What can we learn from the Mauna Loa CO2 curve?

Guest post by Lance Wallace

The carbon dioxide data from Mauna Loa is widely recognized to be extremely regular and possibly exponential in nature. If it is exponential, we can learn about when it may have started “taking off” from a constant pre-Industrial Revolution background, and can also predict its future behavior. There may also be information in the residuals—are there any cyclic or other variations that can be related to known climatic oscillations like El Niños?

I am sure others have fitted a model to it, but I thought I would do my own fit. Using the latest NOAA monthly seasonally adjusted CO2 dataset running from March 1958 to May 2012 (646 months) I tried fitting a quadratic and an exponential to the data. The quadratic fit gave a slightly better average error (0.46 ppm compared to 0.57 ppm). On the other hand, the exponential fit gave parameters that have more understandable interpretations. Figures 1 and 2 show the quadratic and exponential fits.

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Figure 1. Quadratic fit to Mauna Loa monthly observations.

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Figure 2. Exponential fit

 

From the exponential fit, we see that the “start year” for the exponential was 1958-235 = 1723, and that in and before that year the predicted CO2 level was 260 ppm. These values are not far off the estimated level of 280 ppm up until the Industrial Revolution. It might be noted that Newcomen invented his steam engine in 1712, although the start of the Industrial Revolution is generally considered to be later in the century. The e-folding time (for the incremental CO2 levels > 260 ppm) is 59 years, or a half-life of 59 ln 2 = 41 years.

The model predicts CO2 levels in future years as in Figure 3. The doubling from 260 to 520 ppm occurs in the year 2050.

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Figure 3. Model predictions from 1722 to 2050.

The departures from the model are interesting in themselves. The residuals from both the quadratic and exponential fits are shown in Figure 4.

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Figure 4. Residuals from the quadratic and exponential fits.

Both fits show similar cyclic behavior, with the CO2 levels higher than predicted from about 1958-62 and also 1978-92. More rapid oscillations with smaller amplitudes occur after 2002. There are sharp peaks in 1973 and 1998 (the latter coinciding with the super El Niño.) Whether the oil crisis of 1973 has anything to do with this I can’t say. For persons who know more than I about decadal oscillations these results may be of interest.

The data were taken from the NOAA site at ftp://ftp.cmdl.noaa.gov/ccg/co2/trends/co2_mm_mlo.txt

The nonlinear fits were done using Excel Solver and placing no restrictions on the 3 parameters in each model.

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Interesting. Need to check the results of other observatories (the time is shorter), to see weather the deviations are global or local.

noaaprogrammer

The late 1980s show a large departure. It would be interesting to plot these residules against the rates of increase/decrease in global temperature.

The fluctuations appear to fit global temperature fluctuations. This intuitively would make sense because warming sea surface temperatures would cause release of CO2 to the atmosphere, and conversely, as sea surface cools, would increase CO2 absorption into the oceans from the atmosphere.

wsbriggs

Because I’m an alround bad guy, I’ll suggest that you could also have fit the data with a scaling distribution, you know, and asymmetrical one with a long tail.
Interesting that it appears the ramp starts kind of when the LIA started petering out. But that couldn’t have anything to do with it…

mondo

Shouldn’t we be looking at this sort of data on a logarithmic rather than arithmetic Y-scale?

Just some guy

Hmmm. It cant follow the same formula forever, of course. If it did,it appears we’ll one million parts per million by the year 2540.

Kasuha

I’d suggest fitting a sine curve to it, too.
And another thing which might be interesting to look at is annual cycle. That would require unadjusted data, though. Does annual cycle follow the concentration curve (i.e. does its amplitude grow with concentration) or does it stay constant?

tango

Mauna Loa had better stop spewing out that CO2 crap other wise it will be slapped with a carbon tax, Australia PM gillard will find a way

Joachim Seifert

All this means that CO2-doubling will be completed by 2050 along with
the climate forcing of 3.7 W/m2…… thus earlier than 2100 as given by
AGW…
Which GMT would result in 2050?

Ian George

The last volcanic eruption of Mauna Loa was in 1984. Prior to that it had erupted quite regularly with 39 eruptions since 1832. Would this be a factor?

Rosco

Doesn’t the constant emission of volcanic gases from the national park mean that perhaps this was not the best choice of monitoring sites for a gas that is known to be emitted from volcanoes ?
I’m sure they adjust the data to compensate.

