This interesting essay by Dr. Spencer is reposted from his blog, link here:
Global Warming Causing Carbon Dioxide Increases: A Simple Model
May 11th, 2009 by Roy W. Spencer, Ph. D.
Global warming theory assumes that the increasing carbon dioxide concentration in the atmosphere comes entirely from anthropogenic sources, and it is that CO2 increase which is causing global warming.
But it is indisputable that the amount of extra CO2 showing up at the monitoring station at Mauna Loa, Hawaii each year (first graph below) is strongly affected by sea surface temperature (SST) variations (second graph below), which are in turn mostly a function of El Nino and La Nina conditions (third graph below):
Click for larger images
Click for larger image
During a warm El Nino year, more CO2 is released by the ocean into the atmosphere (and less is taken up by the ocean from the atmosphere), while during cool La Nina years just the opposite happens. (A graph similar to the first graph also appeared in the IPCC report, so this is not new). Just how much of the Mauna Loa Variations in the first graph are due to the “Coke-fizz” effect is not clear because there is now strong evidence that biological activity also plays a major (possibly dominant) role (Behrenfeld et al., 2006).
The direction of causation is obvious since the CO2 variations lag the sea surface temperature variations by an average of six months, as shown in the following graph:
So, I keep coming back to the question: If warming of the oceans causes an increase in atmospheric CO2 on a year-to-year basis, is it possible that long-term warming of the oceans (say, due to a natural change in cloud cover) might be causing some portion of the long-term increase in atmospheric CO2?
I decided to run a simple model in which the change in atmospheric CO2 with time is a function of sea surface temperature anomaly. The model equation looks like this:
delta[CO2]/delta[t] = a*SST + b*Anthro
Which simply says that the change in atmospheric CO2 with time is proportional to some combination of the SST anomaly and the anthropogenic (manmade) CO2 source. I then ran the model in an Excel spreadsheet and adjusted an “a” and “b” coefficients until the model response looked like the observed record of yearly CO2 accumulation rate at Mauna Loa.
It didn’t take long to find a model that did a pretty good job (a = 4.6 ppm/yr per deg. C; b=0.1), as the following graph shows:
Click for larger image
The best fit (shown) assumed only 10% of the atmospheric CO2 increase is due to human emissions (b=0.1), while the other 90% is simple due to changes in sea surface temperature. The peak correlation between the modeled and observed CO2 fluctuation is now at zero month time lag, supporting the model’s realism. The model explained 50% of the variance of the Mauna Loa observations.
The best model fit assumes that the temperature anomaly at which the ocean switches between a sink and a source of CO2 for the atmosphere is -0.2 deg. C, indicated by the bold line in the SST graph, seen in the second graph in this article. In the context of longer-term changes, it would mean that the ocean became a net source of more atmospheric CO2 around 1930.
A graph of the resulting model versus observed CO2 concentration as a function of time is shown next:
If I increase the anthropogenic portion to 20%, the following graph shows somewhat less agreement:
Click for larger images
There will, of course, be vehement objections to this admittedly simple model. One will be that “we know the atmospheric CO2 increase is manmade because the C13 carbon isotope concentration in the atmosphere is decreasing, which is consistent with a fossil fuel source.” But has been discussed elsewhere, a change in ocean biological activity (or vegetation on land) has a similar signature…so the C13 change is not a unique signature of fossil fuel source.
My primary purpose in presenting all of this is simply to stimulate debate. Are we really sure that ALL of the atmospheric increase in CO2 is from humanity’s emissions? After all, the natural sources and sinks of CO2 are about 20 times the anthropogenic source, so all it would take is a small imbalance in the natural flows to rival the anthropogenic source. And it is clear that there are natural imbalances of that magnitude on a year-to-year basis, as shown in the first graph.
What could be causing long-term warming of the oceans? My first choice for a mechanism would be a slight decrease in oceanic cloud cover. There is no way to rule this out observationally because our measurements of global cloud cover over the last 50 to 100 years are nowhere near good enough.
And just how strenuous and vehement the resulting objections are to what I have presented above will be a good indication of how politicized the science of global warming has become.
REFERENCES
Michael J. Behrenfeld et al., “Climate-Driven Trends in Contemporary Ocean Productivity,” Nature 444 (2006): 752-755.
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I’m not buying it. There are several inconsistencies.
If Bristlecone Pines can be considered as a proxy for CO2 levels, then the hockey-stick millennial CO2 reconstruction is confirmed. If we reject the reconstruction, we must also reject a key piece of evidence against Michael Mann’s millennial reconstruction.
