-
ozone is first measured
first discovery and measurments of ozone layer recorded -
chlorofluorocarbons
chlorofluorocarbons are synthisised by Thomas Midgley Jr. -
the ozone hole was discovered
nasa found a hole in our ozone layer -
no change in ozone hole
no significant change was found in the ozone layer -
ozone was measured
the levels were so low that the scientists thought their equipment was faulty -
ozone half
ozone is half the size it was in 1970