Latitude

If this trend continues……
who would have thought that man’s measly 5%

Billy Liar

Joachim Seifert says:
June 2, 2012 at 3:58 pm
Which GMT would result in 2050?
Your guess is as good as anyone’s …

My shot at explaining the residuals is that the dips reflect recessions in the West — the 70s and early 90s. So why isn’t there a dip for 2008+? Ans: China never had a recession.

mobihci

i would say the response to human emissions would be linear due to the time frame being considered mainly being from an upward slope of temperature rise.
if the natural component due to increasing ocean heat content is considered, then the ‘man made’ portion will be a fraction of the increase. to just draw a line through a complex system smacks of climate science at work.
what happens when the temps fall is the question, not what curve it fits.

David L. Hagen

Thanks Lance. Keep exploring.
For some detailed CO2 data and analysis with latitude and time see:
Fred H. Haynie, Future of Global Climate Change http://www.kidswincom.net/climate.pdf
And CO2 & OLR
David Stockwell in his Solar Accumulation theory predicts a Pi/2 (90 degree) phase lag for ocean temperature vs solar forcing for the Schwab solar cycle. e.g. 2.75 years for the 11 years solar cycle forcing. See Key evidence for the accumulative model of high solar inuence on global temperature
From that I predicted a similar 3 month (12/4) lag between annual solar forcing and ocean temperature, and thus the CO2 signal. similarly, the Arctic lag should be 6 months displaced from the Antarctic lag in the annual cycle. This appears to be supported by Haynie’s slides 16, 10, 11 and 18/59:

Adding the 9 day or 0.3 mo difference between the winter solstice (Dec 22) and January 1st, nominally gives 0.23 year (3 mo) and 0.63 year ( 7.6 mo) delays from the insolation minimums to the CO2 minimums. The CO2 curves also look like a ~0.4 year or 5 month difference between them. That is close to the 0.5 year (6 mo) difference expected from the North versus Southern hemisphere annual solar cycle. These phase lags suggest the CO2 pulses are driven by the temperature changes which lag the insolation by 90 degrees (2.5 years or 3 months) supporting Haynie’s evidence. See Haynie’s slide 18/59

(Note the Antarctic lag is reduced from the solar forcing because of less polar latitude). See also CO2 & Temperature discussion under <a href=http://judithcurry.com/2011/09/15/on-torturing-data/On Torturing the Data
The CO2 lags corresponding with the ocean temperature lags which are predicted from the annual solar forcing and with the Arctic ~6 months different from the Antarctic lag provides strong evidence for solar driven temperature with annual CO2 variations responding to the temperature.
For economic activity vs CO2 see:
Detection of Global Economic Fluctuations in the Atmospheric CO2 Record

Werner Brozek

Just some guy says:
June 2, 2012 at 3:43 pm
Hmmm. It cant follow the same formula forever, of course. If it did,it appears we’ll one million parts per million by the year 2540.

As well, the oxygen would get too low for life to exist. See
http://www.disclose.tv/forum/atmospheric-oxygen-levels-fall-as-carbon-dioxide-rises-t29534.html
“…we are losing nearly three O2 molecules for each CO2 molecule that accumulates in the air.
“if the oxygen level in such an environment falls below 19.5% it is oxygen deficient, putting occupants of the confined space at risk of losing consciousness and death.”

