Later On

A blog written for those whose interests more or less match mine.

Honest graph of carbon dioxide levels

with 20 comments

This graph meets all criteria of honesty:

CO2-Emissions-vs-Levels

It’s from a good post by John Cook at Skeptical Science, who notes:

In an earlier post on the human contribution to CO2 levels, cbrock suggested integrating CO2 emissions to obtain the cumulative CO2 emissions. This would allow a direct comparison between the amount of CO2 in the atmosphere and the amount of CO2 we’ve emitted into the atmosphere. Now I never pass up the opportunity to plot new graphs and this was no exception. The only problem was the data available for CO2 emissions (gigatonnes carbon) used different units to the data for CO2 levels (parts per million by volume).

To compare the two time series, I decided to convert both sets of data to gigatonnes of CO2. The CO2 emissions data is expressed in gigatonnes carbon (GtC). This means they’ve only included the carbon element of the carbon dioxide molecule. The atomic mass of carbon is 14, while the atomic mass of CO2 is 44. Therefore, to convert from gigatonnes carbon to gigatonnes of carbon dioxide, you simply multiply 44 over 12. In other words, 1 gigatonne of carbon equals 3.67 gigatonnes of carbon dioxide.

Atmospheric CO2 levels are expressed in parts per million by volume (ppm). To convert from ppm to gigatonne of carbon, I consulted the conversion tables of the Carbon Dioxide Information Analysis Center. 1 part per million of atmospheric CO2 is equivalent to 2.13 Gigatonnes Carbon. Using our 44 over 12 rule, this means 1ppm = 7.81 Gigatonnes of Carbon Dioxide.

So putting it all together, Figure 1 is a plot of the total amount of CO2 in the atmosphere (top) versus the total amount of CO2 humans have emitted into the atmosphere (bottom). Several features jump out. Firstly, the similar shape of the curves (dare I say hockey-stick shaped). We have correlation but do we have causality? Could it all be just a coincidence? It isn’t too much of a stretch to imagine the amount of CO2 we put into the atmosphere might have a causality link with the amount of CO2 that remains in the atmosphere (but if you’re still not convinced, there’s always the isotope fingerprint for confirmation).

Lastly, it’s worth noting that the amount of CO2 emitted exceeds the amount that CO2 levels have risen. Not all the CO2 we emit remains in the atmosphere but some is taken up by carbon sinks such as the ocean. There’s nothing new in this – it was all well covered in the previous post on CO2 levels. This was just an opportunity to plot a new graph with lots of shiny colours.

For more info about downloading and converting CO2 data, I recommend you check out CO2: Emissions & Changes in Atmospheric Levels by Climate Charts & Graphs – a very useful resource if you’re interesting in climate data.

This post is dedicated to conservative09.

Written by LeisureGuy

13 October 2009 at 9:50 am

20 Responses

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  1. I know that since 1850, CO2 has gone up.

    Note that they do not use ppm…

    Conservative09

    13 October 2009 at 3:52 pm

  2. He’s certainly totally open about using gigatonnes, and even provides the necessary information if you want to convert the chart. I don’t quite understand the point you’re making.

    It’s not just that the CO2 level has increased, it’s that the increase is due to man’s activity, which (as he notes) is established by the isotope signatures.

    This pretty conclusively shows that global warming is from anthrogenic activity, given the fact that CO2 is a greenhouse gas—and I don’t think anyone’s denying that.

    LeisureGuy

    13 October 2009 at 6:58 pm

  3. I just realized why he used gigatonnes of carbon: to show humanity’s contribution—i.e., our carbon footprint—it makes sense to use the amount of carbon we generate, not ppm: we don’t really generate “ppm”. My car, for example, has a certain carbon footprint, and knowing its mileage and how many miles I drive each year, I can figure out how much carbon it throws into the atmosphere. But the car produces carbon, not “ppm”.

    So if our contribution is shown in gigatonnes of carbon, then the chart really should allow us to see also the total carbon content of the atmosphere in the same metric. Right? So the chart shows gigatonnes of carbon.

