There is a new push to reduce CH4 emissions as a possible quick ‘win-win’ for climate and air quality. To be clear this is an eminently sensible idea – as it has been for decades (remember the ‘Methane-to-markets’ initiative from the early 2000s?), but it inevitably brings forth a mish-mash of half-remembered, inappropriate or out-of-date comparisons between the impacts of carbon dioxide and methane. So this is an attempt to put all of that in context and provide a hopefully comprehensive guide to how, when, and why to properly compare the two greenhouse gases.
First of all, let’s be clear about the relative magnitude of the gas concentrations. In 2020, CO2 was at ~410 parts per million, while CH4 was around 1870 parts per billion (or 1.87 ppm, a factor of more than 200 smaller). However the relative rise since the pre-industrial is three times larger for CH4, around 150%, compared to the 50% increase in CO2.
The radiative forcing from these changes in concentrations can be easily calculated using standard formulas (from Etminan et al, 2016 which supersede the slightly simpler ones from IPCC TAR), as about 2 W/m2 for the CO2 change and 0.65 W/m2 for CH4.
But methane’s role in atmospheric chemistry and as a source of stratospheric water vapour means that it has a bigger effect on climate than just the direct effect of its concentration. Methane emissions have a feedback on its own lifetime, serve as an ozone precursor, and reduce the production of sulphate and nitrate aerosols (and consequently indirect cloud-aerosol effects), all of which amplify its net warming effect to about 1.2 W/m2 (to about 60% of the CO2 effect since 1750). There is also a very small impact of the CH4 oxidation to CO2 itself for any fossil-fuel derived methane.
This implies that if you convert the impacts of each set of emissions into temperatures, as was done in the IPCC AR6 report, you get about 0.75ºC from the changes in CO2 and 0.5ºC for CH4 (from the late 19th C, see figure below) or 1ºC and 0.6ºC, respectively, from 1750. Thus despite the smaller concentrations and changes in methane compared to carbon dioxide, the impacts are comparable.
Stocks and flows
Before we go any further though, we need to understand that the effective perturbation time for CO2 and CH4 in the atmosphere are very different. CO2 emissions embed themselves in the atmosphere/biosphere/upper-ocean carbon cycle and have very long-term impacts (under natural conditions, some 15% of the CO2 perturbation will still be in the atmosphere thousands of years from now). In contrast, methane has a perturbation time-scale of about 12 years. This implies that the impact of CO2 on temperature is cumulative (a function of the total emitted CO2 or stock), while the impact of CH4 is a function of current (~decadal) emissions (the flows). Stabilizing temperature effects from CO2 means getting down to net-zero anthropogenic emissions, while stabilizing temperature effects from CH4 means simply stabilizing emissions.
The impacts of emissions of CH4 compared to CO2 then will have a time-varying component. Over a short time, the enhanced effectiveness of methane will be important but on very long time scales the effects of CO2 will be dominant. This is the source of the difference between the “Global Warming Potential” (GWP) numbers calculated at 20 years or 100 years which have been used for decades. You might recall that GWP is defined as the ratio on per-kg basis of the temperature impact of other greenhouse gases compared to CO2 over a specific time period. But as is clearly stated in AR6, the suitability of comparative emission metrics depends on your end goal or values.
For instance, if you use GWP-100 to trade off emissions on the way to a temperature stabilization scenario, it simply doesn’t work (since you can’t balance any net CO2 emissions with a particular level of CH4 emissions – you would need to have constantly decreasing CH4). Hence, newer concepts like GWP* have been developed that take that into account. Nonetheless, the UNFCCC (and the EPA) use the GWPs from IPCC AR4 for calculating CO2eq emissions and have not updated them as the science has progressed.
People tend to be most interested in comparisons related to future choices, and it’s worth bearing in mind that while there are many ways to do this, most don’t relate to real choices that people have, nor do they clearly match up with a consistent set of values. I’ll return to that issue below. So let’s go:
- Molecule-to-molecule concentrations: On a per-ppm basis, methane is 25 times more effective as a direct greenhouse gas. Including the indirect effects, increases that to 45 times as effective.
- kg-to-kg: On a mass basis, methane is 70 times more effective as a greenhouse gas. This takes into account of the different molecular weights of the molecules. That would mean 126 times as effective including indirect effects.
- kgC-to-kgC: an equal amount of kgC as CH4 or CO2 gives rise to the same ppm change, so kgC-to-kgC, methane is again 45 times more effective as a greenhouse gas.
- kg to kg emitted: This is where it starts to get hairy because of the different timescales. Current (AR6) estimates for fossil-sourced methane are ~83 for GWP-20 and ~30 for GWP-100 (AR6 Table 7.15). (It’s slightly smaller than this for biogenic (non-fossil) methane since the oxidation product of CO2 in that case is carbon neutral). The assessed uncertainties in these values (largely related to direct and indirect aerosol effects) are ±25 and ±11. The AR4 value for methane GWP-100 was 25.
- kgC emitted to kgC emitted: For some applications, for instance judging the impact of flaring natural gas vs. releasing it directly into the atmosphere, the kg-to-kg comparisons are not relevant, since the same amount of carbon is being emitted, rather than the same total mass. For that, the GWP-like value over 100 years, choosing to release methane directly would be 30*16/44 = 11 times worse than flaring [Corrected 9/20/21].
- Emissions for temperature stabilization: Each additional GtC of carbon dioxide contributes to about 0.00165ºC of eventual warming (the TCRE), while a sustained TgCH4/yr of methane emissions (0.00075 GtC/yr), leads to ~3 ppb increase of methane concentrations (AR6 Table 5.2), about 0.0024 W/m2 in total radiative forcing, and, assuming a median climate sensitivity of 3ºC for 2xCO2, roughly 0.002ºC of equilibrium global warming. That implies you need a sustained reduction of 0.8 TgCH4/yr (0.0006 GtC/yr of methane) to compensate for a one-off GtC pulse of CO2.
Whatever way you slice this it implies that CH4 reductions have an outsize effect on climate, as well as an undeniably positive impact on air pollution, crop yields and public health (mainly through ozone reductions). It is therefore not a complicated decision to pursue methane reductions, taking care not to assume that doing so gets you off the hook for reducing CO2, whatever the EPA says.
I’d like this page to be useful and current, so if you think I should add an additional comparison, or use case, or if you think I’ve got something wrong, please let me know in the comments.
- M. Etminan, G. Myhre, E.J. Highwood, and K.P. Shine, "Radiative forcing of carbon dioxide, methane, and nitrous oxide: A significant revision of the methane radiative forcing", Geophysical Research Letters, vol. 43, 2016. http://dx.doi.org/10.1002/2016GL071930
100 Responses to "The definitive CO2/CH4 comparison post"
Gerald. Jurasinski says
Thank you very much for this very clear and informative description of the difference between CO2 and CH4. Maybe it would be worth to add a short paragraph on the sources of CH4 we need to address. Because there can be cases where we would accept CH4 emissions:
We are talking a lot about rewetting drained peatlands lately and often have to discuss CH4 emissions that of course increase after rewetting. However, we have shown, that the effect of ongoing high CO2 emissions from drained peatlands would be worse for the climate than rewetting (https://www.nature.com/articles/s41467-020-15499-z) although this will cause non-negligible CH4 emissions.
Helge Drange says
Thanks Gavin! Not directly on-topic, but some discussion – or references/links – to methane locked in permafrost and it’s potential climate impact – would be great.
Andrew Simmons says
Methane in general, and hydrates and permafrost in particular, have been covered here a few times over the years (for instance here: https://www.realclimate.org/index.php/archives/2012/01/much-ado-about-methane/
That said, those are all rather old in Internet years. No doubt observations and theory have moved on a bit since then, but I assume any findings of major significance would have been covered here too. (?)
Stocks and flows, OK if we (crudely) consider only fossil C oxidation important, and carbon cycle
living-terrasphere C waxing and waning under various influences, should not the ultimate stock of fossil C in natural gas be the only consideration of long term threat?
Oxidation of methane by burning natural gas is not rate limited, unlike atmospheric CH4.
And, unlike reserves of cheap oil, there are huge reserves of natural gas available for use. In other words, the huge stock of CO2 potential in nat gas that will be in the atmosphere for a very long time belie the apparent short term rate-limited CH4 warming potential from (say) bovine ferment.
And the burnt nat gas percent of the CO2 atmospheric stock has likely increased a lot lately.
Obviously biogenic methane has an effect, and fiddling with the dynamics of the carbon cycle helps.
But the real problem isn’t as clear when the two CO2/CH4 stocks and flows are considered together, rather than separated out.
