frequency and intensity due to global warming, the formation of SCVs and their effects on the stratosphere could become more common, threatening the delicate balance of the ozone layer.

Understanding these newly discovered atmospheric processes is vital as we continue to combat climate change. This research opens up new avenues for investigating how wildfires and other climate events could impact stratospheric chemistry and ozone dynamics in the future.