The CFC's are broken down into chlorine by the sun's ultraviolet rays, thus causing the depletion. While the ozone hole did shrink to its smallest size since 1988, scientists say it was thanks to an unstable and warm atmosphere - not a drop in harmful chemicals.
The ozone layer protects the Earth from the sun's ultraviolet radiations which can cause skin cancer and cataracts, supress immune systems and harm plants. Just two years after the hole was discovered, the world jumped quickly to solve the problem.
Hailed as an example of how concerted global action can help solve a planetary crisis, a new study conducted by NASA scientists documented the first direct evidence that an worldwide effort to ban chlorofluorocarbons (CFCs) has led to the recovery of the Antarctic ozone hole.
It wasn't until the late 1980s that the world finally came to terms with the fact that manmade chemicals were destroying the Earth's ozone layer.
Strahan's study is the first to look directly at measurements of chemicals to argue that the shrinking hole stems from the ban of CFCs. Chlorine, in particular, is very harmful since these atoms are extremely reactive with ozone.More news: Ranking the best, worst diets for heart health in 2018
Former Secretary of State John Kerry gestures as he delivers a speech during the 28th Meeting of the Parties to the Montreal Protocol in Kigali, Rwanda on October 14, 2016. The abrupt discontinuity in the 2017 plot is due to the orientation of the ozone hole rotating as the satellite gathered its data over the full 24 hour period. However, their study found that hydrochloric acid concentrations in the ozone hole were declining by comparison, by an average of 0.8 per cent per year. The second was nitrous oxide (N2O), another long-lived chemical that is capable of reaching the stratosphere, which acts as an excellent baseline for comparison to CFCs because its concentration is not declining, and it is affected by the same atmospheric motions that would impact measurements of hydrochloric acid.
Since 2005, NASA scientists have used the Aura satellite to measure ozone depletion rates during the winter months.
"This is very close to what our model predicts we should see for this amount of chlorine decline".
Scientists at NASA said they had located the largest ozone hole ever recorded, in a report released October 3, 2000.
There is still a long way to go for a complete recovery. "But we're not yet seeing a clear decrease in the size of the ozone hole because that's controlled mainly by temperature after mid-September, which varies a lot from year to year". Using measurements from the agency's Aura satellite, scientists have been looking at the Antarctic ozone hole's chlorine over the last several years, watching as the amount slowly decreased.