Oxygen as a Cause of Warming?

[wylie]

All,

I have thinking over some of the things that Kiwi and others have posted about the mechanism(s) for atmospheric warming. I was wondering if the effects of the chemistry of oxygen might be the source of some of the "amplification" of some of the solar cycle effects that have recently been observed. The specific 3 discussion points that I thought I would mention are listed below. Note, these are only vague hypotheses/discussion points without any sort of proof, so any and all constructive comments would be much appreciated.

Possible amplification mechanisms to account for the apparent correlation between sea surface temperatures and the solar cycle with heat content changes considerably greater than the ~0.1% peak to trough change in total solar irradiance over the whole solar cycle:

1) Ozone formation as influenced by DUV irradiation (additional greenhouse gas?)

Ozone is formed in the upper atmosphere when atomic oxygen is subject to DUV radiation at a wavelength shorter than 180nm, forming atomic oxygen which reacts with molecular oxygen to form ozone. DUV radiation flux varies much more than TSI over the solar cycle. A recent NASA report mentioned that total UV radiation flux was now 6% lower than at Solar Max. Presumably DUV (the energetic UV that can break the oxygen double bond) variance has an even greater dependence on the solar cycle since an active sun emits more short wavelength lights in response to magnetic activity in relatively small concentrated areas on the solar surface.

If ozone formation in the stratosphere varies with the solar cycle and since ozone is also a good greenhouse gas (polyatomic) with an absorption band near the peak of Earth's black body emission at ~290K (~15um?), then presumably it would influence the heat balance in the atmosphere directly (in a similar manner to H2O and CO2) and be directly dependent on the solar cycle.

Is this a possible candidate for the amplification mechanism? And if not, why not?

2) Oxygen and Ozone (more likely) direct UV absorption of incoming and outgoing UV radiation as affected by the solar cycle

Since UV varies more than TSI over the solar cycle and since both oxygen and ozone absorb UV (at difference wavelengths), could they directly contribute to atmospheric heating? Specifically, as the UV and DUV radiation flux increases at solar max and ozone concentrations are increased by the UV flux, wouldn't UV light that would otherwise be scattered or reflected by ice (or water) be absorbed and heat the atmosphere directly? A significant fraction of UV is scattered back from the surface and the atmosphere of the planet into space. Couldn't some (or a larger fraction) of this scattered/reflected UV that would otherwise not contribute to heating the surface/atmosphere be absorbed (and therefore heat the earth's atmosphere)? There is also a Near IR absorption of O2 (777nm?) that might also be candidate for this kind of direct heating from near IR that would otherwise be reflected back into space.

3) Expansion of the atmosphere affecting #1 and #2 above

I understand that atmospheric drag on satellites and space debris is lower now because of the solar minimum and because the atmosphere "breathes" (expands during solar max and contracts during solar min). Oxygen (and presumably ozone?) might expand during solar maximum and increase the cross-sectional area of the planet that would intercept UV light (or other wavelengths) that was directly incoming or outgoing after reflecting off the surface or the atmosphere. Couldn't this also contribute to an amplification of the solar cycle signal?



IWylie

[poitsplace]

Well they must all have SOME affect, the question is how much. My money's on the expansion of the atmosphere increasing the capture cross section of the earth (substantial variation...something like a POTENTIAL of 2.7%). The problem is this is little understood. We've only "known" for certain about this issue (at these extremes anyway) as of this minimum.

All of these affects are CERTAINLY sufficient to cause some sort of change in the atmospheric circulation. This could lead to more clouds, an increase in convection currents carrying away heat, expansion of the polar vortexes, changes to the jet stream and quite possibly some things we've never thought of.

[ron]

For each molecule of CO2 created, one O2 molecule is destroyed.

Since the hugely vast majority of CO2 created is then sequestered somewhere -some log or some ocean, wherever- then many more O2s are "permanently" removed from the atmosphere than CO2s are "permanently" added.

If the negative "greenhouse" effect of O2 loss is small, is it because it is massively less than the positive effect of CO2, or is it because the band of absorption of energy for O2 is saturated, or something else?

