Steve Fitzpatrick writes in with a short essay:
On May 11 you reposted a blog from Dr. Roy Spencer, where he suggests that much of the increase in atmospheric CO2 could be due to warming of the oceans, and where he presents a few graphs that he claims are consistent with ocean surface temperature change contributing more than 80% of the measure increase in CO2 since 1958. Dr. Spencer’s suggestion is contradicted by many published studies of absorption of CO2 by the ocean, with some studies dating from the early 1960’s, long before “global warming” was a political issue. In this post I offer a simple model that shows why net absorption of CO2 by the ocean is most likely the main ocean effect.
If the rise in CO2 is being driven by human emissions, then the year-on-year increase in atmospheric CO2 ought to be a function of the rate of release of CO2, less any increase in the rate of removal of CO2 by increased plant growth and by absorption and chemical neutralization of CO2 by the ocean. Both ocean absorption and plant growth rates should increase with increased CO2 concentration in the atmosphere. To simplify things, I focus here only on ocean absorption.
On the other hand, surface temperature changes ought to have a relatively rapid effect, because the surface of the ocean is in contact with the atmosphere and so can quickly absorb or desorb CO2 as the water temperature changes. In fact, the ocean surface continuously absorbs CO2 where the temperature is falling, mostly at high latitudes, and emits CO2 where the water is warming, mostly at lower latitudes. Cold upwelling water from the deep ocean warms at the surface and desorbs CO2, while very cold water at high latitudes absorbs CO2 before it falls to the deep ocean. An increase in average ocean surface temperature will cause more CO2 to be emitted from surface water, but this effect is limited to a very small volume fraction of the ocean. Effects due to rapid temperature changes (annual time scale and less) are limited to a relatively thin layer, while the gradual absorption/neutralization process takes place at a rate controlled by ocean circulation and replacement of the surface water with upwelling (and “very old”) deep ocean water.
Any change in sea surface temperature should add to or subtract from the atmosphere’s CO2.
Annual change = (Annual emissions) – K1 * (CO2 – 285) + K2 * (delta SST)
Where “CO2” is the atmospheric concentration, K1 is a unitless “ocean uptake constant”, and K2 is a sea surface absorption/temperature constant, with units of PPM per decree C. Delta SST is the year-on-year change in average sea surface temperature. K1 is related to how quickly surface water is replaced by deeper water, and it should be a relatively small number, since ocean circulation and mixing are slow. K2 should be a relatively large number, since surface water temperature changes are relatively fast and we know that there is a strong short-term correlation between the rate of change of CO2 concentration and SST changes.
The model performs an iterative calculation (a step-wise approximation of integration) of the evolution of CO2 in the atmosphere. Each year a change in CO2 is calculated using the above equation, that change is added to the atmospheric CO2 concentration from the previous year, and the process is then repeated. The calculation starts with 1959, using a starting CO2 concentration of 315 (the value from Mauna Loa in 1958).
Measured CO2 values and measured year-on-year changes are from Mauna Loa. Average SST’s are from GISS. CO2 emissions, expressed as PPM potential increase in CO2 in the atmosphere, are based on worldwide carbon emissions (according to CDIAC at Oak Ridge) converted to an equivalent weight of CO2, divided by an assumed atmosphere weight of 5.3 X 10^9 million tons. This result was scaled by a constant factor of 0.7232, which is 28.96/44 = 0.6582 (to convert weight fraction CO2 to volume fraction), multiplied by 1.099 to match up with the range of CO2 emissions that Dr. Spencer used in his May 11 blog post. Note that nobody really knows the total carbon emissions, so different sources offer different estimates of total emissions. The final two years of CO2 emissions I had to estimate beacause the CDIAC data ended in 2006. I assumed an equilibrium ocean CO2 level of 285 PPM. I optimized K1 and K2 by hand so that the model had a reasonable fit with the data; the values were 0.0215 for K1 and 5.0 for K2. So the model equation is:
Annual change = (Annual emissions) – 0.0215 * (CO2 – 285) + 5.0 * (delta SST)
The graph titled “Annual Increase in CO2” compares the measured and calculated year-on-year changes along with the potential increase from fossil fuels.
The graph titled “Correlation: Model Increase vs. Mauna Loa Increase” shows that the model does a decent job of capturing the year-on-year temperature driven change in atmospheric CO2.
