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Author Topic: Giant ozone hole found above Arctic  (Read 4171 times)
martin
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« on: October 03, 2011, 09:44:47 AM »

from http://www.independent.co.uk/environment/climate-change/giant-ozone-hole-found-above-arctic-2364849.html

"Scientists have discovered a hole five times the size of Germany in the ozone layer above the Arctic, allowing harmful ultraviolet radiation to hit northern Canada, Europe and Russia this spring.

The 2 million square kilometre Arctic hole is similar to the hole over the Antarctic, researchers write in the journal Nature, released yesterday.

They say 80 per cent of the ozone was lost about 20km (13 miles) above the Arctic and that a prolonged spell of cold weather when chlorine chemicals which destroy ozone are at their most active was to blame.

"Why [all this] occurred will take years of detailed study," said Michelle Santee from Nasa's Jet Propulsion Laboratory, part of the group that monitored the hole from space using satellites. "It was continuously cold from December through April, and that has never happened before in the Arctic."

It is thought global warming could be responsible for some of the damage because greenhouse gases trap energy at lower altitude, heating up the atmosphere nearer the ground but cooling the stratosphere, creating conditions for the formation of chemicals that break apart oxygen molecules of ozone"
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EccentricAnomaly
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« Reply #1 on: October 03, 2011, 11:08:26 AM »

Quote
It is thought global warming could be responsible for some of the damage because greenhouse gases trap energy at lower altitude, heating up the atmosphere nearer the ground but cooling the stratosphere, creating conditions for the formation of chemicals that break apart oxygen molecules of ozone.

I used to think that but somebody who'd gone into the maths and physics of global warming in a lot more depth than I have said no, it's totally wrong. I didn't fully understand his explanation but went looking for something written for a bit more study. I've never found an explanation I both understood and which made physical sense to me but putting together the half understood bits I've come up with this description for my own use:

Think of a cube of stratosphere, say 1 m. It contains oxygen, nitrogen, carbon dioxide and so on in pretty much the same proportions as the lower atmosphere (because, on a timescale of many years, the atmosphere is pretty well mixed even across the tropopause for all but very short lived gasses like water vapour).

Because the stratosphere is stratified (hence its name) most of the energy flows into and out of this cube are by radiation rather than convection or conduction. It absorbs long-wave infra-red from all around but slightly more from below than other directions (because the surface of the planet and lower part of the atmosphere is warmer) and radiates it in all directions. The amount it does this is proportional to the amount of CO₂ in the cube.

It also absorbs short-wave radiation from the Sun (UV, visible light and short-wave IR) as the result of the action of other molecules, particularly ozone absorbing UV. Because the air is cold it doesn't emit any noticeable amount of short-wave radiation (as is true of most natural things on or above the planet's surface other than fires or volcanoes).

The energy absorbed as short-wave radiation therefore goes to slightly warm the air in the cube causing it to radiate a little more long-wave IR. If the power of the short-wave from the Sun is swi (short-wave in), the long-wave IR from the surroundings in lwi and the long-wave radiated out is lwo then, because the cube is in energy balance, swi + lwi = lwo.

However, the amount of long-wave emitted and absorbed is a function of the amount of CO₂ in the cube. Suppose we call that factor C. Changing the meaning of our variables a bit we can write the balance equation as swi + Clwi = Clwo.

Note that the absorption of short-wave radiation is not affected by the amount of CO₂. Therefore if the amount of CO₂ is increased then the equation doesn't balance any more - the long-wave output increases more than enough to balance the short-wave input with the result that the cube cools. Cooling the cube reduces the amount of long-wave out without affecting the inputs thereby bringing the cube back into balance.

In symbols: using T for the factor by which temperature affects the long-wave output (it'll actually be the fourth power of the absolute temperature) we can mess with the equation a bit more to get:

  swi + Clwi = TClwo

Keeping the swi, lwi and lwo factors fixed, if there's an increase in the CO₂ in the cube (C) then for the energy flows to continue to balance T must decrease.

This is all a bit beside the point for most discussions but for having any understanding of the interaction between global warming and the ozone holes I think it's fairly important to be a little clearer on why the stratosphere cools in a warming world.

