Four newly detected ozone-depleting substances started to emerge in the atmosphere in the 1960s, reports a study published online in Nature Geoscience. Although emissions of these compounds have been small, they are contrary to the intentions behind the Montreal Protocol, an international treaty designed to phase out emissions of ozone-depleting substances.

Johannes Laube and colleagues examined the composition of air samples collected from Tasmania and extracted from deep compacted snow in Greenland. They identify three new chlorofluorocarbon compounds, and one new hydrochlorofluorocarbon compound - man-made substances once common in various household appliances, that destroy ozone in the upper atmosphere - in the air samples. The authors show that all four compounds started to appear in the atmosphere in the 1960s, and that, since then, two of these compounds have continued to increase in concentration in the atmosphere.