An international team of researchers led by Susan Solomon at Massachusetts Institute of Technology (MIT) has identified the “first fingerprints of healing” of the Antarctic ozone layer, published this week (30 June 2016) in the journal Science.
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 discovery by British Antarctic Survey (BAS) of the Antarctic ozone hole provided an early warning of the dangerous thinning of the ozone layer worldwide, and spurred international efforts to curb the production of CFCs. The provisions of the Montreal Protocol of 1987 on Substances that Deplete the Ozone Layer have been revised and strengthened and are being followed by virtually all UN Member states.
Jonathan Shanklin from BAS was one of the scientists who was part of the discovery in 1985. He says:
“It is very clear that the Montreal Protocol is working, that it is clearly leading to a reduction in the amount of ozone destroying chemicals in the atmosphere, and that this reduction is probably leading to a recovery of the Antarctic ozone layer. Nevertheless we will still have ozone holes for perhaps another half century.”