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. The dotted grey lines in each panel show the average ozone level from 1970 to 1979 calculated from the WOUDC data.