Comments 1 to 14:

1. nigelj at 04:57 AM on 5 December, 2018

   I appreciate that CO2 is the greater problem than methane, but I wonder if the short residence time of methane in the atmosphere creates a false sense of security. The shortness doesn't matter if we just go on emitting methane, which looks likely if humanity goes on consuming meat etc. 

   There is also risk that if temperatures reached 5 degrees, then the melting of permafrost and methane release in Siberia would become irreversible, and would obviously go on for many centuries guaranteeing a lot of methane with probably no way of stopping it. The arctic permafrost is many metres deep. However this simply highlights the need to reduce CO2 emissions.

   www.businessinsider.com.au/hothouse-earth-climate-change-tipping-point-2018-8?r=US&IR=T

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2. Evan at 06:31 AM on 5 December, 2018

   nigelj@1 I agree with your assessment. It seems that many are not concerned as much about methane because hypothetically most of it goes away in a matter of decades if we stop emitting it. In the meantime, it is a potent greenhouse gas ... and in the meantime its concentration is increasing not decreasing.

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3. CBDunkerson at 23:42 PM on 5 December, 2018

   Methane 'goes away' whether we stop emitting it or not.

   If it didn't then the atmospheric methane level would grow every year there was an imbalance between sources and sinks (i.e. the way the CO2 level does) and any level of imbalance would eventually lead to atmospheric doubling. Instead, because atmospheric methane quickly breaks down, to double the amount of atmospheric methane you would need to double the amount of rice production (which, BTW, is actually the largest source of human methane emissions), double the number of livestock, double the number of leaking drill sites, etc... and then keep those elevated levels of these things year after year... all while not decreasing any of the major natural methane sources (i.e. wetlands, termites, wild animals). A virtually impossible task with current technology.

   Thus, the extent of damage which can be done by atmospheric methane is inherently limited in ways that carbon dioxide is not.

   That said, while methane on its own would likely never be a significant global warming problem, with the growing CO2 concentration methane adds a small additional amount of warming which could potentially push us past one or more tipping points that we might have avoided based on CO2 warming alone.

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4. Evan at 01:56 AM on 6 December, 2018

   CBDunkerson@3 Although an individual methane molecule may go away, I am referring to the net atmospheric concentration, which only goes away if we decrease emissions ... which we are not. Current atmospheric methane concentrations are just under 2 ppm. Molecule for molecule methane has about 100 times the warming potential of CO2. I think that people are not concerned about methane because the argument is that if we decrease its levels the methane goes away on a decadal time scale. But today, with CO2 levels at about 400 ppm, and methane at about 2 ppm with 100 times the warming potential of CO2, the warming today from methane is about half that of CO2. If tomorrow we have the same CO2 and methane concentrations, then tomorrow as well the warming from methane will be about half that of CO2. Like CO2, the atmospheric concentration of methane is increasing. With global population increasing (more people eating rice), and with the standard of living increasing in many parts of the developing world (more people eat meat), it seems likely that methane concentrations will remain high. Therefore, as one methane molecular goes away, another comes along to replace it, so that the net effect is that methane is not going away, but increasing.

   Worse yet, since the start of the industrial revolution, in broad strokes CO2 has increased about 50%, whereas methane concentrations have increased about 300%, and are still increasing.

   I would be greatful if someone can show the error of my logic (seriously, I would be greatful to be shown that my argument here is wrong), but it seems to me that every day that we maintain high methane levels that it does not matter if methane is a "short-lived" greenhouse gas. The real point, I think, is that it is a very potent greenhouse gas whose net effect rivals that of CO2. Just because we can conceptually reduce methane concentrations more easily that we reduce CO2 concentrations does not mean that methane is not a big problem.

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5. SirCharles at 02:37 AM on 6 December, 2018

   I certainly believe, ClimateAdam should cease his channel until he's got the right education. I just posted the following comment on his YT video:

   "A ton of Methane warms the world ten times more than a ton of carbon dioxide does"?
   That's a MYTH!
   Methane is 87 times as potent as CO2 on a 20-year timescale. As we're just approaching the time of no return to keep temps below 2°C we also have to concentrate on CH4 emissions
   https://sites.google.com/site/irelandclimatechange/Atmospheric%20CH4%20history.jpg
   https://sites.google.com/site/irelandclimatechange/2013%20IPCC%20GWP%20%26%20GTP.jpg
   In particular fracking for oil and gas has made methane emissions skyrocketing.
   https://sites.google.com/site/shalegasbulletinireland/all-previous-issues/issue-no-56---may-15-2015#Oil_and_gas_is_sector_top_source_of_US_methane_emissions_ahead_of_agriculture
   https://sites.google.com/site/shalegasbulletinireland/all-previous-issues/issue-no-75---march-1-2016#Global_spike_in_methane_emissions_over_last_decade_likely_due_to_US_shale
   https://sites.google.com/site/shalegasbulletinireland/all-previous-issues/issue-no-83---july-1-2016#US_oil_and_gas_methane_emissions_equivalent_to_14_coal-fired_power_plants
   Why misinforming your audience, ClimateAdam? Maybe you should inform yourself a bit more before coming out with the next myth. If you need more information, don't hesitate to send me a PM.
   Also watch "Scratching the 1.5°C Jazz" https://www.youtube.com/watch?v=9a6JeqX1BHI

   And I will add this link to the comments:

   https://sites.google.com/site/irelandclimatechange/that-s-how-fast-the-carbon-clock-is-ticking

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6. One Planet Only Forever at 02:58 AM on 6 December, 2018

   There is another way to consider the importance of reducing human activity creation of methane, starting now.

