New Ozone depletion over the Tropics

Published on - July 18, 2022

Source: DtW 

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 spring season.

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.