    LeisureGuy

    14 October 2009 at 7:41 am

  4. ppm is a unit used to measure the amount of CO2 in the atmosphere.

    Anthony

    14 October 2009 at 10:12 am

  5. Yes, that’s quite well known. And the reasons for the graph showing gigatonnes of carbon I just explained—or tried to. Apparently it wasn’t clear. The idea is to show in one graph both the cumulative CO2 footprint of mankind so that it can be compared to the total atmospheric CO2. For the comparison to be valid, the same units of measure must be used for each. With me so far?

    The idea is that our activities emit CO2, not “ppm”. So that drives the unit chosen toward gigatonnes of CO2. The author carefully explains how he was able to convert ppm of atmospheric CO2 to gigatonnes of CO2. Obviously, you can back-convert if you want, but the graph would be dishonest (something we all hate) if the two units were different.

    At any rate, the graph shows clearly how human activity has raised the CO2 in the atmosphere, and the isotope fingerprint shows clearly that this excess in historical times is due to man’s activity.

    I do not understand the point you’re trying to make. Can you explicate? I really did think you would be interested in an honest graph that shows the increase in CO2, a well-known greenhouse gas.

    LeisureGuy

    14 October 2009 at 10:22 am

  6. It is also well known what the anthropogenic CO2 amount in ppm is. So to use gigatonnes to determine the anthropogenic CO2 amount is pointless.

    …that is, unless you want a VERY sharp increase on a graph to drive forward a point.

    http://brneurosci.org/global-co2-levels.png

    CDIAC says: Atmospheric CO2 concentrations rose from 288 ppmv in 1850 to 369.5 ppmv in 2000, for an increase of 81.5 ppmv

    http://cdiac.ornl.gov/faq.html#Q7

    Not so sharp of an increase now, ya think?

    Anthony

    14 October 2009 at 2:11 pm

  7. I can’t believe that you still do not understand why the graph is stated in terms of gigatonnes of CO2 and not ppm. Since the conversion is linear, I believe that the graph would have the same shape. In any event, your second link states the content in both ppm and in mass. And in terms of ppm, the increase since 1850 of atmospheric CO2 is 81.5/288, or a 28% increase. that’s a lot, in case you don’t understand—especially since CO2 levels had been flat for the last 10,000 years or so, and had not reach the level of today for 15 million years.

    Whether you think the increase is sharp or not, it’s real and it’s due to humanity and it’s trapping global heat. And if you’re making the point that atmospheric CO2 hasn’t (so far) increased all that much (“just” 28%), I point you to this note on the effects of that increase.

    LeisureGuy

    14 October 2009 at 2:32 pm

  8. BTW, it was not “pointless”, it was to get the same metric. PPM doesn’t reallly apply to humanity’s carbon dioxide emissions, since some of those are absorbed and recycled (as the honest graph in the post makes clear, and as the comment states).

    I think you’re resisting beyond all reason.

    LeisureGuy

    14 October 2009 at 2:34 pm

  9. Read very carefully this from the author’s explanation:

    The only problem was the data available for CO2 emissions (gigatonnes carbon) used different units to the data for CO2 levels (parts per million by volume).

    To compare the two time series, I decided to convert both sets of data to gigatonnes of CO2. The CO2 emissions data is expressed in gigatonnes carbon (GtC). This means they’ve only included the carbon element of the carbon dioxide molecule. The atomic mass of carbon is 12, while the atomic mass of CO2 is 44. Therefore, to convert from gigatonnes carbon to gigatonnes of carbon dioxide, you simply multiply 44 over 12. In other words, 1 gigatonne of carbon equals 3.67 gigatonnes of carbon dioxide.

    Atmospheric CO2 levels are expressed in parts per million by volume (ppm). To convert from ppm to gigatonne of carbon, I consulted the conversion tables of the Carbon Dioxide Information Analysis Center. 1 part per million of atmospheric CO2 is equivalent to 2.13 Gigatonnes Carbon. Using our 44 over 12 rule, this means 1ppm = 7.81 Gigatonnes of Carbon Dioxide.

