Life on Earth started in the water. One of the reason why is that water is a protected environment against the Sun’s ray capable to sterilize the planet. During Earth’s middle life, plants in the water started to absorb the abounded carbon dioxide in the air and breathe out oxygen. This long process created an atmosphere, and later on an ozone layer. These two elements made life possible outside water.
The ozone layer is situated at a distance of 30 km to 100 km from the ground. It is a concentration of ozone molecules, which is an association of three oxygen atoms (O3). The so called good layer situated in the stratosphere, the higher atmosphere, protects the surface from the excess of ultraviolet sunlight. The bad one situated in the troposphere, the lower atmosphere, reacts to the Sun by issuing toxic gas and is one of the causes of smog. We and the vegetation would prefer to see the ozone only higher in the stratosphere.
Today, the ozone layer continues to filter part of the UV ray, but loses efficiency in some areas. We often refer to this problem as the “hole in the ozone layer”, but it is more likely depletion. The poles, and especially Antarctica, are the regions that suffer the most due to their snow and ice reflection. The depletion is caused by chlorofluorocarbons (CFC) gas that we use in air conditioner, refrigerator, fire extinguisher, etc. But this problem is more under control today.
After several studies on the ozone layer, the international community decided to meet in Montreal in 1987 to respond to the problem of depletion. The objective was to regulate the use of product responsible for the destruction of the ozone layer. The outcome of this protocol was a success. Most of the gas responsible for the depletion are banned or diminished, which make it less of a problem today. Normally, it would take close to 50 years for the ozone layer to recover.