So, assuming we accept the hockey-shape CO2 reconstruction along with Loehle’s millennial temperature reconstruction, we could not also attribute the modern CO2 increase to increasing oceanic temperatures. If this were the case, why are historic CO2 levels so flat when oceanic temperatures were so variable?
It looks like the Realclimaters have come out of the woodwork and are providing posts that are full of “Schmidt”. Apparently the Gavinizer has run out things to blog about recently. Welcome! I know I prefer to hear healthy debate on these issues. It certainly seems that blogs about the CO2 record seem to cause the greatest debate. The constant increase of CO2 in the atmosphere is the one measurable item that agwers hang their hats on ……… and are clinging to dear life on to.
I agree in your general assertion that not all climate change is man-made but disagree with the reality of the figure you generated at 10%.
I believe the more critical issue is pollution in general and not specifically CO2 emissions but as you pointed out this issue has been politicized by both sides and rational debate is rare.
Mike McMillan (21:22:05) :
“That must have been one gutsy peer reviewer.”
Thats one of the problems with peer review, in most cases the reviewer is anonymous to the writer of the article. On the Quantum mechanics issue, Einstein was thought to be behind the times-too old.
Eric Lightborn (22:23:24)
“I believe the more critical issue is pollution in general and not specifically CO2 emissions but as you pointed out this issue has been politicized by both sides and rational debate is rare.”
Nice to see a truthful, non-partisan comment in the climate debate.
I found this a useful (and for me at least easy to read) piece when looking at CO2 and ocean carbon sinks – it also gives an explanation of Henry’s Law:
http://motls.blogspot.com/2007/11/ocean-carbon-sink-henrys-law.html
I hope it helps with the debate
RW (16:21:26) :
“Conclusion: the oceans cannot be the source of the extra CO2, because if they were, then a) the amount of CO2 in them would be falling, not rising ”
You seem to have bought the IPCC mantra hook line and sinker.
How accurately do we know the CO2 levels in oceans relative to the amount of CO2 it releases into the ocean. What is the uncertainty? Over 200 GtonsC/yr are emitted into the atmosphere via natural processes against only 8 GtC/yr from man. The oceans hold 38,000 GtonsC. A 1% error is 380 GtC, half as much C as in the entire atmosphere. It is not possible to measure changes in ocean C content -3 Gtons C per year (1/13,000 of the oceans C content), with enough accuracy to rule out the oceans role in changes to atmospheric CO2 if the uncertainty in this number is accounted for. Isotope measurement has even greater uncertainty.
ASSUMPTIONS are the heart of IPCC science. For example, assuming the surface layer of the oceans to be in equilibrium leads IPCC to conclude that the measured increase in CO2 is from man’s emissions, without increases due to background effects or warming of the ocean.
The IPCC use the MLO record to represent global CO2, since they calibrate CO2 measurements from other sources to make them all agree, on the assumption that atmospheric CO2 is well-mixed. This contradicts observations of CO2 gradients in latitude and longitude.
IPCC ignores the global flow of CO2 through the atmosphere and across and through the surface layer of the ocean, and then into and out of the Thermohaline Circulation. CO2 is absorbed near 0ºC at the poles, more so in the cold waters of the Antarctic, and returned about one millennium later to the atmosphere at the prevailing tropical temperature. Much of it returned to the atmosphere near the MLO as the MLO sits in the outgassing plume of the Eastern Equatorial Pacific, and CO2 circulates with measurable gradients around the globe.
IPCC does not model the oceans temperature-dependent exchange of about 90 gigatons of carbon per year, even though it dwarfs mans emission of 8 gigatons per year. The outgassing of CO2 is a positive feedback of global warming.
IPCC considers the ocean to absorb mans CO2 at a few gigatons per year, or 50% of its emission rate. It reports natural CO2 outgassed from the ocean as being exchanged with the atmosphere at about 90 gigatons per year
( 100% of the oceans emission rate). IPCC offers no reasonable explanation for the accumulation of mans CO2 (50%), but not natural CO2 (0%).
IPCC’s conclusions are wrong that CO2 is long lived (do the math on the exchanges and the total CO2 in the atmosphere), that it is well mixed, and that it is a forcing, meaning that it is not a feedback.
IPCC assumed cloud cover to be a constant (due to lack of understanding and lack of historical data and accurate historical observations) and not a dynamic feedback and thus ignored what is likely the dominant feedback in the climate system, the negative feedback of cloud albedo.
“If, despite the isotopic evidence, you want to believe that warming has caused the rise in CO2, then you can see from ice cores that the relation between CO2 and temperature that held for 800,000 years or so was that a 1°C rise in temperature corresponded to about an 8ppm rise in CO2.”
