Does CO2 really drive global warming?

May 2001 Chemical Innovation, May 2001, Vol. 31, No. 5, pp 44—46 ^ | May 2001 | Robert H. Essenhigh, E. G. Bailey Professor of Energy Conversion, Ohio State University

[E. Pluribus Unum]

Does CO₂ really drive global warming?

I don’t believe that it does.

To the contrary, if you apply the IFF test—if-and-only-if or necessary-and-sufficient—the outcome would appear to be exactly the reverse. Rather than the rising levels of carbon dioxide driving up the temperature, the logical conclusion is that it is the rising temperature that is driving up the CO₂ level. Of course, this raises a raft of questions, but they are all answerable. What is particularly critical is distinguishing between the observed phenomenon, or the “what”, from the governing mechanism, or the “why”. Confusion between these two would appear to be the source of much of the noise in the global warming debate.

In applying the IFF test, we can start with the clear correlation between the global CO₂ profile and the corresponding temperature signature. There is now in the literature the report of a 400,000-year sequence clearly showing, as a phenomenon, that they go up—and down—together (1). The correlation is clear and accepted. But the causation, the mechanism, is something else: Which is driving which?

Logically, there are four possible explanations, but only two need serious consideration, unless they both fail.

• Case 1: CO₂ drives the temperature, as is currently most frequently asserted; and

• Case 2: Temperature drives the level of CO₂.

Both appear at first to be possible, but both then generate crucial origin and supplementary questions. For Case 1, the origin question is: What is the independent source of CO₂ that drives the CO₂ level both up and down, and which in turn, somehow, is presumed to drive the temperature up and down? For Case 2, it is: What drives the temperature, and if this then drives the CO₂, where does the CO₂ come from? For Case 2, the questions are answerable; but for Case 1, they are not.

Consider Case 2. This directly introduces global warming behavior. Is global warming, as a separate and independent phenomenon, in progress? The answer, as I heard it in geology class 50 years ago, was “yes”, and I have seen nothing since then to contradict that position. To the contrary, as further support, there is now documentation (that was only fragmentary 50 years ago) of an 850,000-year global-temperature sequence, showing that the temperature is oscillating with a period of 100,000 years, and with an amplitude that has risen, in that time, from about 5 °F at the start to about 10 °F “today” (meaning the latest 100,000-year period) (2). We are currently in a rise that started 25,000 years ago and, reasonably, can be expected to peak “very shortly”.

On the shorter timescales of 1000 years and 100 years, further temperature oscillations can be seen, but of much smaller amplitude, down to 1 and 0.5 °F in those two cases. Nevertheless, the overall trend is clearly up, even through the Little Ice Age (~1350–1900) following the Medieval Warm Period. So the global warming phenomenon is here, with a very long history, and we are in it. But what is the driver?

Arctic Ocean model
The postulated driver, or mechanism, developed some 30 years ago to account for the “million-year” temperature oscillations, is best known as the “Arctic Ocean” model (2). According to this model, the temperature variations are driven by an oscillating ice cap in the northern polar regions. The crucial element in the conceptual formulation of this mechanism was the realization that such a massive ice cap could not have developed, and then continued to expand through that development, unless there was a major source of moisture close by to supply, maintain, and extend the cap. The only possible moisture source was then identified as the Arctic Ocean, which, therefore, had to be open—not frozen over—during the development of the ice ages. It then closed again, interrupting the moisture supply by freezing over.

So the model we now have is that if the Arctic Ocean is frozen over, as is the case today, the existing ice cap is not being replenished and must shrink, as it is doing today. As it does so, the Earth can absorb more of the Sun’s radiation and therefore will heat up—global warming—as it is doing today, so long as the Arctic Ocean is closed. When it is warm enough for the ocean to open, which oceanographic (and media) reports say is evidently happening right now, then the ice cap can begin to re-form.

