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Author Topic: Toward Improved Discussions of Methane & Climate  (Read 27093 times)

salbers

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Re: Toward Improved Discussions of Methane & Climate
« Reply #50 on: May 06, 2017, 10:53:35 PM »
The issue is not whether landmasses move from the rotational adis, they don't (except by tectonic movements which is totally different).  the rotational axis itself shifts, tilting or wobbling its position relative to the sun.  this is a historical cycle that normally does affect the cycle of glacial and interglacial periods.  however, climate change is progressing far more rapidly than any recent period, so i don't think any major earth changes that happen over a thousand years from now are particularly relevant today.  i DO think it's important to understand this in the context of paleoclimate data.
Indeed the Milankovitch cycles are important in the paleoclimate context. More specifically there are changes in the Earth axis tilt. Precession will also change which hemisphere is closest to the sun during a particular season. For example presently Antarctica has its summer when the Earth is near perihelion, so there is more reflection by the ice sheet. The lowers the Earth's overall temperature. A third cycle is changes in the eccentricity, so this would modulate the precession effect.

VaughnAn

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Re: Toward Improved Discussions of Methane & Climate
« Reply #51 on: May 10, 2019, 06:44:21 AM »
Paul Beckwith recently posted a video where he describes the short term effects of methane being about 150 times that of carbon dioxide.  With methane concentrations being about 1.8ppm if we multiply 1.8 X 150 we get a short term co2e of 270ppm.  The standard conversion is about 25 times over a 100 year time span which gives us a CO2e of 45ppm CO2e over a 100 year time span.  However since we are dumping so much methane into the atmosphere it seems we should be using the 270 CO2e number when discussing the very short term effects of methane; such as the next 3 years.  Along with Nitrous oxide being at about 0.33 ppm with a multiplier of 296 we get a nitrous oxide CO2e of about 97ppmCO2e  If we add the short term CO2e of these 2 gasses to the 411ppm of CO2 we get a total short term CO2e of 778 CO2e. 
This number seems more compatible with what is happening in the atmosphere concerning climate change right now or are these numbers giving me a false sense of alarm?
Paul Beckwith talks about these 2 gasses in his video and the is a part 2 to this linked video:

https://paulbeckwith.net/2019/04/21/arctic-emissions-of-nitrous-oxide-worse-than-expected-radio-ecoshock-mention-on-counterpunch/

Laurent

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Re: Toward Improved Discussions of Methane & Climate
« Reply #52 on: May 16, 2019, 09:45:09 AM »
Only the instantaneous global warming potential is consistent with honest and responsible greenhouse gas accounting

https://www.earth-syst-dynam-discuss.net/esd-2018-22/esd-2018-22.pdf

...

oren

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Re: Toward Improved Discussions of Methane & Climate
« Reply #53 on: May 16, 2019, 10:14:07 AM »
I agree. As atmospheric methane is constantly replenished and its level is in fact even going up, it makes absolutely no sense to assume it will follow its 100 year removal curve. Current forcing sees current methane. When (IF) all anthropogenic methane emissions stop, then we can talk about the rate of atmospheric removal of methane, adjusted by the rate of natural/feedback methane emissions that will continue.

Rich

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Re: Toward Improved Discussions of Methane & Climate
« Reply #54 on: May 16, 2019, 10:15:04 AM »
If we add the short term CO2e of these 2 gasses to the 411ppm of CO2 we get a total short term CO2e of 778 CO2e. 


I think you need to go through the same exercise at the beginning of the industrial revolution for an apples to apples comparison.

782 ppm CO2 equivalent seems reasonable. What was the number 200 years ago. Methane and nitrous oxide existed back then as well.

Tor Bejnar

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Re: Toward Improved Discussions of Methane & Climate
« Reply #55 on: May 16, 2019, 03:09:17 PM »
Laurent and Oren, I'm so glad to see your posts.  It matches my sense from a year or so ago, but I doubt I wrote anything, figuring that I must be missing something.

A similar 'argument' can be made for H2O forcing.  Even as increasing atmospheric H2O is a consequence of global warming and any H2O molecule has a short stay in the air, its "instantaneous global warming potential" is what matters, not the half-life of the airborne-ness of a molecule.
Arctic ice is healthy for children and other living things.

VaughnAn

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Re: Toward Improved Discussions of Methane & Climate
« Reply #56 on: May 17, 2019, 05:59:15 AM »
Thanks for your input Lauren, Oren, and Tor.  That confirms my thinking.  So, we are really facing a much worse mess based on this reasoning.  This also helps explain why other climate scientists are claiming that the rate of change in the climate system is happening "much faster than expected."  I think my cause for alarm is more than justified.  we really should be using the "immediate" methane CO2e of 150x instead of the 100 year methane CO2e of about 28x.

