Its molecules act as a shield protecting us from solar radiation. When the radiation reaches the ozone layer, it passes through the ozone molecules and these are responsible for returning part of radiation back to space, in this way the radiation that reaches us is minimized.
Although this hole is due to the natural fluctuations of ozone in the atmosphere, it also caused by human activities which emit gases that end up in the stratosphere and degrade the ozone molecules, increasing the size and effect of this hole in the ozone layer. This is an environmental and health problem, since the excess of solar radiation is a threat to any form of life.
The Antarctic ozone hole, as it came to be known, made depletion of the ozone layer a real and present danger to lawmakers and the public at large. Predictions of significant increases in the incidence of skin cancer resulting from continued use of CFCs spurred international action. In 1987, 56 countries agreed under what became known as the Montreal Protocol to cut CFC production and use in half. In subsequent years, the protocol was strengthened to require an eventual worldwide phaseout of the production of CFCs and other ozone depleting chemicals.
The phaseout of controlled uses of ozone depleting substances and the related reductions have not only helped protect the ozone layer for this and future generations, but have also contributed significantly to global efforts to address climate change; furthermore, it has protected human health and ecosystems by limiting the harmful ultraviolet radiation from reaching the Earth.
A number of commonly used chemicals have been found to be extremely damaging to the ozone layer. Halocarbons are chemicals in which one or more carbon atoms are linked to one or more halogen atoms (fluorine, chlorine, bromine or iodine). Halocarbons containing bromine usually have much higher ozone-depleting potential (ODP) than those containing chlorine. The man-made chemicals that have provided most of the chlorine and bromine for ozone depletion are methyl bromide, methyl chloroform, carbon tetrachloride and families of chemicals known as halons, chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs).
The scientific confirmation of the depletion of the ozone layer prompted the international community to establish a mechanism for cooperation to take action to protect the ozone layer. This was formalized in the Vienna Convention for the Protection of the Ozone Layer, which was adopted and signed by 28 countries, on 22 March 1985. In September 1987, this led to the drafting of The Montreal Protocol on Substances that Deplete the Ozone Layer.
The principal aim of the Montreal Protocol is to protect the ozone layer by taking measures to control total global production and consumption of substances that deplete it, with the ultimate objective of their elimination on the basis of developments in scientific knowledge and technological information. It is structured around several groups of ozone-depleting substances. The groups of chemicals are classified according to the chemical family and are listed in annexes to the Montreal Protocol text. The Protocol requires the control of nearly 100 chemicals, in several categories. For each group or annex of chemicals, the Treaty sets out a timetable for the phase-out of production and consumption of those substances, with the aim of eventually eliminating them completely.
The ozone layer sits in the stratosphere between 15 km and 30 km above the earth. It absorbs most of the sun's ultraviolet radiation (UV-B), limiting the amount of this radiation that reaches the surface of the Earth. Because this radiation causes skin cancer and cataracts, the ozone layer plays an important role in protecting human health. It also prevents radiation damage to plants, animals, and materials.
In the 1970s, scientists noticed that the ozone layer was thinning. Researchers found evidence that linked the depletion of the ozone layer to the presence of chlorofluorocarbons (CFCs) and other halogen-source gases in the stratosphere. Ozone-depleting substances (ODS) are synthetic chemicals, which were used around the world in a wide range of industrial and consumer applications. The main uses of these substances were in refrigeration and air conditioning equipment and in fire extinguishers. Other important uses included aerosol propellants, solvents and blowing agents for insulation foams.
To halt the depletion of the ozone layer, countries around the world agreed to stop using ozone-depleting substances. This agreement was formalised in the Vienna Convention for the Protection of the Ozone Layer in 1985 and the Montreal Protocol on Substances that Deplete the Ozone Layer in 1987. In 2009, the Vienna Convention and the Montreal Protocol became the first treaties in the history of the United Nations to achieve universal ratification. Substances covered by the protocol are referred to as 'controlled substances'. The main substances include chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), halons, carbon tetrachloride, methyl chloroform and methyl bromide. The damage to the ozone layer caused by each of these substances is expressed as their ozone depletion potential (ODP).
