What have humans done to the ozone layer?
Humans have damaged the ozone layer by adding molecules containing chlorine or bromine that lead to ozone destruction. The largest group among these are chlorofluorocarbons (CFCs). At ground level, these molecules are stable and have many uses in industrial and domestic applications. However, when they are released into the atmosphere, they drift up to the stratosphere, pushed by winds and atmospheric mixing. At that high altitude, energetic light rays (UV-C radiation) can break down such molecules in a reaction that liberates an atom of chlorine (Cl). This chlorine atom can react with ozone and break it down to chlorine oxide and O2. Chlorine oxide will break down as well, releasing the Cl to go on destroying ozone. In fact, one Cl can destroy up to 10,000 ozone molecules! As a result, ozone in the stratosphere has been reduced to such an extent that a hole opens up above Antarctica each spring that has, in each of the past four years, measured 8.2 million square miles — larger than