Harold Pierce Jr

EVERYBODY PAY ATTENTION!!! THE FOLLOWING IS SUPER IMPORTANT!!!
The concentration of CO2 in the atmosphere as determined at Mauna Loa is valid only for highly-purified, bone dry air which is comprised only of nitrogen, oxygen, the inert gases, and carbon dioxide and which does not occur anywhere in the atmosphere. In real air, there is always water vapor and the concentrations of the gases are lowered in portion to that volume fraction of water vapor.
The use of the concentration of CO2 based upon the data from Mauna Loa is an absolute fatal flaw for all climate model calculations. For fluid dynamic calculations, mass per unit volume should be used.
At STP (273 K and 1 atmosphere pressure), one cubic meter of dry air presently has about 390 mls (390 ppmv) or 17.4 mmoles. If this dry air is heated to ca. 333 K (60 deg C), which slightly higher than max temp every recorded in the desert in Pakistan, the concentration of CO2 is still 390 ppmv but its mass is 14.3 mmoles. If the dry air is cooled 183 K (-90 deg C, lowest temp ever recorded in Antarctica), the concentration of CO2 is still 390 ppmv but its mass is 26 mmoles.
The mass of atmospheric gases in any unit volume of the atmosphere depends upon temperature, pressure and absolute humidity. Weather maps show there is no uniform distribution of temperature, pressure and rel humidity in space and time. Thus there is no unifrom distribution of the greenhouse gases in real air.
The reason the climate scientists say the greenhouse gases are well-mixed is due to the methods of atmospheric gas analysis. In general a sample of local air is filtered to remove particles, dried to remove water, scrubbed to volitile organic compounds, oxides of sulfur and nitrogen, and CFC’s. This procedure produces the highly-purified bone dry air mentioned above.
The composition of the atmosphere of local air from remote locations is fairly uniform thu out the world except for minor variations in the concentration of CO2. However, in locals where there is lots of human activities the concentration of CO2 can vary greatly in space and time suchas during rush hour in major cities or in winter in temperate zones.
All the guys who do atmo. gas analyses know what I have stated above is the absolute truth. But they keep their mouths shut so the climate scientists can make the claim that the greenhouse gases are well-mixed and to avoid vilification. We all know what happened to Ernst Beck after he published he review of atmospheric CO2 gas analyses.
For really good data on the composition and properties of the atmosphere go to:
http://www.uigi.com/air.html
Ya know, these climate science guys really don’t know what they are doing.

I plotted Mauna Loa with tropics temps over at woodfortrees and there is no correlation.

NZ Willy

I presume the curve matches the world population curve without much of a residual. Still, the CO2 sinks into the oceans eventually, don’t know how fast that happens.

fp

So strange that the curve follows such a simple mathematical pattern and doesn’t seem correlated to economic activity, world oil consumption, etc. The residual doesn’t seem correlated either. See http://www.indexmundi.com/energy.aspx Oil consumption was dropping in the early 80’s and here the residual is increasing.
The fluctuations in the residual do seem to track the fluctuations in global temperatures though. Makes me wonder if outgassing from the oceans is what’s driving CO2, not fossil fuel use.

Caleb

I recall reading that the guys on Mauna Loa throw out the “outliers,” when they take CO2 readings. The reasons for throwing out the high CO2 readings involved possible burps of the volcano, and mobs of exhaling tourists in belching busses. However the reasons for throwing out the low readings of CO2 always puzzled me, (and made me a little nervous, because if you throw out enough low readings you can get the reading that “fits” a preconcieved theory.)
My understanding was that the low readings were due to “upslope winds.” Can anyone explain what happens downslope that uses up the CO2? Lush foliage?

AnonyMoose

There may also be information in the residuals—are there any cyclic or other variations that can be related to known climatic oscillations like El Niños?


http://www.woodfortrees.org/plot/esrl-co2/isolate:60/mean:12/scale:0.2/plot/hadcrut3vgl/isolate:60/mean:12/from:1958
(from http://forum.wetteronline.de/showthread.php?p=181540 )
It looks like the temperature changes are similar to El Nino/La Nina, with CO2 lagging temperature.

Dr Burns

From 1948, there seems to have been a steady downward trend in global atmospheric RH. Could this effect Mauna Loa CO2 measurement ?
http://members.shaw.ca/sch25/FOS/GlobalRelativeHumidity300_700mb.jpg

just some guy

Harold Pierce Jr says:
…For really good data on the composition and properties of the atmosphere go to: http://www.uigi.com/air.html
Harold, don’t take this the wrong way, but that link leads to some sort of classified ads website.

Robert of Texas

What I fail to understand is how climate scientists attribute all the increasing CO2 to man… If
– man only contributes (less than) 5% of the total new atmospheric CO2 annually
– the amount of man-made CO2 is increasing faster than most models assumed
– CO2 is the primary cause of warming
– since 1992 (or there-abouts) most global warming is caused by humans
then shouldn’t we see a deviation of some sort from a nice curve? (starting around 1992)
If on the other hand the ocean’s are degassing we would not see such a man-made deviation – it would be too small to measure. Hmm, and that’s what we see…

Bill Illis

I think if you take more recent data, you will find the growth starting to approach a more linear rate. The latest number are only accelerating at 0.002 ppm/yr/yr which is very, very, just slightly exponential.

