There is a very large new ozone hole over the northern polar region. In a story released this week on Space.com, scientists report that the hole is more than three times the size of Greenland. The hole is visualized in this video from the European Space Agency.
The ozone layer in our atmosphere is what helps shield animal and plant life from excess ultraviolet radiation. There is an annual ozone hole that opens over Antarctica. It had been expanding and threatening people in the Southern Hemisphere with too much UV exposure and an increase in skin cancers. But in 1987, most of the world came into agreement that human-released gases that are destructive to the ozone layer would be banned from manufacture. The Montreal Protocol was put into effect in 1989, and has more than 200 signatories. Over the decades, slow but large scale improvement developed with the southern ozone hole due to the lower volume of reactive gases such as chlorine and bromine reaching the stratosphere.
The continued presence of a smaller ozone hole over Antarctica, even with the improvement, is largely due to the stable, colder air over that continent. Interestingly, warmer than average upper air temperatures over Antarctica this past year allowed the ozone hole to shrink further. When the air aloft is typically frigid, high altitude clouds form. Those clouds contain some chlorine and bromine, which is destructive to ozone. The warming this past year allowed the southern hole to shrink to a record small diameter, as seen in this Space.com video.
At the same time, our mild winter in the Northern Hemisphere was tied to the polar vortex remaining over the North Pole most of the time, trapping the coldest air at the surface and in the stratosphere in the polar region. There is usually more variability in the Arctic, allowing periodic warming (and record warming the last few winters prior to 2019-20). The anomalous cold in the polar region this past winter produced the kind of conditions more typically found over Antarctica, and is considered to be closely correlated with this rare Northern Hemisphere hole. If it persists, it will probably expose some far northern latitude peoples to more UV than usual for a while. However, it’s more likely as spring progresses and the polar vortex fades that the new ozone hole will begin to shrink and become diffuse for the summer.
As a matter of concern, there is peer-reviewed evidence that China has been violating the Montreal Protocol, at least since 2013 and verified again in a 2018 investigation. Reuters reported that China had been found to be releasing comparatively large volumes of banned ozone depleting substances, with emissions tied directly to factories in eastern and northern China. Included in these substances are carbon tetrachloride (you may remember that compound from cleaning fluid) and a banned refrigerant with the shorthand name CFC-11, belonging to an ozone-destroying class of chemicals called chlorofluorocarbons. While CFC-11 had been used as an efficient refrigerant, Chinese plants have recently been using it to manufacture polyurethane foam, according to Britain’s Environmental Investigation Agency.
The Chinese government claims they have investigated these emissions and closed 2 plants in violation of their emissions laws. As might be expected, China’s Ministry of Ecology and Environment has called into question the volumes and sources of the chlorofluorocarbons charged in external scientific measurements, but there was still, even by the Ministry’s admission, an “unexpected” increase in emissions in 2019. With or without this rare northern ozone hole, we’ll soon be needing to wear sunscreen as seasonal UV increases.