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.

[qam1]

Actually the biggest problem with that chart for the AGW proponents is the rise in CO₂ is too linear

The rise has been steady at about +1.5 ppmv per year (15 ppmv per decade)

However, if you look at the world's CO₂ output

the emissions have of course been increasing

So the question is why is the rise in CO₂ levels per year staying linear? As emissions increased you should see the rate of the increase in CO₂ levels per year in the atmosphere also increase.

For example, if pumping out 4000 million tons of CO₂ 1970 caused the rise of 1.5 ppmv atmospheric CO₂, then you would expect that in the year 2000 when we pumped out 7000 million tons of CO₂, the atmospheric level should have rose about 26 ppmv that year. But they didn't, it's been holding steady at +1.5ppmv

The reason is obvious, 4000 million tons or 7000 million tons put out by man are both insignificant compared to natural emissions and the rise in CO₂ has to be coming from somewhere else. Even 7000 million tons is barely a blip on the seasonal differences.

Looking at the ice cores we see CO₂ level changes lag temperature changes by 800 years, well 800 years before the 20th century was the 1100s which was the height of the medieval warm period so that's most likely what we are seeing. The temperatures rose in 1100s and 800 years later in the 20th century the CO₂ levels followed suit.  

[Scott from the Left Coast]

Unfortunately, the truth doesn't matter...the mass hysteria has already been effected.

The tyranny of opinion now rules.

[E. Pluribus Unum]

The annual CO2 cycle at Mauna Loa is tracking yearly temperature changes indirectly as a secondary effect (plant growth and decay), not the capture/retention of CO2 in the ocean or another direct "geophysical" event.

I still consider the Manua Loa data to be fatally flawed without the corresponding sea surface temperatures.

It is a relevant variable that would reasonably have been collected at the same time, if they were going to all the trouble of recording the CO₂ and air temperature values.

Do you know if this data is available? I have not been able to find it.

[M. Dodge Thomas]

"I still consider the Manua Loa data to be fatally flawed without the corresponding sea surface temperatures... do you know if this data is available? I have not been able to find it."

Worldwide sea surface temperature data is available from NOAA.

The cause of the yearly CO2 cycle - which is also evident in data from non-oceanic monitoring sites (for example at the south pole) - is well studied and isn’t in dispute, even AFAIK by reputable skeptics of AGW. If you are reading otherwise check the cites (if any) for the source of alternate opinion.

[E. Pluribus Unum]

Thanks.

[E. Pluribus Unum]

This graph is from A dangerous climate, an April 11, 2007 article in the London Daily Telegraph by Bob Carter, research professor at James Cook University, Australia and former chair of the Earth Sciences Panel of the Australian Research Council and former Director of the Australian Office of the Ocean Drilling Programme.

This graph does not appear to show global warming.

Is it fraudulent?

If so, how?

[M. Dodge Thomas]

"This graph does not appear to show global warming... Is it fraudulent?

No, just wrong.

He's not been paying attention for the last 4 years - and neither, apparently, have his editors.

That graph turns on this:

“The first (claim) is that, over the 20th century, global average temperature increased by about 0.7C, which it did, if you accept that the surface thermometer record used by the IPCC is accurate… However, our most accurate depiction of atmospheric temperature over the past 25 years comes from satellite measurements (see graph below) rather than from the ground thermometer record.”

Now, why one would assume that the satellites measurements were more accurate is unstated and unclear; there are questions about the older instrumented data, but it’s pretty hard to understand how there could be been systematic and consistent errors in the ground level instrumented record as complied over the last few decades.

So for most climate scientists, it’s been a case of “who ya’ gonna’ believe – that satellite, or your lying eyes?”

And the (IMO reasonable) assumption has been that there was something wrong with the satellite measurements.

(Actually it’s a bit more complicated that that, when comparing the records you also have to consider a number of other things, for example the level of the atmosphere at which readings are taken and how that relates to assumptions about atmospheric behavior.)

However, the problem has been resolved: we have known for the last four years that the satellite data had been misinterpreted:

“Previously reported discrepancies between the amounts of warming near the surface and higher in the atmosphere have been used to challenge the reliability of climate models and the reality of human induced global warming. Specifically, surface data showed substantial global-average warming, while early versions of satellite and radiosonde data showed little or no warming above the surface. This significant discrepancy no longer exists because errors in the satellite and radiosonde data have been identified and corrected. New data sets have also been developed that do not show such discrepancies."”

http://www.climatescience.gov/Library/sap/sap1-1/finalreport/sap1-1-final-execsum.pdf

Turns out we should have believed our lying eyes all along!

[E. Pluribus Unum]

The cause of the yearly CO2 cycle - which is also evident in data from non-oceanic monitoring sites (for example at the south pole) - is well studied and isn’t in dispute, even AFAIK by reputable skeptics of AGW. If you are reading otherwise check the cites (if any) for the source of alternate opinion.

I have degrees in biology and chemistry and have worked in analytical chemistry most of my working life.

I can tell you by looking at that perfectly reproducible annual subcycle that it's cause most definitely is NOT biological. It is far to reproducible.