I suspect that if the model used monthly data and the 6-month lag between SST changes and CO2 changes that Dr. Spencer used, then the model fit would be better.
The graph titled “Measured CO2 versus Ocean Uptake Model” shows the final result of the calculation.
The evolution of CO2 in the atmosphere calculated by the model between 1958 and 2008 is reasonably close to the Mauna Loa record. The model suggests that about 2.15 PPM equivalent of emitted CO2 is currently being absorbed, or about half the total emissions.
My only objective is to show that the CO2 released by human activities, combined with slow ocean absorption/neutralization and sea surface temperature variation, is broadly consistent with the measured historical trend in atmospheric CO2, including the effect of changing average SST on short term variation in the rate of CO2 increase. Temperature changes in ocean surface waters cause shifts of a few PPM up and down in the rate of increase, but surface temperature changes do not explain 80% to 90% of the increase in atmospheric CO2 since 1958, as suggested in Dr. Spencer’s May 11 post. Because of its relatively high pH, high buffering capacity, enormous mass, and slow circulation, the ocean is, and will be for a very long time, a significant net sink for atmospheric CO2.
With a bit of luck, continuing flat-to-falling average surface temperatures and ocean heat content will discredit the model predictions before too much economic damage is done.
Dave Middleton (12:02:58) :
‘ The record includes four CO2 minima of 260–275 ppmv (ca. A.D. 860 and A.D. 1150, and less prominently, ca. A.D. 1600 and 1800). Alternating CO2 maxima of 300–320 ppmv are present at A.D. 1000, A.D. 1300, and ca. A.D. 1700.’
I do not know how to average the several minima and maxima noted, nor do I know how to compare the relative accuracy/consistency of the stomata derived CO2 concentration with the trapped air in ice cores. One thing is certain, the ice core record shows no similar variation in CO2 on the time scales above, but it does show substantial temperature varaitions during that same period. What to make of this? I just do not know.
George E. Smith (11:19:48) :
‘If it is a real model, the values of K1 and K2 would need to be justified by some physical or chemical rationale based on the processes going on.’
Yes, I agree that a truly robust model would do exactly that, but I was only trying to make a model similar in form to what Dr. Spencer offered. In the case of my model, I did not even try to include the increase in rate of plant growth, because I expected that both ocean absorption and increased plant growth rate would be roughly proportional to the rise in CO2, so that with optimized constants the “ocean only” model ought to fit the historical data pretty well.
That being said, I do want to point out a couple of things:
1. Nothing I used as the basis of the model is inconsistent with well established physical behaviors. It is not like I was pulling new physical principles out of the air. There was no combination of roots of prime numbers, no 10 adjustable parameters for a 10th order polynomial curve, or anything similar, and I was not arm-waving about unmeasured or difficult to measure parameters like changing aerosol concentrations.
2. Even a “curve fitted model” that doesn’t accurately fit the historical data is for certain incorrect (eg. Dr. Spencer’s model), while a curve fitted model that does hind-cast well has at least the possibility of being a fair representation of reality….. if it can make accurate predictions, not accurate hind-casts.
3. A reasonable expectation is that when you add something to an existing quantity of that same something (in this case CO2 added to CO2 already in the atmosphere) the total quantity will increase. What motivated me to create my simple model was that Dr. Spencer’s model and comments seemed to me quite disconnected from this very reasonable expectation.
4. Climate models all have the same “curve fit” problem unless they are carefully tested against future data. The climate modelers will say that their adjustable parameters are, as you suggest, all “justified by some physical or chemical rationale based on the processes going on”. But if you search for such justifications hard enough you will probably find them. This does not eliminate the need to make accurate predictions.
John Doe (11:47:58) :
‘We don’t need to wait for 10 years, because we can use different time periods for calibrating the model and using it for predictions. Let’s take for example years 1959-1979 to calibrate K1 and K2 and then observe its behavior in 1980-2009. Using several time periods to avoid cherry picking the data, gives more confidence on the findings.’
