Although the ozone hole over Antarctica is well known, few people are aware that the protective ozone in the stratosphere periodically breaks down over the Arctic, depleting the ozone layer there.
Prior to that, it occurred in the spring of 2011 and most recently in the months of spring 2020.
Ozone depletion on the north pole
Climate scientists have recorded weather abnormalities every time the ozone layer has been breached, which has affected the whole northern hemisphere.
Those springtimes were extremely warm and dry in Siberia, central and northern Europe, Russia, and notably in the former Soviet Union.
However, there were other places, like the arctic regions, where it was damp, as per ScienceDaily.
These meteorological irregularities were most noticeable in 2020.
Additionally, that spring in Switzerland was abnormally warm and dry.
Climate science is divided on the issue of whether the loss of stratospheric ozone causes the observed weather anomalies.
Another factor is the stratospheric polar vortex, which develops in the winter and dissipates in the spring.
The facts and conclusions reached by scientists who have so far investigated the phenomena are incongruous.
The researchers performed simulations that included ozone depletion in two separate climate models in order to find potential causal relationships.
Due in part to the need for significantly greater processing capacity, most climate models solely take into account physical variables and ignore changes in stratospheric ozone concentrations.
The new estimates, however, make it abundantly evident that ozone loss over the Arctic is mostly to blame for the weather abnormalities seen in the northern hemisphere in 2011 and 2020.
The two models' simulations closely matched observational data from those two years, as well as eight more similar incidents that were used as comparisons.
However, the researchers were unable to replicate similar findings when they "switched off" ozone destruction in the models.
As currently understood by academics, the problem started with stratospheric ozone loss. The Arctic must have extremely low temperatures in order for ozone to be destroyed there.
Doctoral student Marina Friedel, member of the group headed by Thomas Peter, Professor of Atmospheric Chemistry at ETH Zurich noted that ozone degradation only takes place in the stratosphere, between 30 and 50 kilometers above the surface, when it is cold enough and the polar vortex is strong.
The current state of the ozone layer
Over the whole globe, stratospheric ozone is being depleted.
However, the Arctic region of the northern hemisphere (where this phenomenon is milder) than the southern hemisphere (Antarctica), as per the European Environment Agency.
This is because the Arctic experiences greater yearly weather fluctuation than the Antarctic.
Additionally, unlike in the Antarctic, the Arctic does not experience prolonged low temperatures in the stratosphere.
Since 2000, the ozone hole has generally shown indications of mending, mostly due to the Montreal Protocol's phase-out of ozone-depleting compounds.
At the same time, the stratospheric temperature has a significant impact on the size of the ozone hole, with warmer temperatures causing a smaller ozone hole, as was the case in 2019.
However, as greenhouse gases typically have a cooling impact in the stratosphere while they contribute to global warming in the troposphere, this is not directly related to human climate change.
With the exception of the polar areas, this stratospheric cooling has a favorable impact on the recovery of ozone.
Here, very cold temperatures may promote polar stratospheric cloud production, which aids in ozone depletion.
Volcanic eruptions can also occasionally have an impact on the ozone hole by increasing the number of particles in the stratosphere and reducing ozone levels.
This helps to explain those sporadic years when the ozone hole is rather substantial.
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