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Climate Hustle

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 40% 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 2009). (A natural change of 100ppm normally takes 5,000 to 20,000 years. The recent increase of 100ppm has taken just 120 years).

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 skeptickev. View Archives

Printable Version  |  Offline PDF Version  |  Link to this page

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.

It's not particularly relevant to this argument but World Resources Institute have posted such a great resource, I had to put it somewhere. It's 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 251 to 300 out of 301:

  1. YubeDude @250, there is not one isotope, but two.

    First, C14 is a radioactive isotope with a short half life (5730 years) as a result of which C14 is effectively undetectable in carbon sources more than 50 thousand years old (at which stage it has fallen to 0.2% of its original value.  Because of that, fossil fuels are almost completely devoid of C14, as are volcanic emissions.  The very rapid decline in C14 in the atmosphere since the onset of large scale combustion of fossil fuels shows that the source of the rapid rise in atmospheric CO2 is devoid of C14, and therefore does not come from recent vegetation, or the ocean.

    Second is C13.  C13 is a stable isotope of carbon, that does not increase or decrease in quantity with age.  It is heavier than C12, however, as a result of which many plants will take up proportionally more CO2 with a C12 isotope than with a C13 isotope.  The result is that carbon from organic matter, including fossilized organic matter in the form of fossil fuels, is deficient in C13.  The decline in the C13/C12 ratio in the atmosphere since the large scale combustion of fossil fuels shows the resulting increase in atmospheric CO2 to come primarilly from an (originally) organic source, ie, from vegetation or from fossil fuels.

    Taking the information from both isotopes, we see that the increased CO2 cannot come from modern vegetation because of the decreasing C14 concentration, and that it also cannot have come from volcanoes because the decreasing C13/C12 ratio.  The only possible source that explains both trends is fossil fuels.  Ergo, the increased CO2 concentration is a result of the combustion of fossil fuels. 

  2. TY Tom for the reply. I understand about the carbon ratio and the meaning what I am interested in is if CO2 also caries the O-18 marker that would link that particular molecule of  CO2 directly to combustion and not just a sink release or another anthropogenic use of older carbon sources such as chemical manufacturing that is petro-chemically based.

    I am wondering if O-18 has any merit whitin the topic as I see no mention or research that attempts to link or associate its presence with A-CO2.


    No quibble on my part as to the evidence rather just a currisoity in regards to this darn O-18. Thanks in advace for any light you may be able to shed.

  3. YubeDude @252, I am not aware of any use of O18 as a marker of CO2 of organic origin.  Of course, I am not expert in the field, so that only means it has not made it into popular presentations (or the IPCC reports).  Further, searching google scholar does not readilly turn up studies using O18 as a marker for the organic origin of CO2. 

    I suspect it is possible in principle.  However, fractionation of O18 in respiration is a confounding factor, and likely to be stronger.  Further, atmospheric O18/O16 ratios will vary more with time than than C13/C12 ratios due to the fractionation of O18 in water by evaporation and condensation.  No doubt there are other complexities of which I am not aware as well.

    Sorry I can't help anymore.

  4. I was wondering if somebody could explain a part of the answer to me?  Fistly, the answer states that rises have been noticed.  If this is true, why is the complete rise solely based on humans and why can this not be a dramatic rise naturally occuring? What is to say that this is a new rise not previously seen in history before that is natural?  I do, think that humans contribute to a rise in clarify.  Secondly, I am assuming that the things I heard on tv were true and that there is a hole in the ozone.  If there is a hole, why wouldnt the co2 just escape through that hole?  Why wouldnt oxygen and nitrogen escape through that too? 

    Im really just trying to get some answers here.  The problem, from my perspective and I think a good majority of others, is that as a lot of the comments show, this is science.  I am not a scientist.  That doesnt mean I was raised to trust anybody telling me what they have is true.  I need this explained is some everyday, simple language please.

  5. Firstly, we know with reasonable accuracy how much coal and petroleum are being burnt every year. We know that not all of that stays in the atmosphere (or the rise in CO2 would be larger). At the moment, the sea is moping up some of those emissions and becoming less alkaline in the process (that is also measured) so CO2 is not coming from the sea. The change in the pH allows us to calculate how much CO2 is being dissolved. As the oceans warm, this will change and eventually the oceans will begin to emit CO2 - hopefully not in the next century or so.

    Sources of CO2 have different ratios of the carbon isotopes C14, C13, C12. For instance, fossil fuels have no C14 (it is short-lived). You can look at ratios of these isotopes in the air and water and check if the proportions match emissions from humans or some other source.

    The "hole in the ozone layer" is a pictureque but inaccurate description. All the gases (including ozone) in the atmosphere are bound to the earth by gravity. The ozone layers doesnt trap any gas. Ozone is produced in tiny amounts in upper atmosphere by interaction of oxygen with UV radiation. This has a very important effect in shielding the lower atmosphere (where we live) from UV. Chemicals released into the atmosphere (CFC) are chemically destroying ozone especially above Antarctic so that it is much thinner ("the hole") in those places.

  6. rdbachel @254, you may be interested to read this summary of how we know the CO2 rise to be anthropogenic.  The mass balance argument (we know how much we have emitted, and it is more than the increase in CO2) and the isotope arguments mentioned by scaddenp are the most important pieces of evidence, but no the only ones.

