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Smoke from Australia bushfires thin ozone layer, research finds

By Justin Malone, Staff Writer

According to new research, intense amounts of smoke from the catastrophic “Black Summer” bushfires that spread across Australia during late 2019 and early 2020 created chemical atmospheric changes which thinned ozone in the Southern Hemisphere.

The study, conducted by professor Peter Bernath and a team of researchers at the University of Waterloo in Canada, found that wildfires like the “Black Summer” bushfires present a new threat to the stratospheric ozone layer. It also concluded these catastrophic wildfires could be cause for additional damaging health effects. This research was published in Science on March 18.

The ozone layer, which is a part of the Earth’s stratosphere, filters most of the Sun’s harmful ultraviolet radiation and protects humans from serious health issues, including skin cancer, premature skin aging and cataracts.  

Ultraviolet radiation also detrimentally impacts the environment since it can hinder photosynthesis and growth processes in plants. According to the World Health Organization, a 10% decrease in ozone could lead to a 15-20% increase in UV exposure, depending on the biological process. This ultraviolet radiation also produces harmful health effects on animals including skin cancer, deprived immune response and effects on the eye.  

The “Black Summer” bushfires produced pyrocumulonimbus clouds, which are thunder clouds produced by intense heat that drive smoke particles into the stratosphere. These molecules, including chloric nitrate, chlorine monoxide and hypochlorous acid, destroy and deplete the ozone layer.

As a result, the chloric acid produced unexpected disturbances in stratospheric gases, and the researchers reported these findings were beyond anything in the previous 15 years of measurements. 

They also found that while chloric acid increased in the stratosphere, the presence of ozone, nitrogen dioxide and hydrochloric acid all decreased.  

Bernath and his fellow researchers utilized the Atmospheric Chemistry Experiment (ACE) satellite and data from the Canadian Space Agency to observe these changes in atmospheric processes and chemistry over the middle latitudes in the Southern Hemisphere. The ACE satellite records changes in the atmosphere that cause the depletion of ozone in the stratosphere, specifically by measuring how different molecules in the atmosphere absorb light according to wavelength. 

The team’s analyses found that the ACE satellite observed enhanced chemicals in the stratosphere in the Southern Hemisphere from January to November of 2020, primarily due to the “Black Summer” bushfires. The satellite detected this with its infrared imager instrument, the Fourier Transform Spectrometer. 

Their research also discovered that many organic molecules caused average ozone concentrations in the stratosphere to significantly increase in January and March of 2020, compared to the average observations from previous years. However, these chemical effects were only temporary because: “Starting in April 2020, mid-latitude ozone levels began to decline in the lower stratosphere compared with the average of all other years and remained low through to December 2020,” according to the study.  

Overall, chemical imbalances in the stratosphere are causing the ozone layer to be threatened by continuing wildfires, directly jeopardizing the impacts of restoring ozone levels through efforts such as the Montreal Protocol on Substances that Deplete the Ozone Layer. The Montreal Protocol is an international agreement signed in 1987 that phased out the production of ozone-depleting substances. 

Bernath and his colleagues state that the protocol, “has been successful in reducing the atmospheric abundances of chlorine- and bromine- containing molecules that destroy stratospheric ozone and are responsible for the Antarctic ozone hole.”  

These imbalances also come at a time when rising temperatures and drier weather are resulting in more frequent wildfires, further endangering global efforts to restore the ozone layer. In a report published by the United Nations Environment Programme in February, the number of extreme wildfires will increase up to 14% by 2030 and 30% by 2050.  

Since the number of wildfires like the “Black Summer” bushfires are only growing, the efforts to restore the ozone layer are constantly being slowed, more costly and threatened by extreme scenarioss. 

“As severe wildfires rise in number, they will play an increasingly important role in the global ozone budget,” the study concluded. 

Photo courtesy of flickr.com