Pamela Gray

Anything as regular as this data says one of two things.
1. Manmade CO2 pump sitting next to the sensor and never shuts off and is exquisitely tuned to a rythmic increasing beat.
2. Artifact of the “fudge” factor part of the CO2 calculation.
Of these two scenarios, I think #2 has the greater chance of being the culprit. It is exceedingly rare for anything on Earth to be that regular (even if caused by human polution) unless someone fine tuned it to be that regular. It’s like finding a perfectly square rock in the mountains and finding out nature made it. Ain’t gonna happen. Chances are something that regular is wholly artifact. That a person can build a simple model to express the regularity of the signal is revealing, to say the least. Someone have the complete maths sequence for the CO2 calculation?

Bill Yarber

The Earth has been warming since the LIA, a 500 year stretch of lower temperatures on land and sea surfaces. We have warmed about 1C since 1860 and over 2C since the coldest portion of the LIA – right around 1730. Can anyone calculate how much net CO2 the world’s oceans would outgas with 2C warming of sea surface temperatures. My guess is that amount will account for 90+% of the additional CO2 in our atmosphere. Would make a great research paper.
I’m also willing to guess, if Earth’s temps remain relatively constant for another decade, the rate of increase in CO2 concentration will slow back to 0.7ppm
Bill

Mauna Loa may not be active right now, but the whole of Big Island is volcanic and various parts erupt at different times. Kiluaea is on the windward side and the station is on the lee side of Mauna Loa, I actual saw the station from the saddle road last year. Kiluaea has been erupting non-stop for about 30 years now but volcanos do not have to be erupting to release CO2. I still naively feel that cyclical changes in the CO2 output of this place must be taken into account but they don’t seem to be.

Doug Badgero

“Interesting that it appears the ramp starts kind of when the LIA started petering out. But that couldn’t have anything to do with it…”
+1
What we know:
There is about 50 times as much CO2 in the oceans as there is in the atmosphere.
Warming water will release CO2 from solution.
The seasonal and short term changes in CO2 correlate well with temperature and lousy with anthro emissions.
Considering only the amount of anthro emissions, the CO2 levels in the atmosphere should be rising faster.
Yet, most scientists don’t seem to even consider the possibility that the rising CO2 levels are due primarily to the long term warming of the earth and oceans since the LIA.

To NZ Willy,
The Arctic Ocean is the big sink that is covered with ice much of the year. When the ice is a minimum, the net sink rate is around 50ppm/year over the cold open water.

jorgekafkazar

Thanks, Lance, this was fun. But there’s not a whole lot of science, here. Using a curve fit for a 56 year period, then extrapolating backwards and forwards is very shaky. There’s no reason to assume that the multiple mechanisms resulting in atmospheric CO2 concentrations are identical at the start and end of the period; thus the exponential, though convenient, is not necessarily valid as a predictor or analytical tool of any sort.
If you have the time, though, you might want to push this a stage further. At a minimum, I’d like to see error bars fore and aft, as well as a correlation coefficient adjusted for autocorrelation. I think you’ll find your 1723 date should be ±200 years. Worse, trying to tie the date of the knuckle of the exponential to any invention is completely unjustified. Natural CO2 variation may likely overwhelm any man made emissions, distorting the actual curve beyond recognition.
NZ Willy says: “I presume the curve matches the world population curve without much of a residual…”
Bad assumption.

Harold Pierce Jr

just some guy says on June 2, 2012 at 5:57 pm:
Harold Pierce Jr says:
…For really good data on the composition and properties of the atmosphere go to: http://www.uigi.com/air.html”
Harold, don’t take this the wrong way, but that link leads to some sort of classified ads website.
You are right. There is real monkey business going. I called company and left a message. I will call on monday to find out about what is happening. Maybe they don’t know.
I googled: Universal Industrial Gases, Inc. The company name with their main web url comes up and links to all their other sites. If you click on any of these, you are taken to the ad site.
UIGI is really big company. I can’t imagine their webmaster hasn’t found about the “hijacking” of their url.
However, most of industrial customers probably don’t use the links, and use email to contact the company directly.

I note that NOAA are tumpeting a record-breaking 400ppm CO2 in the Arctic http://researchmatters.noaa.gov/news/Pages/arcticCO2.aspx

Brian H

Harold;
That domain leads nowhere now; uigi.com is a blank screen, all sub-pages included.

