Stratospheric Ozone Variability and Trends

Stratospheric ozone exhibits complex spatial and temporal variability driven by chemical, dynamical and radiative processes. Ozone is formed primarily in the tropical upper stratosphere and redistributed by the Brewer–Dobson circulation towards mid- and high latitudes, where it shields the biosphere from harmful ultraviolet radiation. Since the 1970s, anthropogenic halogenated compounds caused substantial ozone depletion, most notably the Antarctic ozone hole in spring. Following the peak in stratospheric chlorine and bromine loading in the mid-1990s, upper-stratospheric ozone has begun to recover. However, the lower stratosphere at mid-latitudes continues to display year-to-year declines in some regions, reflecting the interplay of residual chemical forcing, changes in atmospheric dynamics—such as mesospheric descent within the polar vortex—and variability in wave-driven circulation. Emerging evidence highlights that global total column ozone trends are now masked by large interannual dynamical variability, underscoring the need for sustained, high-quality observations and improved representation of transport processes in chemistry-climate models.

Research from Nature Portfolio

Recent studies have characterised the drivers of the renewed large Antarctic ozone holes observed during 2020–2022. Detailed analysis of daily and monthly ozone profiles shows a 26 % decline in the October middle stratosphere since 2004, linked to enhanced mesospheric descent and altered polar vortex dynamics. This work emphasises the critical role of continuous monitoring to capture the coupling between dynamical changes and chemical loss, even as halogen levels fall.

Complementary modelling has quantified the benefits of the Montreal Protocol by comparing simulated worlds with and without ozone-depleting substances (ODSs). By 2013, adherence to the Protocol had already prevented deep Arctic ozone holes and restricted Antarctic depletion to its observed extent, averting substantial increases in solar UV radiation at the surface. The study projects a gradual return to pre-1980 ozone levels by mid-century under continued compliance.

Stratospheric Ozone Variability and Trends publication trend

The graph below shows the total number of articles in stratospheric ozone variability and trends across all publications each year (not limited to Nature Index journals).

Technical terms

Brewer–Dobson circulation: Large-scale stratospheric circulation that transports ozone from the tropics to polar regions.

Polar vortex: A circulating mass of cold air and strong winds in the polar stratosphere that confines and isolates ozone-poor air.

Ozone-depleting substances (ODSs): Halogenated chemicals, such as chlorofluorocarbons, that catalyse ozone destruction in the stratosphere.

Dobson Unit (DU): A measure of total column ozone; one DU corresponds to a 0.01 mm thickness of pure ozone at standard temperature and pressure.

Mesospheric descent: Downward movement of air from the mesosphere into the stratosphere, affecting ozone concentrations in polar regions.

References

1. Potential drivers of the recent large Antarctic ozone holes. Nature Communications (2023).
2. To what extent can the ozone valley over the Tibetan Plateau influence the East Asian summer precipitation?. npj Climate and Atmospheric Science (2023).
3. Montreal Protocol's impact on the ozone layer and climate. Atmospheric Chemistry and Physics (2023).
4. Evidence for a continuous decline in lower stratospheric ozone offsetting ozone layer recovery. Atmospheric Chemistry and Physics (2018).
5. On the Cause of Recent Variations in Lower Stratospheric Ozone. Geophysical Research Letters (2018).