Go right ahead, I gave you all the data sources. But remember that the model leaves out plant influences, which are likely to be similar to ocean absorption, but not identical. The influence of increases in plant growth should start at zero, and gradually increase, while the influence of ocean absorption would start at a value above zero and increase from there. In other words, the absorption of the ocean should be linearly proportional to the increase above an assumed “equilibrium” ocean CO2 content (I used 285 PPM, but some folks in this thread claim this value may not be right), while plant growth increases will likely be proportional to the increase from the start of the model (that is, increases above 315 PPM CO2 in 1958), so you would have three parameters to work with, not two. Would this make the model hind-cast more accurately? Probably. Would it make the model forecast more accurately? Maybe. Would I take the time to do it? Nope.
A very accurate model was not the point. I wanted only to show that it is altogether reasonable for CO2 emissions to increase CO2 concentrations in the atmosphere, and that the measured increases over the past 50 years are not terribly out of line with what you would expect based on the emissions and the capacity of the oceans to absorb CO2.
Steve Fitzpatrick (10:08:12) :
Hummm,
1. Given: We can see fluctuations due to natural causes (volcanoes) and CO2 has not “reached a dangerous tipping point” and temperatures have not run away
2. And: We cannot see major fluctuations in man’s emissions in the graphs.
Doesn’t than mean that man’s contributions to CO2 must be much, much greater to seriously affect the earth’s temperature? I’m talking observations here, not anyone’s crystal ball. /end rhetorical comment/
Hey! Let’s pump the CO2 output as high as we can! Then we can find this mythical “tipping point”, then turn it back down.
“daily” unmodified (probably) dplot for Barrow
http://img29.imageshack.us/img29/5084/barrowdailylong.jpg
Here’s one to ponder. Using the barrow daily data and estimating the day of minimum for each year and then plotting the minima time since 1st January for that year against data (together with SST and Land temp) gives this plot:
http://img269.imageshack.us/img269/6543/barrowdateofminimachngw.jpg
There seems little correlation between yearly temperature patterns and days until minimum.
But as temp increases days decrease (approx .2 days per year – x axis is in microsoft date).
So if temp peaks are not driving the time for minimum – what is?
“My only objective is to show that the CO2 released by human activities, combined with slow ocean absorption/neutralization and sea surface temperature variation, is broadly consistent with the measured historical trend in atmospheric CO2, including the effect of changing average SST on short term variation in the rate of CO2 increase.”
Is that “slow absorption/neutralization” a famous time of the residence of “50-200 years” hypothesized by Houghton and IPCC, contrary to more than 40 studies performed by 6 various methods during 30 years prior to “global warming era” that almost found 5-8 years time-residence with almost all finding time-residence longer than 10-12 years?
Ivan,
The IPCC’s TAR said:
Savor that statement for a moment. The IPCC is saying that a molecule of anthropogenic CO2 acts differently than a molecule of “natural” CO2.
More evidence that the IPCC’s assessment reports are edited by political appointees, not by unbiased scientists.
James G (5:18:37) wrote:
…what oceanographers actually know about ocean movements is continually confounded and wrong. Witness the number of oceanographers who still say that the gulf stream warms Europe and it could be interrupted by the warming…”
The Gulf Stream, which is a wind-driven current, does indeed warm northern Europe. Physical oceanographers, including Prof. Wunsch, never claimed it to be a feature of the thermohaline (density-driven) circulation that “climate scientists” mistakenly presumed. The latter should not be confused with the former, no matter where they may be employed.
Ivan:
The residence time you are taking about (5-8 years) is correct, for a specified group pf CO2 molecules, and many of the best studies were based on the rate of removal of radioactive C14- CO2 from the atmosphere that was formed by atomic bomb tests in the 1950s and 1960’s.
There is a very large exchange of CO2 each year between the biosphere, the ocean and the atmosphere; about ~20% of the total mass of CO2 in the atmosphere gets swapped each year. Since the pool of CO2 in the biosphere and ocean is vastly larger than in the atmosphere (hundreds of times), a “tagged” CO2 (eg. radioactive C14 tagged CO2) is lost from the atmosphere quickly, and becomes very dilute… essentially lost… in the very large stores of CO2 in the biosphere and ocean, but most all of it is replaced with CO2 that was earlier in the ocean or the biosphere. This is why you can’t use radiocarbon dating for biological samples that formed after the start of the atomic age; the C14 from bomb tests (in the form of CO2) got rapidly picked up by the biosphere and incorporated into plants and animals… messing up the expected C14 concentrations that had historically come only from cosmic ray flux.