    To slightly complicate things, had the temperature increase we experienced over the last century occurred without any increase in anthropogenic emissions over pre-industrial levels, we would still have experienced about 10% of the increase in CO2 levels that have actually occurred.  This is known due to the known (from experiment) solubility of CO2 in water with temperature, and from comparisons to CO2 increases in past eras when temperatures have risen (as at the end of glacials).  However, the rise in directly anthropogenic CO2 has been far faster than that potential increase.  That is known from mass balance, and from the fact that ocean acidity increased over that period whereas it would have decreased if the CO2 increase in the atmosphere was due to thermal sources.  Further, even if some of the increase should be attributed to temperature, that temperature increase is itself primarilly anthropogenic so that any CO2 increase in the atmosphere caused by it is also anthropogenic.

    So called "skeptics" about AGW sometimes argue that the CO2 increase is natural and due to temperature rise.  To do so they entirely ignore the rates at which CO2 rises in the atmosphere with increased global temperature (which are too small by a factor of 10 to account for the actual rise experienced), and the concurrent increase in ocean acidity, which proves the amount of CO2 dissolved in the ocean is increasing at the same time.

  7. TC. I would have to humbly disagree with you on this one. I dont believe that we would have received a 10% increase - yet. Ocean mixing delays that solubility response.

  8. scaddenp @257, based on ice core data, there is approximately a 90 ppmv rise in CO2 concentration between glacial and interglacial.  That yields a CO2 increase per degree C between 11.25 and 30 ppmv per degree C with the former for an 8 C increase in temperature, and the later for an assume 3 C increase.  A reasonable central estimate is 18 ppmv per degree C (5 degree increase).  For the 0.8 C increase in temperature experienced since the industrial revolution, that yields and expected increase of 14.4 ppmv or 12% of the CO2 increase todate.  As you say, it is unlikely that all of that increase would have happened over so short a time.

    As an alternative emperical measure, taking the global temperatur anomaly from 1010 AD to 1800 AD (Mann 2008) and ice core CO2 records, the regression shows an 8.1 +/- 2.9 ppmv increase in CO2 per degree C.  Based on that regression the expected increase for the global temperature increase since the pre-industrial of 0.8 C is 6.5 +/- 2.3 ppmv of CO2, or 3.5 - 7.3%.  The time resolution of the CO2 record is 75 years, and I used a 75 year average of the temperature record to maintain equivalent resolution.  That regression, therefore, yields a reasonable but not precise estimate of the increase that would have occurred from temperature increase alone.

    As far as showing the absurdity of the pseudo-skeptic claims that the increase in atmospheric CO2 was caused by the temperature increase goes, the difference between 3% and 10% is not relevant.  Therefore I indulged my habit of using conservative (for my position) estimates for rough figures where it makes little difference.  The long and short, then, is that, yes I agree with you.  But I don't think the difference is enough to warrant keeping track of for rough estimates.

  9. Hi All, 

    I'm new here and hope, although this question is indirectly related, that it is not too far off topic to not be answered.

    I understand how the oceans absorb c02 and the forces at play.

    What I would like to know is how does c02 absorbed 'heat' from the atmosphere get into the ocean itself. What are the mechanisms at work that makes it possible for the ocean to be a 'heat sink' for atmospheric heat?

    i.e "90% of the atmospheric heat ends up in the ocean" - Tim Flannery.

    This assertion on face value appears to be in violation of the Laws of Thermodynamics.

    i.e Two thermodynamic systems that are not in equilibrium with each other must have net sum energy transfer move in one direction only. 

    Because clouds are the observable evidence that net sum energy transfer occurs from the ocean to the atmosphere, and that net sum energy transfer between the atmosphere and the ocean can only be in one direction, how can the ocean be a heat sink for atmospheric heat as it would have to be a net sum value, which would be a violation of thermodynamics?

    Any assistance here would be greatly appreciated.



    [DB] This post explains how increasing levels of CO2 heat the ocean.  For continued questions on that mechanism, place those questions there, not here.  Thanks!

  10. Gac73,

    I posted a response to your question here.

  11. This landed in my mailbox a day or so ago. It comes from a gentleman whose speciality is Heliophysics. In addition to what he has to say here, I'd like to add that, the best I can tell, about .006, just over 1/2 of 1% of the atmosphere is made of CO2. And of that, depending on who you believe, the manmade portion of that amount is only 2%-7%. Either way, we're talking about an infinitesimal figure. Using the 7%, that still only comes to .000042 of the atmosphere is affected by manmade CO2 emmissions.

    Color me stupid, but I just have a hard time believing that has any impact whatsoever.

    Now, I do not claim in any way whatsoever to be a scientist. Those numbers are what I grabbed from a few of what I consider to be reliable internet sources.  Please, if you have evidence to prove me wrong, by all means, do so. I'm open minded about science, and willing to listen to anyone who can provide substantive information. I think the main thing, which I've found from many sources, as the guy I'm quoting below points out, is that CO2 levels FOLLOW rising temps, not vice versa. Like I say, I just study as much as I can on something which interests me and try to make a sound conclusion based on what I find. And I am in no way offended by conflicting information. We'll just have to look deeper into the backgrounds of the sources to see if they have anything to gain or lose one way or the other.

