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Continuing Problems with Paleoclimate Proxies

Lord of Planar said:
It only makes sense at extremely small levels and equal levels of a gas released. Not the levels released in annual volumes.
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GWP seems to me to do exactly what it is advertised to do. If the GWP explicitly takes into account the RF and the RF is a log function of the relative concentration of a gas then it makes sense that that portion of the factor would be higher for CH4 than CO2. The fact that the equation clearly states that delta F is a function of ln(C/Co) for some gases owing to saturation of the absorption bands and that the definition of the GWP is a form of "snapshot" of the atmosphere it doesn't matter that CH4 and CO2 are at different concentrations, the relative concentration to the concentration at some initial state dictates the RF. Why would one expect the measure to be taken at the same concentration for the gases? CH4's spectral absorbance is not as near to saturation as CO2 in the atmosphere.

But again, GWP appears to be a kind of "shortcut" means to compare, as closely as possible, the potential for warming between two unrelated gases. It may be a somewhat synthetic measure but it serves its purpose. CH4 is a serious consideration.


So, given what we know about CH4's absorption of IR I'm comfortable with the regular science approach that a CH4 is a serious concern.

(Also just found this interesting simple model from UChicago: Methane vs. CO2 help)
 
istodolez said:
GWP seems to me to do exactly what it is advertised to do. If the GWP explicitly takes into account the RF and the RF is a log function of the relative concentration of a gas then it makes sense that that portion of the factor would be higher for CH4 than CO2. The fact that the equation clearly states that delta F is a function of ln(C/Co) for some gases owing to saturation of the absorption bands and that the definition of the GWP is a form of "snapshot" of the atmosphere it doesn't matter that CH4 and CO2 are at different concentrations, the relative concentration to the concentration at some initial state dictates the RF. Why would one expect the measure to be taken at the same concentration for the gases? CH4's spectral absorbance is not as near to saturation as CO2 in the atmosphere.

But again, GWP appears to be a kind of "shortcut" means to compare, as closely as possible, the potential for warming between two unrelated gases. It may be a somewhat synthetic measure but it serves its purpose. CH4 is a serious consideration.


So, given what we know about CH4's absorption of IR I'm comfortable with the regular science approach that a CH4 is a serious concern.

(Also just found this interesting simple model from UChicago: Methane vs. CO2 help)
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OK, which is going to cause more warming? If I add 30% CO2, or if I add 30% CH4 from present levels?
 
Lord of Planar said:
OK, which is going to cause more warming? If I add 30% CO2, or if I add 30% CH4 from present levels?
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(REALLY GROSSLY ROUGH CALCULATIONS, Bear with me... For simplicity's sake and probably blasting past a few key points...)


30% more CO2 (at current 400ppmv) = 120ppmv additional (to 520ppmv total)
30% more CH4 (at current 1875ppbv) = 560ppbv additional (2437ppbv total)

Let's simplify the situation by basing everything on STP. Molar volume of a gas at STP: 1mol of CO2/22.4L, Approximately 1mol CH4/22.4L.

120ppmv CO2 should work out to be about:

(At STP) 120ppmv CO2 = 0.012vol%* 1L = 0.00012L of CO2. (Remember we're looking at STP here, so I can use the molar volume of the gas 1mol/22.4L) to calculate the mol of additional CO2 this amounts to. 0.00012L CO2*1molCO2/22.4L = 5.4E-6mol CO2 * 44g/mol = 0.0002g CO2 added.

Let's repeat for CH4:
560ppbv = 0.0000560vol%*1L = 0.000000560L of CH4. =2.5E-8mol CH4. *16g/mol = 4E-7g CH4 added.


By bumping up the CO2 by 0.0002g we are adding something like 500X the amount of CO2 than CH4 (assuming 30% increases for both) so I'm going to assume that bumping up CO2 by 30% will provide a significantly higher amount of warming than the much smaller amount of CH4. (Even taking into account the higher GWP of methane, you've proposed a scenario where there's MUCH more added CO2 than CH4).

This seems to bear out as well if I simply compare the DeltaF for CO2 and CH4.

CO2 going from 400 to 520ppmv yields an RF = 1.4W/m2 whereas going from 1875ppbv CH4 to 2437ppbv (assuming no change in NO2) yields 0.207W/m2 for the RF

But note that by adding 0.0002g CO2 I was able to get 1.4W/m2 deltaF, but I was able to get about 14% of that amount by merely adding in 0.0000004g CH4!

500X as much CO2 yields only 7X the amount of warming.

That would seem to confirm the idea that CH4 is a more potent greenhouse gas.

And it stands to reason. The CH4 spectral absorption bands are not yet near saturation, hence it is "earlier" in the logarithmic curve of Delta F as a function of relative concentration.

It takes more added CO2 to get a boost than it does CH4.



NOTES:
I'm using these as the RF calculations for CO2 and CH4

cornell-fig-2.jpg
 
istodolez said:
But note that by adding 0.0002g CO2 I was able to get 1.4W/m2 deltaF, but I was able to get about 14% of that amount by merely adding in 0.0000004g CH4!
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As you say, that 30% (120 ppm) increase of CO2 yields 1.4 W/m^2. You would have to increase CH4 from 1.875 ppm to about 30.9 ppm for that same 1.4 W/m^2 of warming.

Where in the real world are we going to ever add that 29 ppm of CH4? Do you see what I mean about the deception of GWP as a metric? At the more realistic comparison of 120 ppm for CO2, and enough CH4 to equal the warming increase, the slopes change so much, that CH4 is not only 4 times stronger because you are adding only 1/4 as much. GWP is a terrible metric, because it does not maintain a constant value. It is only used to deceive.

How can you rationalize GWP as a proper metric? Especially when the earth system of gas solubility in fluids don't allow for that. The equilibrium would be so far off with CH4 that much higher, that the velocity of sinking would dramatically increase. To output enough CH4 to maintain such a change would likely be impossible.
 
Lord of Planar said:
As you say, that 30% (120 ppm) increase of CO2 yields 1.4 W/m^2. You would have to increase CH4 from 1.875 ppm to about 30.9 ppm for that same 1.4 W/m^2 of warming.

Where in the real world are we going to ever add that 29 ppm of CH4? Do you see what I mean about the deception of GWP as a metric?
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Not in the least.

Indeed, as my rough and horribly oversimplified calculations bear out: CH4 is clearly a stronger greenhouse gas. The GWP does exactly what it is supposed to do.

It shows that on a common basis CH4 can provide more warming per unit of added gas than CO2.
 
istodolez said:
Not in the least.

Indeed, as my rough and horribly oversimplified calculations bear out: CH4 is clearly a stronger greenhouse gas. The GWP does exactly what it is supposed to do.

It shows that on a common basis CH4 can provide more warming per unit of added gas than CO2.
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LOL...

You will not accept that it is deceptive to the general public.
 
Lord of Planar said:
LOL...

You will not accept that it is deceptive to the general public.
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Correct.

Because, as noted, it is not deceptive. It does what it is advertised to do.

I will grant that this sort of "exercise" in creating standardized comparisons can often feel like they hide something deeper, but indeed they usually don't. It is quite common in science to create means of comparison of disparate items on a specific basis. The fact that YOU don't like the basis of the comparison does not make the comparison less valid.

The key here is that even by the rough calcs I did there based on your 30% increase we can easily see that 500X more CO2 than CH4 added resulted in only 7X more warming for CO2 than CH4. That's pretty sobering, wouldn't you say?

CH4 is not near saturation with regards to its absorption bands so even modest increases in it are serious additive to the overall warming. Couple that with disastrous events like a massive melting of permafrost (which is already happening and accelerating) and the possibility of catastrophic release from clathrates in the ocean. While it isn't necessary going to be as much volumetrically as all our CO2 emissions it's like bringing a small but powerful gun to knife fight.
 
istodolez said:
Correct.

Because, as noted, it is not deceptive. It does what it is advertised to do.

I will grant that this sort of "exercise" in creating standardized comparisons can often feel like they hide something deeper, but indeed they usually don't. It is quite common in science to create means of comparison of disparate items on a specific basis. The fact that YOU don't like the basis of the comparison does not make the comparison less valid.

The key here is that even by the rough calcs I did there based on your 30% increase we can easily see that 500X more CO2 than CH4 added resulted in only 7X more warming for CO2 than CH4. That's pretty sobering, wouldn't you say?

CH4 is not near saturation with regards to its absorption bands so even modest increases in it are serious additive to the overall warming. Couple that with disastrous events like a massive melting of permafrost (which is already happening and accelerating) and the possibility of catastrophic release from clathrates in the ocean. While it isn't necessary going to be as much volumetrically as all our CO2 emissions it's like bringing a small but powerful gun to knife fight.
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OK, we agree to disagree it looks like.
 
Examples of misconduct in climate and paleoclimate research.


I got to ruminating again; a third WUWT retrospective post
By Rud Istvan My first recent ‘ruminative’ post was about basic climate science misconceptions. My second was about their resulting failed basic climate predictions over now 4 decades (e.g. Viner 2000–children will soon not know snow!). This third ruminative post (celebrating roughly my 10th WUWT anniversary post here) introspects climate ‘science’ misconduct in the dubious…
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