Is chlorine bad for the ozone layer?

The ozone hole was created by the damage to the ozone layer, which protects the earth from harmful ultraviolet rays. Man-made influences cause this layer to lose its substance. International measures have taken effect quickly and prevented the ozone hole from spreading, but this topic has tended to be forgotten again in the meantime. While climate change and the energy transition are among the dominant environmental issues today, the ozone hole used to preoccupy politics and the media for years. Instead of the greenhouse gas CO2, the focus in the 80s and 90s was on so-called chlorofluorocarbons (CFCs), which destroy the ozone in the atmosphere.

How the ozone hole came about

In the past, CFCs were used in most refrigerators and aerosol cans. As it was released and distributed, this gas rose increasingly into the stratosphere. Since the temperatures in this sphere are higher than in the troposphere below, the gases can no longer escape there - which has serious consequences: In the stratosphere, they encounter UV rays that destroy the CFC molecules and produce chlorine . The chlorine in turn reacts with the ozone molecules and destroys them. This created a huge hole in the ozone layer over Antarctica.

The ban on CFCs shows success

The ozone layer over the southern polar region has been monitored regularly since the early 1980s. In 1985 fears that the release of CFCs could have a negative impact on the ozone layer was confirmed with the discovery of the ozone hole. This was followed by international efforts to prevent its further spread. The use of CFCs in refrigerators and aerosols has stopped around the world and the gas has been replaced with harmless substances. These measures were successful: it was possible to prevent the ozone hole from expanding beyond the Antarctic. Fortunately, thanks to peculiarities in the earth's atmosphere, the ozone hole formed almost exclusively over the Antarctic and not over densely populated areas, so mankind got away with a black eye again. However, the dwindling ozone layer over Australia shows that the problem is far from being solved.

Will the ozone hole close again?

Even if the spread of the ozone hole could be stopped - a worldwide thinning of the ozone layer can still be measured by satellite monitoring. According to these measurements, the destruction of the ozone layer did not progress any further between 1996 and 2002, but in 2005 the third lowest level of ozone ever measured was determined over the Antarctic. And the values ​​continued to deteriorate in 2006: At 27.45 million square kilometers, the ozone hole over the South Pole was once again one of its largest to date.

Since then, however, researchers have seen a turnaround. The worldwide ban on chlorofluorocarbons is taking effect and the ozone hole is slowly closing again. In 2012, the ozone hole over the Antarctic was only around 18 million square kilometers - an area 50 times the size of Germany. Due to the severe degradation of greenhouse gases, the closure of the ozone hole is not expected until 2075 at the earliest.

Consequences of the ozone hole for nature and people

A further destruction of the ozone view would have catastrophic consequences for humans and nature: The sun's UV rays would strike unhindered and threaten all life on our planet. More UV light would hit the earth's surface, which in humans can lead to skin damage, skin cancer or even blindness. But while humans could protect themselves in some form from the dangerous UV rays, plants would be exposed to the aggressive sun rays without protection. Wild plants hardly have a chance of survival. And enormous crop failures could also be expected, which in turn would lead to famine.

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