The Vostok record, especially the 450,000 year reduction, includes the dominant period of ice ages. The warm periods are the interglacial maxima which are geologically brief, and even instantaneous if you consider that the sampling interval of ice core samples is 1.3 millennia. The present interglacial is within a few degrees of the ceiling interpreted from the previous four maxima. It also suggests that CO2 levels lagged temperature by as much as 800 years.
CO2 levels as measured via chemical analysis with an accuracy of 3% have shown CO2 levels in the 19th century and even in the 1940’s to be at or above levels of CO2 today. The argument to discard these levels is not very convincing if you accept that CO2 is well mixed in the atmosphere. Also, there is some uncertainty in measurements of gaseus inclusions in ice, since the assumption the gas is representative of global atmosphere at the time is not verifiable. Furthermore, an untested assumption that the air in bubbles in ice is 90 to 200 years younger than the ice in which the bubbles are entrapped was made in order to explain the concentrations
of GHG in air bubbles from ice deposited in the 18th and 19th century were similar to those of the present atmosphere. This way 100-200 year old ice is considered to contain air bubbles from 20th century air.
Your own assumption that CO2 and temperature is linear is not true, and even IPCC agrees. An 8 ppm increase at 200 ppm has a much greater effect on temperature than an 8 ppm increase at 360 ppm. The effect of doubling CO2 from 180 to 360 ppm (180 ppm) would be similar to a doubling CO2 from 360 ppm to 720 ppm (360 ppm).
A cooling hydrosphere will scrub a lot more CO2 out of the atmosphere and result in lowering of the CO2 detected during this period.
Plant life on this planet is an almost steady state carbon cycle and can not cause the changes observed.
Only a planet with huge, dirty (with salts) oceans can have a oxygen enriched atmosphere. CO2 is very easy to scrub with sea water as the CO2 goes into solution with water easily and then combines with light metal ions to make carbonates that percipitate out. Solar radiation in the upper atmosphere breaks down H2O into hydrogen that leaks into space and oxygen that sinks toward the surface.
Global cooling causes lowering of CO2 in the atmosphere.
Global warming causes raising of CO2 in the atmosphere.
CO2 has almost nothing to do with the temperature in the atmosphere, it is an effect not the cause. CO2 is a very poor green house gas and comprises only 1/30 of 1 percent of the atmosphere, and carbon is the most important element for life on this planet. The amount of carbon in circulation is the limiting nutritant in all life on this planet
IT IS THE SUN.
The total output of the sun causes the goldylocks zone to move in or out and the planet to cool or warm depending on the amount of energy it encounters, and the amount of CO2 to lower or raise with the temperature changes.
As a farmer and an inventor and designer of industrial fume scrubbers I believe I have some insight in the creation and maintaince of an atmosphere.
“Global warming theory assumes that the increasing carbon dioxide concentration in the atmosphere comes entirely from anthropogenic sources”
No it doesn’t.
It does assume that some of the increasing carbon dioxide concentration in the atmosphere comes from anthropogenic sources.
It turns out that the oceans and the terrestrial biosphere are net carbon sinks, so the increase is entirely due to anthropogenic sources. But when the oceans get warm enough to outgass, creating a further positive feedback, this will be entirely consistent with global warming theory.
Pardon me Roy (is that the cat that chewed your new shoes?)…
Excel spreadsheet, you say… how on earth can that be right? Try again on a super-duper-computer.
Fuelmaker:
My point is simple. Follow the C. We burn about 10 Gt Carbon per year, and 5-6 new Gt are found in the atmosphere, where we put it. Dr S’s case is that that new C in the air came from the ocean, not from the obvious suspect (the C we put there). OK, then where did ours go?
Dr S didn’t say into vegetation, but JamesG, to whom I was replying, did. The question remains,
Now you seem to be saying that our C goes into the ocean, even while other C is coming from the ocean to replace it. How does that work?
Actually, there is of course some exchange of atoms, so after a time not all the C in the air are the actual atoms that we burnt. But the overall flux of C follows the concentration gradient, from the air into the sea. And we drive that by burning fossil fuels.
“a change in ocean biological activity (or vegetation on land) has a similar signature…so the C13 change is not a unique signature of fossil fuel source.”
However the C14 from biological activity in the ocean is not depleted as it is from a fossil fuel source. So by simply looking at all Carbon Isotopes, and not just C13, it can be shown that the increase in atmospheric carbon dioxide concentration is from the combustion of fossil fuels.
