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Ozone depletion over the Tropics

  • Published
    18th Jul, 2022
Context

Recently a study done by AIP Advances claimed that a new ozone hole has been detected over the tropics, at latitudes of 30 degrees south to 30 degrees north.

Background
  • Ozone depletion consists of two related events observed since the late 1970s;
  • A steady lowering of about four per cent in the total amount of ozone in Earth's atmosphere, and
  • A much larger springtime decrease in stratospheric ozone (the ozone layer) around Earth's Polar Regions.
  • The latter phenomenon is referred to as the ozone hole.
  • The main causes of ozone depletion and the ozone hole are manufactured chemicals, especially manufactured halocarbon refrigerants, solvents, propellants, and foam-blowing agents (chlorofluorocarbons (CFCs), HCFCs, halons), referred to as ozone-depleting substances(ODS).
  • Hence, several measures have been taken worldwide for conserving ozone depletion.
  • In 2019, NASA reported that the ozone hole was the smallest ever since it was first discovered in 1982.

Key highlights of the study

  • According to the study the ozone hole is located at altitudes of 10-25 km over the tropics.
  • The tropical ozone hole is about seven times larger than
  • The hole has become significant since the 1980s, and makes up 50 per cent of Earth’s surface.
  • It appears across all seasons, unlike that of Antarctica, which is visible only in the
  • It is likely to cause skin cancer, cataracts and other negative effects on the health and ecosystems in tropical regions.
  • Cause: Chlorofluorocarbon’s (CFC) role in depleting the ozone layer over Tropics also.
  • Evidence: The tropical stratosphere recorded a low temperature of 190-200 Kelvin (K), which is lower than the normal tropical stratospheric levels.
  • Procedure Adopted: Comparative study of the relative ozone changes in per cent in the 2000s with those in
  • These observed results were then compared to datasets from combined ground-based and satellite measurements used by other researchers.

Different definitions to Ozone Hole

  • Normally, a region of marked thinning of the ozone layer in high latitudes, chiefly in winter, attributed to the chemical action of CFCs and other atmospheric pollutants.
  • According to NASA, an ozone hole is an area where ozone levels drop below the historical threshold of 220 Dobson Units(DU is the measure of ozone concentrations).
  • Mechanism of Ozone depletion:
  • The pollutants are transported into the stratosphere by turbulent mixing after being emitted from the surface, mixing much faster than the molecules can settle.
  • Once in the stratosphere, they release atoms from the halogen group through photo dissociation, which catalyse the breakdown of ozone (O3) into oxygen (O2).


Is this study accepted worldwide?

  • Other experts not involved in the study have raised doubts about the study’s claims.
  • Issues aroused:
  • There were very few observations in the 1960s, from which the study’s data has been compared for tropical ozone depletion.
  • There are other better ozone datasets which are used widely in the community to determine ozone trends from the 1960s. They do not show this large drop in ozone.
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