 A proposed solution to reverse the effects of global warming by
spraying sulfate particles into Earth's stratosphere could make matters
much worse, climate researchers said on Thursday.
They said trying to cool off the planet by creating a kind of
artificial sun block would delay the recovery of the Antarctic ozone
hole by 30 to 70 years and create a new loss of Earth's protective
ozone layer over the Arctic.
"What our study shows is if you actually put a lot of sulfur into
the atmosphere we get a larger ozone depletion than we had before,"
said Simone Tilmes of the National Center for Atmospheric Research in
Boulder, Colorado, whose research appears in the journal Science.
The sulfur injection idea has been proposed by a number of climate scientists as a potential solution to global warming.
Tilmes said the idea was intended to mimic the effects of a major
volcanic eruption. Such eruptions in the past sent plumes of
sun-blocking sulfur into an upper layer of the atmosphere known as the
stratosphere that cooled temperatures on Earth.
Ozone in the stratosphere provides a protective layer high above Earth's surface that guards against harmful solar radiation.
Antarctica's ozone layer has been steadily thinning, resulting in a seasonal "hole" above the South Pole.
"We know that particles would result in the cooling of the planet," Tilmes said in a telephone interview.
But such cooling would come with unintended side effects. She said
sulfate injections could react with chlorine gasses in cold polar
regions, triggering a chemical reaction that would further deplete
atmospheric ozone.
Tilmes and colleagues looked specifically at the impact of plans to
repair holes in the ozone over the poles and concluded that regular
injections of sulfates over the next few decades would destroy between
one-fourth to three-fourths of the ozone layer above the Arctic.
That would affect a large part of the Northern Hemisphere because of
atmospheric circulation patterns, they said. The impact would be less
during the second half of the century because of international pacts to
ban the production of ozone-depleting chemicals.
In the Antarctic, a sulfate-injection scheme would delay the
recovery of the ozone hole by 30 to 70 years, or at least until the
last decade of this century.
Tilmes and colleagues used different measurements and computer models to make their predictions.
She said her findings did not close the door on the idea of
artificially cooling the planet in that way but raised a flag of
caution.
"We need people to have atmospheric models to understand the process in more detail," she said in a telephone interview. Source
|