Ian Enting says
Enting and Clisby (At Chem Phys, 21, 4699, 2021) have argued that getting a CO2 equivalence from a pathway
of CH4 emissions involves defining an index (cf various financial indices) so that the frequency
response of CO2 defined by the equivalence is the same as the frequency response of the actual
methane emissions. Thus the index has to emphasise the high frequencies in the equivalence and
attenuate the low frequencies. The index is acting like an equaliser in an audio circuit. In the frequency
domain the ideal index can be defined as the ratio of the Fourier transforms of the impulse response functions of
CO2 and CH4, multiplied by the ratio of radiative forcing per kg. (Since the response functions are zero
for t < 0, the calculations are more naturally done as Laplace transforms rather than Fourier transforms).
This analysis shows how the various indices such as GWP*, developed by Myles Allen and collaborators
at Oxford, give much better approximations to equivalent radiative forcing than using GWP (where the
index is a single multiplicative factor) or using an index defined by rate of change of emissions for CH4
and other short-lived gases.
Geoff Beacon says
Good piece – but GWP* gets off much too lightly.
GWP* has the enormous flaw that at zero GWP* neither CO2 or methane emissions need be zero. Isn’t Neil Enright (sustainsuccess.co.uk) right when he says
There is also the reductio ad absurdum that to make it easier achieve “net-zero” GWP* in, say 2060, methane emissions should not be cut yet.
Perhaps we should also remember that the RCPs that save our climate require negative CO2 emissions making CO2 have a shorter residence in the atmosphere. Does this blur the difference between short-lived methane and long-lived CO2?
Does GWP* really show that “the science has progressed” or is it a means to allow more emissions at “net-zero”?
Urs Neu says
This is a question that has been raised in a few discussions on the topic. However, one had to look at CO2 in the same way. In many emission trading schemes, emitters have initially got emission rights at an amount of their current emissions and then can start to reduce from that level. And country define their reduction goals on the basis of their emissions at a certain time (be it 1990 or 2000 or whatever). So we have the same problem with CO2. So we probably should discuss this issue for all GHGs, not only for methane.
Thank you for this – I’ve been trying to put together something similar on my own! A couple of initial comments, though I may have more thoughts later:
1) on the forward-facing kgC to kgC comparison – is it possible that you flipped the conversion? E.g., per kg the ratio is 30. Since methane is lighter than CO2, a kg has about 3x as many molecules of methane as CO2… so when you move to a kgC (or ppm) basis, you are reducing the amount of methane, so you should be reducing the impact of methane relative to CO2, not increasing it (like happens above for your atmospheric comparison).
2) in the forward-looking list, you might also include the “economic damage” metric: you could either look at the US government social cost of methane v. social cost of CO2 as a measure (though that includes the CO2 fertilization effect as a confounder), or you could look at the papers which relate GWPs to global-damage-potentials (Sarofim & Giordano, and Mallapragada & Mignone)
Also, while recognizing the ozone-mediated benefits of methane mitigation for health & crops, it might be a useful parallel to point out that CO2 reductions have benefits for reducing ocean acidification (and mixed effects in terms of CO2 fertilization… CO2 fertilization is probably beneficial on the whole, but has saturation limits and some negative effects in terms of its effects on micronutrients, weeds, and invasives).
Thanks for your work,
On 1) Oops! you are correct. I’ve updated the text. I will look up the other references too. Thanks. – gavin
As long as I’m nitpicking: according to 7.SM.7, I actually calculate the per ppm ratio to be 3.88/.133 = a factor of 29, and per mass then to be a factor of 80.
(when including indirect effects, relying on Table 7.15, I get the per ppm ratio to be 44, and the per mass ratio would then be 121 times)
I can hardly believe that Ozone will react to methane in the lower troposphere, because I looked over traditional chapters on it fror other reasons.
Ozone is produced from air by sharp UV or high voltage coronal electric discharge. In the lab, the Siemens ozone device is made of carefully cleaned glass or better fused quarz, to be absolutely free from nitrous lab gases, and mounted together by purest paraffin wax. Becaus ozone eats rubber and cork.
And if so, pure straight alkanes like CH4 will also be resistant to ozone.
But turpenes equal to rubber is quite more reactive and makes “ozonides”, that stinks and can detonate.
Conclusion: half burnt hydrocarbons, diesel and coalsmoke, obscure odeours and perfumes, bacteriae, virus, and the refreshing smell of harz, coniferes, and “balsam”, is rather what will react spontaneously with ozone.
Further burnt sulphur in air SO2 react with water and oxygen with “NOx” as catalyst” and give H2SO4. But a dilute H2O2 solution in water does also oxidixe S4+ into S6+., wherefore Ozone will surely also do the same.
Ozone detonates at any temperature if its pressure, partial or in mixtures, comes above 0.12 bar.. Thus cannot be confined and transported. For necessary use of ozone, one must set up that “Siemens ozonizer”.
H2O- gas hardly rises higher than the tropopause in our atmjosphere. Still, it is surely there higher up in the sub- arctic stratospheric clouds, that are shown to be HNO3 . H2SO4 . H2O in nanocristaline form. And still further up in the Noctilucent clouds, in the polar mesosphaeric clouds.
The theory for that is actually that CH4 is able to get that high up, and get scratched and oxidized by very sharp UV. For nitric acid, ammonia may be the source.
What surely will eat ozone down here where we live, is the combustion of stinky diesel and cheapest bunkers oil and cheapest coal, giving very acid rain and corrosion on cars and buildings and photochemical smog as fameous byproducts.
Hitgher up, cheapest military grade jet- fuel especially russian, will do the same.
The Space shuttle did add a lot of H2O to the mesosphere, and the subpolar mesos0phaeric clouds were quite impressive in those days. It is hard to believe, but remember that the exhaust volumes get extreemly large under those low pressures.
I think you misunderstood what Marcus wrote: “ozone-mediated benefits of methane mitigation” translates into: If methane emissions are reduced the amount of ozone near the ground is reduced. In other words he is not claiming that ozone reacts with methane rather the opposite. An impact of increased methane is an increase in surface ozone due to reactions with NO in the reaction chain from CH4 to CO2. In other words reducing methane is good both for reducing both climate change and surface pollution.
As Ozone hardly interferes and reacts with CH3 IN VITRO at any relevant temperatures, I think you must look for other explainations, “NO” will hardly help you.
That “NO” product out of Birkelands oven and later out of spontaneous oxidation of NH3 from the Haber Bosch synteti9s with common air over a very exspensive platinum- catalyzer,….
………was conducted into the bottom of a so called “Syretårn”, the acid towers, of granite, with stones inside for higher reactive surfaces, and water sprayed from above. Those towers are obsolete but came on Unesco heritage- list. Thin, HNO3 could be tapped from below and concentrated to commercial grade by destillation. For fertillizers and don`t forget theb bulk of all the nitro- explosives of WW1 and WW 2.
Those acid towers did work!
This true history entails that “NOx” and “NO” in moist air will react and settle down rather efficiently. . The easly pioneering industrialists did discuss all that, and knew it and earned on it.
It is Liebigs agro- chemical theory of nitrogen due to electric sparks, along with Benjamin Franklin.
NO does not cause the ozone, it follows it and reduces- breaks down ozone catalytically., The patented high voltage , electric “ozonizers” must be thorroughly rinsed and cleaned of nitrous gases on the surfaces, else the ozone production will be miserable. Meaning, Ozone is not stable in the environmentb of “NOx”, but rather efficiently reduced by it.
Reduction of metane happens in any case.
I know Eten is a bacterial nutricient, and tend to have learnt that also Metan the common moore- gas is oxidized by microbes in the moors and marshes. But what about in the air?
It disappears after a short while in any case. But after all, I tend to believe that due to the lack of concentrations and lighter sparks, this rather happens due to sunlight and sharp UV higher up, in the atmosphere by high enough E= h.ny in electronvolts to overcome the activation energies, to rip up and to split the quite stable CH4 molecule into highly chaotic and reactive free radicals., as an electrical spark the Birkieland way also would do.
I have not claimed that ozone reacts with CH3 either. Also an enclosed room that are hosed with water is not very relevant for non-cloudy atmospheric conditions. This is really chemistry textbook material so you should read those for details but some points. The reactions mentioned is taken from Richard P Wayne: Chemistry of Atmospheres, but any atmospheric chemistry book will give close to the same description
NO may break down ozone catalytically in vitro but UV light even near the surface regenerates the ozone to a large extent. As you say the processes are different in liquid water / clouds, but the high concentrations of ozone typically occur at daytime in high pressure situations with few clouds in particular near the ground. Typical reaction cycle in daytime atmosphere is
NO+O3 –> NO2 + O2 (1)
NO2+ hv –> NO + O (2)
O+O2+M –> O3+M (3)
So no loss or gain of neither of the components.
This is a simplification since some of the NO2 is also oxidized to HNO3 so there will be some ozone loss from these processes
However methane can change this. The first part of the CH4 breakdown is
CH4+OH –> CH3 + H2O
CH3+O2 +M –> CH3O2 + M
CH3O2+NO –> CH3O+NO2
So instead of reacting with O3, NO reacts with CH3O2. Photolysis of NO2 is still going on so reaction 2 and 3 still happens so ozone is created as a net result.
