September 16: The Montreal Protocol is signed in 1987, in order to protect the ozone layer in the stratosphere and avoid retrenchments: The Montreal Protocol on Substances that Deplete the Ozone Layer.

The largest Antarctic ozone hole recorded as of September 2006. http://www.nasa.gov/vision/earth/lookingatearth/ozone_record.html

The United Nations agency for environmental protection is known by its acronym UNEP (United Nations Environmental Programme) which formalized an international agreement on substances that deplete the protective ozone layer of the Earth.

Since 1987 science has advanced considerably and we are learning that the Protocol is even more important than its designers realized back in the mid 1980s.

Protocols differ from those treaties which are agreements of wills. While treaties are agreements between subjects of international law, mainly between States and between international organizations and whose duties should become law within each State which signs it.

The Montreal Protocol was designed to reduce the production and consumption of chemicals that deplete the ozone layer. The protocol was signed on September 16, 1987, and it entered into force on 1 January 1989.

Chlorofluorocarbons (CFCs or CLFC) are gaseous substances derived from the exploitation of hydrocarbons that when mixed with sunlight hydrogen atoms replaced by atoms of chlorine and fluorine. In the 70s, two US chemical engineers, F. Sherwood Roland and Mario Molina theorized the effects of CFCs. His theories were validated in 1985 when it was shown that there was a "hole" in the ozone layer in the stratosphere of the Antarctic.

The Montreal Protocol on Substances that Deplete the Ozone Layer and the Kyoto Protocol have been ratified by 197 parties, which includes 196 states and the European Union, making them the first universally ratified treaties in United Nations History.