In 2016, environmental scientists celebrated victory in an almost-two-decade battle. The stratospheric ozone layer—a blanket of molecules made up of three oxygen atoms that protect the planet from some of the sun’s ultraviolet rays—was finally rebounding. It seemed like international collaboration had paid off: The Montreal Protocol, a multilateral treaty that restricted the problematic chemicals that were putting holes in the ozone around the poles, seemed to be working, and the layer was bouncing back.   READ MORE HERE