The ozone hole appears to be recovering and is driving positive changes in atmospheric circulation, according to Canadian and American research. The findings underline the immense potential of international cooperation in the face of environmental crises, a message which rings true today with the current climate crisis.
The ozone layer’s recovery is linked to the 1987 Montreal Protocol, which initiated the phasing out of ozone-depleting chemicals like chlorofluorocarbons (CFCs). The hole’s expansion may now have paused or even reversed, according to the team.
“This study adds to growing evidence showing the profound effectiveness of the Montreal Protocol,” said lead author Antara Banerjee in the press release. “Not only has the treaty spurred healing of the ozone layer, it’s also driving recent changes in southern hemisphere air circulation patterns.”
Banarjee commented to the Financial Post that their work is the first to credit the treaty with a return to pre-pollution atmospheric behaviour.
Ozone layer protects us as well as the environment
The ozone layer is seated in the stratosphere and protects humans, plant life, and more from harmful UV rays by absorbing them. The ozone hole was discovered in 1985 and is located in the southern hemisphere.
The damage is primarily linked to CFCs which became common in consumer products like refrigerators and aerosol sprays starting in the 1960s. Atmospheric CFCs’ destructive potential is fully unleashed in springtime when the cold air breaks them down and releases their reactive chlorine element which destroys ozone.
In turn, ozone depletion leads to a cooling of the air, and this has caused major shifts in heat and moisture circulation trends.
Prior to 2000, a group of air currents in the southern hemisphere known as the mid-latitude jet stream had been progressively moving towards the South Pole. These shifts have affected rainfall in places like New Zealand and Patagonia as well as ocean temperature and salinity.
What the researchers have found is that around 2000, southern hemisphere circulation trends started to stop spreading so far south. At the same time, stratospheric concentrations of ozone-destroying chemicals like CFCs were on the decline, leading researchers to the conclusion that healing is in process.
Positive results, but increasing emissions could undo work
As part of their work, the team ran simulations of atmospheric forces using computer models based on data from 1980 to 2017. The simulations illustrated the curbing of the jet stream’s southbound movement starting around 2000.
Demonstrating the significance of the CFC ban required the team to strip away confounding factors from the data like greenhouse gases. After they were accounted for, it became clear that CFCs were by far the biggest villain.
However, the authors did caveat that rising CO2 levels could end up resuming the southward push. This is still speculative since the total amount of CO2 emissions that humans will end up emitting remains to be seen.
“This is an object lesson in how the international community should react to global environmental challenges,” wrote field expert Alexey Karpechko in an accompanying commentary. “Restricting dangerous emissions and changing business practices is also the way to combat global warming caused by greenhouse gases.”