Total Global Ozone began to decrease around 1980. The Global Ozone Change % (red
ID: 282965 • Letter: T
Question
Total Global Ozone began to decrease around 1980. The Global Ozone Change % (red line) is compared with a 15-year average (striaght black line) taken from 1964-1980.
(First image)
a.) What role did Dupont (Chemical Company) play in determining the shape of this graph? Specifically, why did Total Global ozone start decreasing around 1980? Why did it level off in the early 1990s?
(Second Image)
b.) There is a maximum of ozone at the South Pole (Antartica) around 15 km in the October average from 1967- 1971 (before the recent depletion). Explain the processes that produce and destroy ozone in the stratosphere and there is a maximum in the blue line at 15km?
c.) What processes led to decreased values at 15km in the 1986 (green) and 2001 (red) curves?
Explanation / Answer
Ans A:
The shape of the graph is highly influenced by production of CFC’s as the ozone destruction is influenced by the chlorine and bromine. Dupont (chemical company) which held patent of many compounds is primarily responsible for increased production and uses of CFCs. Thus the shape of the graph with increasing ozone depletion coincides with wide scale production of CFCs by Dupont, which was used in aerosol spray and refrigeration.
The total global Ozone start decreasing around 1980 due to increasing consumption of CFC’s for aerosol spray and refrigeration.
The total global Ozone, level off in early 1990s this is due to the abundance of human induced chlorine and bromine in atmosphere, since at that times only US has proposed a ban on aerosol spray.
Ans B:
The production and destruction of Ozone is caused by interaction of Oxygen/Ozone with UV radiation. The stratosphere receives high energy UV radiation which causes splitting of the Oxygen molecules (O2 into O), these Oxygen molecules latter combine with oxygen to produce Ozone.
The destruction of Ozone can be caused by natural as well as human induced process. Ozone molecules destruction occurs as it gets dissociated in the Oxygen molecule due to influence of UV radiation, in addition chlorine and bromine can combine with ozone to produce oxygen and thus causing destruction of ozone. .
The blue line at 15 km defines the concentration of ozone at 15 km over pole, in this reference it is imperative to note that since ozone is produced at equator and is carried to the pole by the wind. The Brewer- Dobson circulation accounts for rise of air at equator and its downward and poleward movement accounts for concentration of Ozone at 15 km altitude.
Ans C:
The decreased values at 15 km in 1986 and 2001 can be attributed to the higher concentration of pollutants at this level and their transportation from equator towards poles by global wind system. This causes concentration of pollutants at lower altitudinal level which results in destruction of ozone. This explains the effects of pollutants and consequent decrease in Ozone levels as shown in green and red curves.