Global Warming and Ozone
Country: United States
Date: July 2008
Does global warming affect the ozone layer? If yes, how?
My answer is based on current thinking. The topic of global warming is
subject of massive discussions (sometimes nasty arguments).
So far as I know today, global warming and the hole in the ozone layer
are 2 distinct subjects. Chemicals called CFC's caused the hole in the
ozone layer. Global warming causes are now focused on greenhouse gases,
especially carbon dioxide.
Global warming does affect the ozone layer, and thus the ozone
layer affects weather and climate. You can find more details
about this on Wikipedia at http://en.wikipedia.org/wiki/Ozone_depletion
and on the web site of the Union of Concerned Scientists at
Briefly, there are several interactions that reduce the
"ozone layer" in the Stratosphere. First, ozone is destroyed
in the Stratosphere primarily by man-made chlorofluorocarbons
and this process is enhanced by stratospheric clouds. Ozone
and chlorofluorocarbons are themselves greenhouse gases; they
absorb solar radiation and thus they heat the air slightly.
So, the destruction of ozone in the "ozone layer" results in
less heat being trapped, cooling of the stratosphere, enhanced
stratospheric cloudiness (because it's colder), and therefore
enhanced ozone depletion.
The stratosphere is also cooled by the warming of the lower
part of the atmosphere (Troposphere). As greenhouse gases
(primarily carbon dioxide) increase in concentration in the
Troposphere, they absorb more terrestrial energy, they warm the
Troposphere (global warming), and they don't allow as much
energy to be lost (it is, in a sense, trapped in the troposphere)
from the Troposphere to the Stratosphere. This also results in
cooling of the Stratosphere, which leads to increased Stratospheric
cloudiness and therefore enhanced ozone depletion.
A cooler Stratosphere has an effect on weather patterns, thereby
affecting the weather (and longer term climate) in the Troposphere,
where we live.
David R. Cook
Climate Research Section
Environmental Science Division
Argonne National Laboratory
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