[wylie]

Thanks Ron,

Good point. A molecule of O3 destroys a molecule of O2 as well. However, I was thinking that Ozone would be the dominant player (between O2 and O3) because it is a polyatomic and therefore has a stronger IR absorption than a diatomic (MUCH). Also, as I remember from one of Kiwi's posts, the main IR absorption for O3 is smack right in the middle of the black-body emission spectrum of the Earth at room temperature.

The UV absorption of O3 is another example where x-1 +1 = not equal to X. That is, since O2 absorption in the UV very quickly saturates (at least at reasonable atmospheric concentrations), the conversion of a small proportion of the O2 into O3 contributes to an overall increase in the absorption of UV through the extension of absorption to the mid-UV (just as well or we would have too much radiation on the Earth's surface).

The key question is whether or not the extension of the atmosphere to higher altitudes during solar max contributes towards an increase in the total amount of UV that is being absorbed. Since the recent solar max more or less coincided with the last big El Nino, this could be an alternative explanation for the increase in temperature of the atmosphere WITHOUT resort to CO2 as an explanation.

SO, the possibility (however vague and unproven) that O2 could have an effect on atmospheric heating in response to the solar cycle brings another dimension to the argument. If O2 (and O3) is automatically discounted without measurement or calculation, this would contribute to a muddling of the science.

Hope this is helpful,

Iwylie

[crakar24]

I have no idea what you are talkin about Wylie but it sure sounds good. Just one comment would not the IPCC AR4 report discuss all this in detail as it would as you say play a part in the overall climate?

[wylie]

May 12, 2009 5:44:47 GMT crakar24 said:

I have no idea what you are talkin about Wylie but it sure sounds good. Just one comment would not the IPCC AR4 report discuss all this in detail as it would as you say play a part in the overall climate?

I am sorry Crakar24,

I have not read much of the IPCC AR4 report. Perhaps I am remiss. I did read the summary for policy makers and I don't remember anything about ozone or direct absorption. Let me see if I can restate the hypothesis a little more clearly:

1) Molecular Oxygen (O2) is very highly concentrated throughout the atmosphere (good thing for us oxygen breathers)

2) Ozone (O3) is produced FROM O2 through UV absorption in the lower stratosphere. The amount of UV light from the Sun varies through the solar (sunspot) cycle because the surface of the Sun has "phages" that are very hot (by magnetic effects) and emit lots of short wavelength(high energy) UV and X-Ray radiation. Lots of sunspots means lots of extra short wavelength UV and few sunspots (like now) mean considerably less short wavelength UV light.

3) Ozone is a good greenhouse gas because it absorbs at the peak of the infra-red spectral region where the Earth emits its heat and (critically) the absorption does not overlap with other greenhouse gases like CO2 and H2O

4) Ozone also absorbs directly in the UV (i.e. when incoming solar radiation, not from the Earth) shines on the Earth, ozone absorbs in the mid-UV and provides a "sunshield" to protect us from the UV (good thing)

5) Some UV light from the sun reflects off the Earth's surface back into space at the wavelength at which Ozone absorbs. If ozone intercepts that mid-UV light then it would heat the atmosphere directly (both on the pathway down to the surface and then back out again as the UV light reflects off the surface).

6) I suspect (but am not sure) that the IPCC AR4 does not take into account this ozone formation mechanism as affected by the UV which follows the solar cycle because they have discounted the solar cycle entirely. I think that they dismissed it by saying that the solar cycle only has about a 0.1% change in total solar irradiation in going from solar minimum to solar max.

7) This mechanism of ozone absorption (and greenhouse gas heating from the same gas!!) should be affected by the height of atmosphere. The height of the atmosphere changes as a result of the solar cycle. It is currently several hundred miles (of very diffuse gas) more concentrated at the surface of the Earth because we are at solar minimum. At solar max, the atmosphere (and the oxygen and presumably the ozone) moves further out from the surface contributing to drag on satellites (and space debris).

