It’s International Day for the Preservation of the Ozone Layer!
In recognition of the United Nations’ International Day for the Preservation of the Ozone Layer – celebrated annually on 16 September – we’ve compiled some educational facts and figures about the ozone layer, the hole in the ozone, the Montreal Protocol and what we can do to help save the atmosphere.
Where is the ozone layer?
If you had to travel directly upwards from the Earth’s surface, after around 25 kilometres you’d encounter the ozone layer.
Discovered in 1913 by French physicists Charles Fabry and Henri Buisson, the ozone layer is not a dense stratum of matter, but rather a layer of oxygen that contains some ozone (O3).
British meteorologist GMB Dobson is credited with discovering a lot of what we know about the ozone layer. He established a worldwide network of ozone monitoring stations that continue to function today.
What does it do?
The ozone layer absorbs between 97 and 99% of the Sun’s medium-frequency ultraviolet light. Without it, the Sun’s harsh rays could potentially damage Earth’s inhabitants.
What is the hole in the ozone layer?
In 1985 measurements by the British Antarctic Survey recorded massive ozone loss over the Antarctic. The area in the ozone layer that showed significant depletion of ozone later became known as the “hole in the ozone layer”.
The image above, recorded by satellite instruments that monitor the ozone in September 2000, shows the average area of the ozone hole at 27.5-million square kilometres.
What caused the hole in the ozone layer?
In 1974, Sherwood Rowland and Mario Molina discovered that emissions of man-made industrial chemicals, or chlorofluorocarbons (CFCs), were threatening the ozone layer.
Their theory, which was proven correct time and time again by later scientists, was that when CFCs enter the second layer of the Earth’s atmosphere, they begin to decompose due to UV radiation from the sun. As the chemicals become unstable, they release chlorine atoms, which in turn destroy ozone molecules.
According to Wikipedia, a single chlorine atom can destroy as many as 100 000 ozone molecules.
What is the Montreal Protocol?
The Montreal Protocol on Substances that Deplete the Ozone Layer is a treaty adopted in 1987 that tabulates global commitment to protecting the ozone layer. With 197 signatories, the treaty has significantly changed global consumption (and production) of controlled ozone-depleting substances.
Thanks to the Montreal Protocol, and global adherence to its principles, the ozone layer is expected to recover by 2075.
The Protocol has been cited as “perhaps the single most successful international environmental agreement to date”, and an example of how the international community can successfully co-operate to solve global challenges.
What do we do today to protect the ozone?
The theme for this year’s celebration is “A healthy atmosphere, the future we want”.
Here are ways to help reduce your CFC emissions:
- Have your car’s air conditioner serviced (leaky aircons equal emissions)
- Don’t buy a halon fire extinguisher for private use
- Check all labels on aerosols (especially foam confetti)