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SkS Analogy 25 - Emissions vs Accumulation

Posted on 29 October 2021 by Evan

Income, Expenses, and Savings

Many people correctly note that human CO2 emissions are only about 4% of natural CO2 emissions. The incorrect conclusion, however, is that because our emissions are a fraction of total emissions, they cannot be causing the current warming. This argument confuses the concepts of emissions vs. accumulation. With regard to the warming effect of GHG’s, it is only the accumulation in the atmosphere that matters, not their emissions. To understand the difference between emissions and accumulation, let’s consider the finances of our fictional friend, Bob.

Bob has an annual income of $50,000. How long will it take him to accumulate $10,000?

Bob’s annual expenses (including taxes) are $50,000. Therefore, Bob will never accumulate $10,000, because his income is balanced by his expenses. In technical jargon we say that his income is in equilibrium with his expenses. In the common vernacular we say that he is living hand to mouth.

But then Bob’s finances change.

  • A relative passes away and leaves him an inheritance of $2000/yr.
  • His expenses do not change.
  • He pays $1000/yr in inheritance tax leaving him a net inheritance of $1000/yr.
  • Bob’s income is no longer in equilibrium with his expenses, and he accumulates $1000/yr.
  • Ignoring the effect of interest,  it will now take Bob 10 years to accumulate $10,000.

Although $2000 is just 4% of $50,000, a fraction of his base income, because $2000/yr is above and beyond Bob’s regular expenses, it accumulates in his savings account, even after paying the 50% inheritance tax. In this manner the relatively small inheritance becomes a big deal in Bob’s finances.

Up to the Industrial Revolution (i.e., up until about 1820), natural CO2 sources were in equilibrium with natural CO2 sinks, so that CO2 did not accumulate in the atmosphere. As of 2020, human CO2 emissions are about 4% higher than natural CO2 sources. About half of the human CO2 emissions are absorbed by the biosphere (i.e., land and oceans), but that leaves the other half to accumulate in the atmosphere.

Therefore, even though human emissions are a fraction of natural emissions, human emissions are a big deal because our emissions put the overall system out of balance. Nature was in a delicate balance before the Industrial Revolution, not accumulating CO2 in the atmosphere, but now our emissions have put the system out of balance. The accumulation of CO2 in the atmosphere of about 2.5 ppm/year is due to human emissions.

Additional Reading/Viewing

Gavin Cawley is a Senior Lecturer in Computing Sciences at the University of East Anglia. He has two very instructive videos on the carbon cycle here and here.


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Comments 1 to 20:

  1. Domestic animal agriculture is a human invention. These animals would likely not survive in nature but for their protection by humans. Thus, the respiration by these animals contributes to excess CO2 in the atmosphere. The amount of respired CO2 by domestic animals is quite similar to the repired CO2 of 8 billion humans, so it is important to count this CO2 when determining the matter of disequilibrium now damaging the pre-19th Century planet.

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  2. Sorry, the auto speller liked repired, reputed and other words, but I missed noticing that repired remained in my last comment.

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  3. Further, I think there is general agreement that CO2 in the atmosphere is the highest it has been in 15 million years, and for that matter, even the lowest it has ever been in that same 15 million years, it hovered around 240ppm. Does anyone, here, have better numbers?

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  4. Swampfox. For domesticated animals to survive they must be eating grass or grains or whatever plant life, and these plants absorb CO2. The whole process looks carbon neutral to me.

    However the demise of the meat eating predators like lions and tigers and the surge in livestock farming over the last hundred years has presumably increased the quantity of methane emissions, a potent greenhouse gas. 

    I'm not an expert and would welcome some clear, precise, umambiguous expert, informed opinion from a biologist.

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  5. nigelj@4, although not the expert your were hoping for, here is another view. Hopefully an expert will chime in at some point. :-)

    We need to be concerned with more than carbon cycling. We need to be concerned with GHG quality. As you pointed out and most people know, methane has about 25 times the warming potential of CO2. So as long as we have cows processing hydrocarbons and emitting them as a higher grade GHG, we have a problem. In this sense, it is not just about the carbon cycle, but also about the GHG grade.

    We calm ourselves down by saying that as soon as we eliminate methane emissions, that methane will disappear in 10-20 years. But if we maintain our herds of cows, they will continue to reprocess hydrocarbons into higher grade GHGs.

    We further calm ourselves down by saying that compared to big bad belching smokestacks that cow methane emissions are much less. But if we are successful eliminating the big bad belching smokestacks, we will find that the reprocessor cows, that increase the quality of GHGs, will represent an increasing larger, remaining part of the problem, even though they are theoretically just cylcing carbon through the system.