This 5 to 8 year “lifetime” of a CO2 molecule does not mean that ~20% of the total CO2 is removed each year (or even that 20% of an excess of CO2 will be removed). It just means that ~20% of the CO2 in the atmosphere is swapped each year. This exchange of CO2 molecules takes place at the same high rate even when the concentration of CO2 in the atmosphere is found by measurement to be at a constant level.
“”” Steve Fitzpatrick (13:52:21) :
George E. Smith (11:19:48) :
‘If it is a real model, the values of K1 and K2 would need to be justified by some physical or chemical rationale based on the processes going on.’ “””
Steve, don’t get me wrong; you explained quite well what you were trying to do and I understand that. I should say I was not overjoyed at Roy’s model either; but he also pointed out it was somewhat of a talking point model.
The point I would make, is simply that all of these statistical processes that seem to be a core part of climatology can serve very well to demonstrate “correlation”; but what is being saught is not correlation; but causation; and correlation does not prove causation.
George
“”” Joanna Lumley (12:34:51) :
Ok so it looks like we’ve all made up our minds about climate change.
I can’t seem to find any mention of ocean acidification though, surely thats what we should also be concerned with if we keep pumping co2 out at the current rate? “””
Well Joanna, I’ll let you worry about ocean acidification; so far nobody has shown that a small change in pH will lead to any catastrophe. There are som many buffer processes going on in the ocean relating to CO2, HCO3- and CO3- – not to mention Calcium carbonate in shells, that I think the world has far bigger problems to deal with that a small change in ocean pH.
Joanna Lumley (12:34:51) :
‘I can’t seem to find any mention of ocean acidification though, surely thats what we should also be concerned with if we keep pumping co2 out at the current rate?’
When CO2 is absorbed/neutralized by the ocean, the pH does go down a bit. Measurements of ocean water indicate a very small drop over the last 50-80 years; may be 0.03 or 0.05 pH unit, which is not a lot. The global warming terrorists ( I think that is the best name) always point to studies about how corals will all die and clam shells will dissolve. Well, like most AGW stories, the reality is a bit different. Corals actually do very well until the ocean pH corresponds to ~500 PPM in the atmosphere; the growth for some types actually increases a bit (their symbiotic aglae love higer CO2). Above 500 PPM coral growth rates do appear to slow somewhat, depending on type, but they do not die. Much bigger dangers to corals are that people like to dive on them too much, and cause damage, and that some are threatened by pollution from land based sources.
Some types of free swimming microorganisms (mini-organisms) that fix CaCO3 in the form of aragonite shells (rather than calcite) would do badly in very cold water (near the poles) if the CO2 level reached >900 PPM. The clams are safe, even at 1300 PPM.
The general consensus is that oceanic pH has declined by 0.1 since about 1750. A pH decline of 0.1 is well within the natural variability of oceanic acidity…Oceanic pH varies from 7.8 to 8.3 on a roughly 50-year cycle (Preindustrial to Modern Interdecadal Variability in Coral Reef pH
Carles Pelejero, et. al. Science 30 September 2005: Vol. 309. no. 5744, pp. 2204 – 2207 ). It has varied within that range over almost the entire Phanerozoic Eon (~600 million years) irrespective of atmospheric CO2 concentrations.
During the Permian period much of current day west Texas was covered by the Capitan Reef. Atmospheric CO2 was 2,000ppm to 4,000ppm and oceanic pH varied between 7.8 and 8.3…Just like it does today.
Here is a good example of how the green agenda contradicts and sabotages itself:
For many years, greenies have been pushing industry to make plastic packaging and products from plastics that degrade and rot in landfills (for instance, MacDonalds styrofoam packaging).
The problem with this is that plastics generally are manufactured from petroleum, so making them degrade and rot means that the carbon in them would over time be released to the atmosphere as CO2, increasing CO2 emissions. If the plastics remained inert, they would thus sequester the carbon long term and reduce CO2 emissions.
Meanwhile, the alternative movement for plastic recycling has become a victim of its own success, with plastics turned in at recycling centers stacking up and overflowing capacity due to oversupply and lack of demand for recycled plastic stock (some of this is due to too much plastic product manufacturing capacity moving offshore to Mexico and China, too far away to enable cost effective use of recycled materials, if Obama does anything with stimulus money, it should be to bring that industry back to the US).
