Signs of the ozone recovery based on multi sensor reanalysis of total ozone for the period 1979–2017

Abstract

The total ozone (TO3) multi-sensor reanalysis data-base, on a global scale, is examined for trend variability during the period 1979–2017. A multiple regression model is applied to the seasonal and yearly time series for zonal belts and 2-D bins covering the entire globe. Piecewise linear trend and independent linear trend pattern consisting of three joined and separated lines, respectively, are used to disclose long-term TO3 variability. The first line is for the ozone decline period forced by the increase of ozone depleting substances (ODS) in the stratosphere, the second one stands for an initial recovery phase starting after the ODS overturning at the end of the 1990s, and the third one is for latest trends. Negative trends are estimated outside the tropics in the first segment, especially during spring and summer. Both trend models provide significant year-round declining trend over the entire globe of ∼2% per 10 yr before the ODS overturning. Afterwards, in most cases trends are insignificant. However, significant positive trends are found for some latitudinal bands and bins at least in one of two post-ODS overturning segments. The number of bins with the upward trend is much larger than the number concerning bins with the downward trend. Significant positive year-round trends (∼2–4% per 10 yr) by both models are found over the entire globe, in the tropics, and poleward of 30° parallel after the ODS overturning. All these results support the emergence of ozone recovery on a global scale following the decline in the 1980s and 1990s.