The Ozone hole over Antarctica is the most notable and well-known depletion of Earth's protective ozone layer but this precious molecule can be destroyed from the poles to the tropics. Now scientists think that the reduction of ozone over the North Pole is leading to unexpected weather repercussions in the Northern Hemisphere.

As reported in Nature Geoscience, the team believes they have found a causal link between the reduction of ozone and unusual weather events. Ozone absorbs UV light from the Sun, warming up the stratosphere and causing the polar vortex – an area of low pressure and cold air around the poles – to break down for spring. But a lack of ozone keeps the temperatures low and the polar vortex strong.

“Ozone destruction occurs only when it is cold enough and the polar vortex is strong in the stratosphere, about 30 to 50 kilometres above the ground,” explained lead author and doctoral student Marina Friedel from ETH Zurich.

“A strong polar vortex then produces the effects observed at the Earth’s surface,” added coauthor Gabriel Chiodo also from ETH Zurich.

The researchers noticed that in 2020 the depletion of ozone in the Arctic was seen together with warm and dry conditions in Europe and across Siberia. Although in places like the polar region, the weather was wetter than expected. Similar scenes were seen in 2011 when the same depletion was observed. 

The team ran two different simulations that included ozone depletion, which is often excluded from models as they make the computational work more laborious. Both models reproduced the events witnessed in 2020 and 2011 as long as the ozone depletion was included.  

“What surprised us most from a scientific point of view is that, even though the models we were using for the simulation are utterly different, they produced similar results,” said Chiodo.

The ozone destruction is due to the presence of chlorofluorocarbons (CFCs) and other substances that have been banned since 1989 lingering in the atmosphere. While some signals of recovery have begun to appear, these chemicals linger up there for up to a century, so the effects of ozone depletion on climate are likely still playing a role.

“Yet CFC concentrations are steadily declining, and this raises the question of how quickly the ozone layer is recovering and how this will affect the climate system,” Friedel wondered. “It will be interesting to observe and model the future evolution of the ozone layer.”