As it expands, the ice increasingly reflects the incoming (shorter-wave) radiation from the sun, so that the atmosphere cools at first. But then, the expanding ice cap reduces the radiative (longer-wave) loss from the Earth, acting as an insulator, so that the Earth below cools more slowly and can keep the ocean open as the ice cap expands. This generates “out-of-sync” oscillations between atmosphere and Earth. The Arctic Ocean “trip” behavior at the temperature extremes, allowing essentially discontinuous change in direction of the temperature, is identified as a bifurcation system with potential for analysis as such. The suggested trip times for the change are interesting: They were originally estimated at about 500 years, then reduced to 50 years and, most recently, down to 5 years (2). So, if the ocean is opening right now, we could possibly start to see the temperature reversal under way in about 10 years.

What we have here is a sufficient mechanistic explanation for the dominant temperature fluctuations and, particularly, for the current global warming rise—without the need for CO₂ as a driver. Given that pattern, the observed CO₂ variations then follow, as a driven outcome, mainly as the result of change in the dynamic equilibrium between the CO₂ concentration in the atmosphere and its solution in the sea. The numbers are instructive. In 1995, the Intergovernmental Panel on Climate Change (IPCC) data on the carbon balance showed ~90 gigatons (Gt) of carbon in annual quasi-equilibrium exchange between sea and atmosphere, and an additional 60-Gt exchange between vegetation and atmosphere, giving a total of ~150 Gt (3). This interpretation of the sea as the major source is also in line with the famous Mauna Loa CO₂ profile for the past 40 years, which shows the consistent season-dependent variation of 5–6 ppm, up and down, throughout the year—when the average global rise is only 1 ppm/year.

In the literature, this oscillation is attributed to seasonal growing behavior on the “mainland” (4), which is mostly China, >2000 mi away, but no such profile with that amplitude is known to have been reported at any mainland location. Also, the amplitude would have to fall because of turbulent diffusive exchange during transport over the 2000 mi from the mainland to Hawaii, but again there is lack of evidence for such behavior. The fluctuation can, however, be explained simply from study of solution equilibria of CO₂ in water as due to emission of CO₂ from and return to the sea around Hawaii governed by a ±10 °F seasonal variation in the sea temperature.

Impact of industrialization
The next matter is the impact of fossil fuel combustion. Returning to the IPCC data and putting a rational variation as noise of ~5 Gt on those numbers, this float is on the order of the additional—almost trivial (<5%)—annual contribution of 5–6 Gt from combustion of fossil fuels. This means that fossil fuel combustion cannot be expected to have any significant influence on the system unless, to introduce the next point of focus, the radiative balance is at some extreme or bifurcation point that can be tripped by “small” concentration changes in the radiation-absorbing–emitting gases in the atmosphere. Can that include CO₂?

This now starts to address the necessity or “only-if” elements of the problem. The question focuses on whether CO₂ in the atmosphere can be a dominant, or “only-if” radiative-balance gas, and the answer to that is rather clearly “no”. The detailed support for that statement takes the argument into some largely esoteric areas of radiative behavior, including the analytical solution of the Schuster–Schwarzschild Integral Equation of Transfer that governs radiative exchange (5–7), but the outcome is clear.

The central point is that the major absorbing gas in the atmosphere is water, not CO₂, and although CO₂ is the only other significant atmospheric absorbing gas, it is still only a minor contributor because of its relatively low concentration. The radiative absorption “cross sections” for water and CO₂ are so similar that their relative influence depends primarily on their relative concentrations. Indeed, although water actually absorbs more strongly, for many engineering calculations the concentrations of the two gases are added, and the mixture is treated as a single gas.

