Rising levels of a banned chemical are threatening the ozone layer (again)

CFC-11 was phased out under 1987's Montreal Protocol and the immediate halt of its usage has done much to reverse ozone depletion in the years since; but since 2012, atmospheric levels of CFC-11 have risen by 25%, eroding the still-healing ozone layer and suggesting that someone, somewhere, has started manufacturing the substance again. (more…)