Ozone is perhaps the most familiar name associated with climate change. Most of us have heard about it and have a general awareness of what it stands for. This name got more global attention when in 1994 the UN general assembly proclaimed 16 September as the ‘International Day for the Preservation of the Ozone Layer.’
This proclamation was made to commemorate the signing of the ‘Montreal Protocol on Substances That Deplete the Ozone Layer’ in 1987.
But how come the simple molecule of 3 oxygen atoms became so significant for the world?
For that, we must look at the timeline from the 19th century onwards.
1839– Ozone is a naturally occurring substance, which was first made in the laboratory by German Scientist Christian Friedrich Schonbein who was interested in studying the chemical, physical and optical properties of chemical substances. In this process, he studied the optical properties of Ozone as a chemical substance.
During this period, physicists were exploring the field of electromagnetic radiations and light. By the late 1800s, they had learned a lot about radiations and knew how objects in general absorb and emit radiations. In one such study about the Sun, scientists discovered that the radiations emitted by the sun at its surface and the radiations reaching the earth’s surface were somewhat altered i.e. the radiations reaching the earth’s surface did not have wavelengths below 310nm from the ultraviolet spectrum. They speculated that there is something in the earth’s atmosphere which is perhaps altering the radiations reaching the earth.
1867– Schonbein identifies Ozone’s existence in the atmosphere.
Upon further investigation, it was discovered that the shape of the spectrum of missing light was similar to the optical properties of Ozone. Thus it was concluded that Ozone is the substance responsible for the absorption of Ultraviolet radiations from the sun. Then began the quest for the measurement of Ozone in the atmosphere.
1913– Fabry and Buisson tried to measure the total amount of Ozone in the atmosphere. They found that if they separated Ozone molecules from all the other air molecules and compressed them, then they would form a layer of 3 mm thickness.
In the 1920s – Gordon Dobson from Oxford University gave a systematic measurement unit for Ozone thickness. It was named as Dobson Unit where 1 Dobson unit is equivalent to 2.68 x 1016 molecules of Ozone per cm2 (1 DU= 2.68 x 1016 Molecules cm-2).
This gave the world a simple measurement of the Ozone layer which amounted to a thickness of 300 DU. It was also found that the Ozone layer varied in altitude with Latitude. At the equator it is found at an altitude of 25km and as we move up the latitudes higher than 20 degrees the altitude at which the Ozone is found keeps on getting lower till the poles where it is found at an altitude of 15 km.
The thickness of the Ozone layer also varies with the latitudes. At equators, the ozone is thin and becomes thicker as we move towards the poles. It is found to be thickest at the North Pole and thinnest at Antarctica (south pole) where the Ozone hole is formed in September when it’s the early fall season in the region.
In the 1970s– the scientific community pushed for a ban on the CFCs used in various products as they were of the view that these CFCs might adversely impact the Ozone layer.
1978– The environmental Protection agency banned the use of CFCs.
At the beginning of the 1980s– Jonathan Shanklin, armed with solid data from the Dobson spectrophotometer installed at Antarctica, concluded that the thickness of the layer has drastically decreased. In certain places, the thickness of the layer decreased by about 1/3 from previous levels.
1985– Jonathan Shanklin and his colleagues published their study in a journal and gave a jolt to the world. A team of scientists confirmed the findings of the Ozone hole. This event served as the final push and helped the world to wake up to the immediate threat of a depleting ozone layer.
1985– Vienna convention held to discuss these new findings.
1987– The world signs the ‘Montreal Protocol on Substances That Deplete the Ozone Layer’. The protocol was signed by 46 nations initially but eventually, all the 197 members of the United Nations signed and ratified the treaty. Thus begin the story of saving the Ozone layer.
1994– The UN general assembly proclaimed 16 September as the ‘International Day for the Preservation of the Ozone Layer.’
In the coming decades, the world phased out Ozone-depleting substances one by one. Binding for both developed and developing nations, this agreement regulates the production and consumption of CFCs and other Ozone-depleting substances. The protocol is adaptive and so far, 6 amendments have been made. Today the protocol targets about 96 such chemicals and keeps amending the list to stay up to date.
The ozone started to heal in a few decades. According to NASA, It is estimated that by 2070 we will achieve the pre-1980s Ozone levels.
The speed with which the world acted and the commitment the world showed is unprecedented. To date, it is the most successful international convention and sets an example for other future international treaties.