8) If ozone (and/or molecular oxygen), directly absorbs UV and that absorption is a function of the total pathlength of the UV through the atmosphere, then an increase in the height of the atmosphere would increase the amount of UV being absorbed and amplify the UV signal as it affects the heating of the atmosphere. That is because the pathlength of UV light that is reflecting or scattering from the surface or the atmosphere itself is not necessarily a direct line. A low angle would mean a long pathlength for absorption by Ozone or O2. So even if the atmosphere was very thin at high altitude, the absorption of O3 or O2 would have a good chance of increasing the temperature of the atmosphere over a long pathlength (hundreds of miles of absorption is certainly possible).

Certainly not a quantitative theory, and I strongly suspect that someone else has already put this forward (I have not done a literature search on it), but that is why I thought I would mention it here, in case someone else has already done such a search.

Hope this helps,

Iwylie

[ron]

It the quantity of O3 produced a fixed amount according to the UV quantity, or would reducing O2 in the atmosphere in small amounts cause lower quantities of O3 to be produced.

I guess I'm asking if the O3 creation process is saturated.

[wylie]

Ron,

It is my impression that the relative concentration of O3 is very low compared to O2 (perhaps several orders of magnitude). Also, I believe that the limiting factor is not the concentration of O2 to react with atomic oxygen, but rather the UV radiation flux available to form atomic oxygen (which then creates O3). O3 is unstable and dissociates back to O2 at a substantial rate, so it is the rate of creation (driven by UV) that mostly determines the overall concentration in a given location.

Note that Ozone is ALSO created at ground level by hydrocarbon smog, but that is a different mechanism. It is also possible that this ground level ozone could contribute to warming but I am very unsure as to a mechanism.

IWylie

[ron]

I have two questions then.

1) Would a reduction in O2 reduce the production of O3 given a stable UV?
2) Is the amount of O2 in the air less than it used to be? Has any decline corresponded to or outstripped the increase in CO2?

[wylie]

Ron,

Here is a quote from a good web-site:

science.jrank.org/pages/4973/Ozone-Layer-Depletion-Stratospheric-ozone.html


"Typically, stratospheric ozone (O3) concentrations are about 0.2–0.4 ppm (parts per million), compared with about 0.03 ppm in unpolluted situations close to ground level in the troposphere. Stratospheric ozone concentrations are also measured in Dobson units (DU). A Dobson unit is equivalent to the amount of ozone that, if accumulated from the entire atmosphere and spread evenly over the surface of the earth at a pressure of one atmosphere and a temperature of about 68°F (20°C), would occupy a thickness of 10 mm (0.01 m or 0.4 in). Typically, stratospheric zone occurs at a concentration of about 350 DU, equivalent to a layer of only 3.5 mm (0.14 in).

Stratospheric ozone is formed and consumed naturally by photochemical reactions involving ultraviolet radiation.

Molecular oxygen (O2) interacts with ultraviolet radiation and splits into oxygen atoms (O) (reaction 1), which either recombine to form O2 (reaction 2), or combine with O2 to form O3 (reaction 3). Once formed, the ozone can be consumed by various reactions, including a photodissociation involving ultraviolet radiation (reaction 4), or reactions with trace gases such as nitric oxide (NO), nitrogen dioxide (NO2), and nitrous oxide (N2O), or with simple molecules or ions of the halogens, including chlorine (reaction 5), bromine, and fluorine. At any time, the formation and consumption of ozone proceed simultaneously. The actual concentration of ozone is a net function of the rates of reactions by which it is formed, and the rates of the reactions that consume this gas. The halogens catalyze the dissociation reaction; in other words, they increase the rate of ozone degradation without themselves being consumed in the chemical reaction. This means that they are available after one reaction to catalyze thousands of other such reactions. The increase of halogens present in the upper atmosphere has caused a shift in the equilibrium between the reactions toward an increased rate of ozone depletion."

So the concentration of ozone in the atmosphere gets as high as 0.3ppm in the stratosphere and 0.04 at ground level(for comparison, the concentration of CO2 is about 0.038ppm). That compares with a ground level O2 concentration of 200,000ppm (20%). So if every O3 molecule that is created destroys one O2 molecule, then the concentration of O2 would be reduced by 200,000.00 - 0.30ppm ~~ the same.

However, the absorption of UV light at the middle UV wavelengths of O3 would dramatically increase over no ozone. So the shorter than 180nm UV absorption of O2 would decrease a negligible amount while the amount of mid-UV absorption (where O3 absorbs) would increase substantially.

