Declared as "perhaps the single most successful international agreement to date" by former UN Secretary General Kofi Annan, the 1987 Montreal Protocol has helped protect life on earth.

The treaty saw world leaders come together to stop harmful chemicals destroying parts of the ozone layer.

The ozone layer formed around the earth after aquatic bacteria began to release oxygen through photosynthesis 2.4 billion years ago. This protective layer keeps out the sun’s most harmful UV rays and helped life on earth to emerge from water onto land.

But scientist discovered a hole in the earth's ozone layer in the late 1970s and they soon realised that it was created by man-made chemicals.

Present in everything from fridges to fire extinguishers, chlorine based gases known as chlorofluorocarbons (or CFCs) were damaging the ozone layer, and as a result harming plantlife and exposing humans to a greater risk of skin cancer.

Today, all 196 UN members have ratified the protocol to restrict CFCs and the ozone-damaging emissions that peaked in the 1980s are now on the decline.

In this earthrise animation, we look at how the ozone layer works and how international action was able stop damage to the earth’s protective layer.

earthrise can be seen each week at the following times GMT: Tuesday: 2230; Wednesday: 0930; Thursday: 0330; Friday: 1630; Saturday: 2230; Sunday: 0930; Monday: 0330; Tuesday: 1630. 

Join the conversation on Facebook, or watch us on YouTube or follow us on Twitter.

Source: Al Jazeera