Canadian scientists write that there is a gigantic ozone hole over the tropics. But colleagues have serious doubts.

So far we have known the ozone hole mainly from the Antarctic, where it occurs every year, and most recently also from the North Pole. But the fact that the ozone layer is also said to be drastically thinned out over the tropics caused a worldwide surprise this Tuesday – and also dismay. An intact ozone layer in the atmosphere is important in order to absorb harmful ultraviolet radiation from the sun. UV radiation is considered to be the cause of skin cancer and other diseases.

The worrying news came from a research team in Canada: Professor Qing-Bin Lu from the University of Waterloo in Ontario and his colleagues report in the journal “AIP Advances” of a previously undiscovered ozone hole that is located in the tropics and is seven times larger than the one in the Antarctic. Although it has existed since the 80s, it has remained unrecognized until now.

In the 1980s, there was a global debate about damage to the ozone layer and possible steps to counteract it. As a result, the Montreal Protocol was passed in September 1987, obliging countries around the world to ban chemical substances that damage the ozone layer, such as chlorofluorocarbons (CFCs), which have hitherto been used as coolants or in aerosol cans. The efforts are now giving hope that the ozone holes at the poles will no longer appear in a few decades.

Canadians write about massive ozone hole in the tropics

But now there is supposed to be a gigantic ozone hole in the tropics? Qing-Bin Lu writes of the existence of a perennial zone of depleted ozone in the lower tropical stratosphere. Particularly alarming according to the team of scientists: The area is located in a region where about half of the world’s population lives. The people in the countries around the equator are exposed to the risk of increased UV radiation.

The Canadian professor points to the possible importance of the ozone holes at the poles and in the tropics for climate change, because these holes played a role in regulating the temperature on Earth.

The ozone hole around the equator was probably caused by the same mechanisms as those at the poles – by the harmful CFCs. After their ban, this effect slowed down, but improvements in the situation on the Poles had recently been observed again and again. However, the ozone layer could also be damaged by large forest fires.

The alleged discovery of the “third hole in the ozone layer” is met with opposition

However, the Canadian research team promptly received objections from experts: several experts who were not involved in the study doubt the existence of this supposedly huge ozone hole over the tropics. “I’m surprised the study has even been published in its current form,” said Martyn Chipperfield, Professor of Atmospheric Chemistry at the University of Leeds. It makes him suspicious that these massive changes in the ozone layer over the tropics cannot be found in any other studies. The results of the new study from Canada are very controversial and he is “not convinced that they are correct,” said Chipperfield.

Another scientist criticizing the Canadians’ method: Paul Young of Lancaster University said Qing-Bin Lu and his team had studied the percentage changes in ozone levels in the atmosphere. However, the absolute changes are relevant. He came to a very clear conclusion: this ozone hole over the tropics simply does not exist.

Sources: “AIP Advances”, “ZME Science”, “Daily Mail”, MDR Knowledge, “Der Standard”, “Newsweek”