During my time at university one of the units I studied that I found was of most ‘practical’ value was “The History of Climate Change”. When I say practical value, I mean it taught me things that are and will be hugely beneficial to my understanding of the climate. One of the things I learnt about was the ozone layer and how human activities have contributed to ozone depletion. The ozone layer surrounds the Earth and is made up of molecules of O3. O3 molecules are not as stable as the O2 we breathe. This means O3 is highly reactive with other molecules such as halogens. How do halogens reach the ozone layer? During the 1980s CFCs (found in fridges and degreasing solvents) were the main cause and contributed significantly to ozone depletion. But why should we worry about ozone depletion?