An ongoing daily feature of climate change news in recent decades has been the Earth’s ozone layer holes over polar regions, with stratospheric ozone levels greatly diminished.
The main cause is from anthropogenic sources of chlorofluorocarbons (CFCs), released from coolants in fridges, air conditioners and spray cans. Restrictions have and remain critical to ozone hole recovery because they have multi-decadal lifetimes in the atmosphere.
While policies exist to heal these ozone holes by 2045 and 2066 over the Arctic and Antarctic respectively, through the stopping of the production and consumption of ozone depleting substances, the 1987 international agreement of the Montreal Protocol, these holes are big and will just be around for a long time.
Direct depletion of ozone by chlorine and bromine compounds and long range ozone transport control Arctic ozone, explains Dr. Newman.
“Most of the temperatures for the former case were too warm for much depletion.” Regarding the latter case, stratospheric waves penetrating into the stratosphere from below bring ozone to the Arctic and heat the polar region and slow down the polar vortex.
For ozone transport, we have examined El Niño events and Siberian snow cover as controlling processes, and they do not seem to have a large effect.
The stronger than normal transport is due to a random weather year that propagates significant Rossby waves in the stratosphere.” “Declining levels of oxygen depleting substances and increasing levels of carbon dioxide were likely factors further elevating Arctic ozone to a record.”
Again, the Montreal Protocol is expected to lead to slowly increasing global ozone as well.” These two factors in combination will contribute to higher polar ozone values.”
“The stronger eddy heat flux into the stratosphere makes the Arctic source of Rossby waves propagate upward much more strongly than found in the mid latitude comparisons.” Therefore, the Arctic’s warmed, the vortex is weakened and there is much more ozone.
“I think because of the very cold vortex we have down there that can contain the reactive chlorine, we have deep ozone holes each year,” Dr. Newman says.
Using this insight, the coupled chemistry and climate models project 10–30 DU increase in Arctic ozone from 2000 to 2025 due to both decreased ozone depleting substances and increased greenhouse backgrounds.
Additionally, comparing this data with the 2024 Arctic ozone levels, one sees a 5 percent decrease in the UV index for a clear sky at noon when there is more UV in the sky.
Ozone recovery, however, is essential for the protection of life on Earth, because increased incoming UV radiation from space could have a number of consequences, including the reduction in plant growth (affecting the ‘lungs of the Earth’ and agricultural food supply), the disruption of marine food chains through impacts on plants or first producers, as well as the increase of skin cancer and immune deficiency disorders in humans.
Reference: Bird H. Arctic ozone reaches record high in positive step for climate.
