It has been more than three decades since a hole was discovered in Earth's ozone layer. While the layer seems to have stabilized to a certain extent in recent years, it is still not showing any signs of recovering from the damage chemicals did to it, and now, there is a brand new threat on the horizon.
Earth's ozone layer, which protects us from the sun's ultraviolet radiation, was discovered to have a hole in it by scientists in 1984. The hole was created, scientists believe, by certain chemicals such as chlorofluorocarbons and hydrofluorocarbons and, a few years after the discovery of the hole, several nations got together and enacted what is known as the Montreal Protocol, which was designed to phase out those types of damaging chemicals.
Since that time, satellites monitoring the ozone hole have reported no sign of improvement.
One reason why there doesn't appear to be any signs of improvement could be because of atmospheric conditions. A study conducted by NASA in 2013 found that heat and wind in Earth's stratosphere change the average size of the ozone hole from one year to the next. In 2016, for example, NASA scientists determined that the fluctuations were due to an unusually warm stratosphere.
And now, some researchers argue the ozone layer is facing a new threat from harmful substances that aren't regulated by the Montreal Protocol. These substances are used in everything from pharmaceuticals to paint stripper, and it had been previously thought that they degraded before they ever reached the stratosphere.
But a recent study found there's more of them in the atmosphere than expected. Levels of dichloromethane, for example, have increased 60 percent over the past decade, and researchers have discovered that substances such as dichloromethane could endanger the Earth's fragile ozone layer and are not regulated under the current global treaty to stop production of ozone-depleting substances.
The study was carried out by an international team of researchers led by David Oram of UK-based University of East Anglia. He spoke recently about how scientists had previously misjudged how strong certain substances were.
"The substances in question were not considered damaging before as they were generally thought to be too short-lived to reach the stratosphere in large quantities."