    "Currently the consensus is that 15% of global climate change is due to the sun. I think that this might be a bit low. for the last 10 years GISS [I assume he's referring to the Goddard Institute for Space Studies at Columbia University] has seen a decreasing, trend of global temperature. I would caution that the decrease is consistent with no change. CO2 continues to increase. Further the glacial record shows that increases in CO2 levels lag global temperature increase."


    [JH] On this site, it's considered to be in poor taste to include more than one denier myth in a single comment. It's also in poor taste to try to disguise where you are coming from by quoting someone else.

    Please note that posting comments here at SkS is a privilege, not a right.  This privilege can be rescinded if the posting individual treats adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Please take the time to review the policy and ensure future comments are in full compliance with it.  Thanks for your understanding and compliance in this matter.


  12. Common Sense > Brain Washed:

    1)  Benjamin Franklin said it best:

    "Common Sense is neither common nor sensical. Much of what passes for common sense is not based on any underlying principle it’s just anecdotes that have worked for the current situation."

    2)  Your "common sense" requires not only that much of the public be brainwashed but that the vast majority of climate scientists have undertaken a conspiracy to delude the public.  That is not common sense in any terms, but much closer to the ravings of a loon.

    3)  And for the moderator, if an offensive wanker (profanity removed) is allowed to use a monikor that amounts to an accusation of massive fraud by scientists, then he should be expected to take his lumps in turn.

    4)  I will be convinced that small concentrations are irrelevant when you sit in a chamber containing 400 ppm Arsenic pentaflouride (LC50 at 20 ppm) for an hour and tell me who little effect it has had. 

    (Warning:  Just in case your sense is as sensible as your post suggests, LC50 means a 50% probability of death as a result of exposure to that concentration for an hour in test animals.  Do not conduct this experiment.)


    [JH] Your point #3 is spot on. I have also issued Standard Moderation Comment #1 on his/her post. 

    [PS] Please observe comments policy  on profanity

  13. Brain Washed wrote: "I'm open minded about science, and willing to listen to anyone who can provide substantive information."

    You might have tried reading/searching first. The various arguments you present are all covered in the 'climate myths' section of this web-site;

    "the best I can tell, about .006, just over 1/2 of 1% of the atmosphere is made of CO2"


    No. The current atmospheric CO2 level is about 400 parts per million... 400 / 1,000,000 = 0.0004.

    the manmade portion of that amount is only 2%-7% (BTW, [400 - 280] / 400 = 30%, whoever told you 2% to 7% is really bad at math)

    Color me stupid, but I just have a hard time believing that has any impact whatsoever. 

    CO2 levels FOLLOW rising temps

    "Currently the consensus is that 15% of global climate change is due to the sun."

    P.S. Seriously, don't do Tom's hypothetical arsenic experiment.

  14. CBDunkerson @263.

    The 0.006 value being quoted is probably ppm CO2 by weight which is roughly 1.5x the 'by volume' value for dry air.

    The 2%-7% is probably that derived from the relative size of CO2 fluxes into the atmosphere, from man-made sources and from natural sources, a particularly stupid value to use as the natural fluxes are bi-directional while the man-made ones only go one way.

  15. MA Rodger @264, I believe the figure originally came from calculations of the residence time of CO2 in the atmosphere made from measurements of the rate at which the C14 spike from nuclear testing dissipated.  From such measurements it was determined that approximately 203 gigatonnes of Carbon in the form of CO2 (GtC) leaves the atmosphere each year.  Given a total atmospheric reservoir of 829 GtC, the average duration of a carbon atom in the atmosphere is just over four years.  Ergo, for a year n years ago, the approximate fraction remaining in the atmosphere is 0.75^n.  Even with an assumed constant emissions of 8 GtC per annum, that means only approx 24 GtC in the atmosphere was emitted from an anthropogenic source, and has never left the atmosphere since emission.  That turns out to be 2.9% of the atmospheric concentration.  (Obviously the figure will vary slightly with more exact calculation.)

    Taking a simple ratio of annual gross natural emissions to annual anthropogenic emissions gives you a ratio of 4.1% if you only include fossil emissions, but 4.7% if you include emissions from land use change and 17.5% if you include all anthropogenic emissions including outgassing due to global warming.

    Both calculations assume that any emissions from the ocean or plants and animals cannot have come from fossil sources.  That is, of course, absurd.  Indeed, it is assumed by both methods that most anthropogenic emissions are stored in either plants or the ocean as a result of the rapid exchange of CO2 between atmosphere and the other surface reservoirs of carbon.  It follows that a certain proportion of the "natural emissions" are emissions of carbon that until a few hundred years ago (and in most cases a decade ago or less) was stored in a fossil reservoir.  A rough calculation of the proportion of CO2 in the atmosphere that was recently in a fossil reservoir is then given by the ratio of the sizes of the combined reservoirs to the cumulative emissions.  That works out to approximately 12% excluding the deep ocean and soil (for which exchange is slow).  The actual number may be lower than that, but not by much.  (It may also be higher given the average life span of trees.)

