OCR Triple Science Physics - Ideas In Context

This is some extra information which you may found helps - sources mentioned in the document. It contains info on sulphate injections, the ozone layer, global warming, Mount Pinatubo and extra scientific data.

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Physics ideas in context
Found from the article: "The sensitivity of polar ozone depletion to proposed
geoengineering schemes"
Authors: Simone Tilmes, Rolf Müller, and Ross Salawitch
Publication: Science Express, April 24, 2008
Sulfates and ozone
Sulfates from volcanoes provide a surface on which chlorine gases in the cold
polar lower stratosphere can become activated and cause chemical reactions that
intensify the destruction of ozone molecules, although the sulfates themselves do not
directly destroy ozone. The new study concluded that, over the next few decades,
hypothetical artificial injections of sulfates likely would destroy between about onefourth
to threefourths of the ozone layer above the Arctic. This would affect a large part of the
Northern Hemisphere because of atmospheric circulation patterns.
Protecting the ozone
Recovery of the ozone hole has been a major goal of policymakers worldwide.
Nations agreed in 1987 to a landmark accord, known as the Montreal protocol, to
restrict the production of industrial chemicals, known as CFCs (chlorofluorocarbons)
that cause ozonedestroying chemical reactions. The ozone layer is critical for life on
Earth because it blocks dangerous ultraviolet radiation from the Sun.
"This study highlights another connection between global warming and ozone
depletion," says coauthor Ross Salawitch of the University of Maryland. "These
traditionally had been thought of as separate problems but are now increasingly
recognized to be coupled in subtle, yet profoundly important, manners."
Ozone impacts
They then estimated future ozone loss by looking at two geoengineering
schemesone that would use volcanic sized sulfates and a second that would use
much smaller injections. The study found that injections of small particles, over the next
20 years, could reduce the ozone layer by 100 to 230 Dobson Units. This is a significant
loss because the average thickness layer in the Northern Hemisphere is 300 to 450
Dobson Units. With large particles, Arctic loss would range from 70 to 150 Dobson
Units. In each case, the larger figure is correlated with colder winters. The ozone loss

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Dobson Units, depending
on the size of the sulfates and the severity of winters. In the Antarctic, most of the ozone
is already depleted and the sulfate injections would not significantly reduce the
thickness of the ozone layer. Instead, they would significantly delay the recovery of the
ozone hole.
The authors caution that the actual impacts on ozone could be somewhat
different than estimated if atmospheric changes led to unusually warm or cold polar
winters.…read more

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