Final answer:
The increase in chlorine in the stratosphere over the past several decades matches the observed decrease in ozone, which has been addressed by international agreements like the Montreal Protocol to reduce the substances responsible for ozone depletion.
Step-by-step explanation:
The rise in the amount of chlorine measured in the stratosphere over the past four decades corresponds with a decrease in stratospheric ozone, often referred to as the "ozone hole." This correlation is due to the release of chlorofluorocarbons (CFCs) into the atmosphere, which break down under ultraviolet light to release chlorine atoms. These chlorine atoms catalytically destroy ozone molecules, contributing to ozone depletion. However, concerted international efforts, such as the Montreal Protocol that banned the use of CFCs, have resulted in a decrease in atmospheric chlorine and the beginning of recovery for the ozone layer.