In the atmosphere, the molar concentration of CO₂ is in the range of 350–400 ppm. Water, on the other hand, has a very large variation but, using the “60/60” (60% relative humidity [RH] at 60 °F) value as an average, then from the American Society of Heating, Refrigerating and Air-Conditioning Engineers standard psychrometric chart, the weight ratio of water to (dry) air is ~0.0065, or roughly 10,500 ppm. Compared with CO₂, this puts water, on average, at 25–30 times the (molar) concentration of the CO_2, but it can range from a 1:1 ratio to >100:1.

Even closer focus on water is given by solution of the Schuster–Schwarzschild equation applied to the U.S. Standard Atmosphere profiles for the variation of temperature, pressure, and air density with elevation (8). The results show that the average absorption coefficient obtained for the atmosphere closely corresponds to that for the 5.6–7.6-µm water radiation band, when water is in the concentration range 60–80% RH—on target for atmospheric conditions. The absorption coefficient is 1–2 orders of magnitude higher than the coefficient values for the CO₂ bands at a concentration of 400 ppm. This would seem to eliminate CO₂ and thus provide closure to that argument.

This overall position can be summarized by saying that water accounts, on average, for >95% of the radiative absorption. And, because of the variation in the absorption due to water variation, anything future increases in CO₂ might do, water will already have done. The common objection to this argument is that the wide fluctuations in water concentration make an averaging (for some reason) impermissible. Yet such averaging is applied without objection to global temperatures, when the actual temperature variation across the Earth from poles to equator is roughly –100 to +100 °F, and a change on the average of ±1 °F is considered major and significant. If this averaging procedure can be applied to the atmospheric temperature, it can be applied to the atmospheric water content; and if it is denied for water, it must, likewise, be denied for temperature—in that case we don’t have an identified problem!

What the evidence shows
So what we have on the best current evidence is that

• global temperatures are currently rising;

• the rise is part of a nearly million-year oscillation with the current rise beginning some 25,000 years ago;
• the “trip” or bifurcation behavior at the temperature extremes is attributable to the “opening” and “closing” of the Arctic Ocean;
• there is no need to invoke CO₂ as the source of the current temperature rise;
• the dominant source and sink for CO₂ are the oceans, accounting for about two-thirds of the exchange, with vegetation as the major secondary source and sink;

• if CO₂ were the temperature–oscillation source, no mechanism—other than the separately driven temperature (which would then be a circular argument)—has been proposed to account independently for the CO₂ rise and fall over a 400,000-year period;
• the CO₂ contribution to the atmosphere from combustion is within the statistical noise of the major sea and vegetation exchanges, so a priori, it cannot be expected to be statistically significant;
• water—as a gas, not a condensate or cloud—is the major radiative absorbing–emitting gas (averaging 95%) in the atmosphere, and not CO₂;

• determination of the radiation absorption coefficients identifies water as the primary absorber in the 5.6–7.6-µm water band in the 60–80% RH range; and
• the absorption coefficients for the CO₂ bands at a concentration of 400 ppm are 1 to 2 orders of magnitude too small to be significant even if the CO₂ concentrations were doubled.

The outcome is that the conclusions of advocates of the CO₂-driver theory are evidently back to front: It’s the temperature that is driving the CO₂. If there are flaws in these propositions, I’m listening; but if there are objections, let’s have them with the numbers.

References

1. Sigman, M.; Boyle, E. A. Nature 2000, 407, 859–869.
2. Calder, N. The Weather Machine; Viking Press: New York, 1974.

3. Intergovernmental Panel on Climate Change. Climate Change 1995: The Science of Climate Change; Houghton, J. T., Meira Filho, L. G., Callender, B. A., Harris, N., Kattenberg, A., Maskell, K., Eds.; Cam bridge University Press: Cambridge, U.K., 1996.
4. Hileman, B. Chem. Eng. News 1992, 70 (17), 7–19.
5. Schuster, A. Astrophysics J. 1905, 21, 1–22.