    All this, however, is as you note, beside the point.  The real question is how much of the increase in atmospheric emissions is due to anthropogenic emissions.  To that the answer is 100%.  Ergo, 30% of the current atmospheric concentration would not have been in the atmosphere without anthropogenic emissions.  That is the case regardless of whether or not any individual atom was recently in a fossil reservoir for the approximately 20% of atmospheric CO2 that would not have been there without emissions, but whose carbon was not recently in a fossil reservoir has merely displaced CO2 whose carbon was recently in a fossil reservoir due to equilibrium exchanges.

    (Note, all figures calculated using values from Fig 6.1 of AR5 WG1.)

  16. Tom Curits @265

    30% of the current atmospheric concentration would not have been in the atmosphere without anthropogenic emissions.

    Any cursory look at two readily available data sets, Mauna Loa CO2 and global temperature by year, clearly shows that temperature is a strong driver in how much CO2 ends up in the atmosphere on a yearly basis. Note especially the 600% difference in 1992's and 1998's CO2, clearly based on temperature. 

    Also look at CO2 increase by year from 2000-2015, hardly changed at 2ppm per year despite a 68% increase in global emmisions over the same time period. Why isn't the rate of CO2 increase responding to human emissions? Because CO2 reponds far more to temperature, which has flatlined for 15 years.


    [Rob P] - Surface warming still continues.....

    And the last 16 years has seen a 50.3% increase in heat taken up by the Earth's climate system than the previous 16 years. Which means there's a lot more warming in the pipeline. The following image is from the IPCC AR5 WG1 on the oceans.


  17. Rickeroo...  A "cursory look" is not going to "clearly show" anything. 

    Another "cursory look" actually contradicts exactly what you're saying. If temperature were driving CO2 then why hasn't the atmospheric concentration of CO2 also "flatlined" over the past 15 years?

  18. And Rickaroo, scientists aren't arguing from the correlation between the CO2 and temp graphs.  Why would you?  The physical mechanism of the greenhouse effect is extremely well-established--to the point of being instrumentally measured from the surface.  If you want to make the argument you've claimed, you'll need to remove the greenhouse effect.

    Temp does drive CO2, of course, because the warming oceans absorb less atmospheric C.  The process is a feedback to initial and ongoing warming, though.

  19. Rickaroo @266, I see what you mean.  There is no correlation between CO2 concentrations and anthropogenic emissions at all, is there?

    "The increase in CO2 concentration over the long term (1850-2005) almost exactly correlates (corr.: 0.997; R^2: 0.993) with cumulative anthropogenic emissions from all sources including Land Use Change (LUC). The close correlation has continued in recent times, with a correlation of 0.9995 when compared to the Mauna Loa record (r^2: 0.999). So exact a correlation would be extraordinary if anthropogenic emissions were not the cause of the increase in CO2 concentration."


    Just out of curriousity, what is the short term correlation between CO2 concentration and temperature that you base your claims on?

  20. DSL @268, the change in CO2 forcing from year to year is very small.  Therefore the greenhouse effect does not explain the correlation between CO2 and temperature at subdecadal, or even decadal time scales*.  Rather, warm water absorbs less CO2 than does cold water.  Therefore in warm years, less CO2 is absorbed, while in cold years, more is absorbed - thus explaining much of the sub-decadal correlation.  (Biological activity also explains some of it.)  The key point, however, is that even in the warmest years, the increase in atmospheric CO2 is less than the amount of CO2 pumped into the atmosphere by anthropogenic emissions.  Ergo that increase is explained by the anthropogenic emissions, with only variations around the mean increase explained by changes in Sea Surface Temperature.  This is one of those areas of climate science supported by so much evidence that denial of it falls into the "flat earth society" level of intellectual analysis.

    * On time scales of thirty plus years, however, it explains nearly all of it, in the last and current century.

  21. There is also the yearly cycle of CO2 related to global vegetation, predominately the Northern Hemisphere which has more land (and hence vegetation) absorbing and releasing CO2 over the season. But that is a very small, short term, and essentially zero based variation, despite being a favorite graph of denialists.

    [ I think that particular correlation and corresponding misleading graph, with long term CO2 growth and temperature changes being removed as (ahem) inconvenient facts, shows up at WUWT about once a month... ]

  22. Rickeroo wrote: "Any cursory look at two readily available data sets, Mauna Loa CO2 and global temperature by year, clearly shows that temperature is a strong driver in how much CO2 ends up in the atmosphere on a yearly basis."

    The correlation between temperature and the annual change in atmospheric CO2 is well known and has been since at least the work of Bacastow in the mid 1970s, and is largely due to the effect of ENSO on precipitation in the Americas, which in turn affects the uptake and release of CO2 by land vegetation (as KR mentions).  This is explained in more detail in my article on Prof. Salby's misunderstanding of this correlation, where I show that a correlation with the annual increase has no mathematical relation to the cause of the long term rise (as the correlation is insensitive to the mean value of the annual increase, but it is the mean value that explains the long term rise.   In particular, see the section "What does Mainstream Science say about all this?".