    LeisureGuy

    14 October 2009 at 2:36 pm

  10. The 81.5 ppm increase was not entirely anthropogenic.

    “The 369.5 ppmv of carbon in the atmosphere, in the form of CO2, translates into 787 PgC, of which 174 PgC has been added since 1850. From the second paragraph above, we see that 64% of that 174 PgC, or 111 PgC, can be attributed to fossil-fuel combustion. This represents about 14% (111/787) of the carbon in the atmosphere in the form of CO2.”

    So 14% of 0.0383% has caused global warming?

    Doesn’t that sound just a little far fetched?

    Conservative09

    14 October 2009 at 3:29 pm

  11. I suggest that you read carefully this post.

    BTW, back to the graph in the post: how would you have constructed a graph that would compare total atmospheric CO2 to the cumulative total CO2 created by humanity? If you use ppm for the first (as you seem to insist), then you’re comparing apples and oranges. The only way to do an honest comparison is by the graph shown. Do you agree? or not?

    LeisureGuy

    14 October 2009 at 4:10 pm

  12. A quick note from the author of that graph. The question of ppm vs gigatonnes of carbon is really a to-may-to/to-mah-to issue. It’s just different units to describe the same thing. The only reason I converted ppm to gigatonnes (of CO2, not carbon) was so I could plot both on the same graph. The point I wanted to emphasise was that we are actually emiting more CO2 into the air than is actually staying there. Eg – we’re emitting around 29 gigatonnes of CO2 per year while CO2 levels in the atmosphere are going up by around 15 gigatonnes of CO2. That should put into perspective the idea that humans are too insignificant to make a difference to the composition of the atmosphere. The graph was an attempt to show that visually.

    The other reason I made that graph was so to streamline this article with one rather than two graphs:
    http://www.skepticalscience.com/Empirical-evidence-that-humans-are-causing-global-warming.html

    John Cook

    15 October 2009 at 9:08 pm

  13. How did they get the value from 1850? Is it a guess, or did they find air from back then??? or in the ice or something?

    I need to know this for a class I’m taking.

    Thanks…

    Kevin

    17 November 2009 at 9:08 pm

  14. Atmospheric CO2 levels in 1850 were determined from Antarctic ice cores.

    Human CO2 emissions were calculated from energy statistics which date back to 1750.

    More info as well as links to sources can be found at:
    http://www.skepticalscience.com/Are-humans-too-insignificant-to-affect-global-climate.htm

    John Cook

    17 November 2009 at 9:23 pm

  15. So, I am trying to identify the PPM of CO2 created in internal combustion engines in cars. I can find information on the amount of CO2 created per gallon of fuel used. But what I am really interested in is what comes out the tail pipe. I suspect is has to do with air fuel ratio, which I haven’t looked up. The ultimate question for me is how much does the proportion of CO2 coming out the tail pipe differ from from ambient CO2, which I read is 380 ish PPM.
    Can you email me your thoughts?
    Mark

    Mark Winn

    30 January 2010 at 9:35 pm

  16. All this CO2 stuff is interesting but it needs to be kept
    in prospective. If you put a million white marbles into
    a swimming pool and then mixed in 380 black marbles,
    you would have a good visual as to how small of an amount
    of carbon dioxide is in our atmosphere.
    Unless there is some sort of magic associated with this gas
    I find it a wee bit difficult to comprehend that it could have
    such a marked affect on global climate as is claimed, as in
    the supposed “greenhouse” affect of which I also find
    dubious at best.
    Overall, it’s remarkable, percentage-wise, just how stable
    the earth’s climate is.
    Grant money has polluted “science” to the degree that it
    can’t be trusted anymore. It has become an agenda driven
    power grab of which trillions of dollars/pounds are at stake
    and the re-distribution of that power and money.
    Meanwhile, that old star that heats our planet is ignored
    because there’s not a damned thing we can do about it.
    Hence, no possibility of a power grab there.
    It’s been joked about that politicians would tax the air that
    you breathe if they could find a way. CO2 has become
    the way……..