Paul P says
To be pedantic. “Bacteria” is the plural form of the noun “bacterium”. “Bacteriae” should be eradicated as quickly as possible.
I am no expert on it, but I have seen “Virae” in context, wherefrore I proudly write Viræ.
Are you jealous for not having Æ on your desktop?
@ Paul P
As I wrote, I am no expert, but I checked further.
…ae may be genitiv, not plural.
I shall eradicate further as quickly as possibhle, thank you.
@ Paul P
I have looked further.
Conniferæ, that is the needlewoods. Betulæ that is all the kinds of birches or belonging to the birches. Rosaceæ….Thus Bacteriæ and viræ…… next question pleace..?????
Richard Creager says
in the virology world, the usual plural is “viruses”
And just to weigh in on the GWP*: it is clear that in terms of scientific equivalence, the GWP* is a superior measure. However, it has some challenges when attempting to use it in policy-relevant applications. The fact that the GWP* is a function of historical as well as present day emissions makes it more complicated to use. Moreover, that positive emissions of methane can have a negative GWP* is going to be confusing for many users.
(however, to respond to Geoff Beacon above: net-zero GWP means a stabilized climate. But cumulative GWP* shows total climate impact. So while delaying methane reductions means that you can stabilize more easily in 2060, you’d be stabilizing at a higher temperature because of the cumulative effect. Moving to a GWP* world means needing to think differently)
Kevin McKinney says
Since this issue has been raised, can someone point to a brief definition/description of GWP*? I’ve searched a bit but no joy, and the above discussion makes me curious about this concept.
Chapter 7 of the IPCC AR6 assessment talks about GWP* along with other metrics, on page 7-123: for me, the best definition is the mathematical one, so here it is:
“To calculate CO2 equivalent emissions under GWP*, the short-lived greenhouse gas emissions are multiplied by GWP100 × 0.28 and added to the net emission increase or decrease over the previous 20 years multiplied by GWP100 x 4.24 (Smith et al., 2021).”
Basically, the concept is that the only way to make CO2 and CH4 equivalent is to compare a pulse of CO2 to a sustained change in CH4. That is approximated with this comparison to 20 years ago for short-lived climate forcers. One nice aspect of the GWP* is that global net zero emissions by GWP* means approximately constant temperature. For example, assume that the world has reached a stabilized climate (zero CO2 emissions, constant methane emissions). If someone were to release a ton of CO2 (say, by burning coal), if not offset, that would lead to a permanent increase in global temperatures due to the long lifetime of CO2. We could try to offset by reducing a GWP-equivalent quantity of methane – but that would actually lead to a short-term cooling, and eventually back to the long-term warming as the methane oxidizes away. The GWP* instead says to reduce methane by only a fraction of the what the GWP-100 would suggest, but then because of this “historical” term (the past 20 years’ emissions), there would be continued reductions of methane, which would just about perfectly offset the long-term CO2 warming.
I don’t know if that helps explain the GWP*?
Geoff Beacon says
Article in Carbon Brief by Michelle Cain is a good start: Guest post: A new way to assess ‘global warming potential’ of short-lived pollutants
But do look at GWP* should not be adopted by the IPCC.
Interesting links, thanks. I can see problems with both GWP100 and GWP*. The second link raises the scenario in which a last-minute fall in methane production can be used to achieve a faux compliance with some form of net-zero greenhouse metric in a certain year. This seems highly undesirable to me, but I lack the climatology background to really pick a winning metric.
Don’t we want nations to commit to a year-by-year reduction in whatever metric we choose, so that achieving net-zero by some date is merely a by-product of improving the situation every year leading up to that date? Without committing to a linear (or at least fairly steady and monotonic) reduction, won’t there always be hypothetical ways to game the metric? I can’t see how any single metric can have the desired results if we are merely saying it has to be net zero in a specific year. I think the whole “net-zero by 2050” is nonsense.
In terms of the relative cost of a specified amount of global warming a hundred years from now versus the same amount of global warming next year, surely a delayed warming is substantially better? It’s not just that we’ll all be dead in a hundred years, but rather that the risk of crossing tipping points is very high now (and in the next two decades), and the risk will be softened if we take sufficiently firm action now. (If we are still close to tipping points in 2100 we’re screwed.) Also, the sort of debates we often see about whether we even need to act to reduce climate catastrophe will have been amply answered by the end of the century, so taxes and other measures to change behaviour will be a lot less necessary then than they are right now. Already, I see that a lot of people who have experienced real-time climate change, such as Australia’s Black Summer, are much closer to accepting the need for major change than they were 2 or 3 years ago. And everyone I know under the age of 20 is already convinced of the need for change. So we need a metric that changes behaviour right now.
On the other hand, letting fossil fuel companies have a last fling before acting responsibly needs to be discouraged, and a wound to the planet that lasts centuries should be taxed accordingly. A policy of pumping out CO2 for 10 years and then reining it in to meet the Paris Accord should not be encouraged, when the effects of that CO2 will still be present centuries later.
So I guess I am torn between metrics with long horizons and those with short horizons.
I’d be happy to be educated on the matter.
Kevin Donald McKinney says
Thanks, both Marcus & Geoff.
Geoff Beacon says
Yes. So it’s even looser than GWP100.
At the suggested stabilisation of surface temperature (i.e. GMST steady in about 2060?), the heat content of the Earth will still be increasing.
This stabilisation will not be an equilibrium, where the Earth’s Energy Balance is zero: oceans will be warming, ice will still be still melting and permafrost will still be thawing.
P.S. After the decay of CH4 in a few decades, the effect on GMST largely disappears, but the heat due to its warming will stay in the Earth for a very long time (centuries?). It stays as warmer oceans, melted ice and thawed permafrost. Good reasons to cut methane emissions now.
How big will the feedbacks that these cause be?
Very interesting and informative post. Thanks.
Andrew Tyler says
This isn’t my field, so forgive a naive question, please!
Using the equation CH4 + 2 O2 -> CO 2 + 2 H2O , we learn that one mole of methane combusted yields 1 mole of carbon dioxide plus 2 moles of water.
Having learned in my youth that “water is the ultimate greenhouse molecule” , how does this play into these calculations ?
Oxidization of methane in the troposphere produces only tiny amounts of water relative to how much is there already, so that gets lost in the noise. When this happens in the (much drier) stratosphere, it’s a different story and it’s one of the indirect effects that are mentioned above that amplify the impact of methane emissions. – gavin
Dan Miller says
What about the comparison of how much a ton of CO2 leads to long-term increased temperature of the Earth vs. a ton of CH4? I believe this is called Global Temperature Potential (GTP) and I believe the GTP of CH4 is ~4. Is this a valid comparison?
The GTP is the relative impact on global temperature at a specific date resulting from a pulse of emissions: so where the GWP-100 is the integrated radiative forcing over 100 years after emission (which weighs impacts early and late in the 100 year period equally), the GTP-100 is the temperature change exactly 100 years after emission. The GTP does not consider impacts before or after that date.
There was consideration of using the time at which we are projected to stabilize as a moving target for the GTP – e.g., if we think that in 2060 we’ll stabilize temperatures, then in 2021, we’d use the GTP-39, in 2022 the GTP-38, and in 2059 the GTP-1. If all we cared about was temperature in 2060, this would be great, but the problem is that we actually care about 2061 and later too…
(there’s also a GTP resulting from sustained emissions… it ends up looking pretty similar to the GWP)
Geoff Beacon says
Climate Change 2007: Working Group I: The Physical Science Basis
The key point is “a given future time horizon”.
Methane decays in the atmosphere over a few decades. As this happens its effect on surface temperature diminishes.
After 100 years, The effect of emissions of CO2 will more-or-less retain their initial effect on surface temperature. 
After initial decades when emissions of methane cause a strong increase in Earth’s surface temperature, the effects on surface temperature subside (as most of the heating goes into the ocean).
Emissions of CO2 cause a long term increase in Earth’s surface temperature so after 100 years, the ratio of surface temperature rise due to methane and that due to CO2 becomes very small.
This means the GTP of methane after 100 years is very small – and small even after 30 years.
So why worry about methane except for short-term relief? That’s because only a small proportion of the heat it accumulates is currently radiated back into space. It is raising the temperature of the oceans, melting ice, thawing tundra. These effects will not be reversed for centuries (or longer).
Is this serious? Has it been sufficiently recognised?
 A clear explanation would be welcome of why the effects of CO2 emissions on Earth’s surface temperature do not decrease when a proportion of these emissions continue to be absorbed by CO2 sinks.
Richard the Weaver says
Yes, it is true, obvious, and irrefutable. If one swings a baseball bat as hard as one can, then it is pretty impossible to put Humpty Dumpty back together. Rate matters, like squared or cubed, and we’re swinging that bat at what? 1000x the rate the fastest natural home run swinger can manage…
So how’s that local ecosystem of yours doing after a summer (or winter – or year) that makes a Babe Ruth homer look like a T-ball shot?
