Destruction of the Ozone Layer - The Causes

Chlorofluorocarbons (CFCs) have been identified as the main cause of the destruction to the ozone layer, but there are also compounds containing bromine, other halogen compounds and also nitrogen oxides which cause damage. 

CFCs were discovered by Thomas Midgeley in the 1930s as a cheap, non-flammable coolant for refrigerators.  They have been used in refrigerators, air conditioning, fast food packaging and propellants. CFCs are very stable, they decay slowly and so endure in the atmosphere for up to a century.

CFCs rise and gradually accumulate in the stratosphere where they are broken down by the sun's ultraviolet light, so releasing chlorine atoms. The chlorine attacks the ozone, one chlorine atom can help to destroy 100,000 ozone molecules.

The Montreal Protocol banning CFCs was signed by leading industrial nations in 1987 though the ozone layer continued to thin for the next decade as countries sought to reduce their use.  Meanwhile other countries such as China and North Korea increased their use of CFCs.  As reported in The Independent in 2000 'China raised its emissions from 29,000 tons in 1986 to 51,000 in 1997; South Korea from 8,500 to 9,200 tons and the Philippines from 1,900 to 2,700 tons'.

But it's not just with ozone that CFCs wreak havoc, they're also a potent greenhouse gas. In 2013 research published in the journal Nature Geoscience linked the ban to a 'pause' or slowdown in temperature increases since the mid 1990s.