Ozone-destroying chemical making comeback, scientists find

mentalfloss

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Jun 28, 2010
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Ozone-destroying chemical making comeback, scientists find

An ozone-destroying chemical long thought to be on the decline in Earth’s upper atmosphere is making an unexpected comeback, an international team of scientists has found.

Backed by years of global observations that includes key contributions from a Canadian satellite, researchers reported in the journal Nature on Wednesday that concentrations of hydrogen chloride in the Northern Hemisphere have been edging upward since 2007.

The effect is pronounced enough to slow the recovery of the ozone layer, which helps to screen out harmful ultraviolet radiation from the sun. Ozone thinned dramatically in the past because of the use of chlorofluorocarbons (CFCs), which were phased out after international adoption of the Montreal Protocol in 1987.

The study reveals that hydrogen chloride – a byproduct of CFC release – began diminishing around 1998 because of the impact of the protocol. But seven years ago the trend reversed.

The result came as “a complete surprise,” said the study’s lead author, Emmanuel Mahieu, an atmospheric scientist at the University of Liège in Belgium.

“Of course, we were anxious that unreported or rogue emissions of chlorine-bearing source gases were responsible for it,” Dr. Mahieu said.

The reversal is seen only in the Northern Hemisphere at high altitudes, peaking in a zone that lies about 20 kilometres above the surface and 50 degrees north of the equator.

After an analysis of high-altitude winds and their effects on hydrogen chloride, the team ruled out rogue emissions and instead concluded that a change in air circulation in the stratosphere is the likely culprit. The effect of the change is that it concentrates “old air” that still carries a higher proportion of hydrogen chloride from years gone by.

The team says it is not clear why the stratosphere has changed. Climate change is unlikely to be directly responsible on such a short time scale, and some climate models predict the opposite effect. The result could simply be due to natural variability, team members said, in which case the stratosphere is showing a broader range of behaviour than was previously known.

The heightened concentration, while a concern, is not expected to be permanent since CFCs and related chlorine-bearing chemicals are no longer being emitted in large quantities. When present in the upper atmosphere, chlorine can react with and disrupt ozone molecules.

“Our results do not change the expectation that the ozone layer will recover from the effects of depletion over the next 50 years or so,” said Martyn Chipperfield, a team member and chemist at the University of Leeds in Britain.

Kaley Walker, an atmospheric physicist and co-author at the University of Toronto, said the result underscores the need for continued monitoring of atmospheric constituents.

SciSat, a Canadian satellite launched in 2003, provided a significant share of the space-based observations used in a study of Earth’s upper atmosphere. © Canadian Space Agency/ SciSat, a Canadian satellite launched in 2003, provided a significant share of the space-based observations used in a study of Earth’s upper atmosphere.
Dr. Walker works with data from SciSat, a Canadian satellite launched in 2003 that provided a significant share of the space-based observations used in the study.

The Canadian Space Agency is expected to approve an extension of the SciSat mission. Dr. Walker and others have also proposed a more advanced satellite that would conduct more-detailed atmospheric measurements. The federal government has not yet weighed in on whether it supports the project.

Ozone-destroying chemical making comeback, scientists find
 

B00Mer

Keep Calm and Carry On
Sep 6, 2008
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Remember to reuse that Tin Foil Cup when your done with it... it's the eco-Friendly tin foil hat.

 

waldo

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Oct 19, 2009
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The effect is pronounced enough to slow the recovery of the ozone layer, which helps to screen out harmful ultraviolet radiation from the sun. Ozone thinned dramatically in the past because of the use of chlorofluorocarbons (CFCs), which were phased out after international adoption of the Montreal Protocol in 1987.

The study reveals that hydrogen chloride – a byproduct of CFC release – began diminishing around 1998 because of the impact of the protocol.

apparently, that protocol didn't have as much wealth distribution for some to successfully oppose it!
 

IdRatherBeSkiing

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May 28, 2007
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Who? Nickelback and Justin Bieber?

Both.

Not sure what big deal is. Bad gasses put in atmosphere in 80s. We stopped using them. Gets better but the gasses are still in the atmosphere in pockets and it causes occasional setbacks. Seems pretty straight forward to me. Nothing to do about it but still straight forward.