Methodology:

1. Description of the problem.
2. Cause of the problem.
3. Analysis of the problem.
4. Control of the problem.
   ➡Introduction to the problem:
   The stratospheric ozone layer protects life on Earth by absorbing ultraviolet light, which
   damages DNA in plants and animals (including humans) and leads to sunburns and skin
   cancer. Prior to 1979, scientists had not observed atmospheric ozone concentrations below 220
   Dobson Units. But in the early 1980s, through a combination of ground-based and satellite
   measurements, scientists began to realize that Earth’s natural sunscreen was thinning
   dramatically over the South Pole each spring. This thinning of the ozone layer over Antarctica
   came to be known as the ozone hole.
   
   This is Dobson’s unit of the first observation on September 17, 1979 and the most recent one
   that is on October 12, 2018. The red region is showing the size of the ozone hole. It’s clearly
   visible in the above data that how in the past years the size of the ozone hole on Antarctica
   increased. Due to this hole on the ozone layer uv rays reaches down on the region of the
   Antarctica which result in the melting of glacier and due to which the sea-level increases and
   due to the increased sea-level cyclones, flooding, storms and other natural disasters occurs
   which highly affects the human lives on the earth.

NOTE:– The measurements were made from 1979–2004 by NASA’s Total Ozone Mapping
Spectrometer (TOMS) instruments; from 2005–2011 by the Royal Netherlands Meteorological
Institute’s Ozone Monitoring Instrument (OMI) (which flies on NASA’s Aura satellite); and from
2012-2019 by the Ozone Mapping Profiler Suite (OMPS) on the NASA/NOAA Suomi NPP
satellite. Red and yellow areas indicate the ozone hole.

➡Cause of the problem:
The ozone hole opened the world’s eyes to the global effects of human activity on the
atmosphere. Scientists found out that chlorofluorocarbons (CFCs)—long-lived chemicals that
had been used in refrigerators and aerosol sprays since the 1930s—had a dark side. In the
layer of the atmosphere closest to Earth (the troposphere), CFCs circulated for decades without
degrading or reacting with other chemicals. When they reached the stratosphere, however, their
behavior changed. In the upper stratosphere (beyond the protection of the ozone layer),
ultraviolet light caused CFCs to break apart, releasing chlorine, a very reactive atom that
repeatedly catalyzes ozone destruction.
The global recognition of the destructive potential of CFCs led to the 1987 Montreal Protocol, a
treaty phasing out the production of ozone-depleting chemicals. Scientists estimate that about
80 percent of the chlorine (and bromine, which has a similar ozone-depleting effect) in the
stratosphere over Antarctica today comes from human, not natural, sources.
Effect of CFCs, HCFC and VOCs on the Ozone layer

•Analysis of the problem:
Serious ozone depletion has been measured every Antarctic spring since the early 80’s. This
ozone depletion is considered to be a result of photo chemical reactions and cat- alytic cycles
resulting from anthropogenic halogen containing gases. In addition, the formation of Polar
Stratospheric Clouds (PSCs) facilitates ozone loss because reac- tive halogen species are
released by heterogeneous reactions on the surface of a PSC particle. Generally, Arctic ozone
depletion is less severe and shows larger variability than Antarctic loss because of the unstable
and warmer condition. However, the Arctic stratosphere has been becoming colder during past
decades and the Arctic ozone loss in the 2011 winter was comparable to Antarctic losses.
Ozone depletion is di- rectly/indirectly linked to the climate because the absorption of UV
radiation changes the temperature field. It is therefore important to quantify the loss for future
climate prediction.
Following picture is showing the concentration of the ozone layer by Dobson’s unit.

➡Control of the problem:
Ways to prevent the depletion of ozone layer are as follows:-
● Avoid the consumption of gases dangerous to the ozone layer.
● Minimise the use of vehicles.
● Use of any other eco-friendly chemical as a substitution of CFCs in the refrigerators.