Climate science: Spring Arctic ozone depletion alters Northern Hemisphere climate

Recurring springtime ozone depletion events over the Arctic — the result of human emissions of ozone-destroying gases — can temporarily alter Northern Hemisphere temperatures and rainfall patterns, according to a study published in Nature Geoscience.

The ozone layer in the Earth’s atmosphere plays a key role in the absorption of potentially harmful ultraviolet radiation from the Sun. The release of gases such as chlorofluorocarbons has damaged the layer in recent decades, affecting the energy balance of the atmosphere. The persistent ozone hole over Antarctica is known to influence surface conditions in the Southern Hemisphere. However, it is unclear whether there are similar surface climate effects in the Northern Hemisphere.

Marina Friedel and colleagues analysed atmospheric data from the last four decades (1980–2020) to identify years with pronounced depletion of the ozone layer over the Arctic. The authors reveal that intervals of particularly low levels of ozone in the spring are typically followed several weeks later by wetter conditions in northern Europe and warmer, drier conditions in southern Europe and Eurasia. Using two climate models — which include accurate representations of ozone chemistry — the authors were able to disentangle ozone depletion effects from unrelated atmospheric circulation processes. Ozone depletion was found to lead to a cooler stratosphere (the second layer of the Earth’s atmosphere). This cooling, in turn, prolongs the presence of the polar vortex — a climatic phenomenon which can bring cold Arctic air southward — further into the spring which causes surface temperature and rainfall anomalies in the Northern Hemisphere.

The authors conclude that consideration of these ozone feedbacks could substantially help to improve the prediction of Northern Hemisphere climatic conditions in the weeks and months ahead.