Early in the 1990s, the developed
countries of the world began phasing out the production
of chlorofluorocarbons (CFCs), a group of chemicals
believed to be responsible for the destruction of stratospheric
ozone. By 1996, all production of CFCs by developed
countries had ceased.
This graph shows the minimum levels
of ozone over Antarctica through the year 2000. The
number above each red dot is the observed ozone level
(in Dobson units), and the number below the dot (e.g.
9/30) is the month and day of that reading.
12. How does the graph of minimum ozone
levels in the late 1990s compare to the graph of levels
before that time?