This ozone layer shields the Earth from the harmful effects of ultraviolet (UV) radiation from the Sun. With the depletion of the ozone layer, more UV radiation can Earth's surface. Long term effects of UV exposure reach the will cause skin cancer and cataract in humans. Plants and animals will be harmed too.
Therefore, we should replace CFCs with other substances that are not harmful. With the signing of Montreal Protocol, the production and use of CFCs will be phased out in stages.
Greenhouse gases such as carbon dioxide, methane, nitrous oxide and CFCs trap heat from the Sun and prevent the heat from radiating back into space. As the amount of these gases increase, more heat is trapped in the atmosphere. This results in the increase of the Earth's average temperature. This phenomenon is known as global warming.