Response to John Quiggin re: longevity of “man-made” CO2 in the atmosphere

Dear John

Here's my response to the first part of the two issues on which I've agreed to provide you with more information (being the question of how long CO2 remains in the atmosphere). I'll talk about the peer review issue separately.

Let me note at the outset that I fully understand how you feel about IPCC's work. Not long ago, when I didn't have time to investigate the issues in detail (I have even now barely scratched the surface, but I believe I've gained enough knowledge to become somewhat intelligently engaged in the debates), I too "believed" that IPCC findings should be taken seriously.

After devoting much time to understanding the science, however, I've been left with more questions than answers, and a poor impression of IPCC's analytical skills. First, it is evident to me that climate science is not settled, with gaping holes in our knowledge. The day all my questions are adequately addressed by IPCC, I'll promote IPCC's findings just like you do. Second, while we should act to prevent catastrophe if there is any reasonable chance of runaway global warming, there is not the slightest shred of evidence that such a risk exists.

On a subject as important as this, on which the fate of the planet itself presumably depends, let me suggest that we can't afford to take anyone's word as sacrosant. We must open our eyes and find out the truth ourselves. We must raise questions and we must be given the satisfactorily answers.

1: We don't know the precise level of CO2 in the atmosphere

Let me begin with the most fundamental and basic area of uncertainty. Before we can say with some confidence that CO2 emissions will last for centuries in the atmosphere, we need to be sure that our instruments are accurately measuring CO2. Unfortunately, CO2 measurement problems appear to be too many to mention. The measured level of CO2 in the atmosphere seems to vary with (a) the method used, (b) the height of the measuring instrument above sea level [CO2 dramatically varies across different heights], (c) time of day, (d) time of year, and (e) the nature of nearby activity.

In particular, CO2 level data prior to 1959 are problematic, being based on different methodologies to those used today. Even today's methodologies are being refined as the complexity of measurement is better understood. Nevertheless, post-1959 data are robust enough, and so I will ASSUME IPCC's reported data regarding CO2 levels since 1959 are valid (given we don't have anything better). But we must be prepared to interrogate even this basic data over the coming years.

2: Scientific debate about carbon cycle and how long CO2 stays in the atmosphere

The carbon cycle is very poorly understood. There are debates not just about "missing sinks" but about the very sources of carbon in the air (given that an overwhelming proportion of carbon is not found in the atmosphere but in the oceans). A plausible theory even suggests that since global warming commenced before 1860 (due to natural causes), it is that warming which is driving the release (degassing) of CO2 from the oceans. This implies that observed increases in CO2 could be due to warming, not warming due to CO2. The matter is stupendously complex.

Even The Guardian's FAQ on climate change notes that: "The lifetime in the air of CO2, the most significant man-made greenhouse gas, is probably the most difficult to determine. Between 65% and 80% of CO2 released into the air dissolves into the ocean over a period of 20–200 years." [Source]

I want to repeat this for effect, that longevity estimates are between 20 and 200 years (a 10 times difference!). Imagine what you would say of a demographer reported that an average Australian lived between 20 and 200 years. In fact the range of estimates in the case of CO2 is probably even wider than this.

Note a key point, that should the smaller figure be valid, most manmade CO2 would be absorbed rapidly – and will not accumulate.

The IPCC itself is constantly changing its mind on this issue. The first assessment report defined the lifetime of CO2 as 50-200 years while the second and third assessment reports lowered the lower limit to 5 years. The most fourth and most recent assessment report changed the language entirely to say (quoted from the paper): "Carbon dioxide cycles between atmosphere, oceans, and land biosphere. Its removal from the atmosphere involves a range of processes with different time scales. … The remaining 20% may stay in the atmosphere for many thousands of years."" This kind of vagueness is amazing for something known as "science"!

A massive chunk of CO2 emitted in the last two centuries (mostly in the last fifty years) has DISAPPEARED from the atmosphere.

Where did it go? That's been a source of great mystery.

"Today's current level of atmospheric carbon dioxide is only around half of what scientists have predicted atmospheric levels should be, based on estimates that humans have contributed 244 billion metric tons of carbon dioxide to Earth's atmosphere. Oceans have taken up 48 percent of all carbon dioxide emitted from fossil fuel burning and cement manufacture (a major source of the gas) between 1800 and 1994." [National Geographic, reporting a peer reviewed study: Source]

But if the view that CO2 is emitted from oceans upon warming is confirmed (a view that sounds plausible to me), then we can expect new estimates which may indicate MUCH greater absorption of man-made emissions, being the only way to account for the modestly increasing total atmospheric CO2.

One-celled plants are like bacteria. Give them food and they multiply. There are almost no limits to their growth. These natural sinks are barely beginning to be understood. Expect the science to change DRAMATICALLY in the coming decades as we start understanding the 100s of factors that operate on the climate, a little bit better.

