Ozone may be a more potent greenhouse gas than previously thought, according to a new study that has found it appears to weaken one of Earth’s most important cooling mechanisms.
The researchers found that changes in ozone levels in two layers of the planet’s atmosphere were responsible for almost a third of the global warming observed over the past 70 years.
Ozone is a highly reactive gas that is created in the upper atmosphere by the interaction between oxygen molecules and UV radiation from the sun.
The high ozone layer in the upper atmosphere shields us from much of the sun’s ultraviolet radiation.
However, in the lower atmosphere, it forms due to chemical reactions between pollutants such as vehicle exhaust and other emissions.
Ozone air pollution at ground level where humans breathe causes serious health problems.
In the study published in the journal Natural climate changethe researchers found that an increase in ozone in the lower atmosphere caused deep and rapid warming of the ocean waters bordering Antarctica.
Dr Michaela Hegglin, Associate Professor of Atmospheric Chemistry and one of the study’s authors, said: “Ozone near the Earth’s surface is harmful to people and the environment, but this study finds that ‘It also has a big impact on the ocean’s ability to absorb excess. the heat of the atmosphere.
“These findings are eye-opening and underscore the importance of regulating air pollution to prevent rising ozone levels and rising global temperatures.”
To improve understanding of the impact of ozone on heat uptake, the team used models to simulate changes in ozone levels in the upper and lower atmosphere between 1955 and 2000 and to isolate them other influences.
These simulations showed that a decrease in ozone in the upper atmosphere and an increase in the lower atmosphere both contribute to the observed warming in the upper 2 km of waters of the Southern Ocean, also known as the Atlantic Ocean. Antarctic.
A startling finding for the researchers is that increased ozone in the lower atmosphere caused 60% of the ozone-induced global warming observed in the Southern Ocean during the study period – far more than previously thought. thought so before.
This was not expected as increases in tropospheric ozone are generally considered a climate forcing in the Northern Hemisphere, as this is where the main pollution occurs.
“We have known for some time that the depletion of the ozone layer in the atmosphere has affected the surface climate in the Southern Hemisphere,” Dr Hegglin said.
“Our research has shown that the increase in ozone in the lower atmosphere due to air pollution, which occurs mainly in the northern hemisphere and “leaks” into the southern hemisphere, is also a serious problem.
“There is hope for solutions, and the success of the Montreal Protocol in reducing the use of CFCs shows that international action is possible to prevent damage to the planet.”