“Tin foil for hats; tin foil for trees. Tin foil will save us, even from RFDs)”
Dominik Lenné says
Thx – very informative. The secondary methane effects are not well known and I am going to spread this further.
Readability remarks (may be nitpicking):
a) bullet list paragraphs could use a font size like the rest
b) I would use Teratons in the “temperature stabilization” paragraph to avoid very small °C values.
Some remarks on the newer GWP* comparison method would be interesting.
Roger Bryenton says
Two further points: Particularly relevnat as we need to quickly reduce temperature increase;
1. Pulse emissions of CH4 vs CO2 and GWP. A pulse of CH4 has a GWP of up to 120, and GWP10 is about 84 to 100. Thus sealing the leaking gas and oil well methane emissions has an immediate and necessary beneficial impact. So too with bovine emissions when we chose a non-bovine alternative food.
2. Stopping vs removing – longer term GHG reductions. Even if we stop emitting CO2, the warming effects continue. We must also therefore plan to remove CO2 if we want to maintain say, a 2C increase; if we do not remove CO2, the temperature will continue to climb.
This is not a hig-school science experiment. Our planet and our lives depend on massive social transformations from our fossil fuel addiction.
We don’t need non=bovine so much as we need regenerative bovine as that acts as a massive C sink. Cutting off one’s nose to spite one’s face is not a recommended strategy.
A lot less domesticated bovines replaced by herds of bovines, ungulates, etc., running about the planet would be the best of both worlds.
Only if the marginal removal to CO2 due to presence of regenerative bovine outweighs that regenerative bovine’s production of methane, multiplied by whichever GWP you use.
Alan Lauder says
Farming soils have less carbon in them than pasture soils. So when cropping country increases to replace sheep, cattle and goats in our diet, there is a release of carbon dioxide to the atmosphere as part of reducing methane produced by livestock. There are so many feedback loops that need to be considered.
S.B. Ripman says
This comes from a non-scientist. My prime take-aways from the article are (i) that methane makes up a large percentage of current greenhouse gas emissions, (ii) that atmospheric “perturbation” caused by CO2 persists far longer than that caused by methane, and (iii) that about 60% of the greenhouse gas warming since 1750 is attributable to CO2 and about 40% from methane (this came as a surprise). One also gathers and that under current emission projections CO2 appears to pose the far greater long-term threat to climate. Also understood is the article’s conclusion: that pursuing immediate and forceful methane emission reductions makes eminent sense.
25 years ago a book by Gelbspan entitled “The Heat Is On” made the point that global warming is especially pernicious because it warms the world’s oceans and they are such massive storehouses of thermal energy that it will take an extremely long time for them to cool down again.
For me this raises the question of whether the heating effect of methane may be greater than it is given credit for. If during its 12-year perturbation it causes significant warming and the warmth is then stored in the oceans, and that stored thermal energy persists far a lengthy period, is that factored into the total negative effect of methane emissions?
Maybe it is already factored in and I’m missing it. If so, my apologies.
Thanks for providing such informative articles and the commentary of actual scientists. For a layman like myself it is a very valuable resource.
S.B., the universal answer applies here…”it’s complicated”. But you have to keep in mind the distinction between
1. stabilizing the CO2 content of the atmosphere
2. stopping the increase of energy in the climate system (does not happen instantly after 1)
3. achieving a final new equilibrium state where the pattern of energy exchanges within the system is stable (what we experience as weather and local conditions; not what it was before we messed things up, but the “new normal”)
The point being that the only way to figure that out is through the models, which obviously have the energy gain from methane incorporated. So I trust the reporting of the specialists on this.
S.B. Ripman says
Thank you Mr. Zebra. Not obvious to me from the article; but now I’ve learned more
so right! Thanks, Gavin.
“Whatever way you slice this it implies that CH4 reductions have an outsize effect on climate, as well as an undeniably positive impact on air pollution, crop yields and public health (mainly through ozone reductions). It is therefore not a complicated decision to pursue methane reductions, taking care not to assume that doing so gets you off the hook for reducing CO2…”
Geoff Beacon says
I asked earlier for
I have found a paper by Solomon et al., which says
The “slower loss of heat” seems to be due to the warmer ocean. Before the cessation of emissions, CO2 warming builds up the heat in the oceans, which then slows the fall of surface temperatures. (The warmer ocean raises surface temperature above what it would have been if the oceans had not been warmed.)
However, the extra heat caused by CO2, previously in the atmosphere, is indistinguishable from the extra heat that methane leaves behind. Doesn’t this mean that the effect of methane on raising surface temperatures (GMST) lasts much longer than its residency in the atmosphere?
Perhaps this effect is very small but it must exist. Can climate models can quantify it?
Has anyone done this? Any references?
Geoff, you just answered your own question:
“However, the extra heat caused by CO2, previously in the atmosphere, is indistinguishable from the extra heat that methane leaves behind.”
So why would you think that the models aren’t taking the energy that was added to the system by methane into account?
Zebra, once again you have not understood the question being asked. Try again.
Hi Geoff: I would encourage you to look at Figure 8.33 from the IPCC AR5: it is an estimate of the additional temperature change resulting from one year of emissions of each of the major greenhouse substances. These results are an interplay of 2 key processes: the lifetime of a gas in the atmosphere, and then the thermal inertia of the oceans.
With CO2, the issue is that once emitted, carbon has to end up somewhere – the ocean, the atmosphere, or the land system. Estimates suggest that after hundreds of years about 20-30 percent of the CO2 remains in the atmosphere. To understand why the oceans can’t absorb more despite the size of the carbon pool in the oceans you should look up the Revelle factor: basically, because of the chemistry of the oceans, in order to increase dissolved carbon in the oceans by 1 percent, you have to increase atmospheric CO2 loading by 8-13 percent or so. Coincidentally, the rate at which CO2 concentrations decrease after a pulse to this 20-30 percent level just about counterbalances the thermal inertia of the oceans, such that the IPCC has determined that a pulse of CO2 leads to an effectively constant increase of temperature. (in the very long term – thousands of years – CO2 in the oceans can react to form calcium carbonate)
In contrast, methane has an atmospheric lifetime of around 12 years, and with thermal inertia you get a peak temperature response from a pulse of methane at about 10 years, and after 60 years the temperature effect has pretty much disappeared.
Marcus, I think you are giving useful explanations; I am not disagreeing with what I know you are trying to say, but I think some of the confusion people experience on this is the result of imprecise language.
“Coincidentally, the rate at which CO2 concentrations decrease after a pulse to this 20-30 percent level just about counterbalances the thermal inertia of the oceans, such that the IPCC has determined that a pulse of CO2 leads to an effectively constant increase of temperature.”
“Constant increase” can easily be misconstrued here by the people asking the question. The temperature is not “constantly increasing”.
If the thermal inertia of the oceans is balancing the effect of the natural decline in CO2, then for the time period in question you have achieved an equilibrium state in which you have a relatively constant GMST, which is higher than the one before the pulse…. rather than one which is slowly declining from that higher level because atmospheric CO2 is decreasing.
It may seem like a nitpick, but if someone is asking the question, it is likely that this may not be obvious to them. Some may figure it out, but some may not.
MA Rodger says
I don’t know about references but I think explaining the phenomenon of how global temperature responds to zero carbon emissions may do the trick. It will be properly accounted within climate models although they cannot predict future emission cuts for any GHG (and not forgetting natural emissions). A whole lot of other stuff is involved but the basis of the phenomenon runs something like:-
Under AGW, if we have an imbalance of global energy, say 1W/sq M TOA, while that will be warming the atmosphere, the majority of the 1W/sq M is warming the oceans, this due to the thermal time-lag resulting from the slow process of getting warmer waters down into the abysmal oceans.
(You could say that the time-lag is the atmosphere getting ahead of itself, but it is perhaps better to see it as the oceans holding the atmosphere back.)
Thus the atmosphere is in imbalance with space at +1W/sq M but also with having to warm the deep oceans, let’s -0.9W/sq M. So the actual rate of warming the atmosphere under rising GHGs would then be +0.1W/sq M. That +0.1W/sq M is what governs the rate of AGW as seen in rising annual temperatures.
In achieving carbon neutrality, we Earthlings would have at last manage to stop collectively prodding our planet’s climate and GHG levels will actually begin to fall. This will be faster with CH4 than with CO2 but in both cases and collectively the fall proves significant.
With falling levels of GHGs, the planet’s TOA energy imbalance is reduced without any change in atmospheric temperatures. But this TOA imbalance is still positive, say dropped by just 10% down to +0.9W/sq M.
But through that same period, the ocean and the atmospheric temperatures are still out of balance and that remains unchanged. So the oceans will keep on sucking that -0.9W/sq M out of the atmosphere.
As a result, the warming of the atmosphere is [+0.9 – 0.9 =] zero. Atmospheric temperature is stable. And will remain stable while the TOA imbalance equals the imbalance into the oceans.