Also, there are various memes around about warming not being caused by extra CO₂ but by the Sun or whatever. This observed stratospheric cooling is a good example of why this doesn't make sense if it was extra solar radiation directly causing warming (yes, I know there are other proposed mechanisms) then the swi part of the equation would be increasing and it'd need a higher temperature in the cube to increase the long-wave radiation out to keep things in balance.
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dhaslam
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« Reply #2 on: October 03, 2011, 11:46:30 AM »

It looks like the  ozone layer will be  almost completely destroyed  within fifty years because CFCs are still being  manufactured and used.

From Wikipedia
a single chlorine atom is able to react with 100,000 ozone molecules. This fact plus the amount of chlorine released into the atmosphere by chlorofluorocarbons (CFCs) yearly demonstrates how dangerous CFCs are to the environment.[5]

 http://en.wikipedia.org/wiki/Chlorofluorocarbon
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zeus
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« Reply #3 on: October 03, 2011, 12:49:46 PM »

It looks like the  ozone layer will be  almost completely destroyed  within fifty years because CFCs are still being  manufactured and used.

From Wikipedia
a single chlorine atom is able to react with 100,000 ozone molecules. This fact plus the amount of chlorine released into the atmosphere by chlorofluorocarbons (CFCs) yearly demonstrates how dangerous CFCs are to the environment.[5]

 http://en.wikipedia.org/wiki/Chlorofluorocarbon
Hi

Check this out regarding CFCs, HCFCs & HFCs ..... http://www.afeas.org/overview.php ... it might be a little more detailed ....  Wink

Z
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martin
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« Reply #4 on: October 03, 2011, 01:24:37 PM »

and the possibility of bias - they are the trade body for the manufacturers of the damn things..... whistlie
« Last Edit: October 03, 2011, 01:31:30 PM by martin » Logged

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Quakered
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« Reply #5 on: October 03, 2011, 05:30:49 PM »

So the ozone layer has disappeared over the Arctic because it has got colder, (No doubt due to CO2 and Global Warming). Will we soon be asked to worry about Polar Bears suffering Hypothermia
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EccentricAnomaly
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« Reply #6 on: October 03, 2011, 07:27:20 PM »

So the ozone layer has disappeared over the Arctic because it has got colder, (No doubt due to CO2 and Global Warming). Will we soon be asked to worry about Polar Bears suffering Hypothermia

No, because the polar bears are not often found in the stratosphere (above about 10 km altitude, a bit lower near the poles, a bit higher near the equator) which is the bit of the atmosphere which is colder. Gravity tends to assist polar bears in their endeavour to remain within the Arctic troposphere which, unfortunately for the bears, is the bit of the atmosphere which is warming the quickest.
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zeus
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« Reply #7 on: October 03, 2011, 09:09:42 PM »

and the possibility of bias - they are the trade body for the manufacturers of the damn things..... whistlie
Hi

Does it really matter ?? ... the issue of CFCs was raised, the referenced report details the replacement of CFCs with the much less destructive HCFCs and then the very much less destructive HFCs since the 90's ....

What really needs to be considered is that if scientists have discovered anything then they have found something which wasn't known to be there before, either because it wasn't there before, they haven't looked before, or they haven't had access to the technology to look before and when they do find something what's better for departmental funding than shouting 'doom' .... I'm actually quite surprised that there are any scientists left to tell us that there's a problem anyway as I thought that we were all supposed to be dead from necrotizing fasciitis by now according to the scare reports from the 1990s (which seems to have been halted), or the antarctic ozone depletion issue from the 1980s (which seems to have reversed), or global warming of the late 90's (which seems to have been rechristened 'climate change' in the unexplained absence of further warming), so (hopefully) this is just another headline in a long procession of science funding issues ..... times are hard, other things have grabbed the headlines, research budgets are being culled, so what other scientific 'global catastrophies' can we expect to see in the press over the next few years to improve cashflow ?   Roll Eyes  Wink  

  
« Last Edit: October 03, 2011, 09:11:47 PM by zeus » Logged

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EccentricAnomaly
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« Reply #8 on: October 05, 2011, 03:33:01 PM »

Earlier in this thread I wrote about why global warming causes stratospheric cooling. I linked to that in a comment thread elsewhere hoping for clarifications/corrections so it's pleasing to see a clear explanation of another reason for stratospheric cooling posted in reply.

This explanation is closer to what is described in the last paragraph of that Independent article but the point is not that energy is trapped in the lower atmosphere, it's that spectrum of the long-wave energy flowing upwards is changed.
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