The Montreal Protocol. It spelled doom for refrigeration and aerosol spray cans, as countries got together and agreed to stop the use of chlorofluorocarbons (CFCs).
Industry balked at the aggressive schedule to fully eliminate manufacture of the molecules blamed for eating away the ozone layer shielding inhabitants of our planet, especially in the southern hemisphere, from harmful ultraviolet (UV) rays from our Sun.
But somehow we survived. Replacements were found. Freon superpower DuPont even swapped sides, advocating for the ban after CFC replacements developed by their chemists showed promise.
It seems like the effort has all been worth it, as Professor Susan Solomon of the Massachusetts Institute of Technology and a team of scientists from NCAS and the University of Leeds report the "first signs of healing" of the ozone layer, confirming predictions that the hole in the ozone layer could close by the middle of this century.
Their measurements, focusing on a time period in September each year -- during which time the colder temperatures in the atmosphere promote the reactions that destroy ozone so that the hole is opening up -- show that since 2000, the hole has shrunk by 1.7 million square miles, an area more than half the size of the continental United States.
Models demonstrate that the trend can be attributed clearly to the reduced concentrations of chlorofluorocarbons in the atmosphere, in spite of some complexity introduced by the particles ejected from volcanic eruptions.
The most recognized international treaties addressing mankinds' impact on our environment also include the Stockholm Convention (persistent organic pollutants or POPs), Rotterdam Convention (requiring prior informed consent before hazardous wastes can be shipped into another country), and Kyoto Protocol (greenhouse gases).
The story is not perfect in any of these cases, as companies and countries still find ways to cheat the agreements, trading in black markets that ignore the bans and the critical impacts that may result. Nonetheless, this success with the Montreal Protocol proves that we can succeed if we can just agree to act, and act fast, to reverse the undesirable changes we discover ourselves to be making in our only home planet.
The study, Emergence of Healing in the Antarctic Ozone Layer (DOI: 10.1126/science.aae0061), appears today in Science.