The difference between CO2 and CH4, which both contribute to these energy imbalances, is that CH4 will react more quickly and reduce the TOA imbalance far quicker. So if AGW was predominantly CH4, there would be a bigger drop in TOA imbalance which would presumably significantly reverse the AGW atmospheric temperature rise. We would see cooling.
And, simplistically, if there was no CH4 in the mix and we relied on the more-sluggish CO2, we may well see some continued warming, certainly because of associated aerosols.
Note that the paper you cite Solomon et al (2008) ‘Irreversible climate change due to carbon dioxide emissions’ considers only CO2 and introduces an immediate zeroing of emissions. A slower reduction would be less dramatic in its transition from warming to stabilized temperature. There is a CarbonBrief article by Zeke Hausfather from this April that graphs the situation for both CO2 and all-GHGs, both with/without aerosols.
Geoff Beacon says
Although I have some reservations about the accuracy of climate models (e.g. missing feedbacks ), I am not suggesting here that they miss this energy. I am asking how much of the reduced flow of heat into the ocean (supporting surface temperatures) is due to previous heating by methane – and this proportion should be attributed to “methane warming” not “CO2 warming”.
Figure 8.33 shows that the heating by methane becoming small after 40 years ( earlier I said ” small even after 30 years.”). Isn’t 12 years just the half life?
However, 8.33 suggests that the extra heat in the ocean due to methane over the 80 years (shown in 8.33) is not as large as the extra heat due to CO2 over this period so methane’s role in slowing the rate of fall of surface temperature (due to warmer oceans) is secondary. However, it must exist, even if it is small. How small?
I came across this issue over a concern for the effects of Earth’s increasing energy content, which will continue after surface temperature is “stabillised”.
Note that Figure 8.32 implies that over 10 years methane causes greater warming than CO2 (as measured by GWP and GTP). This warming raises ocean temperatures, melts ice and thaws tundra. These may not have an impact as direct as surface temperature but I worry that the focus on surface temperature means the sub-surface accumulation of heat in the Earth is somewhat overlooked.
Geoff, you can’t answer a complex question if you can’t answer a simple one. So my approach in trying to understand this stuff is to first “design an experiment” in which we change only one variable.
-Go back to when the CO2 in the atmosphere had been constant for a long time, and keep it that way.
-Say something happened which caused the Sun to create an instantaneous pulse of radiant energy.
-She result of that pulse was to raise the energy level of the climate system exactly the same as what we have attributed to methane, and with the same distribution in the climate system… 90% in the oceans, some goes to raising air temperature, some to melting ice, some to evaporating water, and so on.
What is the effect?
What Marcus is saying it that this is how we can think of the effect of methane… as a pulse of energy, which has a transient effect. You seem to be stuck on this idea that it would have a permanent effect of some kind. But that’s not what the physics…the models… tells us; the system would just return to the original equilibrium. That energy would radiate to space, water would refreeze, the temps would go back down, yadda yadda.
If you think the models are wrong because there may be some positive feedback or synergistic effects that would cause the energy in the system to continue to increase, you would have to justify that with more than speculation.
Michiel van Weele says
One policy issue with methane mitigation is that stabilizing emissions would inderd be sufficient to stop further warming. Any existing installation or farmer will argue that nothing has changed in decades or they even applied slight improvements through mitigation measures at their spot. The growth is always ‘elsewhere’. Targets need to be kept somehow on regional methane emission reductions, not stabilization in order to stabilize or reduce methane globally. Last words not said yet.
Geoff Beacon says
This follows a widespread misuse of the word “warming”.
When methane emissions are ‘stabilised’ (rates of emissions staying steady), the Earth is still accumulating heat due to the methane in the atmosphere.
This methane in the atmosphere is maintaining the Earth’s surface at a higher temperature – not allowing surface temperature to fall.
In keeping the Earth’s surface at this higher temperature, methane in the atmosphere is responsible for more heat flowing into the Earth.
In this sense, stabilising methane emissions does not stop further warming. The Earth continues to accumulate heat. It’s just that its surface temperature is no longer rising – but the oceans are still warming, ice is still melting and permafrost still thawing.
P.S. I hate silly analogies but exasperation on this point has pushed me to this …
Look at the BBC’s How to make the ultimate baked potato.
After a few minutes in the oven the surface of the potato reaches a temperature close to that in the oven (200C or 180C). However, it takes rather longer for the insides of the potato to heat up to begin cooking.
At this point (and in normal usage) we would say that the potato is still warming up (and the potato’s energy imbalance is still positive).
I would like to see more discussion of the consequences of Earth accumulating heating on the inside. This discussion is stifled by the sloppy use of the word’ warming’.
Alan Lauder says
Hope this further adds to the discussion you would like to see around the true warming effect of methane.
I want to start by stating that the atmosphere does not see all methane as the same, so that what follows is kept in context. Fossil methane adds a new carbon atom to the atmosphere whereas ruminant methane (sheep/cattle/goats) does not.
“Ongoing stable methane emissions from cattle do not change the net balance of greenhouse gases i.e. not changing the climate.”
Provided the emissions have been stable for a few decades, stable methane emissions do not change the net balance of greenhouse gases i.e. don’t change radiative forcing.
With reference to to not changing the climate, the stability period has to be some decades more because, with all greenhouse gases, CO2 included, there is “committed warming”, which means some of the effect of past emissions is still to come because of the thermal inertia of the earth’s oceans.
I am inclined to agree with the comment made by Marcus:
“In contrast, methane has an atmospheric lifetime of around 12 years, and with thermal inertia you get a peak temperature response from a pulse of methane at about 10 years, and after 60 years the temperature effect has pretty much disappeared.”
Ladies and Gentlemen
Let me make you aware of another process for CH4.
If CH4 is sent through Birkelands electric flame oven, it gets split into elementary carbon and hydrogen gas.
(Birkelandes oven was pioneering for artificial production of nitric acid and “salpeter” fr9om air. It is an electric arch in a high frequency magnetic field, giving “Birkelands sun”. splitting the very resistant N2 tripple bond and giving some %s of NO in the air.)
In the same “oven” , CH4 is efficiently split into elementary black soot and hydrogen gas.
That hydrogen is supposed to be burnt or to go into the Haber Bosch process for ammonia and ammonium nitrate fertillizers. And the carbon in the form of elementary and very pure soot, is suggested to get buried.
The process has been shown to work, but the disadvantage is, as with that fameous salpeter process of Birkeland Eyde, that it takes a terrible lot of hydroelectric power, that can better be used for other purposes..
But there we have another interesting source for Killians soil systems, waggons of amorph, elementary carbon sold to be buried for his regenerative soil improovements. .
Wherefore I came to think of it.
I could use some of it for blacksmithing when coal and cokes gets strictly forbidden.
Todays hydrogen and salpeter industries use Metan LNG that reduces H2O into CO and 2H2, and full reaction is CH4 + 2H2O gives CO2 + 4H2. That however is a very pure source of CO2 to be taken better care of.
When hydrogen is sold or propagated today, this is mostly the true and practical source. An improovement however from reducing water with white hot blasted cokes. For the haber Bosch and Frischer Tropsch- methods.
John Henry says
If it consumes more energy to make then the greenhouse effect it causes, you’re barking up the wrong tree (squirrel!!!). It will never come to scale in other words, if that isn’t plain enough for you.
@ John Henry
You miss the point totally.
You associate it with stupid squirrels clinbing up wrong trees.
Whereas I discuss the stability of the CH4- molecule at temperatures above 3000 K and give an experimental industrial example. once used for HNO3- production , That could be possibly valid for
an open and unknown ammount of possible new use.
Such things are allways conscidered in qualified and possibly pioneering science and industries.
Looking back into to the museums and rather find it there and perhaps update it a bit for the needs of today and the future is quite an art.
Now that DAC CO2 capture is available on a retail basis from Climeworks new ORCA plant in Iceland, how long before the botique offset business starts selling direct methane capture portfolios to Vogue readers who tire of sequestering carbon in the Certified Vegan synthetic diamond jewelry offered by Aether Inc.?
John Henry says
“However the relative rise since the pre-industrial is three times larger for CH4, around 150%, compared to the 50% increase in CO2.”
Getting real tired of the bogus “pre-industrial” date setting game. Why does this keep happening?
This article uses the CORRECT 1750 “pre-industrial” while other articles use the “other” pre-industrial date (usually 1850, but elsewhere and perhaps here I’ve even read 1901).
Why can’t you guys figure this out? Why bounce around – unless you’re still fudging your numbers? There is absolutely NO EXCUSE for this incredible sloppiness.
Why it matters: We’re already a LOT closer to 2C then most reports, publications and articles will admit. ZERO chance of limiting warming to 1.5C, which makes EVERY article that makes this claim utter garbage, because they’re all using the wrong pre-industrial.