    Some claim that this correlation is due to Henry's law, which suggests that the solubility of CO2 in the oceans depends on ocean temperature.  However this neglects an important fact, which is that Henry's law also tells us that the solubility is proportional to the difference between the partial pressure of CO2 in the atmosphere and the concentration in the surface waters.  Thus as atmospheric CO2 rises, its solubility in the oceans increases and the oceans take up CO2 in opposition to the rise in atmospheric CO2.  It is the constant of proportionality that is sensitive to temperature.  This is a good thing as it is a negative feedback that keeps the climate system more stable than it would otherwise be.  So which factor dominates?  The fact that atmospheric CO2 is rising more slowly than we are emitting CO2 into it shows that the natural environment as a whole is a net carbon sink, which tells us that the long term rise is being opposed by the natural environment, rather than being caused by it.

  23. I am not sure what favourite WUWT graph KR refers to, but I imagine it looks something like this:

    As you can see, there is a clear correlation between the CO2 records, and the temperature record.  Of course, these are not the simple records.  What I have done is to take each year from 1964-2009, and divided by the average of the eleven nearest years (inclusive).  The purpose of doing that is that it eliminates any long term trend while retaining the annual variation.  That is a good thing, because it allows me to take a regression of the two time series against each other, thereby determining the natural scale that maximizes similarity between the time series.  In this case, that natural scale is 8.7, as indicated in the title.  That is, for every 1 degree C increase in temperature, from this data we expect an 8.7 ppmv increase in CO2 concentration.

    Put another way, based on the actual temperature and CO2 data, we expect the 1 C increase in Global Mean Surface Temperature (GMST) from 1910 to 2010 to have resulted in an 8.7 ppmv increase in CO2 concentration.  As it happens, it has increased a little more than that.

    Just using the GISS LOTI and Mauna Loa data used in constructing the graph, we can determine the approximate increase in CO2 from 1964 to 2009 was 67.95 ppmv (difference of eleven year means), while the temperature increase was 0.61 C.  From that data, using the regression above, we can determine that just 5.29 ppmv of the increase was due to the increase in GMST, ie, just 7.8%.  

    However, there is still a strong correlation between temperature and CO2 over the period of Mauna Loa observations.  Indeed, the correlation is 0.935 (RSQ = 0.874).  That is not as good as the correlation between CO2 and cumulative emissions I mentioned @269 above.  But it is still impressive.  Very much better, for example than the 0.574 correlation (RSQ = 0.329) between the values once the trend is removed.  That stronger correlation between the trend than the annual values tells us that, most probably, one is significantly responsible for the other.  That is, either temperature is largely responsible for the CO2 trend; or CO2 is largely responsible for the temperature trend.  However, we have excluded the former already with our regression.  Ergo, the correlation between the annual data shows that the increase in CO2 is causing the increase in temperature (or at least, is largely responsible for it.)

    It is no wonder Rickeroo (@266) invites us to have a "cursory look" at the data.  If we only had a cursory look at the data, you might believe his interpretation of it.  Once you analyze, it, however, you can see it conclusively refutes all of his claims.  

  24. Co2 from Man made drinks. Is co2 from say beer. A natural co2 emission? or a human emision. Or does it change after it is consumed. Some co2 is absorbed and expelled by the lungs. The remainder is belched back out? 

  25. DangerousDan @274, CO2 in beer and some softdrinks (ie, brewed Ginger Beer) comes from fermentation, and as such was originally drawn from the atmosphere by photosynthesis.  Because they are originally drawn from the atmosphere, their return to the atmosphere merely completes the cycle.  It does not increase atmospheric concentrations.

    CO2 in carbonated drinks, however, may come from a variety of sources including fossil CO2, by cracking CO2 from the air by refrigeration, or from by products of other processes.  The Coca Cola company, in particular, have stated that most of their CO2 used in drinks comes from by products of other processes, and hence do not constitute additional emissions to those other processes.

    Finally, even if all the CO2 in soft drinks was additional emissions, it would constitute a tiny proportion of total emissions.  Roy Spencer estimates total emissions from soft drinks as 1.46 million tonnes of CO2 per year.  For comparison, the annual emission from fossil fuels 28.6 billion tonnes of CO2 per year.  That is, soft drinks would contribute 0.005% of the problem if (contrary to fact) they used no recycled CO2.

  26. In terms of identifying MM Co2 emissions, how should the CO2 exhaled by the planet's population be counted?  Should CO2 emissions resulting from farming, crop or livestock, be counted as MM or natural?  Same question for CO2 generated from natural decomposition on our world's landfills.  Human waste, treated in sewage plants and piped into rivers and oceans, generates CO2 - natural or anthropogenic? Should the definition of MM Co2 be limited to only that which exits a tail pipe or smoke stack?    Even if all CO2 emissions from burning fosil fules could be sharply curtaild or eliminated through sequestration,  each year there are more people on the planet, and with each year life expectancey is longer.  We all  need to eat and breath and as a consequence of life need excrete waste.   Surely all sources of MM Co2 should be considered and counted in an appropriate way.


    [TD] See "Does Breathing Contribute to CO2 Buildup in the Atmosphere?"  It has both Basic and Intermediate tabbed panes.