In any event, your assumption that CO2 remains unchanged for a hundred years is very likely to be incorrect. You can't multiply annual temperature estimates by 100. You must factor in the dissipation of the carbon which would have naturally occurred.

Climate science has almost no linearities, only complex physical non-linearities and organic feedback loops. Simplistic kindergarten arithmetic doesn't work.

Once again, my purpose of writing this is NOT to provide you with a definitive answer on what is correct (I have no time to find that out – even assuming the correct answer exists), but to point out that there is a DEBATE on this issue. You should not take IPCC as bible, for even IPCC (rightly) keeps changing its mind.

Finally, you asked for peer reviewed papers, so here are a couple:

Essenhigh, R.E. 2009: Potential dependence of global warming on the residence time (RT) in the atmosphere of anthropogenically sourced carbon dioxide. Energy & Fuels 23: 2773-2784.

  • He finds that the RT for bulk atmospheric CO2, the molecule 12CO2, is ~5 years, in good agreement with other cited sources (Segalstad, 1998), while the RT for the trace molecule 14CO2 is ~16 years. Both of these residence times are much shorter than what is claimed by the IPCC.
  • He points out that the annual oscillations in the measured atmospheric CO2 levels not be possible without a short atmospheric residence time for CO2 molecules [This is because you can't expect CO2 to start fading out in a few months, unless it was being rapidly re-absorbed by Earth.]

Moore, B., III, and B. H. Braswell (1994), The lifetime of excess atmospheric carbon dioxide, Global Biogeochem. Cycles, 8(1), 23–38, doi:10.1029/93GB03392.

  • This papers notes that "Our best estimate is that the single half-life for excess CO2 lies within the range of 19 to 49 years, with a reasonable average being 31 years".

3. The mere existence of greater CO2 levels doesn't imply runaway global warming

I don't want to extend this discussion, but there is a fundamental problem with this fuss about CO2: Even assuming CO2 remains in the atmosphere for hundreds of years, its [proven, warming] effect on global temperature is dissipated by many self-correcting effects.

The proof is in the pudding. Global temperatures have not risen anywhere close to IPCCs model predictions. There are therefore many dampening effects at work, mostly unknown to science. The challenge for scientists today is to find out more about what might be happening.

They need to understand (a) how to measure CO2 (and temperature) properly, (b) what the sources and sinks of CO2 are,  (c) the longevity of man-made CO2 and (d) what's preventing the Earth from over-heating with existing CO2, given its greatest proportion of warming effects are at the lower, not higher densities.

IPCC, in trying to get politicians involved, has significantly reduced its value as a scientific body.


Essenhigh's study has been later refuted. See John Quggin's comment below.


The complete discussion

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  1. Thanks for this. I note that Essenhigh is a mechanical engineer whose work focuses mainly on coal, and not a climate scientist. As I quickly found out the journal published a subsequent piece pointing out the error in his work
    Did you not see this?

    The bigger point, though, is why you are doing this. Your website shows you to have strong political views, views that are, in my experience, highly correlated with opposition to mainstream science on this topic. That’s why I asked for a demonstration of good faith on your part by citing one of the many demolitions of the absurd errrors of Plimer and Monckton.

    I’ll make the general observation that the wishful thinking implied in denying mainsream science because it leads to political implications you don’t like is a reliable, and well trodden path to intellectual collapse.

  2. John

    Thanks for pointing this new article out. No, I did not see it, and I welcome your input.

    Do note, though, that if this is true, it further proves the point I will separately make: that peer review is not the same as being the truth.

    But this article still doesn’t, in my mind, address the issue, namely, that you can’t multiply an annual reduction by 100. That is still incorrect, for at least half is absorbed into the air at least over a century, which means the factor is <100. What it is, I don’t know. It is for you to prove to that 100 is the correct factor. That’s why I asked for your assumptions on your blog.

    Let’s note that it is in the nature of science to make mistakes, repeated mistakes. And the truth on complex matters (like the climate/ human body) takes many decades of repeated false starts, to emerge. It is that sense (a willingless to admit to mistakes) I don’t get from IPCC’s work, which is why I no longer rely only on IPCC reports.

    While I’m a PURE scientist and my interest in almost everything is purely related to the truth (to the extent I can spend time on exploring the issues), IPCC seems to me to be driven by a political agenda. I am definitely a strong votary of freedom, but you’ll notice that in my book, Breaking Free of Nehru (2008), available at, I argue for a carbon tax.

    Pigovian taxes are valid to the extent (a) there is a genuine externality, and (b) there is no way the market will work out a solution by itself (cf.Coase). While (b) is true in this case (with caveats, since not just markets, but even governments can’t work out a solution themselves), (a) is no longer an evidence based claim.

    In other words, I have a political agenda for INDIA, an agenda of freedom, but that doesn’t preclude carbon taxes. Freedom is not license to harm others! And why would I not care if CO2 was a genuine externality worth bothering about? Do I not have children? Do I not want to see them – and their children (when they have any) prosper well into the distant future?

