A new study has suggested that increasing greenhouse gases could delay, or even postpone indefinitely the recovery of stratospheric ozone in some regions of the Earth.
The study, by Darryn W. Waugh, an atmospheric scientist at Johns Hopkins University in Baltimore, and his colleagues,
Researchers at NASA Goddard Space Flight Center in Greenbelt, Maryland, collaborated with Waugh in the new study.
The team forecast effects on ozone recovery by means of simulations using a computer model known as the Goddard Earth Observing System Chemistry-Climate Model.
Their findings suggested that climate change could provoke variations in the circulation of air in the lower stratosphere in tropical and southern mid-latitudes - a band of the Earth including Australia and Brazil.
The circulation changes would cause ozone levels in these areas never to return to levels that were present before decline began, even after ozone-depleting substances have been wiped out from the atmosphere.
"Global warming causes changes in the speed that the air is transported into and through the lower stratosphere (in tropical and southern mid-latitudes)," said Waugh. "You're moving the air through it quicker, so less ozone gets formed," he added.
According to Dan Lubin, an atmospheric scientist who has studied the relationship between ozone depletion and variations in the ultraviolet radiation that reaches the Earth, Waugh's findings could bode ill for people living in the tropics and southern mid-latitudes.
"If ozone levels never return to pre-1960 levels in those regions, "the risk of skin cancer for fair-skinned populations living in countries like Australia and New Zealand, and probably in Chile and Argentina too, will be greater in the 21st century than it was during the 20th century," he said.
While scientists have long suspected that climate change might be altering the dynamics of stratospheric ozone recovery, Waugh's team is the first to estimate the effects of increasing greenhouse gases on the recovery of ozone by region.
Waugh said that his study will help scientists attribute ozone variations to the right agent.
"Ozone is going to change in response to both ozone-depleting substances and greenhouse gases," he said. "If you don't consider climate change when studying the ozone recovery data, you may get pretty confused," he added.