6. Schwarzschild, K. Gesell. Wiss. Gottingen; Nachr. Math.–Phys. Klasse 1906, 41.
7. Schwarzschild, K. Berliner Ber. Math. Phys. Klasse 1914, 1183.
8. Essenhigh, R. H. On Radiative Transfer in Solids. American Institute of Aeronautics and Astronautics Thermophysics Specialist Conference, New Orleans, April 17–20, 1967; Paper 67-287; American Institute of Aeronautics and Astronautics: Reston, VA, 1967.

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Robert H. Essenhigh is the E. G. Bailey Professor of Energy Conversion in the Department of Mechanical Engineering, Ohio State University, 206 W. 18th Ave., Columbus, OH 43210; 614-292-0403; essenhigh.1@osu.edu.

[Excellence]

This looks very promising. Thank you. That website is a great resource, too. Thanks again!

[Excellence]

Thanks for your help. If I can figure out how to do that, I will.

[redangus]

Yes but, but the Polar bear cubs are going to die. You are so heartless, geez!

[M. Dodge Thomas]

One thing at a time.

Before we get onto the “ocean CO2 sink issues”, are we in agreement that the portions of this paper centered on discussion of the physics and chemistry of the relative contributions of *atmospheric* water vapor and CO2 are fundamentally flawed?

[capt. norm]

I am way too curious. Going by your screen-name, could it possibly be that you like to fly gliders?

[E. Pluribus Unum]

One thing at a time. Before we get onto the “ocean CO2 sink issues”, are we in agreement that the portions of this paper centered on discussion of the physics and chemistry of the relative contributions of *atmospheric* water vapor and CO2 are fundamentally flawed?

Which paper, my paper or your paper?

You need to put a reference at the beginning of your comment like I do so I know what you are talking about.

It's a common courtesy.

PS - Yours is a typical tactic of anthropogenic global-warming advocates: make things as confusing and complicated as possible so your point can't even be understood, much less refuted.

[M. Dodge Thomas]

Which paper, my paper or your paper?

Sorry if that was unclear, I was referring to the paper being discussed in the header of this topic.

Yours is a typical tactic of anthropogenic global-warming advocates: make things as confusing and complicated as possible so your point can't even be understood, much less refuted.

The author makes a "complicated" technical argument.

As is sometimes the case when someone analyzes a problem from the perspective of narrow technical knowledge, some of his fundamental assumptions are in error and/or the author is unaware that questions raised have already been settled, or at least discussed in a fuller and more relevant context.

In this case the errors were discovered shortly after the time of publication, were discussed at the time (including in the journal where the original paper was published) and have been noted repeatedly since.

The article, however, keeps reappearing, stripped of the context that would allow readers to evaluate it.

The nature of these questions is often such that they are "confusing and complicated" to non-specialists, and in many cases intelligent lay readers are eventually going to have to make their pick of authorities.

But when you find an old paper which has attracted fundamental criticisms shortly after publication and has few if any technically competent current defenders, it's generally safe to assume that the critics were right.

[E. Pluribus Unum]

In this case the errors were discovered shortly after the time of publication, were discussed at the time (including in the journal where the original paper was published) and have been noted repeatedly since.

I presumed that you linked to one of these articles.

Show me something from your article that proves my article "fundamentally flawed."

As you said, "One thing at a time."

[M. Dodge Thomas]

The Realclimat.org link (and the discussion which follows, do a search in comments for “Essenhigh” and follow the links there) outlines the problems with the atmospheric chemistry and physics in Essenhigh’s paper. Essenhigh remains a “global warming skeptic’, but as far as I know he has not responded to professional criticism of this paper subsequent to 1992.

[E. Pluribus Unum]

The Realclimat.org link (and the discussion which follows, do a search in comments for “Essenhigh” and follow the links there) outlines the problems with the atmospheric chemistry and physics in Essenhigh’s paper.

I'm not going to do your work for you.

If you have an argument, make it.

If you don't, shut up.

[M. Dodge Thomas]

"'m not going to do your work for you.

If you have an argument, make it.

