The restoration of the ozone layer

The ozone layer acts as a protective barrier between the ultraviolet rays emitted by the Sun and the Earth. This is an essential element to the proper functioning of the various ecosystems of the planet. However, for several decades it has been damaged by human action and this has resulted in a depletion of it until the formation of a hole that has become problematic!

The ozone layer

Also known as the "ozonosphere", it has the major role of protecting the human beings and ecosystems of the planet Earth. It has this name because it is characterized by a much higher concentration of this gas than the other parts of the atmosphere. It is one of the four strata that make up our atmosphere: the troposphere (10 km), the ozonosphere or stratosphere (between 20 and 50 km), the mesosphere (100 km), the thermosphere (600 km altitude) and the exosphere.

It is an essential element for the proper structure of the Earth’s atmosphere and for life on Earth. Indeed, it is what absorbs most of the ultraviolet rays (UV-B) emitted by the Sun and that can cause damage. These damaging rays can be extremely harmful on the biological level and are considered as extremely mutagenic (alteration of the DNA of the plants, animals and insects).

Atmosphere layers credit: brgfx

The concentration of ozone in the atmosphere and in the stratosphere remains variable. Many factors are to be taken into consideration such as temperature, geographical area or atmospheric and meteorological conditions. Some substances contained in the emissions of volcanic gases and ashes can also be responsible for certain variations in the ozone concentration.

It should be noted that these different natural factors only cause variations in the amount of gas in the atmosphere, but are not responsible for the level of deterioration observed and the creation of a hole in this protective barrier.

The hole in the ozone layer

Indeed, it is not natural events as previously mentioned that have caused a hole in the ozone layer.
In 1974, Mario Molina and Frank Sherwood Rowland, two American scientists and chemists, expressed the possibility that the ozone layer was in the process of depleting. They quickly identified the source of this depletion, which will develop over the years into a hole in it. The cause is identified as ChloroFluoroCarbons, better known as CFCs.

CFCs are artificial chemical substances that appeared in 1938 and were made popular in the 1970s by various equipment such as refrigerators, aerosols, air conditioners and fire extinguishers. These were mainly addressed to the industry and to consumers.

ozone layer aerosols

These substances are the reason why the ozone layer has been closely monitored since the early 1980s. Their use did not damage it only slightly but did cause the creation of a gaping hole over Antarctica. This hole is located at the South Pole and was almost as big as North America at the time of its discovery by scientists (about 25 million km2).
Its size can be calculated via satellites equipped with specific cameras that can detect ultraviolet light and therefore ultraviolet rays. These satellites have therefore been able to identify its location and can, thus, evaluate the fluctuations and evolutions (positive or negative). For example, thanks to this technology, it was possible to determine that the phenomenon of ozone layer deterioration increases particularly over the period from August to November.

The hole in the ozone layer is caused by man and is currently the second biggest negative impact that man has ever had on the environment and the climate just after the increase in greenhouse gases (carbon dioxide).

Consequences on Man and biodiversity

Being inevitably exposed to excessive UV rays and not filtered by the ozone layer, human beings encounter new risks.
Among the direct and most serious consequences, we find a risk of developing different types of skin cancers. The external mucous membranes can also be damaged, for example, the eyes can be affected and risks of cataracts can occur. The immune system is also strained and tends to be weakened by such exposure to UV radiation. These different health risks for humans are the same for animals when exposed to UV-B for a long period.

This hole is also a concern for the well-being of the environment and our planet because our entire ecosystem could be damaged by too high and too long exposure to UV rays.
Firstly, the growth of all organisms is affected because it leads to a reduction in agricultural productivity since plants no longer react in a usual way and must adapt to a new environment.
We must also consider that if the hole in the ozone layer does not reabsorb quickly, it could lead to the disappearance of certain plant species. Besides, plants and ecosystems are intrinsically connected, the disappearance of certain species due to UV-B radiation could have a butterfly effect and lead to the disappearance of other species.

Global warming credits: Reuters

Let's also remember that plants are a major source of oxygen production, so if a multitude of plant varieties were to disappear, this would result in a major risk for humanity and environment. The aquatic ecosystem is impacted as well.
Finally, one of the main and inevitable ecological consequences in such conditions is global warming.

The Montreal Protocol

The Montreal Protocol is an international agreement signed and implemented on September 16, 1987. When it was signed, 24 countries and the European Economic Community agreed on certain measures to be taken in order to tackle the climatic emergency that the hole in the ozone layer represents.

The first and essential decision adopted by this protocol is a very strict restriction on CFCs (chlorofluorocarbons), on HCFCs (hydrochlorofluorocarbons), methyl bromide and other halons. Indeed, the member countries of the Montreal Protocol must respect certain fundamental rules of this agreement in order to limit the use of these unregulated products. To achieve this, member countries must ban all use, manufacture, import or export of these substances or products using them as a component. Imports and exports are also prohibited from or to non-member states of the protocol.
Only essential uses of these products may be allowed.
The ban on these products has been gradually completed, starting with the most developed countries. Chlorofluorocarbons (CFCs) were officially banned worldwide in 2010 and controls are carried out annually through reports provided to the Protocol Secretariat to verify imports, exports and consumption of each member country.
This protocol had a global resonance and is the first international environmental protocol to be established. It became, in 2009, the first treaty to reach "universal ratification". There are now 197 countries that have committed to act to restore the ozone layer.

There are tools such as fixed or portable freons detectors to monitor the presence of these substances.

Restoration of the hole in the ozone layer

Fixing this hole is not a quick and easy task. It will take many years and even decades to achieve a total result.
Of course, thanks to the Montreal Protocol and the recent environmental awareness, the restoration of the hole in the ozone layer is on the right track, however, we must continue to multiply our efforts in order to achieve a rapid result.
According to many studies, the situation should return to normal by 2030 in the northern hemisphere, by about 2050 in the southern hemisphere and by 2060 in the polar regions. In order to do so, it is of course necessary to continue the efforts and to maintain taking adequate measures.

If it takes so long to turn the tide, it is because the majority of substances (CFCs, HCFCs, methyl bromide, etc.) released by human activities stagnate in the stratosphere for many years.

In a statement, the UN said that "the ozone layer in parts of the stratosphere has been recovering at a rate of 1 to 3 percent per decade" since 2020. When the hole was discovered in the 1970s, 10% of its surface had already disappeared.

Hole ozone layer credits: Nasa

A fragile stability

Ozone hole restoration, even if it is on the right track, is still fluctuating and can stagnate or even regress.
In 2022, scientists report that the hole in the stratosphere was the largest ever observed since 2015 and that it has continued to increase over the past 3 years. In the last investigations, it measured 26.4 million square kilometers.
This depletion therefore remains to be observed very closely even if scientists believe that it should not be considered alarming for the moment.