Today is World Ozone Day. It is celebrated to cause awareness among people about conservation of Ozone Layer and possible solutions to preserve it. Life on Earth would not be possible without sunlight. But life on Earth would also not be possible without the stratospheric ozone layer because it provides shield from the sun’s harmful ultraviolet radiation and so it is crucial to life on Earth. “Ozone for life” is the slogan for World Ozone Day 2020 and we are celebrating 35 years of global ozone layer protection.
Ozone depletion, gradual thinning of Earth’s ozone layer in the upper atmosphere caused by the release of chemical compounds containing gaseous chlorine or bromine from industry and other human activities. In 1969 Dutch chemist Paul Crutzen discovered ozone depletion; he found that nitrogen oxides react with free oxygen atoms and decompose ozone into nitrogen dioxide (NO2) and oxygen gas (O2) and finally slow down the process of ozone formation. In 1974, American scientists Mario Molina and F. Sherwood Rowland of the University of California discovered that anthropogenic chlorofluorocarbons (CFCs), molecules containing only carbon, fluorine, and chlorine atoms, could be a major source of chlorine in the stratosphere and this chlorine could destroy extensive amounts of ozone after it was liberated from CFCs. Later research revealed that bromine and certain bromine-containing compounds, like bromine monoxide (BrO), were more effective at destroying ozone than were chlorine compounds. In 1995 Crutzen, Molina, and Rowland received the Nobel Prize for Chemistry for their research on ozone depletion.
Later, scientists discovered that the ozone layer was being depleted by a wide range of industrial and consumer applications, mainly refrigerators, air conditioners and fire extinguishers which releases chlorine and bromine via CFCs and other halocarbons. The anthropogenic ozone-depleting substances remained in the stratosphere for decades and make ozone layer recovery very slow.
Earlier, Ozone depletion was greatest at the South Pole of the Earth. During peak depletion, the ozone is often completely destroyed in large areas. This severe depletion created the so-called “ozone hole” that can be seen in the satellite images of the Antarctic region.
The adverse effects of ozone depletion include increases in certain types of skin cancers, eye cataracts and certain immune deficiency, mutational disorders and genetic diseases due to UV radiation. The ozone depletion also affects terrestrial and aquatic ecosystems, altering growth, food chains and biochemical cycles. UV rays also affect plant growth and reduce agricultural productivity.
On September 16, 1987, the United Nations and 45 other countries signed the Montreal Protocol, to reduce the production and minimize the use of substances that are responsible for Ozone layer depletion. On December 19, 1994, the United Nations General Assembly proclaimed September 16 the International Day for the Preservation of the Ozone Layer, commemorating the date, in 1987, on which the Montreal Protocol was signed. Since then, September 16 has been celebrated as the International Day for the Preservation of the Ozone layer, every year. Global action taken under the Montreal Protocol has halted the depletion of the ozone layer and allowed it to start recovering. Due to the Montreal Protocol, global consumption of ozone-depleting substances has been reduced by some 98%. As a result, the ozone layer is showing the signs of recovery. Due to continuous international efforts, good news came in 2016 when scientists announced that stratospheric ozone concentrations had actually been increasing in the upper stratosphere since 2000 while the size of the Antarctic ozone hole had been decreasing. The Montreal Protocol became the biggest successful human effort to save the environment and life on Earth.
The man-made ozone-depleting CFCs are more potent greenhouse gases, also; these are “super greenhouse gases” with an extremely high “global warming potential” in comparison to carbon dioxide. Some of them have a global warming effect up to 14,000 times stronger than carbon dioxide (CO2), the main greenhouse gas. It means that a kilogram of currently used CFC has about 14000 times the effect on global warming as a kilogram of carbon dioxide and are capable of trapping enormous amounts of infrared radiations in the atmosphere, like carbon dioxide and thus can cause a greenhouse effect more stronger than carbon dioxide.
Therefore, the global phase-out of ozone depleting substances such as hydrochlorofluorocarbons (HCFCs) and chlorofluorocarbons (CFCs) has also made a significant positive contribution to the fight against climate change.
World community should learn from the success of the Montreal Protocol and should make the “Paris Agreement” successful to change climate change and to control related pandemics and climate disasters.