Scientists have found further evidence for the existence of an elusive intermediate implicated in chemical reactions that degrade atmospheric pollutants. A new method of directly detecting the simplest form of this intermediate, as well as more measurements of the intermediate’s reactivity, provide indications that atmospheric models need to improve how they account for them.More than 50 years ago, German chemist Rudolf Criegee proposed that alkenes in the atmosphere, released either by plants or human activities, degrade by reacting with ozone to form a cyclic ozonide. One of the products formed when this ozonide falls apart is a carbonyl oxide called...