Scientists confirm the effectiveness of the Montreal Protocol for the restoration of the ozone layer

The measures taken more than thirty years ago had a positive effect on the earth’s atmosphere.

The chemicals that destroy the ozone layer also have a significant effect on atmospheric circulation in the Earth’s southern hemisphere. A study published in Nature shows that these atmospheric changes are stopped and reversed – thanks to the Montreal Protocol, which limits emissions of substances that destroy the ozone layer.

“This study complements a growing body of evidence that proves the effectiveness of the Montreal Protocol,” said Antara Banerji, lead author of the paper. “The treaty not only stimulated the restoration of the ozone layer but also led to recent changes in air circulation patterns in the Southern Hemisphere”.

“The objective of this work is to prove our hypothesis that ozone reduction actually leads to changes in atmospheric circulation, and this is not just a coincidence,” Banerjee explains. First, using computer modeling techniques, scientists showed that the observed processes in the atmosphere cannot be caused only by natural shifts of winds in the polar regions. Then, the authors separately analyzed the potential effect of ozone and greenhouse gases on these shifts.

The ozone hole above the South Pole of our planet was first discovered in 1985. It appeared annually in August and dragged on by December. Such depletion of the ozone layer led to air cooling, which, in turn, strengthened the polar vortices. As a result, this led to the migration areas of wind’s jet stream as well as the displacement of arid regions on the border of the tropics closer to the South Pole.

After the adoption of the Montreal Protocol in 1987, the concentration of harmful chemicals that provoke the appearance of the ozone hole began to gradually decline. Since 2000, the average annual area of the ozone hole above Antarctica has been gradually decreasing. As the study conducted by Antara Banerjee shows, around the same time, the winds displacement towards the South Pole also stopped.

Calculations have shown that gases such as carbon dioxide (CO2) also affect wind migration. But the halt of this process and its partial reversal can only be caused by the influence of ozone. If it were not for the constantly increasing concentration of carbon dioxide in the atmosphere, the reverse displacement of the jet flows would be more active.

Scientists say that by the middle of this century, the wind cycle in the southern hemisphere will have to fully normalize. Around the same time, a large ozone hole above Antarctica should disappear.