In 1985, the British Antarctic Survey alerted the world that in the atmosphere high above the South Pole a giant hole was forming in the Earth’s protective ozone layer. World leaders swiftly assembled to work out a solution. Two years later, the United Nations agreed to ban the chemicals responsible for eroding the layer of the stratosphere that shields Earth from the sun’s ultraviolet radiation. Known as the Montreal Protocol agreement, it is still one of the UN’s most widely ratified treaties.

The Montreal Protocol was a win for diplomacy and the stratosphere. But unbeknown to its signatories at the time, the agreement was also an unexpected ward against climate catastrophe. As new research shows, the aptly named ozone-depleting substances that created the hole over Antarctica are also responsible for causing 30 percent of the temperature increase we saw […]