World governments agreed in the late 1980s to protect Earth’s ozone layer by phasing out ozone-depleting substances emitted by human activities, under the Montreal Protocol. The phase out of these substances has not only helped protect the ozone layer for future generations but has also protected human health and ecosystems by limiting the harmful ultraviolet radiation from reaching Earth. On 16 September, the International Day for the Preservation of the Ozone Layer, we take a closer look at this year’s ozone hole.