These international agreements helped to greatly reduce the worldwide use of ozone-depleting substances in Europe and around the World (Figure 1). Scientific monitoring shows signs that the ozone layer is starting to recover. Full recovery is not expected to occur before the middle of the 21st century.
The reduction in ozone-depleting substances has also had a beneficial side-effect. Ozone-depleting substances are also very potent greenhouse gases, contributing to the phenomenon as other substances widely known to have a greenhouse effect like carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). Therefore, by reducing emissions of ozone-depleting substances, the Montreal Protocol has protected both the ozone layer and the climate at the same time.
The reduction of ODS emissions is not a uniformly positive story. In fact it has indirectly led to new problems. Fluorinated gases (F-gases) have been introduced as substitutes for ODS in many sectors such as refrigeration and air conditioning applications. F-gases include hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulphur hexafluoride (SF6). These gases do not deplete the ozone layer, but they are greenhouse gases. This means that these new gases also contribute to climate change. And to make matters worse, these F-gases often have a far larger impact on the climate than 'traditional' greenhouse gases such as carbon dioxide (CO2). For example, some F-gases have a greenhouse effect that is up to 23 000 times more powerful than the same amount of carbon dioxide. Fortunately, the emissions of F-gases are far smaller than those of CO2, but the use of F-gases and their presence in the atmosphere have increased since the 1990s. As a result, the significant contribution of the Montreal Protocol to fighting climate change is in danger of being wiped out by the growing importance of F-gas emissions.
Because F-gases contribute to climate change, businesses are now looking to replace them with other substances. Alternatives that do not damage the ozone layer or contribute to climate change have become available over recent years in a variety of applications such as refrigeration, air conditioning, foam blowing and aerosols. Many of these alternatives lead also to higher energy efficiency which is important as the indirect emissions from energy use during the lifespan of a product are often considerably higher than direct emissions of F-gases.
Preventing human activities which destroy Ozone layer; this entails regulating manufacturing companies which emit chlorofluorocarbon to the atmosphere. Chlorofluorocarbon is a leading cause of ozone layer depletion. It is important to conserve the environment through restricting deforestation and encouraging people to plant trees in order to increase plants growth and oxygen concentration in the atmosphere.
Introducing policies geared to protect ozone layer depletion; governments should adopt rules and regulations to prohibit activities which emit Ozone layer depleting substances. These policies should block manufacturers from producing products which contain substances which deplete Ozone layer like chlorofluorocarbon and methyl bromide.
Individuals should report incidences posing threat to ozone layer like use of bromethane in fields and on crops. It is vital for people to reduce activities leading to air pollution like servicing their cars and others machines regularly and use alternative means for transport like use of common buses, bicycles and walking.
Additionally, it is important to minimize high altitude aircrafts rockets and air crafts because they contribute to Ozone layer depletion. Also, companies should decrease or control realizing of high temperature steam to atmosphere since it is one of the contributing factors to ozone layer depletion.
Financial support from the government and well wishers to promote and facilitate activities promoting Ozone layer protection is required. This includes funding of programs like tree planting, sanitation program and public education program geared to protect ozone layer.
As far as decades go, the 1980s were nothing if not tumultuous. The fall of the Berlin Wall in 1989 reshaped the future, heralding the dawn of a new world order. But another significant, but lesser known, event of that decade took place two years earlier when governments came together to reverse damage to the ozone layer and ensure we had a viable future to reshape.
The results have been dramatic. Around 99 per cent of ozone-depleting substances have been phased out and the protective layer above Earth is being replenished. The Antarctic ozone hole is expected to close by the 2060s, while other regions will return to pre-1980s values even earlier. Every year, an estimated two million people are saved from skin cancer and there are broader benefits too, as many of the ozone-depleting gases also drive up global temperatures. 2b1af7f3a8