  27. toolate: As the mod's suggested link points out, respiration doesn't really have a net impact. The domesticated ruminant (eg cows, sheep, goats) population is another matter though - entric fermentation of plant matter in their stomachs generates methane, a potent GHG.

  28. The chart at the top tells me that vegetation and land, plus the oceans absorb 17 more gigatons than they emit. Assuming we can't do much about the oceans, all we need to do is increase veg&land absorption by 12 gigatons to balance human production of CO2!

  29. Well mushrumps, I have made a mess of this sort of calculation in past but lets see how I go.  The difference between emissions and absorption of land/vege is 11Gt. Land area of earth is 150,000,000 km2. 1/3 is desert, so non-desert is 100,000,000 or .1Gkm2. So land/vege currently is moping up 110 tonne/km2. To mop up an extra 17Gt at current rate, then need 17G/110 = 150,000,000km. That's current area of planet. Cant plant that much forest. Looks like a challenging problem to me.

  30. One other little gotcha is that turning desert/grassland to forest say reduces the albedo of the planet - it doesnt reflect as much radiation to space but I think that would be a minor concern.

  31. According to the IPCC report Table 1. published in 2001, 98.5% of all CO2 is absorbed, not 40%.  The charlatan IPCC since removed that table.

    CO2 is CO2 whether from man or nature; someone had to lay wake at night, probaly on drugs to say less CO2 from Man gets absorbed.

    Table 1. Global Sources and Absorption of CO2

    Carbon Dioxide:           Natural     Human Made   Total       Absorption

    Annual Million Tonnes 770,000      23,100         793,100     781,400

    % of Total                      97.1%          2.9%            100%           98.5%

    Source: Intergovernmental Panel on Climate Change, Climate Change 2001: The Scientific Basis  (Cambridge, UK Cambridge University Press, 2001), p. 188.)


    [JH] If you continue to lace your comments with snark and absurd accusations, they will be summarily deleted.

    Please note that posting comments here at SkS is a privilege, not a right.  This privilege can be rescinded if the posting individual treats adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Please take the time to review the policy and ensure future comments are in full compliance with it.  Thanks for your understanding and compliance in this matter.

  32. Bob Ashworth @281, what appears on page 188 of the IPCC TAR working group 1  is Fig 3.1:

    The units used are Petagrammes of Carbon (= Gigatonnes Carbon), and in none of the four parts of the figure are values matching those you show.  More imporantly, in Fig 3.1 B, the human perturbation is shown to clearly dominate the net natural fluxes, a fact that lead the IPCC to write:

    "Atmospheric CO2 is, however, increasing only at about half the rate of fossil fuel emissions; the rest of the CO2 emitted either dissolves in sea water and mixes into the deep ocean, or is taken up by terrestrial ecosystems. Uptake by terrestrial ecosystems is due to an excess of primary production (photosynthesis) over respiration and other oxidative processes (decomposition or combustion of organic material). Terrestrial systems are also an anthropogenic source of CO2 when land-use changes (particularly deforestation) lead to loss of carbon from plants and soils. Nonetheless, the global balance in terrestrial systems is currently a net uptake of CO2."

    (My emphasis)

    And as you add your own little conspiracy theory to your misrepresentation of the IPCC TAR, here is a direct copy of the original report as published, demonstrating that as published the IPCC TAR agreed with the view presented in the OP above.

    Finally, for good measure there is a table 3.1 in the IPCC report, appearing on page 190, which reads:

    "Table 3.1: Global CO2 budgets (in PgC/yr) based on intra-decadal trends in atmospheric CO2 and O2. Positive values are fluxes to the atmosphere; negative values represent uptake from the atmosphere. The fossil fuel emissions term for the 1980s (Marland et al., 2000) has been slightly revised downward since the SAR. Error bars denote uncertainty (± 1s), not interannual variability, which is substantially greater.


    Atmosphere increase
    3.3 ± 0.1
    3.2 ± 0.1
    Emissons (fossil fuel, cement)
    5.4 ± 0.3
    6.3 ± 0.4
    Ocean-atmosphere flux
    -1.9 ± 0.6
    -1.7 ± 0.5
    Land atmsphere fluux*

    *partitioned as follows

    Land use change
    1.7 (0.6 to 2.5)
    Residual terrestrial sink
    -1.9 (-3.8 to 0.3)

    * The land-atmosphere flux represents the balance of a positive term due to land-use change and a residual terrestrial sink. The two terms cannot be separated on the basis of current atmospheric measurements. Using independent analyses to estimate the land-use change component for the 1980s based on Houghton (1999), Houghton and Hackler (1999), Houghton et al. (2000), and the CCMLP (McGuire et al., 2001) the residual terrestrial sink can be inferred for the 1980s. Comparable global data on land-use changes through the 1990s are not yet available."

    (Sorry for loss of formatting.)

  33. Bob Ashworth:  I don't see that "Table 1" on page 188 of Chapter 3 ("The Carbon Cycle and Atmospheric Carbon Dioxide") of the IPCC's TAR WG1 "The Scientific Basis."  Nor are there any results from searching for the exact quoted phrase "Global Sources and Absorption of CO2."  Are you claiming that the IPCC does not have that table in its post-2001 reports, or are you claiming that the IPCC removed that table from its 2001 (TAR) report after final publication?  Perhaps instead that table was in only a preliminary draft of the report (which was not published because, um, it was preliminary.  Duh.).