The fact that this misrepresentation is SO CONSISTENT in publications and articles is glaring – and indication of a deliberate deception to appease editors, authors, lawmakers, industry and politicians – as a “best guess”. I cannot think of any other valid nor scientific reason for the WRONG PRE-INDUSTRIAL to inhabit so many articles.
Barton Paul Levenson says
The low point of the exponential curve is so gradual that there wasn’t a lot of difference between the volume fraction of CO2 in 1750 and in 1850. I would be very surprised if it was as high as 10 ppmv.
That said, I agree that people should agree on a standard.
Please stop accusing people of misrepresentation when you haven’t put a little effort into understanding.
We use 1750 as pre-industrial for greenhouse gas concentrations because we have good records (using ice cores) of concentrations dating back that far. We use 1850-1900 as pre-industrial for temperature because that’s when we had sufficient coverage of the planet using direct measurement to have some confidence about global temperatures then. However, based on indirect measures (such as tree rings), global temperatures pre-1850 were not much lower than 1850: according to the IPCC, the 1450 to 1850 period was all of 0.03 degrees colder than the 1850-1900 period.
Reality Check says
We use 1750 as pre-industrial for greenhouse gas concentrations …
We use 1850-1900 as pre-industrial for temperature …
Aha, so it’s a distinction with a difference this time.
I do wonder how many others besides John didn’t notice that important, nay critical distinction, amongst all the detailed noise and disparate media reporting? :)
Geoff Beacon says
This year has seen big climate events. They have happened since the cut-off of papers for IPCC AR6. Do they show a step change in climate or are these events just chance?
Would a step change make removing CO2 from the atmosphere more urgent? If so, should we be taking the argument by Myles Allen in his Ted Talk seriously? (i.e. that fossil fuel companies should extract the CO2 their operations cause?)
If extraction becomes a serious operation, CO2 becomes a short-lived gas. Should this change the way we think about the relative importance of “short-lived methane” and “long-lived CO2″ – and give more attention to stopping methane emissions?
Yes, I agree with Myles that we must attempt to decarbonize fossil fuels – as well as reduce their use. If we are to pull out of this, we will need to do both, and soon. The cost associated with decarbonizing fossil fuels will make them a much more expensive, less competitive product, so it would be doubly effective.
Of course, none of this will happen unless we create financial incentives and disincentives that reflect the true damage these products are doing, and guide the economy to safer practices.
And that won’t happen until the voting public understands the seriousness of the situation.
John Pollack says
It looks more like chance to me than any sort of “step.” I also don’t know which “big climate events” you’re referring to, and how they distinguish themselves from those of recent years that made it into AR6.
Regarding Myles Allen’s TED Talk, he’s putting a lot of faith on an off-the-cuff response by some junior engineers who may not have thought through the question thoroughly. The problem with storing CO2, and the ability of fossil fuel companies or anybody else to do it effectively, is that if the fossil fuel you are burning is coal, it’s nearly pure carbon. It will take more net energy to capture, move, compress and store the CO2 than you get from mining it, hauling it, and burning it. This is especially true once you scale up to the level where you are storing an effective amount of it, not just some little demonstration project that stores a few tons here and there. There is no amount of money that can make a process that uses energy more effective than just leaving the carbon in the ground where it’s already stored. There is some chance that you could end up with an energy surplus from burning hydrocarbons (e.g. oil and natural gas), because you are getting energy from oxidizing hydrogen as well as carbon. However, there would need to be a complete energy analysis. How much energy does it take to extract, refine, and transport the hydrocarbons? How much energy do you get from burning them? How much energy does it take to capture the CO2, transport it somewhere else, and compress it for quasi-permanent storage? Even if the answer is a net energy gain, the next question is whether you can keep doing that at the required scale?
Reality Check says
Q should we be taking the argument by Myles Allen in his Ted Talk seriously?
A : I think not. The only place source point CCS is practical and cost effective is in imaginary hypothetical scenarios.
CCS has looked like smoke and mirrors since the day it first appeared. Decades later it still has nothing to show for the Billion$ of tax dollars given to the FF companies.
Prof, Myles Allen is clearly intelligent scientist but I have no idea why he is thinking what he thinks about CCS. Especially the storage part and the whole cost effectiveness of the concept. .
CCS destroys the massive advantage of Cheap coal/gas powered electricity and energy. Best to start there.
Being so incredibly cheap, efficient, easily mined and transportable raw materials, and the economies of scale are critical to coal/gas use in power stations. That’s why they are so successful and critical to maintaining the economic system up to now.
After 20 years only 4 CCS Projects are operating. the two biggest are used for oil recovery not sequestration. Storage is technically possible but is not universally available nor possible at the longterm scale required for sustainability. (yet a few papers suggest storage sites are available, so I am unsure)
Of course it’s possible the energy companies are lying, intentionally dragging their feet by making it look like CCS is not practical and too expensive? I see no reason to believe anything they say or submit to Governments or academic studies. Especially in regard to actual costs and other financial data.
2018 Carbon Capture and Sequestration (CCS) in the United States
DOE has funded R&D of aspects of the three main steps leading to an integrated CCS system
since 1997. Since FY2010, Congress has provided more than $5 billion total in annual
appropriations for CCS activities at DOE. The Recovery Act provided an additional $3.4 billion
to that total.
15th International Conference on Greenhouse Gas Control Technologies, GHGT-15
15th 18th March 2021 Abu Dhabi, UAE
Flexible CCS technologies to reduce the cost of net-zero carbon electricity systems
Since 2009, the South African Centre for Carbon Capture and Storage (SACCCS) has been investigating the technical feasibility of carbon capture and storage (CCS) in South Africa.
But, still in India the adoption of CCS in coal fired power plant is poor.
positive Hypothetical scenarios?
We find that in the 2∘C scenario with EPPA’s base-case technology cost and performance assumptions, CCS plays an important role in the second half of the century: by 2100 CCS is applied to almost 40% of world electricity production, with a third coming from coal with CCS and the other two-thirds from gas with CCS.
2021 paper says Yes, but no?
SCENARIOS FOR THE DEPLOYMENT OF CARBON CAPTURE AND STORAGE IN THE POWER SECTOR IN A PORTFOLIO OF MITIGATION OPTIONS
adding CCS to a coal-fired power plant will de-rate the plant by 20–25%, unless
additional heat or electricity is provided.
Our modeling shows that a low-carbon energy system requires a portfolio of
technologies. CCS has the potential to play an important role in many regions of the
world. In the base two degree scenario, technologies with CCS contribute to about
40% of global electricity generation by the end of the century.
CCS deployment in the model becomes limited as emissions constraints get tighter
and the carbon price rises when it is assumed that the capture fraction remains at 95%
for coal. One way for CCS to avoid this potential problem is by co-firing with enough
biomass to offset the uncaptured emissions and become a “net zero”technology.
Our sensitivity analysis regarding the cost of competing low-carbon technologies
shows that nuclear generation, if public acceptance and economic issues are resolved,
can be a substitute for CCS for providing clean dispatchable power. Renewables could
also outcompete CCS, depending on how the costs of intermittency are accounted. If
integration issues are successfully resolved, wind and solar can be a dominate source
of power generation. CCS deployment and the resulting generation mix also depend on
how quickly new technologies can expand.
The speed and level of CCS deployment is also affected by the stringency of the
climate policy. By 2100, different carbon tax cases result in CO2 captured and stored of
about 9 to 13 Gt CO2 per year. Higher carbon prices lead to an earlier development and
expansion of CCS in many regions.
You are perhaps a little unfair to Myles, as you finish up saying CCS will play a role – I agree he states things a bit too simply, though. I also fully agree that CCS is mostly smoke and mirrors at this stage, but high carbon taxes would encourage people either to improve what is possible on the capture front or find out that it is mostly impractical. Of course, we should not use impractical or nonexistent technologies to balance the books, but insisting that fossil fuel companies take full responsibility for their product seems sensible to me. Anything is better than letting them get rich by passing on the hidden costs of their product to governments, taxpayers and future generations. The prohibitive cost of what Myles proposes might push fossil fuels into a few niche applications, instead of being something we buy en masse at a falsely low price at the bowser. That would be entirely appropriate.
Either way, I agree we will need a lot of solutions all working together. Merely imagining an electric vehicle transition is also smoke and mirrors, as is merely encouraging thoughtful people to downsize. The world won’t ever be saved by relying on large numbers of people to be thoughtful.
I generally agree with what you say, though. We’ve moved from widespread denialism to widespread green-washing (woke-washing). We need far more action far more urgently than the general public realises.
Reality Check says
TWoE we will need a lot of solutions all working together yes yes yes. Including heavy Govt regulation, pollution controls and new tech framing regulations with support. Plus probably carbon fee on those FF regimes allowed to still operate. End users must pay the full price incl air travel, and actions taken by Govt on the basis of pushing down consumer demand. examples https://twitter.com/KevinClimate/status/1440977910370816000/photo/1
might push fossil fuels into a few niche applications Yes. Though I prefer that being done rapidly on the basis of Science facts (not market forces) progressively and quickly by Govt Regulated out of existence as the most logical certain approach. Today’s global religion precludes this and lowering demand policies.
