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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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How do human CO2 emissions compare to natural CO2 emissions?

What the science says...

Select a level... Basic Intermediate

The natural cycle adds and removes CO2 to keep a balance; humans add extra CO2 without removing any.

Climate Myth...

Human CO2 is a tiny % of CO2 emissions

“The oceans contain 37,400 billion tons (GT) of suspended carbon, land biomass has 2000-3000 GT. The atpmosphere contains 720 billion tons of CO2 and humans contribute only 6 GT additional load on this balance. The oceans, land and atpmosphere exchange CO2 continuously so the additional load by humans is incredibly small. A small shift in the balance between oceans and air would cause a CO2 much more severe rise than anything we could produce.” (Jeff Id)

Before the industrial revolution, the CO2 content in the air remained quite steady for thousands of years. Natural CO2 is not static, however. It is generated by natural processes, and absorbed by others.

As you can see in Figure 1, natural land and ocean carbon remains roughly in balance and have done so for a long time – and we know this because we can measure historic levels of CO2 in the atmosphere both directly (in ice cores) and indirectly (through proxies).

Figure 1: Global carbon cycle. Numbers represent flux of carbon dioxide in gigatons (Source: Figure 7.3, IPCC AR4).

But consider what happens when more CO2 is released from outside of the natural carbon cycle – by burning fossil fuels. Although our output of 29 gigatons of CO2 is tiny compared to the 750 gigatons moving through the carbon cycle each year, it adds up because the land and ocean cannot absorb all of the extra CO2. About 60% of this additional CO2 is absorbed. The rest remains in the atmosphere, and as a consequence, atmospheric CO2 is at its highest level in 15 to 20 million years (Tripati et al. 2009). (A natural change of 100ppm normally takes 5,000 to 20,000 years. The recent increase of 100ppm has taken just 120 years). [Paragraph updated July 2022, to correct information on % of additional CO2 that is absorbed.]

Human CO2 emissions upset the natural balance of the carbon cycle. Man-made CO2 in the atmosphere has increased by a third since the pre-industrial era, creating an artificial forcing of global temperatures which is warming the planet. While fossil-fuel derived CO2 is a very small component of the global carbon cycle, the extra CO2 is cumulative because the natural carbon exchange cannot absorb all the additional CO2.

The level of atmospheric CO2 is building up, the additional CO2 is being produced by burning fossil fuels, and that build up is accelerating.

Basic rebuttal written by GPWayne

Update July 2015:

Here is the relevant lecture-video from Denial101x - Making Sense of Climate Science Denial

Last updated on 5 July 2015 by gpwayne. View Archives

Printable Version  |  Offline PDF Version  |  Link to this page

Argument Feedback

Please use this form to let us know about suggested updates to this rebuttal.

Further reading

Both graphs from this page are taken from Chapter 2 of the IPCC AR4 report.

Real Climate goes in-depth into the science and history of C13/C12 measurements.

The World Resources Institute have posted a useful resource: the World GHG Emissions Flow Chart, a visual summary of what's contributing to manmade CO2 (eg - electricity, cars, planes, deforestation, etc).

UPDATE: Human CO2 emissions in 2008, from fossil fuel burning and cement production, was around 32 gigatoones of CO2 (UEA).


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Comments 351 to 354 out of 354:

  1. MA Rodger @350 :

    Quite so.   There is also kind of disjointedness to the "laundry list".   Almost as if someone were using a program to generate random denialist phrasings.

    Or pehaps the list is a sort of Poe.   Une blague.

  2. 1. More testing for temp & c02 happens in or close to rural areas. Common sense logic. I need no link to prove. Why would you?

    2. Saying the ocean increase of 8 inches since 1800's? When was the last time you saw vast amounts of brilliant scientists up & down the coastlines with yardsticks or God help me dipsticks measuring the lines as the ocean ebbs and wanes a great amount of times more than eight inches many times within decades yrs mnths wks days hrs mins? Maybe the guys back in the 1800's were comparing satellite images to determine the beginning rises? I do not need a link to prove this is b.s. Nor should you.

