On September 16, the world observes ‘World Ozone Day’ in order to increase awareness about the layer’s depletion. According to the United Nations Environment Protection program, Ozone day proves that, “collective decisions and action, guided by science, are the only way to solve major global crises.”
The Ozone Day 2020 marks 35 years of Vienna Convention, and three decades of global interventions towards ozone protection.
What is Ozone?
In the stratosphere (second layer of atmosphere), there is a thin layer of a chemical compound known as Ozone. The gas is a compound of oxygen and formed when three oxygen atoms combine (O3). The ozone is like a thin sheet blanketing the earth which absorbs almost 98% of Sun’s harmful, cancer-causing Ultra-Violet B-light.
The Ozone is a ‘trace gas’. The rare compound has a ratio of 3-parts per million molecules of air (in the densest areas its 10 parts per million). Apart from its already rare existence, the layer is also threatened by human development and activities.
Ozone layer was first observed in 1913 by French Scientists, Charles Fabry and Henri Buisson. They realised there was a difference between the radiation emitted by the sun in the upper atmosphere and that within the lower atmosphere. They deduced there must be something absorbing away the majority of radiation in between.
However, it was also discovered within a few decades that the layer was under severe threat. Thinning was observed over specific areas, especially Australia and Antarctica. The biggest ‘hole’ was discovered over the South Pole in 1985. Among natural compounds, Nitric oxide, Nitrous oxide, Hydroxyl and Chlorine free radicals can damage ozone. The most ubiquitous culprit, however, are human-made compounds chlorofluorocarbons and Bromo fluorocarbons.
Since the discovery, international treaties have been made to limit the use of these compounds. They are mostly used in cooling devices like air-conditioners and refrigerators as well as aerosol products like deodorants.
In 1990s, the Ozone was considered to be at its worst. However, in 2003, scientists announced that the layer might be recovering as the depletion rate slowed down significantly. They chalked it up to the international ban on ODS (ozone depleting substances).
Scientists from the University of Colorado Boulder observed that the O3 ratio has been rising steadily over the last two decades, especially in the northern hemisphere. The great ozone hole was also counted to be at its smallest in 2019.