Yes, this is on the back or more water vapor as well.  Time to get out the waders. 

sidd

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Re: Toward Improved Discussions of Methane & Climate
« Reply #57 on: May 17, 2019, 09:33:56 AM »
Climate models already do use the "immediate" impact of methane and everything else. They use the modtran codes and derivatives to calculate instantaneous radiative imbalance. Then they integrate over time to get the long term results. And thats the right way to do it.

sidd

Tor Bejnar

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Re: Toward Improved Discussions of Methane & Climate
« Reply #58 on: May 17, 2019, 07:16:10 PM »
I'm sure Sidd is correct.  For laypersons like me, the formula to predict/forecast how much methane will be contributing to CO2e goes something like: Current-methane - Decayed-into-CO2 methane + New-methane.  I'll leave it to the atmospheric chemists to discern if the removal rate (or half life) is 22 years or 88 years or whatever, and a more accurate representation of the formula (to boot)!  [For CO2, the formula is something like:  Current-CO2 + New-CO2 - CO2-taken-up-by-nature-quickly [oceans, plants] - CO2-taken-up-by-geological-processes [not a humankind-friendly component in the formula]].

The 'thing' that has bothered me has been how frequently 'the press' talks about the removal rate of a methane molecule, which I consider to be a side issue until the day we seriously (I mean really do it) reduce methane emissions. 
Arctic ice is healthy for children and other living things.

VaughnAn

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Re: Toward Improved Discussions of Methane & Climate
« Reply #59 on: May 18, 2019, 05:16:16 AM »
According to what I am understanding about the numbers I am seeing used for the Paris Agreement and IPCC Protocol a 28x number to determine CO2e is being used.  This is a far cry from the immediate 150x for methane being discussed.  Maybe the models sidd is referring to use the 150x multiplier but it appears that the IPCC discussions must use the 28x multiplier per the agreement.  This would underestimate immediate effects thusly:
Current concentration of methane = 1.88ppm.
1.88ppm methane x 28CO2e/methane = 53ppmCO2e
1.88ppm methane x 150CO2e/methane = 282ppmCO2e
This is a difference of 229CO2e which should have an immediate effect from methane greater than 50% of current CO2 concentration.  This would seem to have a significant effect on calculations of the immediate effects of methane.


https://www.ghgprotocol.org/sites/default/files/ghgp/Global-Warming-Potential-Values%20%28Feb%2016%202016%29_1.pdf

sidd

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Re: Toward Improved Discussions of Methane & Climate
« Reply #60 on: May 18, 2019, 06:17:43 AM »
Re: " Maybe the models sidd is referring to use the 150x multiplier "

Grr, I have not made myself clear. Models have no concept of "multipliers." They use a representative concentration pathway (RCP, CMIP5) or a shared socioecoconomic pathway (SSP, CMIP6) and use the concentration at a given time to calculate the instantaneous radiative forcing using the MODTRAN/successor codes. Then they integrate this calculation in time for the cumulative heating. This implicitly includes everything that is simplistically called a "multiplier." They also have the atmospheric chemistry modules that calculate decay of methane and other unstable greenhouse gases, and they have fluxes for water vapour, and CO2 and CH4 and many other fluxes in/out of the atmosphere/ocean/land.

The Paris agreement for 2.0C was done using RCPs and CMIP5. That used a straight scaling of RCP2.5 .  I dont know what the hell the 1.5 C target uses.

"Multipliers" are a hopelessly simplistic concept to use for the incredibly varied gamut of radiative forcing by greenhouse gases. Use the models instead.

sidd

oren

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Re: Toward Improved Discussions of Methane & Climate
« Reply #61 on: May 18, 2019, 06:49:08 PM »
While the models use the correct fomulas as explained by sidd, multipliers and CO2eq are used in simplified communications about the issue, and are important as well when trying to educate the masses. I think the CO2eq numbers communicated should be higher.

Steven

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Re: Toward Improved Discussions of Methane & Climate
« Reply #62 on: May 18, 2019, 08:34:29 PM »
Current concentration of methane = 1.88ppm.
1.88ppm methane x 28CO2e/methane = 53ppmCO2e
1.88ppm methane x 150CO2e/methane = 282ppmCO2e
This is a difference of 229CO2e which should have an immediate effect from methane greater than 50% of current CO2 concentration.

That calculation is nonsense.

You are using global warming potential (GWP), which is defined for emissions rather than concentrations.  It makes no sense to multiply those numbers by the atmospheric methane concentration. 

Moreover, GWP is defined in terms of mass rather than volume.  You are using parts per million volume, but you didn't take into account that a CO2 molecule is almost 3 times heavier than a methane molecule.

I think it's more instructive to look directly at radiative forcing rather than GWP.  Radiative forcing is about 3 times higher for carbon dioxide than for methane (since preindustrial), and in the past few years it is rising almost 10 times faster for carbon dioxide than for methane:


https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2016GL071930

See also this thread: https://forum.arctic-sea-ice.net/index.php/topic,2383.0.html

Tom_Mazanec

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Re: Toward Improved Discussions of Methane & Climate
« Reply #63 on: May 29, 2019, 09:42:40 PM »
SHARKS (CROSSED OUT) MONGEESE (SIC) WITH FRICKIN LASER BEAMS ATTACHED TO THEIR HEADS

be cause

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Re: Toward Improved Discussions of Methane & Climate
« Reply #64 on: May 29, 2019, 10:05:27 PM »
 .. well Frack me .. b.c.
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 ...

Susan Anderson

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Re: Toward Improved Discussions of Methane & Climate
« Reply #65 on: June 13, 2019, 09:10:07 AM »
Unexpected surge in methane levels:
https://climatenexus.org/climate-change-news/methane-surge/

"Freedom gas" "molecules of freedom" - ugh!!!