The hole in the ozone layer above the Antarctic is the smallest it's been since it was first spotted in 1982, scientists from NASA and NOAA have reported this week.

However, we shouldn’t be patting ourselves on the back too prematurely. The scientists working on this project believe this is the result of a sudden shrinking caused by a shifting polar vortex and wonky weather in the upper atmosphere over Antarctica. 

“It’s great news for ozone in the Southern Hemisphere,” Paul Newman, chief scientist for Earth Sciences at NASA's Goddard Space Flight Center in Maryland, said in a statement. “But it’s important to recognize that what we’re seeing this year is due to warmer stratospheric temperatures. It’s not a sign that atmospheric ozone is suddenly on a fast track to recovery.”

The ozone layer is a region of Earth's stratosphere with a high concentration of a gas called ozone that helps to shield the planet from the Sun's harmful ultraviolet (UV) rays. Certain human-made chemicals, such as manufactured refrigerants and solvents, can act as ozone-depleting substances after they are transported into the stratosphere, causing a “hole” to form. 

The hole in the ozone grows and shrinks each year with the changing of the seasons. This year, the ozone hole grew to its biggest, 16.4 million square kilometers (6.3 million square miles), on September 8, before shrinking down to less than 10 million square kilometers (3.9 million square miles) over the rest of the month and October. 

This would be outstanding in a typical year. Unfortunately, this isn’t a typical year.

The past couple of months have witnessed a weakening of the Antarctic polar vortex, paired with unusually strong warming in Antarctica’s stratosphere. The altered conditions and spike in temperature have set the scene to limit the chemical reactions that result in the ozone-depletion process.

While this recent trend is primarily down to climatic factors, humans have made an impressive effort to help curb ozone-depleting chemicals. Just two years after the ozone hole was first discovered in 1985, 196 countries and the European Union signed the Montreal Protocol – currently the only United Nations treaty to be adopted by all member states – to phase out the production of nearly 100 ozone-depleting chemicals.

Just last month, the latest Scientific Assessment of Ozone Depletion concluded that parts of the ozone layer have recovered at a rate of 1 to 3 percent every 10 years. It also suggested that, thanks to the Montreal Protocol, the Northern Hemisphere and mid-latitude ozone will heal completely by the 2030s, with the Southern Hemisphere repaired by the 2050s. 

“We should remember that the Montreal Protocol is both an inspirational example of how humanity is capable of cooperating to address a global challenge and a key instrument for tackling today’s climate crisis,” UN Secretary-General, António Guterres, said in a statement.