“as you finish up saying CCS will play a role I was quoting sharing that info from pro-CCs papers, including them for fairness and openness. Maybe 50 years from now things could be different?
Overall it appears to me the No camp has much stronger evidence and quantity of studies to date. Myles bullishness certainty surprises me absent multiple lines of clear positive evidence.
I believe CCS is a known impractical Lemon sold to Govts (hoping to look like they were doing something) by the FF industry as just another deferment of taking serious action against reducing FF use. The same reason why DAC is being funded by FF companies, who again use the prototypes for EOR and then make all kinds of Promises for the future.
It’s not that (democratic?) Govts are always dumb, gullible and corrupt. But the one’s we’ve had the last several decades certainly are.
@ Mr Rodger renewables and energy efficiency are always essential mitigation options … Yes
@nigelj , move away fast from fossil fuels and new options must be zero carbon, safe Yes.
And never believe a word coming out of the mouths of a FF Executive (or Engineer) even under Oath. :)
MA Rodger says
It might be useful to set out what the Myles Allen TED-talk says rather than expect folk to watch it, although it is only 10 minutes (plus the pre-adverts) long.
The argument runs:-
For my own view:-
So we learn that today we have 0.1% FF being decarbonised and a bunch of reportedly confident “young engineers” who respond to the ‘Would you be able to do this?’ question with “Of course we would, like it’s even a question.” As myself being an old engineer,, perhaps I should point out there are similar engineers and their views who also appear in this talk with the comment “Remember nuclear energy was meant to be too cheap to meter in the 1970s”
My main concern is that, to say that in addressing AGW “there’s really only two options” is very dangerous talk. Such a statement must always be couched in the context that ignoring renewables and energy efficiency is never ever going to be “an option”!!!.
Regarding CCS. The thing with climate change mitigation is we have a wide range of options including renewable energy, solar power, wind power, nuclear power,. energy efficiency, CCS in various forms, planting trees, regenerative agriculture, etcetera. It looks hard to theorise which is best judging by the endless debates. Although I don’t particularly like CCS, I think the best solution is to have a serious carbon tax or equal subsidies for all mitigation options and let market forces and the private sector particularly electricity generating companies sort out their preferred option or options.
I’m not sure governments know enough to pick specific preferred options, other than to say they have to ensure we move away fast from fossil fuels and new options must be zero carbon, safe and so on. So governments set parameters rather than prescribe options. Other people like Zebra have alluded to a similar approach. Given that, I doubt CCS applied to coal fired power stations would be a preferred option due to the costs but its a decision for generating companies.
and let market forces and the private sector particularly electricity generating companies sort out their preferred option or options.
Market Capitalism got us here.
“We cannot solve our problems with the same thinking we used when we created them.” Albert Einstein.
You never change things by fighting the existing reality. To change something, ***build a new model*** that makes the existing model obsolete.” – Buckminster Fuller
Hmmm…. I believe that is exactly what I have done. I’m 100% certain your suggested pathway of do nothing but repeat the past failings vs my suggestion of a new model = Me 1, You 0.
This is, imo, the result of you getting lost in the weeds of secondary, tertiary, and beyond, issues while bypassing First Principles and First Order thinking.
I think that’s as gently as I can make this point.
I’m not sure governments know enough to pick specific preferred options,
Correct. Ergo…? “Sustainability is ultimately local.” – Me, 2011.
Geoff Beacon says
Should the FF industry be made contribute to a fund so that, when the time comes, when the technology works at scale the funds are there to do the job.
It would be a shame if they had the option of bankruptcy after paying their share holder handsomely.
Probably it would be bankruptcy, with massive bonuses to the executive, who also happen to have shares in the phoenix company that will be selling expensive capture solutions.
Geoff Beacon says
Myles has kindly replied to an email and says:
A clean-up fund would certainly get my vote.
Geoff Beacon says
The article, “Operationalizing the net-negative carbon economy”, was in Nature in July. It’s pay-walled and I haven’t read it. A comment from someone who has would be useful.
Reality Check says
Geoff I was able to download the full pdf doc , try that.
Geoff Beacon says
I’ve downloaded it
It would get my vote, too. Anything that put a fair cost on carbon would get my vote, where a fair cost is paying for the total environmental damage done by each product.
Thomas Pritchard says
Ir seems to me that the vast tundras on the northern coasts of North America, Greenland, Europe, and Asia and the submarine continental shelves are melting methane hydrates in Polar and southern regions are releasing so much methane, as in Siberia, this trend is not controllable and the impact of released CH4 will be dangerously monumental. I have asked several researchers and none have responded.
Thomas, I think the problem is that “dangerously monumental” is your subjective reaction to reading whatever you have come across in various media, but actual researchers deal with numbers and physical principles, as described in this post and several of the comments.
There is, at the moment, no “uncontrollable trend”, for the reasons discussed. If we stop producing CO2 and methane tomorrow the methane will go away fairly soon and the CO2 will be around a long time but start to diminish. So the energy increase that is driving that melting will be constrained.
Of course, if we do continue producing GHG at the current rate, there will eventually come a point where things get “dangerously monumental”, and you do get, effectively, “uncontrollable trends”.
What we hope for is that somewhere between now and then, reduction of GHG production becomes the norm, and that extreme end state never happens.
John Pollack says
We have an analog from the last warm interglacial period. The polar regions were actually warmer than currently, as shown by higher sea levels around 120,000 years ago than today, and various other indicators. The amount of CH4 in the atmosphere can be determined by the composition of the air in the Antarctic ice deposited during that period, and it did NOT show a big spike.
Of course, this doesn’t make us safe if we keep warming the Arctic a lot more, but it does take a while for heat to conduct into permafrost. In fact, the rate of heat conduction declines exponentially as you go down, so you are just thawing the area right near the surface. But, CH4 breaks down fairly quickly. In order to create a large methane spike, you would have to release a lot of methane all at once, say over a couple of decades, because you have to keep accelerating the rate of CH4 release to get ahead of the rising rate of breakdown.
I would judge the larger hazard to be the amount of carbon now locked up in permafrost and tundra soils. There is more of it, and the CO2 will be around a lot longer than the CH4.
JP says: “I would judge the larger hazard to be the amount of carbon now locked up in permafrost and tundra soils. There is more of it, and the CO2 will be around a lot longer than the CH4.”
I think, well, if we allow permafrost to thaw, both CH4 and CO2 will be released and will cause us harm.
I think it’s like setting up a firing squad at a gallows and instructing the firing squad to shoot when the trap door opens up. It may be difficult to determine which event(s) caused the most pain and damage after the fact, but the fact would remain the same in any case – death by execution.
With warming, we will be looking climate catastrophe driven by permafrost thaw. I am sure there will be argument as to whether we got shot to collapse or got hung to collapse, but in any case, we are likely to see a collapse if we let enough warmth to accumulate on the planet. I think we should avoid that if we can.
Kevin McKinney says
Hi, Mike, and greetings. The problem I have with your framing is that it’s a strict binary: you fall (or get shot) and you’re dead. Or not.
Our situation isn’t like that. “Collapse” isn’t a neat binary. For instance, by 2100 we could imagine:
1) Human population reduced by 30% from peak, with global GDP -10%;
2) Human population -70%, GDP -90%;
3) Human population -100%, GDP as if it had never existed.
Whether any of these seem remotely plausible now isn’t the point; what matters is that these would be vastly different worlds, all of which would merit that slippery little term “collapse.”
Believe me, KM. I agree that the term “collapse” is a very broad umbrella that would cover your 3 ideas.
My point was that whether we get pushed into the age of consequence by NH4 or CO2 could end be an academic point, a difference that makes little difference.
Maybe I am not grasping a distinction that you are making?
J Doug Swallow says
John Pollack says; “Of course, this doesn’t make us safe if we keep warming the Arctic a lot more, but it does take a while for heat to conduct into permafrost”. Are ‘we’ really warming the Arctic when these are the valid temperature extremes for Alaska?
If ‘we’ are warming the Arctic, why was the all-time high temperature for the state of Alaska set 106 years ago above the Arctic circle at Fort Yukon? What was the permafrost doing back 106 years ago? For the permafrost to melt, the surface above it must be disturbed.
Alaska Maximum Temperature 100°F June 27, 1915 Fort Yukon 26413 E
Alaska Minimum Temperature -80°F Jan 23, 1971 Prospect Creek Camp 507778 E
I would like a little more detail on the differences between CO2e for fossil fuel and agricultural methane emissions if that would be possible. I’m seeing more and more arguments from farming lobbies that enteric methane is just part of the natural carbon cycle and should be exempt from emissions restrictions, while of course the carbon capture possibilities of the land should also provide carbon credits to those same farmers. Being able to give the numbers for how effective methane reduction is from this article is nice, but having numbers specific to non-fossil methane would be a helpful addition.
