Final answer:
Chlorine in the upper atmosphere comes from chlorofluorocarbons (CFCs), industrial chemicals that release chlorine atoms when they break down in the stratosphere. These chlorine atoms then react with ozone molecules, causing ozone depletion. This depletion leads to higher levels of UV radiation reaching the Earth.
Step-by-step explanation:
The chlorine in the upper atmosphere comes from industrial chemicals called chlorofluorocarbons (CFCs), which were widely used in the past but have been phased out due to their harmful effects on the ozone layer.
These CFCs release chlorine atoms when they break down in the stratosphere, and these chlorine atoms react with ozone molecules, breaking them down and depleting the ozone layer. This reaction is a chain reaction that can destroy thousands of ozone molecules. The depletion of the ozone layer has serious consequences, including increased levels of UV radiation reaching the Earth.