Total Global Ozone began to decrease around 1980. The Global Ozone Change % (red
ID: 283462 • Letter: T
Question
Total Global Ozone began to decrease around 1980. The Global Ozone Change % (red line) is compared with a 15-year average (straight black line) taken from 1964-1980. a) What role did Dupont (Chemical Company) play in determining the shape of this graph? Specifically, why did Total Global Ozone start decreasing around 19680? Why did it level off in the early 1990s? b.) There is a maximum of ozone at the South Pole (Antarctica) 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 why is there a maximum in the blue line at 15 km? c) What processes led to decreased values at 15 km in the 19686 (green) and 2001 (red) curves?Explanation / Answer
Dupont was the largest producer of CFC, that destroy ozone layer.
The observed global ozone depletion in the last three decades is attributable to increases in reactive halogen gases in the stratosphere. The lowest global total ozone values since 1980 have occurred in the years following the eruption of Mt. Pinatubo in 1991, which temporarily increased the number of sulfuric acid-containing particles throughout the stratosphere. These particles significantly increased the effectiveness of reactive halogen gases in destroying ozone and, thereby, increased global ozone depletion by 1–2% for several years following the eruption.
The depletion worsened for a few years after 1991 due to the effect of volcanic aerosol from the Mt. Pinatubo eruption. A
(b) steps are:
Halogen source gases are emitted at Earth's surface by human activities and natural processes.
Halogen source gases accumulate in the atmosphere and are globally distributed throughout the lower atmosphere by winds and other air motions.
Halogen source gases are transported to the stratosphere by air motions
Most halogen source gases are converted in the stratosphere to reactive halogen gases in chemical reactions involving ultraviolet radiation from the Sun.
Reactive halogen gases cause chemical depletion of stratospheric ozone over the globe.
Low-temperature surface reactions on polar stratospheric clouds (PSCs) significantly increase reactive halogen gases and thereby cause severe ozone loss in polar regions in late winter and early spring.
Air containing reactive halogen gases returns to the troposphere where the gases are removed by moisture in clouds and rain.
Why maximum:Low-temperature surface reactions on polar stratospheric clouds (PSCs) significantly increase reactive halogen gases and thereby cause severe ozone loss in polar regions in late winter and early spring.
C) because of CFC production and later full recovery may be complicated by stratospheric cooling caused by increased levels of atmospheric CO2 (red line) Ozone depletion has stabilised, total ozone levels are not expected to decline further.