The gaping hole in the Earth’s protective ozone layer is shrinking and its the smallest it's been since 1988, according to NASA.
This year, the hole measured 7.6 million square miles wide (19.7m square kilometers wide), about two and a half times the size of the United States, in September.
Though the numbers seem threatening, the hole seen this year is markedly smaller than last, around 1.3 million square miles (3.4m square kilometers) smaller and it continues to shrink.
“NOAA ground- and balloon-based measurements also showed the least amount of ozone depletion above the continent during the peak of the ozone depletion cycle since 1988. NOAA and NASA collaborate to monitor the growth and recovery of the ozone hole every year,” stated NASA.
The reason for this change is the warmer than usual weather conditions in the stratosphere since 2016. The warmer air helps prevent chemicals like chlorine and bromine from eroding the ozone layer. However, another reason could be effort since the 1980s to reduce the carbon emissions of ozone-depleting chemicals.
"Weather conditions over Antarctica were a bit weaker and led to warmer temperatures, which slowed down ozone loss," said Paul A. Newman, chief Earth scientist at NASA's Goddard Space Flight Center in Maryland as reported by the Washington Post.
However, scientists at NASA say that the change in the ozone hole between last year and this one is mostly due to natural variability and is no indication of a miraculous recovery. We’re not out of the woods yet.
The Ozone Hole
Ozone is a molecule made of three oxygen atoms that occur naturally in small amounts. Th ozone layer protects earth from harmful ultraviolet radiation “that can cause skin cancer and cataracts, suppress immune systems and also damage plants.” On Earth, ozone can also be created by a photochemical reaction between the sun and pollution from harmful emissions.
This reaction can take the form of dangerous smog. Another culprit is laughing gas or nitrous oxide according to a 2009 study.
"The overall lifetime of nitrous oxide is about a hundred years, comparable to many CFCs," study leader A. R. Ravishankara of the National Oceanic and Atmospheric Administration told National Geographic at the time.
The Antarctic ozone hole was first detected in 1985, where it was discovered that it forms during the Southern Hemisphere’s late winter when the resurgence of sun rays catalyze reactions in human-made, chemically active forms of chlorine and bromine — both destroy ozone molecules.
In 1987, international governing bodies signed the Montreal Protocol on Substances that Deplete the Ozone Layer. From there, regulations began on ozone-depleting compounds.
The ozone hole over Antarctica is expected to gradually become less severe as chlorofluorocarbons—chlorine-containing synthetic compounds once frequently used as refrigerants – continue to decline.
Scientists expect the Antarctic ozone hole to recover back to 1980 levels around 2070.