As the world marks the 20th anniversary of the Montreal Protocol to protect the ozone layer, new research has come to light that may shatter established theories of ozone chemistry. As explained in the journal Nature, if the data are right, scientists will have to rethink their understanding of man’s contribution regarding how ozone holes are formed . Long-lived man-made chlorofluorocarbons have long been thought to be the main cause of seasonal ozone losses. But this new research reveals that inaccuracies in the presumed light-activated splitting of an important compound may have greatly exaggerated man’s impact, and that at least 60% of any ozone destruction must be due to an unknown mechanism. A stunning discovery, indeed!