The theory of ozone depletion was first suggested in the mid-1960s when research began to focus on the effects of water vapour and chlorine from rocket exhaust and supersonic transport aircraft.
Fun Fact: Ozone originates from “ozien” (Greek word for smell), because of the unusual smell emitted during lightning storms.
In 1970 Dutch chemist Paul Crutzen began investigating how chemical compounds, such as nitrogen oxide (NO), stimulated the destruction of ozone molecules
Through his research he found that non-reactive nitrous oxide (N2O), which is produced naturally in soils by bacteria, ascends into the stratosphere where it is separated by solar radiation into two reactive compounds; NO and nitrogen dioxide (NO2)
These newly-formed compounds, which remain fairly active in the stratosphere for some time, were seen to react catalytically with ozone by separating it into molecular oxygen (O2) and atomic oxygen (O)
During the 1970s, research into the effects of chlorine in the atmosphere was well underway
By 1974 a theory linking ozone destruction to human-made sources of chlorine (chlorofluorocarbons or CFCs)
Their theory was met with harsh criticism
There was still a great deal of uncertainty behind the science of ozone depletion at the time
It took another ten years, before their theory was proven by British scientist Joe Farman whose team discovered a severely depleted layer of ozone: