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From: William Hyde <wthyde1953@gmail.com>
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Subject: Re: AGW. LNG Worse Than Coal.
Date: Thu, 7 Nov 2024 12:48:54 -0500
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Robert Carnegie wrote:
> On 05/11/2024 01:13, Cryptoengineer wrote:
>> On 11/4/2024 4:34 PM, Robert Carnegie wrote:
>>> On 30/10/2024 01:37, Cryptoengineer wrote:
>>>> I'd like to see some numbers on this.
>>>>
>>>> Yes, burning methane generates less CO2 per BTU than
>>>> methane.
>>>>
>>>> But:
>>>>
>>>> A significant amount of methane escapes the system in leaks
>>>> and gets into the atmosphere without being burnt. In the US,
>>>> about 1.4%. Other countries do much worse, and a recent satellite
>>>> has started mapping the problem:
>>>>
>>>> https://www.msn.com/en-us/money/other/nasa-s-methane-satellite-just- 
>>>> mapped-its-first-plumes/ar-AA1spd3X?ocid=BingNewsSerp
>>>>
>>>> Coal that 'leaks' out of the system just sits on the ground.
>>>>
>>>> AND
>>>>
>>>> Methane, molecule for molecule, is a far more potent greenhouse
>>>> gas than CO2. 120x as potent, in fact.
>>>>
>>>> This is mitigated by the fact that methane only  lasts about 10
>>>> years in the atmosphere, while CO2 lasts far longer.
>>>>
>>>> https://www.epa.gov/ghgemissions/understanding-global-warming-potentials 
>>>>
>>>>
>>>> So, I'd like to see some actual numbers to support of debunk this
>>>> claim, not a simple declaration.
>>>
>>> I understand that methane in the sky is slowly
>>> converted to CO2.
>>
>> Yes, and far faster then CO2 gets recycled. But it's also a far
>> more portent as a greenhouse gas, pound for pound, as C02. Numbers
>> matter, and figuring out the relative contribution of each to
>> warming \caused is a non-trivial calculation.
> 
> I wanted to make the point that the increase of
> methane in the atmosphere means that CO2 in the
> atmosphere increases as well.
> 
> Another thing - I heard an argument, which may
> be completely wrong, or even right but irrelevant,
> that a certain level of CO2 blocks heat radiation
> from,the surface by about 100% at relevant infrared
> wavelengths.  That seems to imply that more CO2
> stops getting worse then

This is the saturation argument, which has been discussed here.  The 
easiest way to see that it is incorrect is to note that absorption is 
nowhere near 100% over most of the spectrum.

However, there is some effect, as the warming is not linear in CO2 but 
logarithmic. So going from 2X to 4X has the same impact as going from 1X 
to 2X, or 10X to 20X, and so on.




  - however, it may be enough
> to remove humans ultimately as owners of the Earth,
> and also of course it makes getting CO2 down to
> a tolerable value that much harder.  I'm bringing
> it up because...  does CH4 affect other wavelengths
> of heat radiation which are passed through by CO2?
> So that it makes a possible "couldn't be worse" CO2
> situation, worse?

The photons absorbed by greenhouse gases cause the molecules to rotate 
and vibrate.  As a linear molecule O=C=O carbon dioxide doesn't have as 
many available modes of rotation-vibration as do more irregularly shaped 
molecules such as H2O and CH4. So a small amount of Methane has a high 
absorption cross section relative to CO2.

Luckily, however, Methane does not absorb in as broad a range of 
frequencies as CO2.  Unluckily, it peaks in areas where CO2 doesn't 
absorb strongly.

The X value in "Methane is X times worse than Carbon Dioxide" varies 
wildly from source to source.  I think a lot of it is being taken out of 
context.  The full-spectrum value I heard of years ago is X=25.  Which 
is quite bad enough.

A standard figure describing the absorptivity of various gases can be 
found in most textbooks on the subject, and here:

https://www.e-education.psu.edu/meteo3/sites/www.e-education.psu.edu.meteo3/files/images/lesson3/absorptivity0304.png




William Hyde