    Johnny56

    14 February 2010 at 6:35 am

  17. Good point: the amount of CO2 added by human activity, though it’s increased remarkably in the course of the 20th century, is still relatively small compared to natural sources. Indeed, that very point is the subject of this post: Are humans too insignificant to affect global climate?. And yet it has been determined (conclusively) that the additional contribution from human activity is enough to increase CO2 emissions beyond the capacity of natural systems to absorb the CO2, so now instead of being stable, the amount of CO2 in the atmosphere is increasing steadily and rapidly. See this post for a succinct and cogent summary: Empirical evidence that humans are causing global warming. If you look at the actual evidence (instead of considering the matter abstractly), the conclusion is clear and inescapable.

    The “magic” associated with CO2 (and some other gases) is the greenhouse effect, which is not dubious in the least and has been solid knowledge for over a century. That fact is absolutely clear and proved.

    The science is not polluted, although the claims that climate change is not happening (laughable now, with so much evidence of warming) or is not being caused by human activity is quite clearly (and visibly) driven by the trillions of pounds/dollars still to be made in burning coal and oil, driving CO2 levels higher. The major oil and coal companies have pour hundreds of millions of dollars in copying the tobacco industry’s tactics to create doubt and uncertainty and stall for as long as they can any action against their business. That conflict of interest is obvious and has been documented, though somehow deniers are able to ignore it.

    LeisureGuy

    14 February 2010 at 8:37 am

  18. Put the fools in a barrel and send them off a waterfall

    Marcel Halewijn

    15 February 2010 at 6:45 pm

  19. Hello, thanks for an informative page.

    It seems very strange to me that so many climate deniers/sceptics/contrarians can’t seem to understand something so basic as the continued effect of the disturbance of balance on dynamic systems – that the absolute quantities involved are NOT the issue.

    To argue by what I consider a very reasonable analogy, I have a patient, his nickname is Tubby. and yes, he’s obese. He weighs 115 kg, he’s sixty, and every GP has a number of patients like this, he doesn’t look after himself, he has diabetes, hypertnsion, angina, his knees and hips are just about worn out and he hasn’t been able to find gainful employment for some years. Yet when he was twenty, he weighed only 75 kg. He’s slowly, but continuously increased his weight by 40kg over 40 years, 1 kg per year.

    This is because he eats ‘”too much”. But how much? Well, if we divided his yearly weight gain by 365 we find this is equivalent to just 3 g fat/day, less than one teaspoonful. We could also work it out using calories. The average mildly active male might expend 2000 calories per day. As long as his average food intake matches this, he will neither gain or loose weight. This arises from the principle of conservation of energy, or the laws of themodynamics.

    3g fat is approximately equal to 25 cals. ie, to gain 40kg over 40 years required an excess of just 25 cals per day, or 2000/25×100 = 1.25% . This is the equivalent of half a boiled potato, or as already mentioned, a teaspoonful of butter on his toast. The is almost certianly completely imperceptable in the vastly greater amount of food consumed through the day, yet the result of this imbalance is a severly impaired functioning of the organism. with significant disease and disability.

    In dynamic systems, such as the human metabolism, or in the vastly larger sphere of the planet’s climate, if the balance is disturbed continuously and for a sufficiently long period of time, the effects can be profound. The absolute quantities involved are irrelevant.

    Why do so many people have such difficulty understanding such a simple concept?

    John Monro (Dr)

    3 March 2010 at 4:35 pm

  20. I think for a few, it’s because they are paid NOT to understand—e.g., lobbyists, employees of oil and coal companies, and the like. And then there’s a large group that don’t WANT to understand because of irrational reasons (e.g., they don’t like Al Gore, or they hate science as being anti-religious). But it is frustrating.

    LeisureGuy

    3 March 2010 at 4:59 pm


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