This image is a chart showing the total ozone at Arosa, 
Switzerland. Arosa has the longest continuous series of ground
based measurements in the world. The charts X axis shows the 
year which ranges from 1930-2000. Its Y axis shows the ozone
measurement in Dobson Units and its range is form 280 
to 380 dobson units. The ozone measurements from Arosa are
shown in a blue line, and TOMS ozone measurments are shown
overlapping the Arosa measurements with a green line. It
is noteworthy that in the past two decades there is a 
significant drop in the total ozone.