Total ozone timeseries 1970 - 2017

Time-series of annual mean total ozone in four zonal bands (a-d) and polar (60°-90°) total ozone in March (NH) and October (SH) . In March (NH) and October (SH) are the months when polar ozone losses usually are largest. Data are from WOUDC (World Ozone and Ultraviolet Radiation Data Centre) ground-based measurements combining Brewer, Dobson, SAOZ (Système D’Analyse par Observations Zénithales), and filter spectrometer. All six datasets have been bias corrected by subtracting averages from the reference period 1998-2008 and adding the multiple data mean from the same period. The dotted grey lines in each panel show the average ozone level from 1970 to 1979 calculated from the WOUDC data. All data from 2017 are preliminary.