That is without the plethora of information showing that the ocean is taking up carbon dioxide, not releasing it, including studies that track the anthropogenic carbon in the oceans, and the oceanic acidification that is apparent everywhere.
pft: the amount of CO2 in the oceans is rising. Therefore, they cannot be the source of the extra CO2 in the atmosphere. Simple as that. 13C measurements both of the current atmosphere and in ice cores are easily accurate enough to show that a dramatic change in the composition of atmospheric CO2 began about 200 years ago, after 800,000 years of almost no variation.
If you want to believe that the oceans are the source of CO2, you have to believe that fossil fuel CO2 is just disappearing, that oceanic CO2 is somehow changing its isotopic composition of its own accord, and that temperatures have risen many degrees since 1800.
“The IPCC use the MLO record to represent global CO2, since they calibrate CO2 measurements from other sources to make them all agree, on the assumption that atmospheric CO2 is well-mixed. This contradicts observations of CO2 gradients in latitude and longitude.”
You had a lot to say about the IPCC there, much of it apparently under the impression that the IPCC itself carries out science. It does not. This one statement in particular is not remotely true. Where on earth did you get this idea from?
I note the oddity of this post’s assertion that ocean warming is the source of the regular annual rise in CO2, when just a few days ago we had another of many posts asserting that the oceans are cooling.
But I’d also endorse RW’s point above. It’s true that in the past, CO2 levels have risen, when the oceans warmed at the end of an Ice Age. But it is usually about 100 ppm or so, in response to a warming of at least 5C. Here we have a bigger rise since industrialisation, with far less ocean warming, raising CO2 to levels higher than any post-ice age period in the last million years.
There’s too much curvature discrepancy for me. The SST data seems to force the curvature whereas the emissions data is relatively linear as is the Mauna Loa data.
As far as I can see a detrended SST anomaly to provide the short-term variability with the emissions anomaly to provide the long-term trend would provide a much better match.
That wouldn’t support Spencer’s hypothesis. Does anyone have the data?
The simple model encapsulates perfectly the notion that the main driver of CO2 changes is natural forcing.
However, it may be more appropiate when adding an anthropogenic element to highlight that this may be largely due to changes in land usage, the impact of aerosols and UHI rather than man-made emissions of CO2; after all we know there is no HOT SPOT in the troposphere, the ghostly AGW radiative driver, to force increases in global temperature.
So to enhance this model we need to breakdown and add-up the natural and anthropogenic temperature elements to improve its ability to do hind-casts.
Say:
delta[CO2]/delta[t] = Natural (Oceans + Atmosphere (clouds + particles + gasses) + Land + Solar) + Anthro(Land usage + Aerosols + UHI + Greenhouse gas emissions)
One aspect of Roy W. Spencer’s model that is worthy of a mention is that it takes the scaremongering out of the equation.
There is a basic reason why this analysis by Dr. Spencer cannot be published in a scientific journal. As alluded to in at least one posting above, his analysis either assumes that the law of the conservation of matter does not apply or that there are order of magnitude errors in our estimates of the amount of fossil fuels that is burned and/or the change in atmospheric CO2.
What mass balance (conservation of matter) estimates tell us is that the rate of increase in atmospheric CO2 is about half the rate of CO2 release from burning fossil fuels. In other words, over the long term, about 50% of the CO2 released by combustion is absorbed by nature and 50% is accounted for by the increase in atmospheric CO2. Since we have not observed massive increases in terrestrial plant matter (a potential sink on land), scientists have concluded that oceans are a net sink for CO2. That is, over a time scale of years and decades, the oceans are absorbing more CO2 than they release.
If we use Dr. Spencer’s results and assume that the oceans are releasing CO2 and that this release is much greater than fossil fuel burning, we can calculate that the rate of increase in CO2 in the atmosphere should be an order of magnitude higher than observed in the Mano Loa data. If Dr. Spencer were to submit his findings to a scientific journal, the discussion section of his manuscript would need to explain these discrepancies between his results and what is known about world fossil fuel consumption, the resulting CO2 release and the increase in atmospheric CO2. The alternative would be to assume that CO2 from fossil fuel (magically) disappears or that the oceans (magically) absorbs CO2 from fossil fuel while releasing CO2 from other sources.
I assume that Dr. Spencer must be aware of these issues. Dr. Spencer said that the purpose of his analysis was to “stimulate debate.” However, without further explanation it is will just cause confusion among the naive public while being ignored by scientists.
A very interesting model.
I have always been suspicious of the claim that the the delta 13C signal proved that the observed increase in atmospheric CO2 was anthroprogenic.