If you don't, shut up.

Spoken like a true seeker after truth.

You have the link. You can follow it or not, as you choose.

If you can find a link where the author of this paper address professional criticism post 2002 please post it, and I will certainly read it.

But at this point we have an old paper, we have criticisms of the author's conclusions, and (as far as I've been able to determine) no response.

At this point, the argument is not mine to make.

[AFreeBird]

Global warming in and of itself does not exist.

Actually, it does exist. And as the article pointed out, it has been happening for millions (billions) of years. The argument is whether mans activities influences it anymore than the natural cycles that have existed since time began, and will exist long after we've turned to dust, and released the CO₂ in our bodies back into the atmo.

I'm of the opinion that the universe is a very large, and very complex place, and we're pretty damn arrogant to think we know it all. We don't.

That, and the global warming "crisis" is in itself a man made phenomenon designed to redistribute the wealth of nations, and hobble continued grown and advancement of the west in general, and the USA in particular.

[E. Pluribus Unum]

You have the link. You can follow it or not, as you choose.

Spoken like a true religious zealot.

No ideas of your own, just things and people you have a religious belief in.

You can't even express or defend your beliefs yourself, you have to post links to the words of your religious leaders.

Global warming dogma truly is a religion, and you just proved it.

[steveab]

Ref #21
Wouldn't’t you like to be the fly on the wall with both Robert H. Essenhigh, Baily and Lonnie Thompson at friendly faculty get together.

[stm]

I guess I sould have done a better job of communicating my point. What I meant to say is that global warming as a consequence of man’s existence does not exist. This earth has been going through climactic changes since it’s beginning.

[M. Dodge Thomas]

"Spoken like a true religious zealot. No ideas of your own, just things and people you have a religious belief in.

You can't even express or defend your beliefs yourself, you have to post links to the words of your religious leaders. Global warming dogma truly is a religion, and you just proved it."

You have it backwards there, I think.

This is exactly the opposite of debating something like religious doctrine, where everybody has an opinion, every body's opinion is of equal validity on an objective basis, and the more adroit debater "wins".

Expressing "my opinion" (except in so far as I might summarize the arguments) in the case of a technical debate over atmospheric chemistry and physics is pretty pointless in such cases, what anyone who wants to understand the question has to do is go back, read the paper, and read the responses, and attempt to evaluate which is the more reasonable position - there just is no other, easier, way to do it, and no one else can do it for you,

I've done my part - read the original, read the responses, attempted to discover if the author as responded to criticism of the original paper, especially in the last few years (as far as I can determine, he hasn't), and reached the best judgement I can, and pointed you the relevant material I have been able to discover.

If you have done the same, and arrived at a different opinion, IMO the productive thing to do is to take up the question with either the original author or his critics - it's easy to post (for example) and realclimat.org, and the moderators ad posters there are generally quick to respond to substantive comments - you will, though, have to raise substantive issues with regard to the criticism of the paper presented there.

[aruanan]

The outcome is that the conclusions of advocates of the CO2-driver theory are evidently back to front: It’s the temperature that is driving the CO2. If there are flaws in these propositions, I’m listening; but if there are objections, let’s have them with the numbers.

More to the point: as he said, if the change in CO2 is driving the change in temperature, what could be driving the periodic changes in CO2? This has not been answered except to assert that the most recent change in CO2 is anthropogenic. This still doesn't account for the cycling going back hundreds of thousands of years before man could ever have been a factor. But if the change in CO2 levels is driven by changes in global temperature, and changes in global temperature can be correlated pretty exactly with changes in solar output, then there is a much greater likelihood that the sun is driving temperature changes that are driving changes in atmospheric CO2 than that changes in atmospheric CO2 are driving temperature changes that are driving changes in solar output or that correlated changes between temperature and CO2 just happen to correlate with changes in solar output. In this case, neither happenstance nor causation is believable.

[tophat9000]

bump