Geoff Beacon says
I saw Cowspiracy on Netflix. That should give you some talking points.
Cowspiracy: The Sustainability Secret
“Learn how factory farming is decimating the planet’s natural resources — and why this crisis has been largely ignored by major environmental groups.”
Also from https://www.cowspiracy.com/
Jordan, could you give a reference to these claims about methane being part of the “natural” carbon cycle? And what “emissions restrictions” they are they arguing against?
See this ABC article for a recent example https://www.abc.net.au/news/rural/2021-09-17/cattle-industry-claims-it-can-reduce-climate-change/100412928 I was referring more to what people have told me in person I’m in agribusiness so I speak to a lot of beef producers.
Reality Check says
While the domestication of animals for meat and dairy has been around for thousands of years, and therefore seen by agribusiness ranchers as “normal and natural” it is the very recent 50 yrs massive growth in numbers globally which is issue regarding GHG emissions today. and btw the largest meat consumption is Pork.
re the abc link, good advice is to never believe any industry pr claims. They always spin it. And lie. eg Hardy’s asbestos the gold medal winner. worse than even tobacco and FF mining corps
Try these sites for info you looking for Jordan
Total emissions from global livestock: 7.1 Gigatonnes of Co2-equiv per year, representing 14.5 percent of all anthropogenic GHG emissions.
Cattle (raised for both beef and milk, are the animal species responsible for the most emissions, representing about 65% of the livestock sector’s emissions
Livestock are responsible for 14.5 percent of global greenhouse gases.
The global cattle population amounted to about one billion head
over the past 50 years, meat production has more than tripled. But the production of meat has large environmental impacts – increasing greenhouse gas emissions, agricultural land and freshwater use.
full 2019 paper with data — Methane, mainly produced by enteric fermentation and manure storage, is a gas which has an effect on global warming 28 times higher than carbon dioxide. Nitrous oxide, arising from manure storage and the use of organic/inorganic fertilizers, is a molecule with a global warming potential 265 times higher than carbon dioxide.
full 2017 paper Climate change and livestock: Impacts, adaptation, and mitigation
Have you ever learnt about the N/C relation?
That is [ N ] / [ C ] or the content concentration of Nitrogen per Carbon.
I learnt it from Composting , knowing also a bit soil science and agro- chemistery.
If you have garden waste and want to speed up the compost- process or metabolism, then add Ca nitrate to it or piss on it. That can work wonders. and let it go at higher temperatures.
Those 2 factors plus proper pH is all that is to be remembered, The N/C proportion, and the temperature. Then decay and digestion- combustion follows naturally.
The same rules further in the Reticulorumen the first stomack, ofr ruminantia, common cattle and deers. Quite obviously. For them to milk and to feed up 1 or 2 calves of flesh blood and bones , claws horns and furs in the season, they must eat an enormeous lot of “empty” calories to get hold of all that ammonium calsium magnesium phosphate sodium potassium and iron and sulphur, that makes up heaqlthy flesh and furs.
They expell that CH3, a highly flameable natural gas, to improove that N/C proportion for their quite very much higher metabolism, and manage to get rid of all those “Empty calories” rather leisurely.
That entails that adjusting their diet a bit could make them burp less methane. And it is understood and done done. They are given extra soya. And even kept on an experimental diet of urea, a special salt mixture, water and industrial finnish paper pulp. (Virtanen & Al)
But the better way might be to give them some seaweed, that they actually seek up for themself if they can. The large moose cow stands with head in the water eating the roots of Nymphaeae in the season feeding up 2 rapid growing calves on that.
I looked into it now. It shows that giving them less of highmolecular carbohydrates may be unhealthy for them. Their bacterial flora will suffer.
But in any case, their “Excretion” of Methane can be regulated quite a bit by diet, and it is known. I red of it several times, but unluckily, Soya seems to be the popular solution also for that.
A proper biochemical appendix
For all and everyone including the Australians.
If you make your own brew of poor materials and pure industrial sugar, it is recommended to add some “fermentation- salt”, I heard from a specialist that it is ammonium phosphate and potassium & magnesium sulphate. So you may just as well take cheapest NPK- fertillizer and some granulated dolomite for your cheapest brews and wines.
Proper fruits and choisest Malt need nothing of that.
What probably matters, as in the stomacks of cows, is enough Ammonium for the amino- acids and the fameous “Phosphorylase” in the bacterial metabolisms.
The involved microbes are rather quite common everywhere in nature.
Even ” the Diesel- animal” that lives in the tank and clogs the filters,…. is sheere and simple common slimy mould mycelium dependent on air and water especially some seawater also to thrive well on your tank. Those fameous friends of ours, common yeasts and moulds, is what can eat away large oil spills at sea and on land, surprizingly soon. . Some cyanobacter also to it is able to catch Nitrogen from the air and make Ammonium for them. Then they eat even stones..
The cows probably excrete enough ammonium phosphate and necessary Kations through Saliva, that feed the microbes for their work, and the cow does feed on those secondary microbes rather than the sheere dry straw, pure sawdust, or finnish paper pulp d/o itself . CH4 gets left over. The excreted bacterial nutricion gets re- cycled further down in the system.
No wonder why Cows are seen as holy in India.
Those large herbivores are known to be especially fond of some salt also to it. No wonder.
Some fameous fruits like Vitis vinifera and also Apples or sweet pears can just be squeezed and let to “go” anaerobically without any additions, …. the result will be known. That process delivers CO2 and thin etanol.. Aerobically, it giver Vinegar.
The settled yeast is known to be especially rich of B- vitamins.
Reality Check says
PS maybe useful refs
natural and anthropogenic source estimates
estimates in tg/yr FF sources 111 ; agriculture/waste 217
Jackson et al. 2020 Increasing anthropogenic methane emissions arise equally from agricultural and fossil fuel sources. Environ. Res. Letters.
Why methane from cattle warms the climate differently than CO2 from fossil fuels
July 07, 2020
Methane is created from atmospheric CO2 – It’s part of the biogenic carbon cycle
The critical difference between biogenic methane and a fossil fuel greenhouse gas, is that methane from sources like cattle begin as CO2 that is already in the atmosphere.
the last ref w video more or less supports the industry ideas in the abc news reports but assuming seaweed diet additives works and becomes universal (globally?) , and other agri sequestration actions are taken.
Unfortunately potential and possible doesn’t usually equal implementation when it comes to ghg mitigations as history shows. Could the benefits / reductions outweigh the expected global growth in total ruminant numbers in the future?
an interesting topic. good luck finding what you’re seeking.
Thank you for your help, there’s plenty in those links I hadn’t heard of before.
I love the details you included, data vise. Students are using your data whist writing research papers.
Mr. Know It All says
OK, so HOW do you propose that we reduce CH4 emissions? How will it affect the lives of people who use CH4 for heat, etc?
One possibility would be to criminalize the emission of waste CH4 during CH4 extraction operations. Make the penalties stiff, maybe 25 years minimum imprisonment for the entire board of directors and chief officers of any corporation that fails to adequately safeguard against such emissions.
Another way would be to imprison politically appointed regulators who fail to enforce regulations limiting the emission of waste gas during methane extraction operations.
This shouldn’t affect people who use methane for heat.
Negative externality curbed.
Mr. Know It All says
OK entrepreneurs, time to save the planet AND get rich. Design a device that attaches to a cow’s rear end, detects the presence of CH4, actuates a piezo-electric sparker that ignites the CH4. Might need a fire blanket around the tail. Better to have more CO2 than more CH4, right?
FYI: As I drove thru “fly-over country” recently, I saw many climate criminals standing out in their fields. They were mostly Black Angus.
Timothy (likes zebras) says
Thanks for this. I’d just like to emphasise the “Stocks and Flows” section. I think that if non-specialists were to take one lesson from this it would be that.
In my view the conclusion to draw is that prioritising the cessation of fossil fuel use is much more important for the future destiny of the globe’s climate, than on worrying about reducing meat and dairy consumption as a means to reduce methane emissions – which cause warming which is essentially temporary.
Donald Condliffe says
The human and political barriers to action to reduce fossil fuel mining and hence burning are our climate reality. All the data and analysis of how much fossil fuel burning must be reduced in the next ten years is based on a false assumption, that doing so is feasible given current human society and governments. The observed human reality is that emissions will not be reduced at all in the next decade. They are in fact increasing. The real climate question is how synergistic and how large will the effects of climate feed backs be when global temperatures have increased another 2 to 3 degrees centigrade?
Mr. Know It All says
You’re probably right. That means we need to start taking CO2 out of the air ASAP. It also means we need a Manhattan Project level of R&D to find new/better/affordable ways to do that quickly. I’ll bet the DemonRATs don’t have much in their multi-trillion dollar porkulus bill to do that.