In fact CO2 relaesed via both fossil fuel combustion and that cycled through biological processes is 13C deleted to a similar amount (approx -30). This is because the photosynthetic enzyme (RUBISCO) discriminates between 12C and 13C so that 13C is depleted in organic (fixed) carbon. This will also happen for fossil fuels because its carbon was “fixed” by the same biological process and both 12C and 13C are stableover geological time.
How can one distinguish between “fossil” and “modern” 13C depletions?
The reference below is useful
ROBINSON, J. J., AND C. M. CAVANAUGH. 1995. Expression of form
I and form II ribulose-1,5-bisphosphate carboxylase/oxygenase
(Rubsico) in chemoautotrophic symbioses: Implications for the
interpretation of stable carbon isotope ratios. Limnol. Oceanogr.
40: 1496–1502.
Carl Wolk (22:13:31) :
If Bristlecone Pines can be considered as a proxy for CO2 levels, then the hockey-stick millennial CO2 reconstruction is confirmed. If we reject the reconstruction, we must also reject a key piece of evidence against Michael Mann’s millennial reconstruction.
So, assuming we accept the hockey-shape CO2 reconstruction along with Loehle’s millennial temperature reconstruction, we could not also attribute the modern CO2 increase to increasing oceanic temperatures. If this were the case, why are historic CO2 levels so flat when oceanic temperatures were so variable?
Mann used the Bristlecone Pines as a “temperature” proxy. Temperature measurements from adjacent weather stations demonstrate that this is in error. It has been theorized that the variation in the rings is due to CO2, but there doesn’t appear to be any confirmation studies. Irrelevant anyway.
The historic CO2 reconstruction by Callandar and continued by Keeling is also problematical.
http://www.biokurs.de/treibhaus/180CO2_supp.htm
The hocky-stick is junk science at its best.
Great job by Dr. Spencer!!!
It really did bring out the AGW trolls.
A newcomer to this stuff.
Is there a network of reliable (i.e. properly audited for accuracy) CO2 measuring sites throughout the world? The one that seems to be mentioned always is near an active volcano. Anyone know why? Surely the atmosphere isn’t homogeneous – is it?
Nick Stokes
You say “We burn nearly 10 Gigatons of C per year. The atmospheric increase is about 5-6 Gt. The rest is thought to go into the ocean.”
But look at this up to date link here:
http://www.guardian.co.uk/environment/2009/feb/18/trees-tropics-climate-change
“Over the world’s tropical forests, this extra “carbon sink” effect adds up to 4.8bn tonnes of CO2 removed each year – close to the total carbon dioxide emissions from the US.”
4.8bn tonnes (or 4.8Gt) is the missing carbon sink that you thought we should assume went into the oceans. So the ocean isn’t a net sink after all. The missing sink was the biosphere all the time. But I now wonder how correct the “10 Gigatons of C per year” calculation is. Bear in mind that the IPCC seems to think that deforestation adds 20% to carbon emissions, which is the opposite of the truth, I don’t give much hope for their other numbers.
Its an amusing debate, some great insights being posted !!
Roy is using similar methods to that of the IPCC where it arrived at its climate sensativity conclusions,
So it should be good enough for Roy to make a claim about co2 being 90% natural, but I bet he does’nt get a mention in the next IPCC report!!
At least we are starting to learn a lot more about the oceans now with the ARGO floats starting to produce usefull information.
If co2 is being absorbed in polar waters and released in tropical waters would there be an observable difference in co2 concentrations between say antartic waters and the tropics. Equally there should be an observable difference between northern hemisphere concentrations where 90% of MMco2 is released and the southern hemisphere.
yet there does not seem to be much difference
http://cdiac.ornl.gov/trends/co2/graphics/JubanyMonthly08.jpg
according to the Italian Jubany monitoring station.
I have some difficulty in understanding how 9-10 gigatons of carbon can be diffused through the atmosphere to the south pole so quickly.
Spencer confuses the temperature modulation of the sink speed (3ppm/y/K) with temperarture sensitivity of the equilibrium sink (10 ppm/K)
The units are completely differerent. In electronics Its comparing a temperature resistor with a temperature sensitive battery.
Mike,
Yes, there are many such sites. Here is the site for the Scripps Institute network – 10 stations across a full range of latitudes. You can look at their results – pretty consistent, and mostly a long way from any volcanoes.
Apologies if this has been posted…I’m travelling and have limited access, so can’t read all the comments to check.
Pretty serious coverage on Hot Air this morning of Senate hearings between Sen. Barrasso and Lisa Jackson regarding the “Smoking Gun OMB memo”, including Youtube clip.
http://hotair.com/archives/2009/05/12/video-epa-memo-says-greenhouse-effect-not-proven/
JimB