This image shows the growth of the average area of the ozone hole
from 1979 to 2004 using data from Version 8 of the TOMS algorithm.
We define the ozone hole as the area for which ozone is less
than 220 Dobson Units, a value rarely seen under normal conditions.
It shows that the ozone this low hardly occured at all in 1980, but by
year 2000 covered an area larger than North America, 26.5 million square 
kilometers.