   The Paris Agreement lays out the objectives of limiting human impacts to a maximum 2.0 C warming, with the aspiration of limiting warming to 1.5 C. Another way of presenting that is: "The long term warming must not exceed 1.5 C. And the peak impact along the way may be as high as 2.0 C. And if there is a peak above 1.5 C along the way then the impacts will have been reduced to 1.5 C by 2100."

   With that understanding of what needs to be accomplished, there are significant benefits obtained by reducing methane impacts now. Any reduction of methane now will reduce the peak temperature along the way to the 1.5 C end objective. Put another way, reducing methane now would allow for a higher peak of CO2 impact along the way to the end requirement of 1.5 C impact (with the understanding that effective sustainable actions to reduce CO2 will be implemented).

   Of course, everytime this matter of the future temperature impacts is presented, it is important to clearly state that it is unfair for the current generations to benefit by imposing Any global warming related climate change consequences on future generations. Even a 1.5 C warming impact is unfair to the future generations. That means already more fortunate people need to be leading the correction to a sustainable future for humanity. And any more fortunate person who is not doing their part should be effectively corrected by their peers (with every level of the global population demanding that those who are better off than they are behave better than they do - which the Island Nations and other developing nations already clearly being threatened by the climate change impacts are correctly doing by demanding corrective leadership and assistance from the more fortunate).

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7. william5331 at 05:13 AM on 6 December, 2018

   I think we should be more worried about the instantaeous effect of Methane when compared with Carbon dioxide.  In other words, what would be the short term effect of a greatly increased output of Methane such as may well happen from the Continental Shelf of Russia in the Arctic.  If you look at the chart a short way down in this site  https://en.wikipedia.org/wiki/Greenhouse_gas  You will see that there is 222 times as much Carbon dioxide in the atmospere as Methane and yet the methane has a third as much green house effect as the Carbon dioxide.  The calculation of their relative instantaneous effects is a little difficult since it involves sensitivity or the fact that doubling the gas in question will cause a linear increase in the warming effect (sort of a reversed exponential curve) and that there is a saturation effect above which no more warming will occur but just on a first glance you can see that Methane is far and away a more serious greenhouse gas than Carbon dioxide if the amount vented into the atmosphere spikes.  Even more worrying is that an initial spike will likely lead to further spikes as more reservoirs of Methane go critical.

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8. william5331 at 05:16 AM on 6 December, 2018

   ps.  Actually an exponential effect but the exponent is less than one.

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9. nigelj at 05:23 AM on 6 December, 2018

   CBDunkerson and Evan, I think you guys are both right.

   Firstly methane doesn't accumulate on century long timescales the way C02 does, this is not contentious, which is why I didn't mention it. My point was entirely psychological that the low residence times create a false sense of security and for example farmers in NZ have used it as an argument to keep on emitting methane "because it breaks down quickly".

   However methane is still a significant contributor to greenhouse warming if we go on emitting it even if total quantities were stable decade to decade. But like Evan says, its increasing for other reasons, because we are increasing methane emissions at source in terms of fracking, agriculture and breakdown of natural methane sinks in Asia as below. 

   e360.yale.edu/features/methane_riddle_what_is_causing_the_rise_in_emissions

   climate.nasa.gov/news/2668/nasa-led-study-solves-a-methane-puzzle/

   Remember methane also breaks down to small but still very significant quantities of CO2...

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10. Evan at 05:28 AM on 6 December, 2018

    nigelj@9 well stated.

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11. MA Rodger at 05:39 AM on 6 December, 2018

    Evan @4,

    I think your numbers need a little attention. Having first mentioned atmospheric levels of CH4, you state that in terms of climate forcing, CH4 is  "about" 100-times as powerful as CO2 molecule for molecule. You then go on to say "the warming today from methane is about half that of CO2." That isn't correct.

    CH4 has about a quarter the forcing of CO2 (as of 2016), or more accurately 0.507/1.985 = 1/3.9 . The rise in CH4 since pre-industrial is some 1.1ppm(v) (to 2016) and CO2 124ppm(v). That would make the molecule-for-moleule comparison CH4 = 29 x CO2.

    The Global Warming Potential is a measure of the warming resulting from equal weights of emissions of the different gases over a set period. CH4 has a GWP of 86 over 20 years which is only very roughly about 100. As CH4 is 44/16 = 2.75 lighter than CO2, the GWP would have to be divided by that factor to obtain a molecule-to-molecule comparison, and that for tonnes of gas emitted not the molecues floating round the atmosphere.

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12. Evan at 05:59 AM on 6 December, 2018

    MA Rodger@11 I see your point and accept your correction on my use of warming potentials where they should be per unit mass and not per molecule. I still maintain that a factor of 100 for methane is more appropriate for the instantaneous effect, because the factor of 86 is for a 20-year period. As long as we maintain CH4 at a high level it is the instantaneous effect that counts. 20- or 100-year periods only matter if we bring CH4 concentrtions down, and we have not, nor is there any indication of that happening soon.

    But I do accept your correction that I should be using warming potentials of 86 or 100 on a per-unit-mass basis and not on a per-unit-molecule basis.

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13. EsaJii at 06:17 AM on 11 December, 2018

    It’s not awful, but as there is just one molecule vibrating, it does not show any mechanisms of heat transfer from the molecule to the world outside of it. I’d like to see a Youtube video showing cartoon just that: molecules of CO2, H2O, CH4 and air (oxygen, nitrogen) doing all this interaction. 

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14. Evan at 00:42 AM on 15 December, 2018

    EsaJii@13. By definition, if a molecule gains an amount of energy that is higher than the average energy of surrounding molecules, it will transfer some of its energy to its neighbors so that on average, its energy returns to the average energy of its neighbors. Molecules are very generous. In fact, there is a constant redistribution of energy among molecules. There is no sense that a single molecule gains energy and keeps it for itself for a period of time exceeding something like 0.0000000000001 seconds.

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