Why is ozone important?

• Ozone (chemically, a molecule of three oxygen atoms) is found mainly in the upper atmosphere, an area called stratosphere, between 10 and 50 km from the earth’s surface. Though it is talked of as a layer, ozone is present in the atmosphere in rather low concentrations. Even at places where this layer is thickest, there are not more than a few molecules of ozone for every million air molecules.
• But they perform a very important function. By absorbing the harmful ultraviolet radiations from the sun, the ozone molecules eliminate a big threat to life forms on earth. UV rays can cause skin cancer and other diseases and deformities, in plants and animals.

When was Ozone hole first detected ?

• During September and October, the ozone hole over the Antarctic has been the smallest observed since 1982, NASA and US National Oceanic and Atmospheric Administration (NOAA) scientists have reported. The annual ozone hole reached its peak extent of 16. 4 million sq km on September 8, then shrank to less than 10 million sq km for the remainder of September and October, satellite measurements show. NASA has described it as great news for the Southern Hemisphere.
• The main cause of ozone depletion and the ozone hole is manufactured chemicals, especially manufactured halocarbon refrigerants, solvents, propellants, and foam- blowing agents (chlorofluorocarbons (CFCs), HCFCs, halons). Since the early 1970's, scientists observed reduction in stratospheric ozone and it was found more prominent in Polar Regions. ODS substances have a lifetime of about 100 years.
• The other ozone depleting substances( ODS) are chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), carbon tetrachloride, methyl chloroform and halons (brominated fluorocarbons). CFCs are the most widely used ODS, accounting for over 80 per cent of total stratospheric ozone depletion.

Where NASA detected this ozone hole specifically ?

• NASA said that this could have happened because of an extraordinarily high temperatures in the stratosphere this year, rather than the ongoing human efforts to contain the ozone depletion. Scientists have reported that temperatures in some areas of the stratosphere — usually over 100 degrees below zero — were 30° to 40°C higher than normal . At least two such extraordinary warming of the stratosphere has been observed in the past, and on both those occasions the ozone hole was also measured to be smaller than usual. But scientists are not sure why this warming happens. This warming has no observed connection with the warming in lower atmosphere that leads to climate change.
• But while this gain might be temporary, the depletion in the ozone layer is consistently being contained, thanks to global efforts to ban the use of harmful chemicals that destroy ozone. CFCs and similar chemicals were being widely used industrial applications like refrigeration, air-conditioning, foams, fire-extinguishers and solvents.
• A 1989 global agreement, called Montreal Protocol, organised international consensus on phased elimination of these chemicals. In subsequent years, the agreement has ensured the phase-out of over 90 per cent of these chemicals. Two years ago, an amendment to the Montreal Protocol cleared the way for a faster elimination of another set of similar compounds, called hydroflurocarbons, or HFCs, which were being used as temporary replacements for CFCs.
• The impact on the ozone layer has been encouraging. In September2019, the UN Environment Programme said that the ozone layer over some areas in the northern hemisphere could be completely restored to their pre-1980 levels by as early as the 2030s. The Antarctica ozone hole could be completely healed by the 2060s, it said. Parts of the ozone layer had recovered at the rate of 1 to 3 per cent every ten years since 2000.

Who carried out this study ?

• The research, carried out by scientists at the Massachusetts Institute of Technology’s Department of Earth, Atmospheric and Planetary Sciences and published in Proceedings of the National Academy of Sciences centered on CFC-11 (trichlorofluoromethane).
• Changes in oceanic levels of this gas have been shown to affect changes in its atmospheric concentrations.
• The researchers observed that oceans, which are a vast repository for gases, would emit more CFC-11 by 2075 than they absorb. They would emit detectable amounts of the chemical by 2130. The shift will occur 10 years earlier due to climate change.
• The emissions of CFC-11 from the ocean will effectively extend the chemical’s average residence time, causing it to linger five years longer in the atmosphere than it otherwise would. This may impact future estimations of CFC-11 emissions.
• The researchers used a hierarchy of models, starting with a simple six-box model, to simulate the mixing within and between the ocean and atmosphere. They began with a simple model of the atmosphere and the upper and lower layers of the ocean in the northern and southern hemispheres.

How Ozone layer is important for human beings ?

• The Ozone layer or also known as Ozone shield, a delicate layer of gas, in the Earth’s stratosphere absorbs most of the Sun’s ultraviolet rays. These rays can cause a numerous skin diseases. In the last few years, the ozone layer has depleted extensively.
• The ozone layer absorbs 97 to 99 percent of the Sun's medium-frequency ultraviolet light, which otherwise would potentially damage exposed life forms near the surface. Thinning of the ozone layer means increased skin related diseases. In recent decades, because of the release of large quantities of man-made organohalogen compounds, especially chlorofluorocarbons (CFCs) and bromofluorocarbons, the ozone layer is depleting. If earth loses the protection of ozone layer, then life on the planet will be at great risk.
• On September 16, 1987, the United Nations and 45 other countries signed the Montreal Protocol, on substances that deplete the Ozone layer. Every year this day is celebrated as the International Day for the Preservation of the Ozone layer.
• The purpose of the Montreal Protocol is to protect the Ozone layer by reducing the production of substances that are supposed to be responsible for Ozone layer depletion.
• Around 99 percent of ozone-depleting chemicals in refrigerators, air-cooling systems and other products have already been phased-out because of the Montreal Protocol.
• On September 16, 2009, the Vienna Convention and the Montreal Protocol became the first treaties in the history of the United Nations to achieve universal ratification.
• The Montreal Protocol, signed on September 16, 1987, is an international treaty planned to protect ozone layer by reducing the production of substances that are responsible for ozone layer depletion. The Montreal Protocol phases down the consumption and production of the different ozone depleting substances (ODS) in a step-wise manner, with different timetables for developed and developing countries. Under this treaty, all parties have specific responsibilities related to the phase out of the different groups of ODS, control of ODS trade, annual reporting of data, national licensing systems to control ODS imports and exports, and other matters.
• The Kigali Amendment to the Montreal Protocol, agreed to by 197 countries , is a milestone agreement. It will avoid global warming by up to 0.5°C by phasing out hydrofluorocarbons (HFCs), a category of greenhouse gases with extremely high global warming potential (GWP). The amendment is the product of seven years of negotiations. Four amendment proposals were submitted — the North American, European, and small island states’ proposals for developing countries advocated an early baseline (2011-13) and freeze (2021), while the Indian amendment proposed a later baseline (2028-30) and freeze (2031).