Thursday, December 9

The hole in the ozone layer returns to record levels: How does it affect the climate?

Does what happens in the stratosphere stay in the stratosphere? How does the ozone hole affect climate and meteorology? According to data from the Atmosphere Monitoring Service of the European Copernicus network, this 2021 season the hole in the Antarctic ozone layer is once again at record levels, both in extent and depth, despite the historic international effort to ban CFC gases that promote ozone destruction.

After an especially small ozone hole in 2019 that sparked a wave of optimism, last year the ozone hole became quite large again, and it lasted until the end of December. An unprecedented fact. This year it is also touching all-time highs, both in size and depth, and it does not seem likely to close, although in principle it should have reached its annual maximum.

But beyond the multiplication of UV radiation on the frozen continent, how does the ozone hole affect us? Is climate change and global warming getting worse, or is it just a matter of tan penguins and radiation on doomsday algae?

The first indications suggest that global warming may favor the destruction of ozone in the stratosphere. However, the hole in the ozone layer also has effects on the climate and meteorology that are still quite unknown to science.

To try to better understand the effects of the ozone hole on the Earth’s climate system, Euronews contacted Vincent-Henri Peuch, Director of Atmosphere Surveillance Service by ECMWF Copernicus.

Last year, a study published in the journal Nature he saw a clear correlation between a possible 2019 ozone layer recovery, which the study attributed to the Montreal Protocol’s ban on CFCs, and a “pause” in atmospheric circulation trends in the southern hemisphere.

Starting in the 1990s, scientists observed several changes in weather patterns in the southern hemisphere that are attributed to ozone depletion. Among them, the reduction of rainfall over Australia or the extension of the tropical rain belt from South America to Uruguay or northern Argentina, opening new fields for agriculture in lands that were previously too dry.

The Nature study was updated in January 2020, just after the hole in the ozone layer reached the smallest size ever recorded, sparking optimism about its future evolution.

Sing victory too soon?

Then came the 2020 season, when scientists looked at the longest-lasting ozone hole ever recorded, which lasted until the end of December, with a massive surface area of ​​almost 25 million square meters at its peak.

And now the ozone layer is behaving unexpectedly again this year, with a sudden growth in September, again to record levels.

Meanwhile, at the other end of the planet, a surprising ozone hole in the Arctic appeared in March 2020, right in the harshest of confinements due to COVID-19. Two recent studies indicate that it could be due to global warming reports the Washington Post.

On the subject of Nature’s 2020 study, Vincent-Henri Peuch believes that we may have claimed victory too soon. “The work said that the Montreal Protocol for reducing gases had made it possible not only to make the hole in the ozone layer disappear, but also to counteract the progression of the polar vortex towards the South Pole by pushing it out”. It was published in 2020, after an especially small ozone hole. I think it was a bit daring, because we have seen that there is a very strong variability from one year to the next. “

All that for nothing?

Does this mean that the Montreal Protocol to ban gases that deplete the ozone layer is ineffective? No, regarding the reduction of CFC gases, says the director of CAMS. “We are on the right track. For chlorine and bromine, levels have started to decline since the Montreal Protocol, but when it comes to the ozone layer we still have no signs of a proper recovery.”

Global warming, by cooling the stratosphere, favors the destruction of ozone. “If we continue to avoid CFC emissions, we will return to normal, but more slowly than anticipated, possibly due to climate change,” Peuch explains to Euronews. “We expect that the hole in the ozone layer will close in 2060 or 2070, so the two or three year scales do not give enough perspective.”

What is the impact of the ozone hole on weather and climate?

Is widely accepted that the ozone hole pushes the polar vortex to the South, concentrating it around the Pole, and as it shrinks, its winds also get stronger. Furthermore, warming has a tendency to cool the stratosphere.

This has had impacts on the atmospheric circulation of the southern hemisphere. Some of these impacts are well understood by scientists, but Vincent-Henri Peuch cautions against jumping to conclusions: “These are fluids, so everything is connected. These planetary motions are not independent, but precisely how do they interact?”

“It is difficult to detect very direct cause and effect mechanisms,” says Peuch. “We look at the long-term trends and we get to understand that if the polar vortex is smaller, the Hadley Cell could get bigger, and we can see how the weather patterns, precipitation here and there could be modified.”

For Peuch, although climate scientists today understand some of the links between the ozone hole and weather patterns, the interactions between the stratosphere and the troposphere are still not very well understood. “It is still difficult for climate models to reproduce what happens in the stratosphere, we have far fewer observations than for the troposphere.”

“We still have a lot of work ahead of us to properly understand the relationship between what happens in the stratosphere and the impacts at our level, on meteorological phenomena, rains, storms, etc.”, he says. “It would be an absolute dream to connect stratospheric anomalies with meteorological trends, it would incredibly improve our seasonal forecasting capabilities, as for our Climate Change Service, but as far as I know there is no such model.” Peuch believes that science needs to remain humble in its ability to make direct links.

The hole in the ozone layer actually has a small cooling effect, allowing some of the greenhouse gases to escape into space.

UV radiation has some impacts on the Antarctic ecosystem, which are not yet fully understood. They favor the decomposition of organic matter, increasing the release of greenhouse gases and warming the ocean. UV radiation does not have a direct heating effect.

Its incidence in skin cancer, eye or immune system disorders is well known.

So what is the impact of climate change on the ozone hole?

Global warming makes our troposphere warmer, but it tends to cool the stratosphere, reinforcing the ozone-depleting capacity of the polar vortex.

Ozone destruction mainly affects the southern hemisphere during the spring (August-September) because the necessary conditions are more common at the south pole: extreme cold (-80º C), polar stratospheric clouds and CFC gases to create a hole in the ozone layer.

Sulfur dioxide, like the one that the La Palma volcano is now emitting incessantly, is also a gas capable of destroying ozone when it is in the stratosphere.

According to some studies, the puzzling ozone hole in the Arctic of March 2020 was possibly caused by record warm temperatures in the North Pacific.

The 2019 tiny ozone hole in Antarctica it was caused by a rare and sudden warming of the stratosphere.

So climate change is likely to make these conditions more prevalent. “We hope that climate change will delay the recovery of the ozone layer,” says Peuch, recalling that, given the variability of previous seasons, we still cannot say that there is a clear trend in the recovery of ozone.

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