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  6. swampfoxh @3,

    The 15 million years since the planet saw CO2 at today's level is what I would say as we are surely now well past the levels of 3 million years bp which likely didn't even reach 400ppm.

    I would suggest your minimum of 240ppm over this 15 million year period to be too high. The usual value bandied about is 180ppm during an ice age while co2levels webpage gives a minimum value on its 800ky record of 172ppm back 670ky ago.

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  7. I'm no biology expert but I can poke around journals to figure out enough to say that when determining the livestock net carbon impacts, more depends on how they are fed and maintained than what is the net carbon balance of the ruminant's physiology. The differences between the various food sources, containment practices, manure management and transportation puts these calculations anywhere from a net carbon sink to a net carbon emission source. Here are just a few sources--there are many more:

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  8. wilddouglascounty@7 I get your point, but one of the problems with these pilot studies is that they hypothesize shifts that may only consider the resource demans of their single study subject, such as cows. The question is whether the proposed changes to feed and grazing patterns will collide with the recommendations of other pilot studies that propose using large swaths of land for BECCS or reforestation. Although I see your points, I remain skeptical that we will ever be able to fully implement the recommendations of all such pilot studies. What will it take to change the feeding/grazing habits of a billion cows or so? And a related question is this. Even if we know what to do, will we have the political/sociological will to follow through?

    All the while cows are reprocessing carbon into higher GWP (global warming potential) gases. I hope you and the studies you cite are correct, but I am skeptical that we either will be able to implement these proposed changes, or that we will have the will to do so.

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  9. evan@5 -"We need to be concerned with more than carbon cycling."

    OK. - CO2 & CH4 are the second and third most important GHG - but what do you think of H2O as the most strongest one ?

    nigelj@4 - "The whole process looks carbon neutral to me."

    CH4 emissions, which are reduced just as quickly as they arise, would be neutral. - ! That is certainly not the case.

    Cows and sheep  livestock generate more greenhouse gases as measured in CO2 equivalents than the entire transportation sector. Livestock accounts for 9 percent of anthropogenic CO2, 65 percent of anthropogenic nitrous oxide and 37 percent of anthropogenic methane.

    But these are not the only CH4 emitters:

    Natural and anthropogenic methane sources, according to the NASA Goddard Institute for Space Studies

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  10. cph @9,
    While it is correct that H2O does the heavy lifting when it comes to the GH-effect, H2O is a vey lazy gas and requires the presence of long-lived GHGs to get it doing any work at all. Thus it is the long-lived GHGs, and particularly CO2 that defines the temperature-boost of the planet's GH-effect.

    I'm not at all happy with your assessment of the GH-increase being caused by "cow & sheep livestock." Combining your numbers, that would suggest a 20% contribution which seem miles high. The OurWorldInData graphic below suggests just 5.8% from livestock.

    GHG emissions by sector

    Evan @5,
    Beyond their source, I don't see reason to account for the anthropogenic climate forcing in any way other than the usual bar charts presented by say IPCC AR6 Fig SPM.2 below. Thus the talk of "GHG grade" or "quality" isn't advancing any analysis that I can see. CH4 from livestock is simply a climate forcing as it has elevated global CH4.

    IPCC AR6 fig SPM.2

    swampfoxh @1,
    The CO2 breathed out by livestock is a component of that part of the carbon cycle represented by Primary Production and one of the fluxes shown in the graphic in the OP above, a carbon flux assessed by Haberl et al (2007) as having been reduced due to humanity (not just since 1750AD) by 10%, this surely through deforestation, forests being far better at Primary Production (and as a store of carbon)  than a field of cows.


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  11. cph: "what do you think of H2O as the most strongest one"

    While H2O is by far the main greenhouse gas, it is condensible at normal Earth temperatures so it can only act as a feedback, not as a driver or forcing. Why? To increase the amount of water vapor in the atmosphere the atmosphere must first warm by some other means, either by an increase in incoming sunlight, a change in surface albedo, or by an increase in CO2 and/or CH4 in the atmosphere, neither of which are condensible at normal Earth temperatures.

    cph: "Cows and sheep livestock generate more greenhouse gases as measured in CO2 equivalents than the entire transportation sector."

    This is shear nonsenese perpetuated by strident vegans who have hijacked climate change to further their own agenda. See the sector graph MA Roger posted. One could commit the same slight of hand by combining portions of the mining, smelting, petrochemical, manufacturing, and construction sectors related to the tranport system into the transportation total. It is fundamentally dishonest to do that with livestock but not with other sectors, and it renders sector attribution meaningless.