George E. Smith;

“””””…..I am sure others have fitted a model to it, but I thought I would do my own fit. Using the latest NOAA monthly seasonally adjusted CO2 dataset running from March 1958 to May 2012 (646 months) I tried fitting a quadratic and an exponential to the data. The quadratic fit gave a slightly better average error (0.46 ppm compared to 0.57 ppm). On the other hand, the exponential fit gave parameters that have more understandable interpretations. Figures 1 and 2 show the quadratic and exponential fits……”””””
So I didn’t see any conclusion as to whether the Mauna Loa CO2 data best fits an exponential curve or whether a power series curve is a better fit for the 1722 to 2050 data.
Just suppose we could, (well I’m not at all saying this is possible but just for now assume it might be) som how best fit an exponential curve itself to a power series; some generic form; for example,
like exp(x) = ax/1! + bx^2/2! + cx^3/3! + dx^4/4! + ….. you get the idea, where a, b, c, d, etc are arbitrary parameters to be statistically determined from a sequence of values for exp(x), over some useful range of that function.
Now if you used that power series instead of the exponential function, do you think you could get an even beter fit to the Mauna Loa CO2 data ?
It might be interesting to try.
Now what would happen if you used the actual real measured data; like what actually was found at the top of Mauna Loa, instead of some seasonally adjusted substitute ? Was Briffa’s Yamal Christmas tree seasonally adjusted ?
Why did you choose to start your extrapolated prediction; excuse me, that’s projection, from the year 1722. Aren’t you concerned about being accusede of cherry picking, by selecting that year; rather than say 1769; the year that Captain Cook, (re)discovered New Zealand ?

DocMartyn

CO2 is a biotic gas and so changes in the biotic affect CO2 and vise versa. If you want to have a gas that is a marker of changes in the temperature of ocean vs. atmosphere than Argon works nicely. Keeling has also looked at the changes in the Ar/N2 ratio at Mauna Loa. I don’t know where the archive for this data is.

Steve Keohane

Dr Burns says: June 2, 2012 at 5:55 pm
Dr. Burns, I have a couple copies of that chart, but do not know the source, nor what data was used to compile the graph. Do you? Any information would be appreciated. Thanks
Here is a more recent version: http://i48.tinypic.com/2qlfnzn.jpg

michael hart

Eureqa Formulize, a free program from Cornell Creative Machines Lab is a tool which allows researchers to sift through huge numbers of different curve fitting algorithms. That is, it not only does the curve-fit and regression analysis for one specified formula, it searches for other formulae according to the user’s choices of mathematical form. Well worth a look.
Of course, it should also carry a scientific ‘health warning’ cautioning of the perils of letting yourself be seduced into unwarranted conclusions by the ease of squiggle-matching with a computer.
[Idiots with computers can cause a lot of grief, but most readers of this blog probably don’t need that warning.]

Harold Pierce Jr says:
For fluid dynamic calculations, mass per unit volume should be used.
And from what do you base this rather unusual claim?
I am afraid that the substance of your claim is no more solid than your link.

The projected co2 chart is scary only ‘cuz it assumes unlimited supply of fossil fuels (as in IPCC scenarios). It is rather more reasonable (423-ppm 2029) when adjusted to reflect peak oil, peak gas & peak coal: http://trendlines.ca/free/climatechange/index.htm#fossil

Laws of Nature

Dear Anthony et al.
Just yesterday I was looking if there would be any news on the discussion of the Essenhigh paper
I found this:
http://www.skepticalscience.com/news.php?n=1259
And would like to direct the interested reader to comments #20 and #26 there.
These two comments kind of summarize in my opinion about the state of the discussion:
Essenhigh came up with a model, which basically removes anthropogenic CO2 from the equation due to its low residence time, the published answer by Cawley uses a very similar model to “reinstate” the anthropogenic CO2, but fails to disprove Essenhighs assumptions and conclussions.
It seems when asked to comment there Essenhigh even said something like “you have your model, I have mine”.
Now here is my question: Is there anywhere a full discussion of the current state of the science? Or perhaps would you be willing to ask Essenhigh or Segalstad to comment on the Cawley paper here at WUWT?
Personally I think this is one of the most important questions, if Essenhigh’s estimates have some merit! (As shown by him and also mentioned in this comment #20 the fact that we produce more anthropogenic CO2 than remains in the atmosphere every year, is not a prove, that this is a cause for anything (due to the low residence times for CO2), especially not since we are still near the end of the little ice age and seeing centuries of high solar activities.
REPLY: I’ll look into this – Anthony

Shyguy

Looks to me like the co2 records got corrupted just like everything else the ipcc get it’s hands on.
Dr. Tim Ball explaining:
http://drtimball.com/2012/pre-industrial-and-current-co2-levels-deliberately-corrupted/

MikeG

Sorry, your curve fitting is quite meaningless and has no predictive properties whatever. The data would make an equally convincing fit to a sine curve, and many other functions.

