The ozone layer is on track to heal across most of the world by 2040 and fully heal, including across the polar regions, by 2066. The depleting ozone layer was once considered the biggest environmental peril facing humanity, and we have effectively overcome it with collaborative and decisive action by governments in the form of the 1989 Montreal protocol. This treaty is now considered the most successful climate treaty in history and sets an important precedent for climate action. We must learn from this and replicate on an even larger scale. The challenge is greater; CO2 emissions are more wide-spread and is more persistent in the atmosphere. But the reward will be greater too!