    Where is there any statement by anybody, that less anthropogenic than natural CO2 gets absorbed?

  34. Bob, did you not read the article or were you not able to understand it?

    Yes, much more CO2 is released by natural sources than human industry. We all know that. The article says it.

    However, the 'conclusion' you draw from this is just nonsense. A>B, therefor A+B cannot be greater than C? Natural CO2 emissions (A) and absorption (C) are roughly in balance. Ergo, the addition of CO2 from human industry (B) tips total emissions over total absorption and causes atmospheric CO2 to increase. Put another way: If, as you proudly say, 98.5% of total emissions are being absorbed, then 1.5% aren't being absorbed. Clearly, without the extra 2.9% from human emissions there would not be 1.5% in excess of absorption and atmospheric levels would not be increasing. Ergo, human CO2 emissions are causing atmospheric CO2 levels to go up.

  35. Tom Curtis @ 273, in order to accurately determine whether the co2 leads or lags temperature, should you not be taking the fourier transform of each data set to accurately determine the phase relationship?  It just seems to me looking at your graph (casually eyeballing it), looks like there is a slight phase shift with co2 lagging temp.  


    [PS] Please do not let this discussion of CO2 lags/leads relationships wander off onto topics discussed in detail on "CO2 lags temperature" or "CO2 increase is natural, not human caused". It is very important to note that Tom has detrended the series because he is looking for change in CO2 in response to a temperature change. Ie Co2 is both a forcing and a feedback. As feedback it does of course lag temperature. Note also that the feedback CO2 is small (8ppm) cf forcing (~100ppm). Please take further discussion to a more appropriate place.

  36. this article is very informative showing how humans are contributing to carbon emissions in to our atmosphere. I would be interested in seeing a more complex version of this showing exactly where natural emissions and man made go.

  37. Can you be more specific about you want? The gory detail can be found in Chapter 6 of the IPCC AR5 WG1 report.

  38. According to some reports, we didn't emit more Carbon dioxide in 2015 than in 2014.  Perhaps our output has leveled off or may even decrease as more and more energy saving, renewable generation and a flat economy take hold.  I find this frightening.  If you look at the Mana Loa Carbon dioxide site for April, Carbon dioxide went up 4.16ppm despite this lack of increased carbon output.  All things being equal one would have expected, possibly, a 2.5ppm increase.  Apparently all things are not equal.  Is this some effect of the strong El Nino we experienced or have one or more carbon sinks started to shut down. If this continues to the end of 2016 and into 2017, we just may be in a spot of bother.  All things being equal, we would expect the line to revert to the long term increase and should see some quite small increases on into 2017. 

  39. william

    I would think its most likely an effect of El Nino. Even if carbon sinks start to shut down, they wont be that precipitous.

  40. William, 

     Most likely the soil causing it. That's good news and bad news. The good news is that it is reversable. The bad news is that we are fairly unlikely to do so. As although it really is easily reversable, there is a huge institutional resistance to even trying, and actually the trends are to accelorate it rather than mitigate it.

  41. Everyone on the world needs to glow at least 10 tree in his/her life. Assume only half of population can grow the trees for some reasons. The current population is 7.4 billions. Then we have 3.7 billions of people grow the trees, eventually, we have more 37 billions of tree. Each big trees can absorb 1 ton of carbon dioxide a year. Each year, 370 billions of carbon dioxide will be absorbed by trees. And we have schedule to control the tree, say to cut away the old trees, to collect the wood (solid carbon oxide) as recycle, reusable materials. The next thing we need to do is to get rid the dairy farm. As we know, the green effect of the methane is 12 times of CO2. A dairy cow can produce 110kg CH4 a year. Some researchs said that cow milk is not for human. Some countries not rely on the cow milk. I think these two method can improve the green house effect.

  42. mr_alanng - I think it would by a lot simpler to just get off using fossil fuels rather than trying to sequester CO2. Also, while methane is an issue, it is less than 30% of total forcing from CO2 because the emissions are far smaller.

    " Some researchs said that cow milk is not for human."

    I dont think any food is "for human" except breast milk but evolution has equipped us to use it. The gene for lactase persistance is highly selected for since the paleolithic particularly in european populations. Ie once you had settled agricultural, humans with lactase persistance survived and bred better than those without.

  43. Your citation to the IPCC AR4 Figure 7.3 seems to be incorrect. The figure shown is shown here:


    This figure states different numbers from yours. And I cannot find the 29 Gt/yr figure anywhere.


    Any further info or clarification is appreciated.

  44. dcordell @293, I think you will find that the figure above shows the fluxes in Gigatonnes of CO2, whereas the IPCC figure shows it in Gigatonnes of Carbon.  The fluxes from right to left in GtC are:

    7.9, 119.7, 122.7, 90.5 and 92.2

    According to the IPCC AR4 Fig 7.3 they are 8, 119.6, 122.6, 90.6 and 92.2, with the differences being down to rounding.

  45. Hi all. I've posted hardly at all on this site due to time constraints. However, I have read the first page and the last page very carefully.

