what CFC’s are and how we knew that is what was causing the destruction of the ozone layer
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CFCs are gases made from carbon, fluorine, and chlorine. They are mostly artificially made. They are neutral and react to combine with almost nothing, so they are good to keep under pressure for things like spray cans. Since nothing will react to them, the contents of the can will remain under pressure and will not go bad. They also make good refrigerants, so we use them to run refrigeration systems.
Unfortunately, there is a situation where they do combine with other things.
In the upper atmosphere, specifically the ozone layer, they are broken up by ultraviolet rays. When this happens, they release fluorine.
Fluorine is incredibly reactive. It will eat almost anything. One of the things it eats is ozone. It eats one of the oxygen atoms, turning ozone into ordinary O2 and oxygen difluoride or other fluorine compounds.
Unfortunately, the ozone layer protects us from ultraviolet radiation. Neither O2 nor oxygen difluoride blocks ultraviolet radiation the way that ozone does, so we get increased ultraviolet radiation reaching the ground and doing damage to our skin and our environment.
How do we know this is what is happening? Well, there are a lot of reasons, but the most clear and convincing one is what we find when we look at the ozone layer itself.
When CFCs break down they leave behind new compounds. These compounds are not found in nature normally, but we are now finding them in the ozone layer.
So, if CFCs caused the ozone layer to break down because they broke down under ultraviolet, we would see odd carbon, chlorine, and fluorine compounds that only come from breaking down CFCs, oxygen difluoride and other oxygen-fluorine compounds, and a lack of ozone. Nothing else known could create this because nothing else would leave behind those compounds.
So, we sampled the ozone layer, and guess what we found?
There are a lot of other reasons, but this was the smoking gun.
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