    3. C02 gauges determining 400 parts out of 1,000,000 are c02? Fancy thermometer you have there & that is all it is. Electrochemical sensors? Did they count the atoms? Did they feel them? Smell them? Sorry el ch sensors only are in c0 detectors. C0 is even lower ppm than c02. C02 detects by measurements of laser intensity. Fancy thermometer. & Considering C02 can only possibly take up .05 to 5% of a given area that would mean variant temp detect would need be within those ranges as well. & Typal it would take the area of 3 average adults to have required amount of oxygen atoms needed to bond with carbon for such a reading of 400 ppm? Fancy thermometer. And this junk measures the laser intensity (pressure on the silicone chip... yes that's all.) in order to assume raises in c02 due temp rises? Fancy. Like if you had a concealed area void of all carbon oxygen etc and you lit a match to it the inner temp would not raise because only c02 can raise a temp! I do not need a link to prove this as quakery nor should you.

    4. Global warming causes tsunamis? Do they mean the consistent average of 2 a yr which has never shown an increase as far as I know to 3 is & has been caused by humans? I do not need a link. Suddenly I am hungry for sausage though. How about you?

    5. If .04 % of atmosphere is c02 & of that .04 we contribute .0016 of it that means we are changing approximate .00005 of atmo. An alien bug shifted a cosmic wind storm with a furt... seriously it did! But .00005% of your outhouse wallscovered in pink panther fiberglass... your still gonna shiver during snowy winter outdoor poo runs. Suddenly I no longer feel like sausage. Do you?

    6. 2 degrees!!!! Omgomgomg! Over 200 yrs! Imagine if that happened in a minute? It does. & Within an hour day week month season decade century Millennium four score seven years etc. I even heard it goes up & down by higher than 2° in those time increments! Could you imagine waking up one morning and it was like 10°!!! This is why Eskimos don't visit Africa... they would melt. Animals, especially humans cannot adapt to extreme 2°+ changes... impossible... especially if they happen over decades... trust me that's what common sense scientists say. I'm trying to make a segue with Abe right now but politics are not allowed here. Shoulda txt 5 score & 8 yrs. Nor should you... sorry just trying to stick to a format here.

    7. It's been millions of yrs since the earth has been this hot or had this much c02 & man was not even in existence back then which proves man did it! So who did it? Wooly mammoths? Hairy hippos? It's like saying your great grandmother to the ten millionth power got pregnant which prove the guy dating your daughter will not where a condom. Yeah I know... poor link. Norse soot dew. 

    8. 8% of our c02 production is what we breathe out. Gw alarmists should put a bag over there heads to help us get to the 0% c02 in the air which is what they want so that all plant life can die followed by all other life but at least surfers will not wipe out when a hundred ft high wave crashes upon them. Annette Fettuccine. Ignore her doo.

    9. Animals breathe too... little effers. Get over here fido. It's time I introduced you to Mr. Gallon size ziplock. I'll leave the pasta in there so you can have a last meal. Dogs don't know it's not seven degrees hotter for Kevin bacon... nor does he.

    10. You would think that after all this blaming mankind for every catastrophic thing that happens in nature from the monsoons to the tidal waves to rats overrunning Portugal the one's hitting the near end panic buttons with all their summits & committees & conferences & picnic BBQs & gov funding & YouTube funny cat video empirical research would come up with a way to significantly bring the average gt down by at least half a degree of our controllable portion so we could have only one & one half the amount of disasters. Like one and one half of a Suzuki. 

    The moral of the story.

    Spending time preparing for the unavoidable will save more lives than attempting to eliminate mankind's effects toward the consequences of a chaotic nature. Therefore gw are murderers by way of their ignorance. It is like they are watching a man beat child while attempting to prove a too many carbohydrates will make man beat child... now if we can just keep Frankie Avalon from the spaghetti we might save a child from abuse!


    [BL] Long, mostly off-topic Gish Gallop snipped.

    To our usual commenters: please refrain from responding to this until we have had the time to check if this particular user is another sock puppet of a previously-banned user.

    [BL] July 20 moderation update. Although this user does not appear to be a previously-banned user, the behavior so far violates several aspects of the comments policy - especially with respect to staying on topic.

    All comments must be on topic. Comments are on topic if they draw attention to possible errors of fact or interpretation in the main article, or if they discuss the immediate implications of the facts discussed in the main article. However, general discussions of Global Warming not explicitly related to the details of the main article are always off topic.


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  3. A note on the Basic tab of this rebuttal. An astute reader noticed that the paragraph under Figure 1 stated that 40% of the additional carbon is absorbed, but this disagreed with the values in the figure. A check of the original source confirmed the reader's observation. It appears that in the original writing, the 60/40 split was reversed.

    The rebuttal has been corrected to use the 60% value.

  4. As this is your first post, Skeptical Science respectfully reminds you to please follow our comments policy. Thank You!

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