Extremely low winter temperatures over the Arctic are becoming more frequent and extreme due to climate patterns associated with warming, according to a new study by an international team of scientists, including a researcher from the University of Maryland. climate. The result is an increase in chemical reactions between substances that humans pumped into the air decades ago, resulting in greater ozone losses.
The new findings challenge the commonly held assumption that ozone loss would start to stop after the 2010 global ban on the production of ozone-depleting chemicals called chlorofluorocarbons (CFCs) and halons.
The study, carried out jointly by UMD, the Helmholtz Center of the Alfred Wegener Institute for Polar and Marine Research and the Finnish Meteorological Institute.appeared yesterday in the review Nature Communication.
“We are in a kind of race between the slow and steady decline of CFCs, which take 50 to 100 years to disappear, and climate change, which is causing the extreme temperatures of the polar vortices to cool rapidly,” Ross said. Salawitch, professor in the Department of Atmospheric and Oceanic Sciences, the Department of Chemistry and Biochemistry and the Interdisciplinary Center for Earth System Sciences. “The increasingly cold temperatures create conditions which favor the depletion of the ozone layer by CFCs. So even though these compounds are slowly disappearing, arctic ozone depletion is increasing as the climate changes.
New data from the study showed the lowest temperatures in the Arctic Polar Vortex and the highest ozone losses on record in 2020, breaking previous records set in 2011.
The polar vortex is a relatively self-contained low-pressure system that forms in the stratosphere at an elevation of about 12 to 50 kilometers (7.5 to 31 miles) above the Arctic each fall and remains for varying lengths of time. throughout winter to spring.
A trend of more frequent and extreme low temperatures in the polar vortex is of concern to researchers, as these conditions favor cloud formation. This in turn promotes the loss of ozone in the polar stratosphere, as clouds provide the right conditions for atmospheric chlorine to change shape and react with bromine and sunlight to destroy ozone.
Despite the drastic reduction in industrial production of CFCs and halons since the Montreal Protocol in 1987 and the subsequent global ban in 2010, airborne chlorine and bromine produced by humans are not expected to fall below 50 % of their highest levels by the end of this century.
The researchers projected the loss of ozone through 2100 based on the long-term temperature trend in the polar vortex and the expected decline in chlorine and brominate compounds. They based their predictions on the results of the 53 best climate models used by the Intergovernmental Panel on Climate Change.
“All of the climate models we’ve looked at except one show that unusually cold winters in the polar vortex will get colder over time,” said Salawitch. “And the more greenhouse gas emissions there are, the stronger the trend, which means greater depletion of the ozone layer.”
By combining these projections with analyzes of meteorological data from the past 56 years, the researchers confirmed that the Arctic is already experiencing a significant trend towards lower stratospheric temperatures and associated increases in ozone loss. Moreover, their observations reveal that these trends are occurring at a rate compatible with the fastest climate change models.
“We are saying that a train has been coming for a number of years now,” said Salawitch, whose previous posts showed extreme Arctic winters were getting colder. “We have now seen the train go at full speed with record ozone loss in 2011 and now in 2020. So this document is really a red flag that something is going on in the atmosphere that is really important for us. ozone, and it looks like a greenhouse gases are driving it.
Because ozone filters out much of the sun’s potentially harmful UV rays, a depleted ozone layer over the Arctic can lead to increased UV radiation reaching the Earth’s surface over Europe. , North America and Asia when the polar vortex plunges south.
But there is hope for preventing future ozone depletion, the researchers say. Their study shows that substantial reductions in greenhouse gas emissions over the next few decades could lead to a steady decline in conditions conducive to significant ozone loss in the Arctic stratosphere.