Hope this helps,

IWylie

[wylie]

There is also a really good article on Ozone in Wikipedia:

en.wikipedia.org/wiki/Ozone_layer

I was incorrect about the concentration of ozone. It is only about 2-8ppm (much less than CO2), but direct absorption of UV is a more direct mechanism of heating. There is also substantial data showing the variation with Ozone over the years and it seems to correlate pretty well with the solar cycle (see Wiki).

Interesting!

IWylie

[ron]

Wylie, thanks....

"So if every O3 molecule that is created destroys one O2 molecule, then the concentration of O2 would be reduced by 200,000.00 - 0.30ppm ~~ the same.
"

Did you mean for every CO2 molecule created rather than O3?

While I understand the reasoning if you intended O3, I'm not sure I agree (or I'm confused) when it comes down to O2 removal by creation of CO2. Most CO2 is removed from the atmosphere, including the vast majority of it that is produced by man's activities, i.e. the burning of fossil fuels. All of that activity would seem to have two effects: 1) an increase in the concentration of CO2 in the atmosphere, 2) an increase in sequestered CO2 and 3) a decrease of O2 in the atmosphere.

However, all of that said, reminding me that we're talking about 200,000 PPM vs. .038 PPM would (at first glance) seem to indicate that the O2 difference would be negligible. However, one might make that very same assumption about the effect of going from .038 to .045 PPM concentration of CO2 on the temperature of the Earth.

So the question I have that is bugging me is if going from 200,000PPM to 199,999 PPM will reduce the amount of energy stored in the system directly or reduce the amount of O3 created in the presence of UV, either of which contributing to a potential temperature forcing.

If the O2 energy absorption bands or O3 creation processes are "saturated" the answer is "No, definitely not." If they aren't saturated, then the answer might be "perhaps but the amount would be so negligible, even the Hubble telescope wouldn't be able to measure it".

[wylie]

Ron,

I meant that every O3 molecule that is created destroys 0.5 oxygen molecules, not CO2. However, CO2 creation also follows the same rationale. The main point to remember however is that radiation absorption follows the Beer-Lambert law (unless it is saturated). It is a logarithmic relation between concentration and absorption. That means that the concentration of the absorber has to increase by a factor of 10 to increase the absorption by a factor of 2. An increase in the concentration above the saturation threshold does no additional absorbing (all the radiation is already absorbed).

The analogy to think of is a very black curtain that blocks all the light falling on it. However, the curtain has holes in it (wavelengths at which the molecules do not absorb). If you take 1/2,000,000th of the blackness (O2 concentration) to make CO2 OR O3 and create CO2 or O3 that "covers the holes" (in the curtain or the spectrum, whichever you think of), then you are increasing the total absorption because it is logarithmic and NOT linear. Even if it were linear absorption, the O2 absorption is completely saturated, so taking away a small percentage (a VERY small percentage) of that absorption to provide an absorption for the "holes" (in the spectrum or the curtain) would increase the total overall absorption.

This is a double whammy for O3 since it absorbs BOTH in the IR and the UV at critical "hole" wavelengths. Also, its concentration seems to follow the solar cycle (not surprising really since it is created by UV!!).

Hope that this helps explain it,

IWylie

[crakar24]

Thanks for the more detailed explanation Wylie, i sort of understood but now it is more clearer. My comment re AR4 was a little tongue in cheek. The IPCC dont have a clue, mind you its defenders will say "oh, yeah we looked at that but it could not account for ALL the warming"

To be honest your theory sounds just as good as theirs, in fact it is better as you say a quiet sun, less UV, less UV less heat the atmosphere cools . As opposed to CO2 goes up so does temp.

Keep up the good work.

Cheers

[crakar24]

Just had a thought, question for all the smart ones. I have read somewhere that the solar cycles seem to correlate well with nth and sth pole temps (is that right) now thinking about Wylies theory could this have anything to do with the hole in the ozone layer.

I am thinking with no ozone (well less than normal ozone) more UV would pass through without being trapped. As opposed to say the tropics. Which is why the global temps dont correlaye quite as well.

Does this make any sense ? If not sorry for any inconvenience caused

Cheers