THE INTERVIEW. The ozone layer is improving, good news for the climate?

Good environmental news is extremely rare. So rejoice! On Monday, January 9, a group of scientists working under the auspices of the UN announced that the ozone layer, which protects the Earth from dangerous solar radiation, “on the right track” recover within forty years.

The problem of the hole in the ozone layer, which prevailed since the 1980s, has since been replaced by climate change. Despite the same evils (human activities), the remedies are more complex in one case than in the other. Explanations by Sophie Godin-Beekmann, research director of the CNRS and president of the International Ozone Commission, on the origin of the report released on Monday.

Is it a surprise that the ozone layer will recover in forty years?

In fact, it is the 195 countries that have ratified the Montreal Protocol since 1987 on ozone-depleting substances, gases in air conditioners, aerosol sprays, etc. It was always the intended scenario from the moment it fulfilled its obligations to reduce. We expected some slowdown due to the fairly long lifetime of these products in the atmosphere. What is new is that we actually see an increase in ozone in certain regions of the atmosphere, such as the upper stratosphere, about 40 km high, and Antarctica. In 2018, China saw banned emissions of CFC-11 (or trichlorofluoromethane), raising concerns about compliance with the Montreal Protocol. In the meantime, diplomatic discussions have allowed to put an end to them.

Is the effort at risk of backfiring or weakening?

There is a risk associated with geoengineering projects that are supposed to slow global warming by injecting aerosols into the stratosphere. This will make ozone-destroying gases even more dangerous. But the first risk is that we no longer follow the Montreal Protocol like China. Fortunately, we continue monitoring measures. We cannot think that everything is solved. We have to prepare a report every four years, every year the governments meet on this issue. The subject always remains on the table.

Protecting the ozone layer is also protecting the climate

Is this good news in the fight against climate change?

At the beginning, we are on another matter. The purpose of the Montreal Protocol is to protect humanity from ultraviolet B rays emitted by the sun, and it is ozone that deals with this at the atmospheric level. If destroyed, living organisms on the surface are at risk of increased regular radiation that causes DNA damage. This would be a very serious problem for plants, animals and humans with an increase in skin cancers. But we realized that these ozone-depleting substances are also much more powerful greenhouse gases than CO2, even if they are present in lower concentrations in the atmosphere. Banning or limiting the production of these gases also protects the climate.

Also read: Weather. There have never been more greenhouse gases in the atmosphere than in 2022

Can the climate benefit be measured?

It’s between 0.5°C and 2°C if you take into account the effect on plants, their absorption of CO2. If the hole in the ozone layer destroys them, it means less carbon absorption and more CO2 in the atmosphere.

To reduce CO2, you need to change your lifestyle

However, some ozone plays a negative role in global warming…

Yes, there is good ozone in the stratosphere, which has little effect on the climate, and bad ozone in the troposphere, which is 8 km high. It is an oxidant that attacks the lungs and is spoken about during episodes of ozone pollution, which is harmful to health. It is also a radiative gas that affects the climate. If it increases in the troposphere, it shows a warming effect on the climate. Ozone has many aspects, so it must be controlled in the atmosphere.

Why can’t what works for the ozone layer transfer to other greenhouse gases, especially CO2?

The gases that attacked the ozone layer were very specific gases released by very specific industries concentrated in a few sectors that agreed to deploy substitutes. The problem with CO2 is bigger. This means changing the way of life, the way of production. Our entire economy is based on oil, coal… That’s why countries find it difficult to reach an agreement on reducing greenhouse gas emissions. We are on a very dangerous trajectory for humanity. This will force us to take drastic action at some point.