Montreal Protocol

On this day in 1987, the Montreal Protocol was adopted by 46 countries to regulate chemicals that were found to deplete Earth’s ozone layer. Beginning in the 1970s researchers had determined that chlorofluorocarbons (CFCs), which were used as refrigerants and in aerosol sprays, could accumulate in the stratosphere and deplete ozone molecules. Ozone, O3, shields us from the Sun’s ultraviolet radiation. In 1985 scientists discovered a hole in the ozone layer over Antarctica. Although some nations had already banned CFCs, the urgency of the situation warranted an international treaty. The Montreal Protocol on Substances That Deplete the Ozone Layer went into effect in 1989 and required nations to significantly cut the production and consumption of CFCs and similar substances. Since then the restrictions have become stricter and the number of signatories has neared 200. A June 2016 study in the journal Science found that the Antarctic ozone hole is already recovering, which is earlier than most scientists expected. (Image credit: NASA/Goddard Space Flight Center Scientific Visualization Studio)

Date in History: 16 September 1987