The gradual recovery of the ozone layer over the Antarctic has apparently stopped the shift of the jet streams towards the South Pole. Since 2000, this trend has been stopped or even slightly declining, reports a research group led by Antara Banerjee from the University of Colorado (USA) in the Trade journal “Nature”. Strong wind bands, the changes of which can influence the regional climate, are called jet streams.
The ozone layer is approximately 15 to 35 kilometers high in the stratosphere. It protects living beings on earth from the harmful effects of ultraviolet radiation from the sun. In the 1980s, scientists demonstrated that the ozone layer over the Antarctic was thinning out for the first time. And they found that this is mainly due to chlorofluorocarbons (CFCs). That is why politicians from numerous countries have banned these substances in the so-called Montreal Protocol of 1987.
The ozone hole may have disappeared in 2050
Consequential problems were associated with the formation of the ozone hole over the Antarctic. Measurements showed that at the end of the 20th century, the summer jet streams around the Antarctic moved further south: around 49 degrees to 51 degrees south. It also contributed to the warming of the Antarctic Peninsula, Patagonia (South America) and New Zealand. West Tasmania and West New Zealand in turn became drier. The circulation, temperature and salinity of the Southern Ocean are said to have been influenced by the shifting of the jet streams.
However, since around 2000, researchers have observed that the ozone hole over the Antarctic is gradually closing. The fact that this process is dynamic and takes a long time is mainly due to the durability of the CFC connections. Recently, according to the German Aerospace Center (DLR), an ozone hole was even measured above the Arctic, which, however, was favored by a specific wind configuration and various chemical processes. According to the DLR, this observation does not contradict the assessment that the ozone layer as a whole is rather recovering. The World Meteorological Organization (WMO) said six years ago that the ozone hole over Antarctica could be history in 2050.
The researchers around Banerjee therefore wanted to find out whether the ban on CFCs has an indirect effect on the strong wind bands and the climate of the southern hemisphere. “The challenge in this study was to prove our hypothesis that ozone layer recovery actually drives these atmospheric circulation changes and is not just a coincidence,” said Banerjee. Because the climate around the South Pole is very variable, so that trends can only be made visible using complex statistical methods.
Montreal Protocol has an impact on the climate
The researchers used data from the years 1980 to 2017 and various climate models. Using numerous simulations, they were initially able to show that the changes in the jet streams are not only due to natural causes such as volcanic eruptions or changes in solar radiation. They then simulated other human-influenced factors for the changes, such as greenhouse gases or the amount of ozone. The team found that the proportion of ozone in the upper atmosphere explains very well why the jet streams are not moving further south, but even a slightly reversed trend can be seen.
In a commentary that was also published in the journal “Nature”, Alexey Karpechko from the Finnish Meteorological Institute in Helsinki writes: “The results of the authors provide a clear signal that human actions can influence the earth’s climate: The Montreal Protocol has it climate change associated with ozone depletion. ” Limiting dangerous emissions and changing economic activity is also the way to combat global warming caused by greenhouse gases.