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Ozone laws updated as report finds ‘Black Summer’ bushfires damaged the ozone layer

Australian federal Minister for the Environment and Water Tanya Plibersek has announced a new bill intended to introduce “stronger measures to reduce Australia’s greenhouse gas emissions and continue to play its part in helping heal the world’s ozone layer”.

In addition to ozone-depleting substances, the legislation also manages synthetic greenhouse gases such as HFCs like R134a that make up just two per cent of global greenhouse gas emissions but their high GWP causes a disproportionate impact on the climate.

“By working together, across national boundaries, we can move away from refrigerants that damage our shared environment,” said Minister Plibersek.

“The Montreal Protocol provides concrete proof that global cooperation can heal the planet. It is the world’s most successful international environmental treaty.

“The mark of its success is that the hole in the ozone layer is expected to be completely healed by mid-century.”

Tanya Plibersek
Tanya Plibersek

Separately, Minister Plibersek singled out a “crackdown” on ozone-depleting substances in a recent speech and announced that a nationwide Environmental Protection Agency would be “a tough cop on the beat to enforce those laws”.

Nations that ratified the Montreal Protocol (every UN member state) have phased out 98 per cent of ozone-depleting substances globally compared to 1990 levels.

Most of these substances are potent greenhouse gases (for example R12 has a GWP of 10,200) so the Montreal Protocol is also a major contributor significantly to addressing climate change.

Antarctic ozone hole
Antarctic ozone hole

Part of the government announcement included additional support for Palau, Federated States of Micronesia, Marshall Islands, Solomon Islands, Vanuatu, Tonga, Tuvalu, Kiribati, Nauru, Niue, Samoa and the Cook Islands to phase out ozone-depleting substances and especially HCFCs like R22.

“Without the Montreal Protocol, the world would have released the equivalent of about 10 additional years of carbon dioxide emissions by the end of the century, and we might have faced an additional 0.4 degrees Celsius of warming,” said Minister Plibersek.

However, all this progress could be undermined by the impact of smoke from major bushfires – which are increasing in frequency and intensity due to climate change – on stratospheric ozone, according to a study published in the Proceedings of the National Academy of Sciences of the United States of America.

Pyrocumulonimbus  storm clouds
Pyrocumulonimbus storm clouds

In addition to impacts on air quality at ground level by almost one million tonnes of smoke emitted by Australia’s ‘Black Summer’ bushfires in 2019 and 2020, pyrocumulonimbus (pyroCb) storm clouds generated by the intense fires funnelled smoke particles well above aircraft-cruising altitudes, where they contributed to a one per cent loss of the ozone layer.

This effectively cancelled out ozone recovery that had taken place over the past decade due to the adoption of the Montreal Protocol, according to Susan Solomon, a professor of environmental studies and chemistry at the Massachusetts Institute of Technology and lead author of the research paper.

“This fire offset that in one blow,” she said.

Professor Susan Solomon
Professor Susan Solomon

Unlike CFCs, which destroy ozone by releasing chlorine into the stratosphere, Professor Solomon and her coauthors found that as smoke particles travel upward through the atmosphere, they accumulate water and create an ideal surface for dinitrogen pentoxide (N2O5) to react.

This can indirectly limit the impact of ozone-depleting compounds, like chlorine monoxide (ClO).

Australia’s record-breaking Black Summer bushfires were of such a massive scale that the plume of smoke sent into the stratosphere was “comparable to a big volcanic eruption that happened in 2015,” according to Professor Solomon.

Using satellite measurements, Professor Solomon and her team found that nitrogen dioxide – which needs N2O5 to form at this altitude – reached its lowest level in 2 decades. Without nitrogen dioxide, “ClO will go up,” Professor Solomon explained. “If ClO goes up, then you’ll get ozone loss.”

It is also thought that smoke can alter the properties of polar stratospheric clouds that help form the ozone hole every spring. Through this method, ozone loss could be as much as 25 per cent at the poles.

The risk of mega-fires like Black Summer keeps growing as the planet continues to warm.

Professor Solomon said smoke from these fires will not halt ozone recovery completely but it could “slow it down significantly” in years with large fires.

Ozone depletion would have increased tenfold by 2050 compared to current levels had action not been taken under the Montreal Protocol.

This would have resulted in millions of additional cases of melanoma, other cancers and eye cataracts.

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