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Late 1800s
Ozone was created first identified and measured intrest to scientists because air currents in the stratosphere move ozone around Earth. Ozone forms over the equator where the rays of sunlight are the strongest and then flows around the poles. -
1800s-1929
Refrigerators from the late 1800s until 1929 used the toxic gases, ammonia (NH3), methyl chloride (CH3Cl), and sulfur dioxide (SO2), as refrigerants. -
British scientist G.M.B Dobson
British scientist G.M.B Dobson began measuring the amount of ozone in the atmosphere. Ozone is formed in the higher regions of the stratosphere, most of it is stored in the lower stratosphere. -
Old refrigerators
Several fatal accidents occurred in the 1920s because of methyl chloride leakage from refrigerators. People started leaving their refrigerators in their backyards. A collaborative effort began between three American corporations, Frigidaire, General Motors and DuPont to search for a less dangerous method of refrigeration. -
Thomas Midgley
In 1928, Thomas Midgley, Jr. aided by Charles Franklin Kettering invented a "miracle compound" called Freon. Freon represents several different chlorofluorocarbons, or CFCs, which are used in commerce and industry. -
DuPont
Chloroflourocarbons were first created in 1928 as non-toxic, non-flamable refrigerants, and were first produced commercially in the 1930's by DuPont. The first Chlorofluorocarbon was CFC-12, a single carbon with two chlorines and two Fluorines attached to it. -
Chlorofluorocarbon (CFC)
Chlorofluorocarbons (CFCs) are a family of chemical compounds developed back in the 1930's as safe, non-toxic, non-flammable alternative to dangerous substances like ammonia for purposes of refrigeration and spray can propellants. -
The beginning
Dramatic loss of ozone in the lower stratosphere over Antarctica was first noticed by a research group from the British Antarctic Survey (BAS) who were monitoring the atmosphere above Antarctica from a research station. -
Halley Bay, Antarctica
The graph to the left here shows the measured total ozone above the Halley Bay station in Antarctica. Each point represents the average total ozone for the month of October. Note the sudden change in the curve after about 1975. By 1994, the total ozone in October was less than half its value during the 1970s, 20 years previous. This dramatic fall in ozone was caused by the use of man-made chemicals known as 'halocarbons' which include the well-known CFCs commonly used in fridges and so on. -
Monthly averages (1980- 1991)
Even though the same processes that lead to ozone depletion occur every year, the effect they have on the ozone is altered by the meteorology of the atmosphere above Antarctica. This is known as the 'variability' of the atmosphere. This variability leads to changes in the amount of ozone depleted and the dates when the depletion starts and finishes. -
British antarctic Survey (1981-1883)
A research group from the British Antarctic survey was monitoring the atmosphere above the Antarctica. They measured low levels of ozone - as low as 160 DU(Dobson Units) - during the antarctic spring of October -
British Antarctic Group (Cont.)
The British Antarctic group reported and confirmed decrease in the amount of ozone in the stratosphere and concluded that the ozone layer was thinning -
refrigerator CFC
Work on alternatives for chlorofluorocarbons in refrigerants began in the late 1970s after the first warnings of damage to stratospheric ozone were published. The hydrochlorofluorocarbons (HCFCs) are less stable in the lower atmosphere, enabling them to break down before reaching the ozone layer -
CFCs (Cont.)
The usage of CFCs grew over the years. Cholrine exist very little naturally in the atmosphere but also CFCs are an excellent way of introducing cholrine to the ozone layer. The ultraviolet radiation at this altitude breaks down CFCs, freeing the chlorine. Under the proper conditions, this chlorine has the potential to destroy large amounts of ozone. This has indeed been observed, especially over Antarctica.
