Healing of Antarctic Ozone Layer

IAS Prelims 2023

Scientists at MIT and elsewhere have identified the “first fingerprints of healing” of the Antarctic ozone layer.

The team found that the September ozone hole has shrunk by more than 4 million square kilometers — about half the area of the contiguous United States — since 2000, when ozone depletion was at its peak.

The team also showed for the first time that this recovery has slowed somewhat at times, due to the effects of volcanic eruptions from year to year. Overall, however, the ozone hole appears to be on a healing path.

The authors used “fingerprints” of the ozone changes with season and altitude to attribute the ozone’s recovery to the continuing decline of atmospheric chlorine originating from chlorofluorocarbons (CFCs).

These chemical compounds were once emitted by dry cleaning processes, old refrigerators, and aerosols such as hairspray.

In 1987, virtually every country in the world signed on to the Montreal Protocol in a concerted effort to ban the use of CFCs and repair the ozone hole.

The ozone hole was first discovered using ground-based data that began in the Around the mid-1980s, scientists from the British Antarctic survey noticed that the October total ozone was dropping.

From then on, scientists worldwide typically tracked ozone depletion using October measurements of Antarctic ozone.

Ozone is sensitive not just to chlorine, but also to temperature and sunlight. Chlorine eats away at ozone, but only if light is present and if the atmosphere is cold enough to create polar stratospheric clouds on which chlorine chemistry can occur — a relationship that Solomon was first to characterize in 1986.

Measurements have shown that ozone depletion starts each year in late August, as Antarctica emerges from its dark winter, and the hole is fully formed by early October.