Detection and attribution in stratospheric ozone recovery
The theoretical foundation of pattern-based “fingerprinting” was introduced by Hasselmann (1983) and has since become a core technique in climate science for detecting and attributing human-induced climate signals amid natural variability. These fingerprints are typically applied to spatial patterns of climate variables.
However, for chemical species like ozone—which are strongly influenced by solar radiation, temperature, and atmospheric transport—analyzing patterns across both month and altitude dimensions is especially useful for distinguishing different forcings. We applied this fingerprinting method in the month–height domain to investigate Antarctic ozone recovery, separating signals from greenhouse gas (GHG) and ozone-depleting substance (ODS) from internal variability noise. Our results show that the observed month–height trend pattern in Antarctic ozone is predominantly driven by declining ODS emissions and is unlikely to result from internal climate variability alone (with 95% confidence).
Illustration of a pattern-based fingerprint approach for surface temperature detection. Image courtesy of Ben Santer.
Related Work
2025
Nature
Fingerprinting the recovery of Antarctic ozone
Peidong Wang, Susan Solomon, Benjamin D. Santer, Douglas E. Kinnison, Qiang Fu, Kane A. Stone, Jun Zhang, and 2 more authors
The Antarctic ozone ‘hole’ was discovered in 1985 and man-made ozone-depleting substances (ODSs) are its primary cause. Following reductions of ODSs under the Montreal Protocol, signs of ozone recovery have been reported, based largely on observations and broad yet compelling model–data comparisons. Although such approaches are highly valuable, they do not provide rigorous statistical detection of the temporal and spatial structure of Antarctic ozone recovery in the presence of internal climate variability. Here we apply pattern-based detection and attribution methods as used in climate-change studies to separate anthropogenically forced ozone responses from internal variability, relying on trend pattern information as a function of month and height. The analysis uses satellite observations together with single-model and multi-model ensemble simulations to identify and quantify the month–height Antarctic ozone recovery ‘fingerprint’. We demonstrate that the data and simulations show compelling 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 increases in ozone consistent with expected month–height patterns.
@article{wang_fingerprinting_2025,title={Fingerprinting the recovery of {Antarctic} ozone},volume={639},issn={1476-4687},number={8055},journal={Nature},author={Wang, Peidong and Solomon, Susan and Santer, Benjamin D. and Kinnison, Douglas E. and Fu, Qiang and Stone, Kane A. and Zhang, Jun and Manney, Gloria L. and Millán, Luis F.},month=mar,year={2025},pages={646--651},}
