Preservation of Ozone Hole

In News

• A recent scientific assessment has suggested that the ozone hole is now expected to be completely repaired by 2066.

Key Findings

• Recovery period: 
  • The ozone layer over Antarctica, where the hole is the most prominent, will take a long time to heal completely. 
  • If current policies continued to be implemented, the ozone layer was expected to recover to 1980 values by 2066 over Antarctica, by 2045 over the Arctic, and by 2040 for the rest of the world.
  • Over the rest of the world, the ozone layer is expected to be back to where it was in 1980 by 2040 itself.
• How it became possible: 
  • Successful elimination of some harmful industrial chemicals, together referred to as Ozone Depleting Substances or ODSs.
  • Implementation of the 1989 Montreal Protocol. 
    • Nearly 99 per cent of the substances banned by the Montreal Protocol have now been eliminated from use, resulting in a slow but definite recovery of the ozone layer.
• Ozone: 
  • Ozone (chemically, a molecule having three Oxygen atoms, or O3) is found mainly in the upper atmosphere, an area called stratosphere, between 10 and 50 km from the Earth’s surface. 
  • It is critical for planetary life, since it absorbs ultraviolet rays coming from the Sun. 
  • UV rays are known to cause skin cancer and many other diseases and deformities in plants and animals.

Damage to the ozone layer

• Origin: 
  • The depletion of the ozone layer, first noticed in the early 1980s, used to be the biggest environmental threat before climate change came along. 
• Hole or just reduction?
  • Though the problem is commonly referred to as the emergence of a ‘hole’ in the ozone layer, it is actually just a reduction in concentration of the ozone molecules. 
  • Even in the normal state, ozone is present in extremely low concentrations in the stratosphere. Where the ‘layer’ is supposed to be the thickest, there are no more than a few molecules of ozone for every million air molecules.
• Sharp reductions in concentrations of Ozone:
  • In the 1980s, scientists began to notice a sharp drop in its presence. 
  • This drop was much more pronounced over the South Pole.
  • It was later linked to the unique meteorological conditions that prevail over Antarctica:
    • Temperature, 
    • Pressure, 
    • Wind speed and 
    • Direction 
• Biggest hole during months: 
  • The ozone hole over Antarctica is the biggest during the months of September, October, and November.
• Main cause deciphered:
  • The use of a class of industrial chemicals that contained chlorine, bromine or fluorine. 
  • The most common of these were the chlorofluorocarbons, or CFCs, that were used extensively in the air conditioning, refrigeration, paints, and furniture industries.
• Montreal Protocol: 
  • It was with this climate change objective in mind that the Montreal Protocol was amended in 2016 to extend its mandate over hydrofluorocarbons, or HFCs, that have replaced the CFCs in industrial use. 
  • HFCs do not cause much damage to the ozone layer — the reason they were not originally banned — but are very powerful greenhouse gases. 
• Kigali Amendment:
  • The Kigali Amendment to the Montreal Protocol seeks to eliminate 80-90 per cent of the HFCs currently in use by the year 2050. 
  • This is expected to prevent another 0.3 to 0.5 degree Celsius of global warming by the turn of the century.

Timeline 

• Before 1979: 
  • Scientists had not observed atmospheric ozone concentrations below 220 Dobson Units (DU; measure of the total amount of ozone in a vertical column of air above the Earth’s surface). 
• 1980s and after:
  • In the early 1980s, scientists using ground-based and satellite measurements began to realise that the 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. 
• In 1979, the maximum depth of the hole was 194 Dobson Units (DU). In 1982, it fell to 173 DU, in 1983 to 154 DU, and in 1985 to 124 DU.
• The image below has been picked from a series published by NASA showing the size and shape of the ozone hole every year from 1979 through 2019. 
• Red and yellow areas in the images indicate the ozone hole. The maps show the ozone hole on the day the lowest ozone concentrations were measured each year.

Image Courtesy: IE 

• In 1991, ozone concentration fell below 100 DU for the first time. The deepest hole was in 1994, when concentrations fell to 73 DU on Sept 30.

Significance

• It covers the entire planet and protects life on earth by absorbing harmful ultraviolet-B (UV-B) radiation from the sun.
• Impact on Plants
  • Plants cannot live and grow in heavy ultraviolet radiation, nor can the planktons that serve as food for most of the ocean life.
• Health impact of UV-B rays
  • With a weakening of the Ozone Layer shield, humans would be more susceptible to skin cancer, cataracts and impaired immune systems.
• Without it, life may have been impossible on earth due to harmful UV-B rays.
• Ozone-Depleting Substances: 
  • Their elimination has an important climate change co-benefit as they are powerful greenhouse gases.
  • Several of them  are hundreds or even thousands of times more dangerous than carbon dioxide, the most abundant greenhouse gas and the main driver of global warming. 
  • Global compliance to the Montreal Protocol ensures the avoidance of 0.5 to 1 degree Celsius of warming by 2050. 
  • That is if the use of CFCs and other similar chemicals had continued to grow the way it did before they were banned, the world would have been 0.5 to 1 degree Celsius warmer than it already is.

Concerns

• Replacements available: 
  • The use of ODSs, though extensive, was restricted to some specific industries. 
  • Their replacements were readily available, even if at a slightly higher cost initially. 
  • The impact of banning these ozone-depleting chemicals was therefore limited to these specific sectors. 
  • With some incentives, these sectors have recovered from the initial disruption and are thriving again.
• Carbon footprints: 
  • Emission of carbon dioxide is inextricably linked to the harnessing of energy. 
  • Almost every economic activity leads to carbon dioxide emissions. Even renewable energies, like solar or wind, have considerable carbon footprints right now, because their manufacturing, transport, and operation involves the use of fossil fuels.
• Greenhouse gas emissions: 
  • The emissions of methane, the other major greenhouse gas, comes mainly from agricultural practices and livestock. 
  • The impact of restraining greenhouse gas emissions is not limited to a few industries or economic sectors, but affects the entire economy, and also has implications for the quality of life, human lifestyles and habits and behaviours.

Way Ahead

• Ensuring that existing restrictions on ozone-depleting substances are properly implemented and global use of ozone-depleting substances continue to be reduced.
• Ensuring that banks of ozone-depleting substances (both in storage and contained in existing equipment) are dealt with in an environmentally-friendly manner and are replaced with climate-friendly alternatives.
• Ensuring that permitted uses of ozone-depleting substances are not diverted to illegal uses.
• Reducing use of ozone-depleting substances in applications that are not considered as consumption under the Montreal Protocol.
• Ensuring that no new chemicals or technologies emerge that could pose new threats to the ozone layer (e.g. very short-lived substances).

Source: IE