It is known that the ozone hole is being remedied, but now we have the evidence that this takes place thanks to the CFC announcement. That is, thanks to a political agreement.
The ozone hole is closing and, for once, we can attribute the merits with (almost) absolute certainty. Mit scientists managed to prove that progress in reducing the ozonosphere eroded area above Antarctica depend on the international call for chemical compounds that erode ozone And not, for example, from the natural variability of the atmosphere. Their discovery, explained in detail on Natureis the first quantitative demonstration of the man’s contribution to the resolution of a global environmental problem. An injection of trust These difficult times for international cooperation.
Ozone hole: origins of a healing
The ozonosphere is that area of the terrestrial stratosphere, between 15 and 50 km in height, where atmospheric ozone is formed, a subtle but effective shield which protects the earth from the ultraviolet radiation of the sun. The effects in the destruction of the ozone in the atmosphere of chlorophalocarbons (CFC), artificial gases once used as refrigerants in refrigerators, air conditioners, insulating and propeller substances for aerosols, have been known since the 70s (We wrote about it widely here).
In 1985 a group of scientists from the British Antarctic Survey discovered a “hole” in the ozonosphere which opened in correspondence with Antarctica during the southern spring (from September to December) and which allowed UV rays to reach the earth’s surface, causing health problems such as melanomas and eye damage.
To sanction the progressive abandonment of the harmful substances of the stratospheric ozone was what is considered the most successful environmental treatythe Montreal protocol. In 1987 the first 90 nations joined it: today they are 197, that is, all the countries represented at the UN. The agreement, which became operational in 1989 but perfected and adapted over the years, requires stringent limits and a path of reduction in view of the definitive abandonment of all compounds harmful to ozone, including chlorophalocarbons.
The ozonosphere is close: is it a coincidence, or do we have to do with it too?
In 2016, a research published on Science And coordinated by Susan Solomon, atmosphere chemistry at the Massachusetts Institute of Technology (MIT) in Boston, reported some key evidence of the recovery of stratospheric ozone. After almost 30 years from the Montreal protocol A reduction in the missing area of Ozone was started to observe especially in Septemberthe moment of the year in which the “hole” usually appears. In September 2015, the study noted, the ozone hole was about 4 million square km smaller than it was in 2000.
However, it was observations qualitative. That is, it was not possible to say safely if the recovery was attributable to the CFC & Co call. o to climatic variability (for example, the influence of climatic phenomena such as El Niño or the Niña, or the polar vortex).
The digital footprint of our virtuous actions
In the new study, Solomon and colleagues They borrowed a set of techniques used in the climate sciences To precisely identify the causes of the recovery of stratospheric ozone. In particular they exploited a method called fingerprinting (“digital footprint”)which allows you to isolate the influence of specific factors from the “noise” of other phenomena natural and meteorological.
This approach was used in climatology to slide the effect on the climate of anthropic activities from that, for example, of volcanic emissions. Each process has a recognizable digital imprintand learning to recognize it is essential to understand the impact of our actions and try to improve. The development of fingerprinting earned the climagoologist of the University of Hamburg (in Germany) Klaus Hasselmann the nobel for physics in 2021 – together with the Japanese climatologist Syukuro Manabe and, for the other half, to our Giorgio Parisi.
Solomon and colleagues used fingerprinting to identify a different anthropogenic signal, that is the impact, on the recovery of ozone, of the reduction of CFCs. They generated various simulations of the global atmosphere to generate many “parallel worlds” in which some starting conditions changed: for example, one in which there had been no increases in greenhouse gases or in the harmful substances for ozone, and in which, therefore, any fluctuation of the ozonosphere was attributable to natural variability, or others that provided that only the substances that impoverish the ozone were in decrease.
The comparison of these simulations made it possible to understand how the ozonosphere varied in the various seasons and different altitudes based on the starting conditions. Thus making the fingerprint of the recovery of the ozone due to the implementation of the Montreal protocol emerge more and more clearly. When scientists used this “digital imprint” to interpret the satellite observations of the ozone hole on Antarctica from 2005 to today, they concluded that It is possible to affirm with a 95% confidence interval that the recovery is due to the reduction of compounds harmful to ozone.
Together we can perform “impossible” businesses
According to Solomon, if the recovery continues at this rate A year will come, probably around 2035, in which the ozone hole on Antarctica will not appear. And, over time, this change will consolidate. All this «It also gives us the trust of being able to solve environmental problems. What we can learn from the studies on ozone is how several countries can quickly follow these treaties to reduce emissions »concludes Peidong Wang, a Mit researcher in the Solomon group and the first author of the work.
