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Ozone hole

The ozone hole is the reduction in the thickness of the ozone layer in the Earth's atmosphere, the layer that protects us from harmful solar radiation. It is caused by the release of certain pollutants by humans, both from productive and consumptive activities. Specifically, the layer thins due to the release into the atmosphere of chlorofluorocarbon (CFC) gases. Currently, the "hole" is mostly located above the South Pole of our planet. It expands by 5% every 10 years. It is one of humanity's major environmental problems because it poses a risk to the ecosystem and life itself on our planet.

The name "ozone hole" is easy to remember but often causes confusion, because it makes it more difficult to understand what the phenomenon really consists of. Therefore, it would be more correct to start calling it "hole in the ozone layer" or "hole in the ozone sphere".

What is ozone?

Ozone is a molecule composed of three oxygen atoms (O3). It is a blue gas and is found in nature in the gaseous state in our planet's atmosphere. This gas has formed over millions of years thanks to the natural activity of blue-green algae that have produced and released oxygen during their life cycle. These algae are responsible for much of the oxygen currently present in the Earth's atmosphere. Molecular oxygen (O2) combines with an oxygen atom (O) to form a molecule of ozone (O3).

Over time, ozone molecules have accumulated in the upper atmosphere of our planet, creating a sort of protective layer that absorbs the most dangerous ultraviolet UV solar radiation. The ozone layer in the atmosphere is called the ozone layer. This protective layer is located in the stratosphere at about 20-30 kilometers above the Earth's surface. It is thinner over the equator and thicker over the poles. Thanks to a photochemical reaction between oxygen molecules and sunlight, new atmospheric ozone is continuously formed, which maintains a constant balance of the thickness of the ozone layer.

Why is the ozone layer important?

This filter has allowed life to leave the marine environment and conquer the land, initiating the evolution of terrestrial species. Prior to the formation of the atmospheric ozone layer, known forms of life only existed in oceanic waters. To understand its importance, it is enough to consider that if the ozone layer had not been present to protect our planet, humans would not exist today. The ozone layer absorbs 100% of UVC rays and 90% of UVB rays, the most energetic and dangerous ultraviolet radiation for life (, while allowing low-energy UVA radiation to pass through, contributing to the functioning of the ecosystem.

Causes of the ozone hole

The thickness of the ozone layer has continuously changed throughout the history of our planet due to natural causes. However, starting from the second half of the 20th century, the layer has gradually thinned out also due to human activities, as a result of the release of some pollutants into the atmosphere. In particular, chlorofluorocarbon (CFC) gases used in spray cans and refrigeration systems. A molecule of chlorofluorocarbon is composed of one carbon (C) atom, one fluorine (F) atom, and three chlorine (Cl3) atoms. In the upper atmosphere, the energy of UV sunlight breaks the CFC molecule, releasing a chlorine atom (Cl) that combines with ozone (O3), transforming it into a molecule of biatomic oxygen (O2) and leaving a free oxygen atom (O). In this way, CFC gases destroy ozone (O3).

Just think that a single chlorine atom released into the stratosphere can modify a hundred thousand molecules of ozone before returning to the troposphere ( In the 1970s and 1980s, CFC gases were banned by international agreements, and the issue continues to be monitored by the scientific community.

Natural variations in the ozone layer have occurred slowly over time, allowing life to adapt and evolve. However, recent anthropogenic changes have been much more abrupt and rapid. According to ecoage, this speed of change can cause a dangerous shock to the balances of our planet's biosphere and to the very existence of life as we know it today. The most severe thinning occurs above Antarctica. This reduction in the thickness of the ozone layer is what we now call the ozone hole.

The consequences of the ozone hole

The consequences on living beings

The ozone layer protects living organisms from the most energetic UV rays from the sun. If the layer becomes depleted, radiation that carries a greater amount of energy can reach the Earth's surface, putting human health and the very existence of life on our planet at risk.

  • Electromagnetic radiation that is too strong affects the life of cells, creating melanomas on the epidermis and skin tumors.
  • They can break the chain of the genetic code or modify the molecules of DNA and RNA of living organisms.
  • Another consequence of UV-B rays on human health is irreversible damage to the retina of the eye, leading to blindness.

Living beings are the result of natural evolution over millions of years, while the shock caused by the thinning of the ozone layer is happening in a short period of time, within a few decades or hundreds of years. Living organisms do not have time to adapt to this external shock.

Le conseguenze sull'ambiente

The more harmful solar radiation inhibits chlorophyll photosynthesis, causing a decrease in plant growth and a decrease in oceanic phytoplankton production. Microorganisms are more exposed to the consequences of excessive exposure to ultraviolet radiation. Both plants and phytoplankton are at the base of the food chain. Therefore, the consequences would severely affect every ecosystem and biome.

The consequences on agriculture and fishing. The slowing of plant growth would also cause a reduction in agricultural yields. The disappearance of phytoplankton would instead have cascading effects on marine life and indirectly on the fish resources available to humans through fishing. In a time of strong demographic growth of the world's population, the supply of agricultural and fish products may no longer be sufficient to meet demand. This situation was already studied by Malthus in the 19th century.

When solar radiation is very strong, the environment becomes inhospitable for the life of many living species, including humans. Under extreme conditions, only a few living species could survive even with continuous direct exposure to high-energy rays. For example, insects with exoskeletons have much greater chances of survival than other species. However, they would find themselves in almost prohibitive living conditions, in a desert planet devoid of greenery.

What is being done to solve the problem?

Currently, the issue of the ozone hole remains one of the main environmental problems on Earth. Humans have already made several decisions to address it through international agreements signed by all countries in the world. One of the most important agreements is the Montreal Protocol, signed in 1987 and in effect since 1989. However, the long-term effects are still uncertain.

For example, the size of the hole varies continuously. Over the last few years, the thickness has reduced less at the South Pole but seems to be extending more in the surrounding regions. It is a complex and chaotic physical phenomenon, so it is unpredictable. For this reason, the situation is continuously monitored by the scientific community.

Why does the ozone thin more quickly at the poles?

In polar regions, the ozone layer is thicker. However, it is precisely in these zones that the ozone reduces at a faster rate. This happens because the polar regions are less exposed to solar radiation, resulting in fewer photochemical reactions between ozone molecules and solar radiation. Additionally, the cold facilitates the degradation of ozone. Above the Earth's poles, there is less ozone production that cannot compensate for the destruction caused by the pollutants (CFCs) released into the atmosphere by human activities.