That cyclic behavior has all the earmarks of a physico-chemical phenomenon.

Why does that cyclical pattern appear in terrestrial atmpospheric CO₂ records? I defy to find that pattern anywhere besides over the ocean.

I emailed Dr. Essenhigh about this, and was embarrassed to learn that he actually addressed it in the article I began this thread with:

"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."

So, are you saying that the solubility equilibrium between CO₂ in the ocean and in the atmosphere does not contribute anything to the annual cycle?

[M. Dodge Thomas]

There are whole disciples devoted to studying how this works, including extensive field observation and research in areas as varied as arctic tundra and tropical rain forests. In fact, evidence that the amplitude of the cycle may be increasing as a result of the response of vegetation to increased CO2 levels an argument often advance by those who believe that increased global temperatures are desirable.

[E. Pluribus Unum]

The cause of the yearly CO2 cycle - which is also evident in data from non-oceanic monitoring sites (for example at the south pole) - is well studied and isn’t in dispute, even AFAIK by reputable skeptics of AGW.

Is Dr. Essenhigh a "reputable skeptic of AGW?"

[kabar]

If you accept AGW as a fact, you also seem to imply that man can control climate change. Similarly, I assume that there can be AGC [C for cooling]. If man has such a determinate impact on the temperature of the earth, then I assume Man can attach what amounts to a thermostat on the earth's climate and dial up the ideal temperature. He can not.

From what I have read on the subject, what I find disturbing is how little impact man will have on climate change even if we do everything the Gore-bots want. Our efforts would be better spent on adapting to the effects of global warming than believing we can control it.

[sonic109]

That way they can tax something.
GIVE THIS MAN A CIGAR BINGO !!!!!!!!
You hit it right on the head pal . See what happens if Klinton gets in , they will be inventing new way to tax the hell out of us based on global warming damage.
It’s an anti capitalism movement in disguise .

[M. Dodge Thomas]

Is Dr. Essenhigh a "reputable skeptic of AGW?"

Well, I'm beginning to wonder about some of these guys, and to reconsider what "reputable" means in this such cases.

For example, no terrestrial measurements of the yearly CO2 cycle? Has he ever looked at data collected at (for example) the south pole? Read any of the the extensive literature on the cycle? If if so, does he assume the people performing this work over the last few decades are total idiots? That they would not have noticed if there was no terrestrial evidence of the cycle?

When you are confronted with this kind of thing, or with someone who confidently states that satellite data we have known for years had been incorrectly analyzed is superior to ground observations, or that solar effects which we know on empirical grounds cannot have contributed more that a third to the observed warming are its primary driver, you really have to wonder...

[E. Pluribus Unum]

You're a paid lobbyist for the AGW cartel, right?

[M. Dodge Thomas]

...then I assume Man can attach what amounts to a thermostat on the earth's climate and dial up the ideal temperature. He can not.

There are a number of technically feasible proposals to deliberately alter the global climate, most at the moment directed toward cooling it if we should find ourselves in a run-away warming situation. The orbital reflectors proposed by Jim Rutt and others - which could be in place an operating within a decade for less we currently spend on major programs such as ABM systems - are one example.

Of course, such efforts might have unpredictable results - as might our current unplanned tinkering with the Earth's atmosphere.

[M. Dodge Thomas]

"You're a paid lobbyist for the AGW cartel, right?"

As if... I'd likely be living a considerable more opulent lifestyle if I was a successful flack on either payroll.

I will say this, though: the by far most financially successfully person I know - someone who has had the business acumen to make several substantial personal fortunes over his lifetime, and is one of the most "conservative" people I know - has increasing investments in technologies which will do well if concerns about AGW prove justified. If you think the big money is all on one side of this issue, or the "Liberals" are the only ones writing the checks, you need to think again.

[kabar]

Of course, such efforts might have unpredictable results - as might our current unplanned tinkering with the Earth's atmosphere.

This assumes that man can actually have the ability to "tinker" with the Earth's climate/atmosphere on any significant and permanent basis. It is part of the hubris of Man until some natural catastrophic event occurs to demonstrate how really powerless and insignificant we are. We would have a hard time just equalling the impact of Krakatoa on the global climate and even that was relatively short-lived. The Earth was here long before man came on to the scene and will survive long after man has disappeared.

[E. Pluribus Unum]

If you think the big money is all on one side of this issue, or the "Liberals" are the only ones writing the checks, you need to think again.

As if that's something new.

The quickest way on earth to get rich is to get the government to pass a law that forces people to buy your product.

The farm lobby here in Missouri is making $$$$ hand-over-fist since they got the legislature to mandate ethanol in gas.

[M. Dodge Thomas]

You are of course correct there are some such events with consequences we would be powerless to control.

[M. Dodge Thomas]

"...got the legislature to mandate ethanol in gas"

Ethanol is a good argument for the proposition that we should processed slowly and carefully when addressing environmental concerns. That said, IMO this particular case is more an example of opportunistic pork-barrel politics than an abuse of scientific methods or conclusions.