Ozone is a gas whose molecule consists of three oxygen atoms (O3), making it different from the oxygen we breathe, which has only two atoms per molecule (O2). Yet ozone is essential for life, because it defends us from the Sun’s ultraviolet radiation. Ozone forms a layer in the atmosphere between 10 and 40 km high that filters sunlight and retains the harmful part.
Between the 1970s and 1980s, scientists detected a thinning of the ozone layer over the polar regions. The cause was identified as the action of the CFC (chlorofluorocarbon) gases commonly used as refrigerants in refrigerators and as propellants in aerosol cans. Thus, the Montreal Protocol was signed in 1987, which led to the phase-out of 99% of CFC production.
Today’s International Day for the Preservation of the Ozone Layer marks 35 successful years since the Montreal Protocol, an agreement that saw governments working together for the common good. Established in 1994, it is no coincidence that the International Day for the Preservation of the Ozone Layer is celebrated on 16 September. Indeed, the Montreal Protocol was signed on 16 September 1987, a global agreement to ban CFCs and protect the ozone layer. Although the problem of the ozone hole has not yet been solved, to date the Montreal Protocol is one of the most successful international environmental agreements. Remember that the ozone hole is still fuelled by historical emissions today: there is enough chlorine and bromine left in the atmosphere to destroy the gas layer at certain altitudes.