Ozone layer depletion and the greenhouse effect are both phenomena taking place in the atmosphere – but the mechanisms, chemistry and physics behind them are very different. Not only that, contrary to popular belief, they are neither connected nor influenced by one another.
Ozone Layer Depletion
Ozone (O3) is a form of oxygen much less stable and common than the “standard” form of oxygen, O2. Some important facts about ozone:
- Ozone is present in the upper layers of the atmosphere, in the stratosphere (between 15 and 50 km above the Earth’s surface).
- O3 is not stable, but is very reactive – ozone can be very dangerous to human health.
- Ozone’s presence in the lower atmosphere (i.e. the air we breath) has negative effects, but its presence in the upper atmosphere is crucial to our health.
- Ozone reacts with ultraviolet radiation and in this way, stops the radiation from reaching the surface of the earth.
- Ultraviolet radiation is very dangerous for humans. It interacts with the cells of the body by damaging them and/or causing cell mutation. Ozone in the upper atmosphere helps to reduce the effect of ultra-violet radiation.
Today’s problems stem from the reduction of the amount of the ozone present in the stratosphere, a phenomenon referred to as ozone depletion. For example, the ozone layer over the Antarctic becomes very thin during springtime, resulting in the formation of an ozone hole. It’s a phenomenon caused by a group of gases called clorofluorocarbons (CFCs).
CFCs were used as refrigerants and propellants beginning in the 1950s because of their stability and low boiling points, but they accumulated in the atmosphere. The reaction of these gases with the ozone provoked a decrease in ozone concentration.
Several treaties and protocols were implemented (Montreal – 1987, Copenhagen – 1992, Vienna – 1995) with a view to replacing CFCs with others and eventually ban them. Hydrofluorocarbons (HFCs) are used today.
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