When the world actually solved an environmental crisis

In 1985, atmospheric scientists in Antarctica noticed something troubling. For decades, they’d been measuring the thickness of the ozone layer in the upper atmosphere, the layer of gas that deflects much of the sun’s radiation. Starting in the 1970s, it had started plummeting. By the mid-1980s, they observed that it was on track to be wiped out in the next few decades.

Their discovery was cause for worldwide alarm and unprecedented action. In short order, the international community marshaled its resources — scientific, economic, diplomatic — to mount a campaign...