Bart

This question has been solved. The derivative of CO2 tracks the variation in sea surface temperature remarkably well. Temperature drives CO2. Human inputs are rapidly sequestered and have no significant observable impact.
A simple analogous (not precise in every detail, but able to provide guidance as to physically possible and plausible behavior) system model is as follows:
dC/dt = (Co – C)/tau1 + k1*H
dCo/dt = -Co/tau2 + k2*(T-To)
C = atmospheric CO2 content
H = human input
Co = nominal set point of CO2 in the atmosphere dictated by temperature
tau1 = fast time constant
tau2 = slow time constant
k1, k2 = coupling constants
For tau2 long, dCo/dt becomes approximately equal to the integral of the temperature anomaly with respect to a particular baseline – in effect, you can say that approximately over a relatively short timeline
dCo/dt := k2*(T-To)
With tau1 short, the H input is attenuated to insignificance and C tracks Co tightly. The requirement that C track Co tightly means that tau1 must be short and must attenuate H to a level of insignificance.
Starting here, I show a series of simulations demonstrating this. Use the “Next” button to forward through the plots, the last one at viewing 6 of 29.
The prevailing paradigm simply does not make sense from a stochastic systems point of view – it is essentially self-refuting. A very low bandwidth system, such as it demands, would not be able to have maintained CO2 levels in a tight band during the pre-industrial era and then suddenly started accumulating our inputs. It would have been driven by random events into a random walk with dispersion increasing as the square root of time. I have been aware of this disconnect for some time. When I found the glaringly evident temperature to CO2 derivative relationship, I knew I had found proof. It just does not make any sense otherwise. Temperature drives atmospheric CO2, and human inputs are negligible. Case closed.

Jerker Andersson

The reason for the large variations in the error is because the model is a just a mathematical curve fit and not based on what really controlls the variation of the CO2 increase. I don’t think you can read much into the error for that model except it does not handle anthropogenic and natural variations.

Kelvin Vaughan

Werner Brozek says:
June 2, 2012 at 5:08 pm
“if the oxygen level in such an environment falls below 19.5% it is oxygen deficient, putting
occupants of the confined space at risk of losing consciousness and death.”
Here is an interesting article on CO2 levels that can be tolerated.
http://www.nap.edu/openbook.php?record_id=12529&page=112

Dave Walker

Caleb- Downslope from Mauna Loa are miles of recent lava flows and then miles of rainforest. The Observatory is 11,000 feet high and enjoys pretty steady wind. They throw out readings tainted with vog or low altitude pollutants. Not a perfect observatory but pretty good.

edim

The ML period (1959 – present) is enough to see some interesting correlations.
http://www.esrl.noaa.gov/gmd/webdata/ccgg/trends/co2_data_mlo_anngr.pdf
The annual growth in atmospheric CO2 correlates very well with the SST ‘anomaly’ and other global temperature indices. The correlation would be even better with the corresponding latitude band SST anomaly. Annual cycle is caused by the annual temperature cycle.
http://2.bp.blogspot.com/-AoUzuwoFQyA/T29AMKmFP7I/AAAAAAAABB8/O58gpDrQ-r4/s1600/co2_sst.gif
Interestingly, according to the dCO2 vs T correlation, it doesn’t take warming to rise the atmospheric CO2 – a sufficiently high constant temperature will cause rising CO2 (dCO2 = const). At some sufficiently low temperature CO2 will stop rising (dCO2 = 0). I once compared HADCRUT3 and ML dCO2 and got:
dCO2 = 2*Ta + 1.2 (R2 ~ 0.6).
Ta = 0.4, dCO2 = 2 ppm/years (like in this decade)
Ta = 0.0, dCO2 = 1.2 ppm/year (like in the ~70s)
If the correlation holds and global temperatures decline, dCO2 will decline too.