The ozone layer, containing high levels of O3, protects life on earth from harmful UV radiation. Ozone is poisonous and a pollutant near the surface. The layer absorbs UV radiation, reducing skin cancer and sunburn. Catalysts, including CFCs, caused the ozone layer to disappear, but the Montreal Protocol limited their production, allowing the ozone layer to recover. The depletion has slowed, and the atmosphere is below historic ozone levels. The ozone layer is an example of nations taking quick action in the face of a global catastrophe.
The ozone layer is a portion of the earth’s atmosphere that contains relatively high levels of ozone, O3. Earth’s atmosphere is made up of many different layers and consists mostly of nitrogen, with oxygen being the second most common element. The ozone layer is important for a variety of reasons, but primarily because it helps protect life on earth from harmful ultraviolet rays.
Ozone itself is a special form of oxygen, in which three atoms of the element have bonded together. It is poisonous for humans to breathe directly and is considered a pollutant if it is found near the surface of the Earth. The name comes from the word for the particular smell it is associated with, which occurs during thunderstorms.
The ozone layer, like the earth’s atmosphere itself, has no precise boundaries. In general, it is seen as the layer of gas 10 to 20 miles (15 to 35 km) above the earth’s surface. The ozone concentration in the layer is high compared to anywhere else, but it is still relatively low. Even in the most densely concentrated portions, ozone makes up only a few parts per million.
Ozone is especially important for humans because it has the unique property of absorbing ultraviolet radiation. There are three main types of ultraviolet (UV) radiation, known as UV-A, UV-B and UV-C. When functioning properly, this layer of atmosphere completely removes UV-C radiation, which is the most harmful to humans. It also dramatically reduces the amount of UV-B that reaches the earth’s surface — UV-B is the radiation responsible for many types of skin cancer and sunburn.
In the 1970s, it became apparent that the ozone layer was slowly disappearing. This was found to be a direct result of the use of certain catalysts released in large quantities by humans. A number of countries have taken small measures to reduce the emission of these catalysts, especially chlorofluorocarbons (CFCs), but the measures have generally been quite limited. In 1985, however, a massive hole was discovered in the ozone layer over Antarctica.
The hole provided the impetus needed for a worldwide movement to help protect this layer of the atmosphere. Within two years of its discovery, the Montreal Protocol was ratified, severely limiting the production of compounds that deplete the ozone layer. By the mid-1990s, the use of ozone-depleting compounds had been dramatically reduced and the ozone layer was on the way to recovery.
Although the atmosphere is still well below its historic ozone levels, its depletion appears to have slowed dramatically and the more immediate danger appears to have passed. The ozone layer is for many people a poignant example that the nations of the world are able to take relatively quick and concrete action in the face of an impending global catastrophe.
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