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  12. MA Rodger@10 - "H2O is a vey lazy gas and requires the presence of long-lived GHGs to get it doing"

    - I would have described H²O rather as a very lively & busy GHG, which absorbs almost all IR bands (by the way, even without the presence of other greenhouse gases), - has a very short residence time in the atmosphere and as a rapidly changing & travelling medium between water - water vapor - ice or snow, - distributes powerful energy and radiation potentials inside the atmosphere. More clouds and ice with certainty could help us - in our self-made hell.


    Jim Eager@11 - " it can only act as a feedback, not as a driver or forcing."

    - Yet the global warming potential (GWP) and radiative forcing of emitted water vapor have not been formally quantified. The fact that H2O is understood primarily as a feedback constituent does not mean these forcings cannot be quantified, and the relatively new concept of "effective radiative forcing" allows for this to be done.

    MA Rodger: "I'm not at all happy... "   

    Jim Eager: "This is shear nonsenese perpetuated by strident vegans..."

    Wikipedia awaits your suggestions for improvement. I don't feel like counting all the cow asses of this world - I'd rather eat them up.

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  13. Are you deliberately missing the point? It has nothing to do with the radiative forcing of H2O, it has to do with the fact that you can not directly increase the amount of water vapour in the atmosphere without first warming the atmosphere, otherwise the added H2O will simply condense out.

    Thought experiment: Remove all other greenhouse gasses from the atmosphere except water vapour. What will happen?

    The greenhouse effect will be reduced, cooling the surface and atmosphere. As a result the atmosphere will be able to hold less water vapour, so it, too, will be reduced by condensation and precipitation, thereby further reducing the greenhouse effect. As a result the atmosphere will be able to hold even less H2O. And so on. Pretty soon this will effect surface albedo as the precipitated water freezes into snow and ice, which will reflect more sunlight and reduce temperature still further.

    The point is you can not directly increase H2O, which means it can not be a driver of greenhouse warming, only contribute to it as a feedback.

    As for referring to Wikipedia as an authority on anything, you're joking, right?

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  14. Jim Eager@13

    - "It has nothing to do with the radiative forcing of H2O, it has to do with the fact that you can not directly increase the amount of water vapour in the atmosphere... / can only act as a feedback, not as a driver or forcing."

    The fact that H2O is understood primarily as a feedback constituent does not mean these forcings cannot be quantified, and the relatively new concept of "effective radiative forcing" allows for this to be done.

    (a) Difference in the feedback parameter (λ) between land and ocean and its decomposition (shown at left), in which the cloud feedback parameters over land and ocean are separately shown (at right). (b) Net ERF, clear-sky ERF, and cloud-sky ERF over land (red) and ocean (blue). Color bars indicate the CMIP6 multimodel mean, and error bars show the one standard deviation.


    If you give me the volume of water from Lake Ontario(1639km³) - I could evaporate it in the Sahara within 20 days - to directly increase the amount of water vapour in the atmosphere (for a few days).


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  15. Cph:

    A quick Google gives the flow of the Nile river as about 90 kmper year.  Where do you plan to obtain 1630 kmof water for your wild scheme?

    Build me a factory that can permanently sequester 10 gigatons per year of carbon dioxide and I can solve the climate problem.  Too bad that is not a practical plan.  Farmers already evaporate as much water as they can.  Little excess water remains anywhere in the world.  You cannot pipe the flow of the Amazon river to the middle of the Saraha dessert.

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  16. michael sweet@15

    "Where do you plan to obtain 1630 km3 of water for your wild scheme?"

    -— Of course, it is initially only about the theoretical possibility of global evaporating such an enormous amount of water(1639km³) in a 9.2 million km² of desert - in response to Jim Eager's@13 claim - which I doubt: JE: - "it has to do with the fact that you can not directly increase the amount of water vapour in the atmosphere..."

    -— But if you want to bring additional water into the Nile and the Sahara, there are still options that have not yet been practiced. To do this, you have to travel to the source of the Nile - Lake Victoria (68,000 km²). Cover a 10% of the lake area with photovoltaics to supply the megacities on the shores of the lake with renewable energy.

    The surface of the lake evaporates about 1.5m³ per m² per year - so that the PV means that about 10km³ of water per year remain in the also somewhat cooler lake and generate additional GWh of electricity in the dams on the long path of the Nile, but also enable additional agriculture. You can multiply this amount on the many other lakes and dams of the Nile, but 1639km³ for the Sahara alone is naturally utopian. BTW ~1639km³ of water is needed by plants to sequester ~10Gt of CO²/year.