    My predilection is that AGW is probably happening, but that mankind's affect [effect?] on the climate is not catastrophic.

    I would like to point out that there are, in my opinion, three sides to the AGW question as it pertains to CO2 emitted by humans. There are those who believe in the "consensus" that humans are forcing the climate. There are those who deny that the human influence on the climate is large enough to force it.

    There is a third group, those people who do not know which side of this matter is correct, and who are looking for truth.

    Anyhow... here's the background, followed by my question.

    I first started reading up on a related thread here on SkepSci...

    ...on Page 1 of that thread, back in 2007, is the argument that warming is likely to be causing CO2 release. This argument holds, as I understand it, that mankind, while emitting a lot of CO2, is not the major CO2 emitter on the planet, but that the current warming cycle is releasing more naturally sequestered carbon into the atmo than mankind is emitting.

    I understand the argument that it is thought that the minsiscule amount of CO2 that is emitted by mankind is forcing the warming, becasue of a logarithmic relationship, but the apparent leverage of that warming has not yet been proven. My understanding is that CO2 on forces the water vapor cycle in some fashion. Thus, less and less of a percentage of human emitted CO2 has a greater and greater effect on the climate.

    My question is this: Is this the proper page/thread to discuss the 'Warming is Releasing' argument?


    BTW, I did notice one comment on page one, even though the comments were made back in 2008.

    Mizimi #30: "It's a complex subject, [fraught] with difficulties - but ... deal with overpopoulation and the 'global warming problem' will fade away."


    [TD] I turned your link into a link; in future please do that yourself with the link tool when you write your comment.

  46. #291 mr_alanng

    "Each big tree can absorb 1 ton of carbon dioxide a year."

    Very few people would disagree that planting trees is a good idea to ameliorate the effects of burning fossil fuels. Here's a popular telling of the carbon sequestration available in a forest:

    "'An approximate value for a 50-year-old oak forest would be 30,000 pounds of carbon dioxide sequestered per acre,' said Timothy J. Fahey, professor of ecology in the department of natural resources at Cornell University. 'The forest would be emitting about 22,000 pounds of oxygen.'"

    30,000 pounds is 15 short tons. 15 short tons is 13.6 metric tonnes.

    Information on forest density is here:

    I'm afraid that your figure is way too high.

  47. JohnFornaro: Your understanding that "the current warming cycle is releasing more naturally sequestered carbon into the atmo than mankind is emitting" is incorrect. As is explained by the post we are commenting on right now, the naturally sequestered carbon (sequestered as "fossilized" substances that we use as fuels) is being released by humans burning those fossil fuels, thereby putting carbon dioxide and other greenhouse gasses into the atmosphere. 

    The amount we thereby release is not "miniscule" in the context that matters for warming. The amount we release is enough to outstrip the abilities of the natural sinks to absorb it. Consequently, humans are responsible for 100% of the increase in CO2 over at least the past 60 years, and nearly that percent since about 1850.

    Please read the Basic tabbed pane at the top of this page, then flip to the Intermediate tabbed pane and read that.

  48. JohnFornaro, for more details, please also read these posts:

  49. JohnFornaro, the claim you read that "the minsiscule amount of CO2 that is emitted by mankind is forcing the warming, becasue of a logarithmic relationship... Thus, less and less of a percentage of human emitted CO2 has a greater and greater effect on the climate" is incorrect.

    First: As I explained in my previous two replies to you, the CO2 emitted by mankind is not "miniscule," because what matters for warming is that humans are responsible for 100% of the rise in atmospheric total CO2, and the rise in that total has been more than 30% since 1850. CO2 emissions do correlate well with total atmospheric level, and the causal link is provided by the evidence described in the original post at the top of the page you are reading right now. (CO2 measurements are indeed reliable.) It is the increase in the amount of CO2 in the atmosphere that matters, not the  proportion of CO2 in the atmosphere relative to other gases.

    Second: The argument you cited has the logarithmic effect backward. An increase in the absolute amount (number of molecules) of CO2 in the atmosphere has less, not more, of an effect the more CO2 already is in the atmosphere. But scientists always take that into account, by referring to the (nearly) identical amount of warming from the absolute amount of CO2 doubling, regardless of whether the initial (pre-doubling) amount was large or small.

  50. JohnFornaro @, if you look at the increase of atmospheric CO2 concentration during past warming events and use those increases to predict the modern CO2 increase, the maximum increase expected for the current warming is about 10-20 ppmv.  This is most obvious in the change between glacial and interglacial shows a change in atmospheric CO2 of 15.8 +/- 0.6 ppmv/oC (Epica Dome C, 2 StDev confidence interval).  Given the current increase of about 1oC over the preindustrial average, that would lead to an expectation of a 16 ppmv increase in atmospheric CO2.

    That is likely an overestimate given that the long intervals involved allow time for slow processes (such as much of the tropical forest turning into open savannah and vice versa) to take place.  Comparison with the CO2 increase over the MWP which, globally, was nearly as hot as the 1990s, shows that short term processes such as would have had an influence on 20th century CO2 levels result in even smaller relative increases in CO2 concentration:

    That's not the only evidence against the idea that the modern CO2 increase is driven by the temperature increase, but it should be sufficient.

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