    Note, though, that for (a) to be valid, I need SCIENTIFIC proof of every step of the theory and empirical data. The first of these proofs is that IPCC models MUST track real observations. They have so far singularly OVER-ESTIMATED real temperature (even given the very likely deliberate inflation of temperatures by many “scientists”).

    But that’s a different discussion. I’m focused here PURELY on your simplistic multiplication. I suggest that is not defensible, since CO2 doesn’t “live” unchanged for 100 years.


  3. To be clear, the IPCC doesn’t have models. It summarizes and reports the work of thousands of scientists in the field. I’ve spoken to lots of these scientists, and they all think the IPCC is doing a pretty good job. By contrast, looking at “sceptical” sites I see both rampant political agendas and routine incompetence.

    So, might I ask, how did you come across Essenhigh’s work? Do you read Energy and Fuels regularly, or did you follow a link from another site. If it was on a “sceptical” site, aren’t you troubled by the failure to report the refutation I found simply by going to the journal website and looking at the citing articles? Doesn’t this suggest, at best, a lack of elementary research skills on the part of those who run these sites?

  4. Thanks, John. I’m aware of IPCC’s role, but also know that there are models it uses. It is these models that have singularly failed to predict accurately.

    While I read fairly widely, my interests are wide-ranging and I don’t have the capacity to research all climate-related information. However, this much is clear – that unlike in economics where an overall trend is usually sufficient to prove a particular case, in the case of real science, a theory’s prediction needs to be PRECISE – up to the 10th decimal (figuratively speaking), if possible.

    What set me off into asking a lot of questions to which I haven’t yet found the answers, was the arrogant tone of some “climate scientists” who seem to have made quite precise predictions in the 1990s, for the 2000s, predictions which were repeatedly falsified. In addition, IPCC has revised its conclusions repeatedly over the past twenty years. The underlying data it has used has also changed continuously, and things like medieval/Roman warming which were acknowledged by IPCC earlier (and now re-proven through a recent peer reviewed paper), rapidly switched.

    There was evidence in the nature of tens of peer-reviewed papers re: medieval/Roman warming, but IPCC took merely ONE paper to switch its story. That warming has been re-confirmed again. Empirical science is not readily proven/disproven by merely one paper. IPCC takes those papers that are alarmist, but ignores others. At least that’s the impression I’ve formed.

    Why, for instance, after the recent re-confirmation of the medieval/Roman warming ( do I not hear the IPCC leaders coming forward to suggest that they will now reconsider their recent report? Why the silence?

    At the same time, these people are at the forefront in promoting panic re: rapidly melting glaciers in the Himalayas, which turned out to be false.

    The main issue is that the increase in global temperatures has CLEARLY plateaued out for more than a decade. There is NO significant increase in warming: temperatures seem to be where they were in the late 1990s.

    That, to me, is a give away that the entire work of IPCC needs complete review.

    I don’t deny that the scientists are doing a fine job. I support their work – all the way, 100 per cent. The problem is those who then take this information and “massage” it to create panic.

    Any good scientist will admit that mankind is still learning about the climate, and there is no firm scientific conclusion (which must ALWAYS be very precise and ALWAYS come true, unlike in economics) that can be drawn from the studies of climate scientists to date.

    The day climate science can predict the average temperature of a given year up to the third decimal place, I’ll know that I can rely upon their models. Till then, as they say, “caveat emptor”: keep your wits about. Don’t trust anyone, not even peer-reviewed publications.


  5. John, if you are reading my comments by email, pl. switch to the blog, since I’ve fixed a couple of typos in the previous comment.

  6. Sure. I googled the question “lifetime of CO2” or some such thing and found a few links that I then explored quickly, to then turn up a few alternative worldviews. If I had more time I’d definitely spend more time on this issue.

    It seems to be well accepted, though, that only about half of man-made CO2 survives (since 1850s) today in the atmosphere. That has implications for your multiplication by 100. What’s the correct figure, I don’t know, but I know it is less (possibly far less) than 100. Time will tell.

    The mere fact of CO2’s survival in the atmosphere, however, doesn’t mean a thing if its temperature impacts are minor. That’s a separate analysis, though.

  7. My point is, since the sources you found were misleading, in that they cited Essenhigh’s erroneous paper, why don’t you go back and point this out. You’ve been happy to spend a lot of time debating me, after all.

    So, here’s my offer. If you return to the sites you Googled, and can get at least one of them to link to the Essenhigh refutation, I’ll continue the debate on this point. Otherwise, I’ll stick with the conclusion that you were and are misled by wishful thinking.

  8. John, over time, google searches will automatically lead to the refutation of Essengigh’s peer-reviewed study. The fastest way to do that, if you so wish, is to publish it as the headline on your blog. Google will pick it up. I did put up the correction immediately after you informed me.

    I’m happy to go back (now) and make it bolder (h2 tag), making it more searchable by google.