A new study from an international team of scientists, shows that extremely low winter temperatures high in the atmosphere over the arctic are becoming more frequent and more extreme because of climate patterns associated with global warming. The study also shows that those extreme low temperatures are causing reactions among chemicals humans pumped into the air decades ago, leading to greater ozone losses. The new findings call into question the commonly held assumption that ozone loss would grind to a halt in just a few decades following the 2010 global ban on the production of ozone depleting chemicals called chlorofluorocarbons (CFCs) and halons.
Most of the chlorine and a significant amount of the bromine in the stratosphere comes from the breakdown of CFCs, halons and other ozone-depleting substances. Normally within the Arctic polar vortex the chlorine is non-reactive, but clouds provide the right conditions for the chlorine to change form and react with bromine and sunlight to destroy ozone.
Despite drastic reduction of the industrial production of CFCs and halons since the Montreal Protocol in 1987 and the global ban that followed in 2010, these long-lasting compounds are still abundant in the atmosphere. According to the World Meteorological Organization, atmospheric chlorine and bromine produced by humans is not expected to fall below 50% of their highest levels until the end of this century.
— source University of Maryland | Jun 23, 2021