Fingerprinting the Robust Recovery of Antarctic Ozone

The Antarctic ozone “hole” was discovered in 19851, and man-made ozone-depleting substances (ODS) are its primary cause2. Following reductions of ODSs under the Montreal Protocol3, signs of ozone recovery have been reported, based largely on observations and broad yet compelling model-data comparisons4. While such approaches are highly valuable, don't provide rigorous statistical detection of the temporal and spatial structure of Antarctic ozone trends, in order to explicitly account for internal climate variability. Here, we rely on trend pattern information as a function of month and height to separate anthropogenically forced ozone responses from internal variability, using pattern-based detection and attribution methods as employed in climate change studies5–11. The analysis uses satellite observations together with both single-model and multi-model ensemble simulations to identify and quantify the month-height Antarctic ozone recovery “fingerprint”12. We demonstrate that the data and simulations show remarkable agreement in the fingerprint pattern of the ozone response to decreasing ODSs since 2005. We also show that ODS forcing has enhanced ozone internal variability during the austral spring, influencing detection of forced responses and their time of emergence. Our results provide robust statistical and physical evidence that actions taken under the Montreal Protocol to reduce ODSs are indeed resulting in the beginning of Antarctic ozone recovery (defined as statistically significant increases in ozone displaying a characteristic space-time fingerprint).