EARTH.COM - The ozone layer is vital for our planet since it stops dangerous ultraviolet radiation from reaching the Earth’s surface. The fundamental role this gas plays was clearly understood in the 1980s, when scientists discovered a hole in the ozone layer high in the atmosphere over the South Pole, due to damage caused by chlorofluorocarbons (CFCs) – a group of chemicals used in industry and consumer products.
Now, a study led by the University of California Riverside has found that changes to ozone levels in the upper and lower atmosphere were responsible for almost a third of the warming of ocean waters surrounding Antarctica in the second half of the 20th century. This deep and rapid warming of the Southern Ocean diminishes its role as one of the main regions soaking up excess heat as our planet warms.
“Ozone close to Earth’s surface is harmful to people and the environment, but this study reveals it also has a big impact on the ocean’s ability to absorb excess heat from the atmosphere,” said study lead author Dr. Michaela Hegglin, an associate professor of Atmospheric Chemistry at UC Riverside. “These findings are an eye-opener and hammer home the importance of regulating air pollution to prevent increased ozone levels and global temperatures rising further still.”
Dr. Hegglin and her colleagues used models to simulate changes in ozone levels in both the upper and lower atmosphere between 1955 and 2000, in order to clarify their impact on the Southern Ocean heat uptake. They found that a decrease of ozone in the upper atmosphere and an increase in the lower atmosphere both contributed to warming detected in the upper two kilometers of the ocean waters in the high latitudes.
The increased ozone levels in the lower atmosphere appeared to cause over 60 percent of the total ozone-induced warming in the Southern Ocean – a surprising discovery, since tropospheric ozone increases were previously thought to have a much stronger impact in the Northern hemisphere, where there is more pollution.
“We have known for a while that ozone depletion high in the atmosphere has affected surface climate in the Southern Hemisphere. Our research has shown that ozone increases in the lower atmosphere due to air pollution, which occurs primarily in the Northern Hemisphere and ‘leaks’ into the Southern Hemisphere, is a serious problem as well,” said Dr. Hegglin.
“There is hope to find solutions, and the success of the Montreal Protocol at cutting CFC use shows that international action is possible to prevent damage to the planet,” she concluded.
The study is published in the journal Nature Climate Change.