In the stratosphere, i.e. the high gas layers above twelve kilometers above the ground, there is a huge hole: the Canadian researcher Qing-Bin Lu from the University of Waterloo found an ozone hole seven times the size when evaluating extensive data from satellites and ground measuring stations , which has so far been described over the poles, especially over the South Pole. The hole that has now been discovered is located between 30 degrees north and 30 degrees south latitude, i.e. above the equator or the tropics. Since about half of the world’s population lives in these latitudes, the effects on humanity are enormous.
Many scientists were surprised: the ozone hole over the tropics was overlooked for years
Ozone holes are defined as areas where the stratosphere has lost more than 25 percent of its usual ozone level. Ozone, a molecule made up of three oxygen atoms, is a gas found primarily in the stratosphere where it filters UV radiation from sunlight. Without ozone, more UV light reaches the ground and damages the coverings of plants and animals. Excessive UV radiation leads to sunburn in humans and, in the long term, to skin cancer.
In the 1980s, researchers first noticed such greatly reduced ozone levels in the atmosphere over the two poles. Fluorochlorine hydrocarbons (CFCs or CFCs) were identified as the cause, and their use in refrigerators and aerosol cans was then banned.
Because the formation and depletion of the ozone layer is a dynamic process that is not easy to measure, previous research teams did not interpret their data correctly, study author Lu writes. Therefore, many scientists are very surprised by the current discovery. However, the evaluation now published in the journal AIP Advances clearly shows that the ozone levels in the center of the hole have been reduced by around 80 percent and that the hole has existed all year round since the mid-1980s.
Ozone hole could have an impact on climate change.
Lu believes that the tropical ozone hole is created by the same mechanisms as the Antarctic one. This would mean that released CFCs have also attacked the ozone layer. Thanks to the CFC ban, the degradation has been slowed down, but it continues. The reason for this could also be other mechanisms, such as the residues of large forest fires in the upper atmosphere. Current work by researchers at the Leibniz Institute for Tropospheric Research (TROPOS) in Leipzig, among other things, points to this possibility. According to this, forest fires could throw organic molecules into the stratosphere and trigger chemical processes there to deplete the ozone.
The tropical and polar ozone holes are also central to the cooling and regulation of temperatures in the stratosphere. As a result, there are three temperature holes in this upper layer of the atmosphere, which could have an impact on climate change, according to Quing-Bin Lu.