For more than two decades, the 1987 Montreal Protocol has served as a shining example of how to get things done on the environment in the international arena. By banding countries together to preserve Earth’s shield against harmful ultraviolet rays, the agreement has already eliminated many ozone-depleting substances and should see off most of the rest by 2030. And in doing so, it has done more to reduce greenhouse-gas emissions than the 1997 Kyoto Protocol, which was signed expressly for that purpose. (Editorial)