To raise global awareness of the need to preserve the ozone layer, the United Nations created the "International Day for the Preservation of the Ozone Layer" 20 years ago. It is celebrated every year on September 16.
Without the ozone layer, life on earth - as we know it - would not be possible. The protective layer blocks most of the sun's rays and prevents too much ultraviolet radiation from reaching the earth. In the mid-1970s, a group of scientists discovered that the ozone layer was under threat. For years, man-made chemicals (so-called CFCs), mainly contained in deodorant and hairspray aerosols, air conditioners and refrigerators, slowly intruded the upper layers of the atmosphere. There they contributed to the depletion of stratospheric ozone. The result: the "ozone hole" was created.
With the signing of the Montreal Protocol in 1987, the international community agreed to phase-out ozone-depleting chemicals. Thanks to the interplay of scientific knowledge and collaborative action, the hole in the ozone layer is expected to close by the middle of the century. The Montreal Protocol is probably the most successful environmental agreement, ratified by every nation on earth.