Mirrored changes in Antarctic ozone and stratospheric temperature in the late 20th versus early 21st centuries

Abstract

Observed and modeled patterns of lower stratospheric seasonal trends in Antarctic ozone and temperature in the late 20th (1979–2000) and the early 21st (2000–2014) centuries are compared. Patterns of pre‐2000 observed Antarctic ozone decreases and stratospheric cooling as a function of month and pressure are followed by opposite‐signed (i.e., “mirrored”) patterns of ozone increases and warming post‐2000. An interactive chemistry‐climate model forced by changes in anthropogenic ozone depleting substances produces broadly similar mirrored features. Statistical analysis of unforced model simulations (from long‐term model control simulations of a few centuries up to 1000 years) suggests that internal and solar natural variability alone is unable to account for the pattern of observed ozone trend mirroring, implying that forcing is the dominant driver of this behavior. Radiative calculations indicate that ozone increases have contributed to Antarctic warming of the lower stratosphere over 2000–2014, but dynamical changes that are likely due to internal variability over this relatively short period also appear to be important. Overall, the results support the recent finding that the healing of the Antarctic ozone hole is underway and that coupling between dynamics, chemistry, and radiation is important for a full understanding of the causes of observed stratospheric temperature and ozone changes.

Radiosondes Show That After Decades of Cooling, the Lower Stratosphere Is Now Warming

“…Changes are considerably smaller in fall (brown). Similar covarying behavior between ozone and temperature changes in the lower stratosphere has recently been observed over Antarctica (Solomon et al, ).…”

“…The reversal from ozone depletion to ozone recovery is likely an important driver for the lower stratospheric temperature trends to switch from cooling to warming, as also emphasized by Maycock (2016) and Solomon et al (2017). Vertical trend profiles derived from radiosonde temperature data show maximum cooling before 2000 and maximum warming trends after 2000, predominantly at altitudes between 20 and 25 km (Figure 3).…”

“…Here the longwave cooling and heating, respectively, by ozone is large, supporting the importance of ozone during the cooling and warming period before and after the turn of the century evident in radiosonde records. Furthermore, the seasonal coherence of trend changes in both ozone and temperature trends observed over Europe (Figure ) and Antarctica (Solomon et al, ) suggest a link between the observed ozone and temperature trend reversal. Recently reported evidence from satellite measurements that ozone in the lower stratosphere between 60°S and 60 N has continued to decline since 1998 (Ball et al, ) is not supported by our results.…”

Troposphere‐Stratosphere Temperature Trends Derived From Satellite Data Compared With Ensemble Simulations From WACCM

“…Figure b shows a similar comparison of ozone changes in the Antarctic spring lower stratosphere, comparing September ozonesonde measurements from Syowa (69°S) with WACCM zonal means sampled at 70°S, motivated by similar comparisons in Solomon et al (). The time series show decreases prior to the late 1990s followed by increases after circa 2000, with reasonable agreement between the model and ozonesonde measurements (consistent with results in Solomon et al, , ). The comparisons in Figures a and b suggest accurate simulation of ozone changes (decrease and partial recovery) in WACCM for the two subperiods.…”

“…Regardless of precise significance levels, the characteristic spatial and temporal behavior of the observed trends, and congruence with the WACCM simulations, provides convincing evidence that healing of the ozone hole reported in Solomon et al () is being reflected in observed temperature trends for the Antarctic lower stratosphere. A similar conclusion regarding Antarctic temperature trends has been reported by Solomon et al (), based on (Modern‐Era Retrospective Analysis for Research and Applications‐2) MERRA2 reanalysis data. Overall, the observed temperature responses to stratospheric ozone changes, in both the lower and upper stratosphere, provide further evidence for anthropogenic influence on stratospheric temperatures.…”