Almost 30 years after the Montreal Protocol put the brakes on ozone-depleting chemicals, one compound remains stubbornly and mysteriously abundant in the atmosphere. NASA scientists are tracking down the source and studying its effect on the ozone layer.
VIDEO: http://youtu.be/rq9EAHyHtu8
WEB STORY: http://science.nasa.gov/science-news/science-at-nasa/2014/05sep_ozonelayer/
