The ozone layer is a region of concentration of ozone molecules (O3) in the Earth’s atmosphere. This layer is located at an altitude between 19 and 30 km. Its function is to protect all living species that inhabit the Earth from the sun’s ultraviolet radiation. Scientists have found a new hole, bigger than any known at the time.
In the 1980s, the scientific community began to warn of a new environmental threat. The issue of a huge hole in the ozone layer over Antarctica took hold in society from 1985 onwards and, especially, in the following two decades.
New terms related to the hole in the ozone layer began to resonate around the world: ‘chlorofluorocarbons’, ‘global warming’ or ‘climate change’, although many are still completely unaware of their meaning and even denying them.
In relation to human health, the population began to know its possible consequences: melanomas, cataracts, skin cancer and weakening of the immune system. And make intensive use of sunscreen, which in turn generates other types of pollutants and skin problems.
the ozone layer
The ozone layer is located in the lowest region of the stratosphere and presents a more or less diffuse area, without clear boundaries like other layers of the atmosphere.
What characterizes this area, as its name suggests, is its high concentration of ozone gas, a molecule formed by three oxygen atoms, capable of absorbing ultraviolet radiation. In fact, it absorbs between 97 and 99% of the high-frequency ultraviolet radiation coming from the sun.
In the lower regions, ozone is produced by electrical storms and, when its concentration is very high, it can be a pollutant. This is because it is a highly reactive and very oxidizing substance.
holes in the ozone layer
The expression “hole in the ozone layer” is not literal. The problem is a thinning of the thickness of this layer as a result of the lower concentration of ozone gas. In turn, this thinning and density loss is variable and generally fluctuates with the seasons.
This thinning of the ozone layer is mainly produced by the presence of pollutants that react with the ozone, breaking it down. Among them, stratospheric aerosols derived from sulfur produced by volcanoes, which have a punctual influence, stand out.
But there are other compounds of anthropogenic origin that cause sustained decreases in ozone concentration over time, halocarbons and chlorine-derived gases, mainly chlorofluorocarbons (CFCs). These molecules, used as propellants and coolants, remain stable in the atmosphere for up to 200 years; when they reach the stratosphere, ultraviolet radiation, which is stronger up there, dissociates the molecule, releasing chlorine that, when reacting with ozone, breaks it down.
The reduction in the amount of ozone in the stratosphere allows the passage of ultraviolet light with greater intensity, which causes greater release of chlorine from CFCs. This concludes in a negative feedback where the destruction of the ozone layer causes more destruction of the ozone layer.
To prevent this from happening in aeternumIn recent decades, CFCs have been replaced by other less dangerous compounds, such as hydrofluorocarbons (HFCs) for refrigeration or isobutane as a propellant. But all those that have been released for more than half a century remain in the atmosphere, causing this degradation.
A new hole, a new threat
The hole in the ozone layer in Antarctica is already well known. Its dynamics have already been studied by scientists: during the southern summer and autumn, ozone levels partially recover, but the cold of winter favors a greater concentration of chlorine compounds, and every year, in spring, the hole is rebuilt. .
There are others of smaller dimensions, over the north pole, and another hole over Tibet, observed in 2006 and 2011.
But a new scientific publication in AIP advances carried out by a team of scientists at the University of Waterloo in Ontario, Canada, warns of a hole in the ozone layer that has gone unnoticed until now, and which is now more than 20 years old.
Unlike the hole in Antarctica, which appears only in the spring, this one remains throughout the year, forming a strip between the tropics. The hole’s magnitude is similar to that of Antarctica, but its size is seven times larger.
The year-round large tropical O3 hole could cause great global concern as it could lead to increases in ground-level ultraviolet radiation and affect 50% of the Earth’s surface, which houses about 50% of the Earth’s surface. population.
The destruction of the ozone layer implies a weaker filter of ultraviolet radiation that reaches the surface more easily and in greater quantity. It is more than proven that ultraviolet radiation has negative effects on the health of people and other living beings; effects that impact terrestrial and aquatic ecosystems, and become the cause of biodiversity loss.
Dunbar, J. 2001. The Ozone Layer. PAN.
Farman, JC et al. 1985. Large losses of total ozone in Antarctica reveal seasonal ClOx/NOx interaction. Nature, 315 (6016), 207-210. DOI: 10.1038/315207a0
Lu, Q.-B. 2022. Observation of large ozone losses in all seasons in the tropics. AIP Advances, 12(7), 075006. DOI: 10.1063/5.0094629