For the first time the concentration of the gas that causes the ozone hole is decreasing

After about 30 years of trying to gradually eliminate hydrochlorofluorocarbons, harmful gases that deplete the ozone layer and warm the planet, researchers have detected for the first time a significant drop in the levels of these substances in the atmosphere and a consequent reduction in the ozone layer depletion potential:This is reported by new research conducted by scientists from the University of Bristol and published in the scientific journal Nature.The authors explained that global concentrations of such gases peaked in 2021 – five years earlier than expected – and that since then there has been a decline which represents a significant "milestone" in blocking dangerous ultraviolet solar radiation.“This is a remarkable success story that shows how global policies are protecting the planet,” commented Veerabhadran Ramanathan, a climate scientist at the University of California who was not involved in the study.

It was more than 50 years ago when researchers they ran that a hole was forming in the ozone layer over Antarctica, allowing dangerous and carcinogenic radiation to reach the Earth's surface.The ozone layer, in fact, is a fundamental screen whose formation takes place mainly in tropical latitudes and which has allowed the development and maintenance of life on Earth, as it completely absorbs the UV-C component and 90% of the UV- B of solar ultraviolet radiation, which has a sterilizing effect on many life forms.The reduction of this layer occurs mainly due to halogenated compounds of anthropogenic source, which reach the stratosphere and strip an oxygen atom from ozone molecules, degrading them to normal molecular oxygen. Among the main culprits were identified chlorofluorocarbons (CFCs), which with a single chlorine atom could destroy thousands of ozone molecules and remain in the atmosphere for hundreds of years.

This led governments to sign the Montreal Protocol in 1987, the international environmental treaty that plans to phase out the production of CFCs.This led richer countries to halt production and provide assistance to lower-income nations, eventually leading to a ban in 2010. However, these substances were replaced by other compounds – hydrochlorofluorocarbons (HCFCs) – which have a tenth of the ozone reduction potential but which could be responsible for other far from insignificant damage.This led to the decision to also abandon these substances and this transition – in light of the new data entered into the study Nature – was “quite successful” according to Luke Western, researcher at the University of Bristol and co-author.The scientist explained that it takes decades for production bans to result in fewer products sold and therefore in fewer HCFCs in the atmosphere.

This phenomenon seems to have come true in recent years, given that by analyzing the data from global air monitoring programs it was discovered that such substances peaked in 2021 and have declined since then.«This milestone is a testament to the power of international cooperation.For me, this signals the potential to do much more and gives me hope for the climate." he commented Avipsa Mahapatra, director of the climate campaign of the Environmental Investigation Agency, an NGO founded in 1984 which aims to investigate and publicize crimes against the environment and wildlife.He then added that the success of the Montreal Protocol could inspire efforts to curb other types of pollution that heat the planet given that the agreement would have the merit of having avoided millions of cases of skin cancer and up to an additional degree Celsius of warming.Finally, however, Mahapatra added that, despite the good news, "the work is not yet finished" because just as HCFCs have replaced CFCs, hydrofluorocarbons (HFCs) are now in use which are still considered "super climate pollutants".Ultimately – added co-author Luke Western – the transition away from fossil fuels will be much more complex than to curb the production of ozone-depleting substances since the Protocol covered a relatively small industry and only required companies to change their products, not their entire business.With climate change, “in a certain sense we are faced with a bigger beast,” he concluded.

[by Roberto Demaio]