While the hole in the Earth's protective ozone layer is slowly
healing, its recovery might have a downside, scientists say: Climate
change could change wind patterns and send ozone from high in the
atmosphere down to the surface, where it is a major component of smog.
The discovery of a hole in the ozone layer
above Antarctica was announced by a team of British scientists in 1985.
The cause of the hole was attributed to ozone-depleting chemicals like
chlorofluorocarbons (CFCs), which were primarily used in cooling units
and propellants. When CFCs reach the ozone layer, they release chlorine
atoms that rip ozone apart and peel away layers of Earth's natural
sunscreen.
Simulations of life without the ozone layer, which is located in the
Earth's stratosphere, are not pretty. The stratosphere (the second layer of the Earth's atmosphere,
just above the one in which we dwell, the troposphere) contains 90
percent of the Earth's ozone at altitudes between 6 and 31 miles (9.6
and 50 kilometers) above us, where it traps most of the sun's harmful
ultraviolet (UV) rays before they can reach the Earth's surface.
Without this shield, we'd be sunburned within 5 minutes of exposure, according to NASA's Earth Observatory.
The Antarctic ozone hole is the closest real-life glimpse at a world without UV protection.
Since its discovery in the 1980s, it has spread over parts of
Australia, New Zealand, Chile and South Africa where the threats of
skin cancer, cataracts, and damage to have raised concerns.
Major efforts have been initiated to speed up the ozone hole's
recovery, including the 1987 Montreal Protocol and the phasing out of
CFCs. Even so, a study by Guang Zeng and her colleagues from New
Zealand's National Institute of Water and Atmospheric Research shows
that that the recovery, in concert with climate change, may do harm as
well as good.
The study, detailed in the May edition of Geophysical Research
Letters, revealed that variations in atmospheric circulation due to
climate change will cause a 43-percent increase in gas exchange between
the stratosphere and the troposphere, the layer of Earth's air at the
surface and our air supply. As more and more ozone is replenished in
the stratosphere it will also have more opportunities to seep into the
air we breathe.
Some ozone is currently present in the troposphere, though mostly as smog from car emissions and other pollutants. It can be harmful to human respiratory systems and the environment.
If carbon dioxide levels in the atmosphere increase as expected from
unabated emission, Zeng said the ozone layer will cool off, blurring
the temperature boundary that separates it from the troposphere. Within
the next century, more ozone than ever before will surge into our air,
her computer model study predicts.
Zeng hopes that future studies of the impacts of climate change will
account for the atmospheric composition of both the stratosphere and
troposphere, as well as the movement of ozone between the two, to paint
a better, more accurate picture of the Earth's environmental future.
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This article was provided by OurAmazingPlanet, a sister site to LiveScience.
- Original Story: The Downside to the Recovery of the Ozone Hole
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