    MS: - "Farmers already evaporate as much water as they can. Little excess water remains anywhere in the world."

    -— Farmers evaporate as much water as is available to them. In many regions, however, this becomes less and less due to pumped-out groundwater in summer - and the land temperatures that are ~1.5 ° C higher inevitably require ~10% more evaporation and water.

    Desertification and water scarcity is not a joke for many region with arid, semi-arid and continental climate- to intensify the water cycle over these land areas is a good idea. Water and rain retention a way to counteract the decreasing mean global relativ humidity over land areas. Even if the water vapor content of the atmosphere stays more or less the same - increased latent heat flux to the atmosphere = less sensible heat and cooling at the surface where we live.

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  17. cph:

    So your plan is to prevent water from evaporating from lakes to provide water to evaporate to increase the amount of water in the atmosphere?  Do you see that preventing water from evaporating would reduce the amount of water in the atmosphere?  This is a zero sum game.

    While it might be beneficial for farmers to obtain more water for irrigation by lowering evaporation of water from irrigation lakes, it would not result in greater water in the atmosphere.  In addition, the amount of water you propose to save is much smaller than the amount you want to evaporate. 

    Please provide a peer reviewed reference to support your wild scheme to evaporate water to affect the climate.

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  18. Michael Sweet@17

    -— To prevent water from evaporating on lake Victoria(wet region) "only" makes more water available in a dry region without any pipeline. 

    To increase/intensify the global amount of evapotranspiration & water vapor in seasonal & regional, unsaturated conditions like drought events  - we can use very simple tools to retain rain/water  from river discharge. This starts with:

    - urban micro-messures like rain barrels, cisterns or rain retention basins with an overflow onto unsealed terrain

    -  changes from groundwater use to flowing waters and / or river filtrate by agriculture, industries

    - anywhere in nature to rewet moors, wetlands and forests using an old hydrological tecnic.

    Please provide a peer reviewed reference to support your wild scheme to evaporate water to affect the climate.

    Changes in summer daytime latent heat [LE in W/m2, (A,B)], sensible heat [H in W/m2, (C,D)], and ground heat [G in W/m2, (E,F)] fluxes due to historical land use (left) and irrigation (right).   


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  19. CPH,

    The paper you lnk describes the effect of irrigation on surface temperatures.  It appears that large scale irrigation lowers the temperature a little.  This has been known for a long time and the authors are increasing knowledge of this effect.

    There is no mention at all of your wild scheme of dramatically increasing irrigation to reduce overall global warming.  In many areas, like California's Central Valley discussed in the paper, all available water is already used for irrigation and no additional water remains.  

    It appears to me that you have made up your wild scheme on your own.  It has been pointed out to you that you would have to increase the amount of water evaporated every year to combat increasing temperatures so your proposal is impractical.  The suggestion of piping enourmous volumes of water to the desert is absurd. The energy required to pump the water alone would be impractical.

    This is a scientific site.  Posters are required to support their claims with references to the scientific literature.  Long posts supporting your wild scheme are not appropriate here.

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  20. michael sweet@19 - "It appears that large scale irrigation lowers the temperature a little. This has been known for a long time..."

    -— What you call a wild plan - I call it water cooling. It is much more efficient than air cooling and is generally described in climate science as the Bowen ratio. While it is ~ 0.1 over tropical oceans and rainforests, it reaches ~ 10 in deserts.

    Decreasing surface BR plays a major role in the surface energy budget. It is estimated that the cloud feedback may increase albedo by 0.13 and reduce Rnet by 25 W m−2 in summer over agricultural land.

    ms: - " The suggestion of piping enourmous volumes of water to the desert is absurd. / ...all available water is already used for irrigation and no additional water remains. "

    -— I suggested a water transfer without pipeline ! Absurd - is to think that you only have to turn on the tap to get water. / Perhaps in the Central Valley people should start thinking about using the water retention measures I described above. - In principle a simple, worldwide request to politics, agriculture, industry but also to private persons to build up extensive water reserves wherever & whenever possible in order to use them generously in plant growth, evaporation, clouds and "water cooling" during periods of drought in spring and summer.

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    Moderator Response:

    [BL] The user cph has been confirmed as a sock puppet of the previously-banned user coolmaster. Until the admins can delete the account of cph, any further posts by cph wll be deleted as soon as moderators find them. Please do not respond to any comments you come across.

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