Intriguing, we will certainly ask about this tomorrow on our tour of an urban garden center. feel free to come if you are in the area. The organization is called Growing Power and the details are found at:
http://tinyurl.com/GreenerBlog
There are two common ways to estimate CO2 concentrations in past atmospheres (before instrumental records began in 1959): 1) Measuring CO2 content in air bubbles trapped in ice cores and 2) measuring the density of stoma in plants. The advantage to the ice core data is that it provides a continuous record of relative CO2 changes going back 100’s of thousands of years…With a resolution ranging from annual in the shallow section to multi-decadal in the deeper section. The advantage to the stomatal data is that the relationship of the Stomatal Index and atmospheric CO2 can be empirically demonstrated.
The problems with the ice core data are 1) the air-age vs. ice-age delta and 2) the effects of burial depth on gas concentrations.
The age of the layers of ice can be fairly easily and accurately determined. The age of the air trapped in the ice is not so easily or accurately determined. Currently the most common method for aging the air is through the use of “firn densification models”
(FDM). Firn is more dense than snow; but less dense than ice. As the layers of snow and ice are buried, they are compressed into firn and then ice. The depth at which the pore space in the firn closes off and traps gas can vary greatly…So the delta between the age of the ice and the ago of the air can vary from as little as 30 years to more than 2,000 years.
The EPICA C core has a delta of over 2,000 years. The pores don’t close off until a depth of 99 m, where the ice is 2,424 years old. According to the firn densification model, last year’s air is trapped at that depth in ice that was deposited over 2,000 years ago (an oversimplification).
There are a lot of doubts about the accuracy of the FDM method. I somehow doubt that the air at a depth of 99 meters is last year’s air. Gas doesn’t tend to migrate downward through sediment…Being less dense than rock and water, it migrates upward. That’s why oil and gas are almost always a lot older than the rock formations in which they are trapped. I do realize that the contemporaneous atmosphere will permeate down into the ice…But it seems to me that at depth, there would be a mixture of air permeating downward, in situ air, and older air that had migrated upward before the ice fully “lithified”.
The DE08 ice core has the lowest delta air-ice age of any core I have looked at…30 years. If I plot the DE08 core using the ice-age and attach it to the Mauna Loa data and overlay that on a temperature curve…I actually get a better CO2 to temperature correlation than the FDM –aged CO2.
The most recent level of ice suitable for analysis is 1939. The FDM method says that the air in the 1939 ice is from 1969. If the air in the 1939 level is actually a blend of the air from 1909-1969…it might actually be more representative of 1939 than it is of 1969. If that’s the case, we really don’t have any CO2 data from 1939 to 1959…including the sharpest cooling period of the 20th century (1945-1950).
The ice core data might be more representative of a long wavelength moving average of CO2 values and be a good indicator of the low frequency component of the CO2 cycle; where as the plant TSI data are capturing the high frequency component. It’s also likely that the pressure effects of burial are affecting the gas partial pressures in the ice core air bubbles.
Steve,
“The residence time you are taking about (5-8 years) is correct, for a specified group pf CO2 molecules, and many of the best studies were based on the rate of removal of radioactive C14- CO2 from the atmosphere that was formed by atomic bomb tests in the 1950s and 1960’s.”
Is there any experimental or observational evidence that fossil fuel CO2 have longer time residence than 5 or 10 years, or it is only model “fudge” factor?
“This 5 to 8 year “lifetime” of a CO2 molecule does not mean that ~20% of the total CO2 is removed each year (or even that 20% of an excess of CO2 will be removed). It just means that ~20% of the CO2 in the atmosphere is swapped each year.”
Do we have any proof or plausible reason to believe that natural flux of about 135 giga tonnes per year is not much more important factor in overall CO2 increase than 6 giga tonnes of human emissions, i.e. that tinny human contribution is not lost in the large natural noise, just like it seems plausible that CO2 greenhouse warming signal is lost in natural climate variability?
As I was travelling around, I was quite late in reply to the note of Dr. Spencer on the correlation (ocean) temperature and CO2 levels. Here Steve Fitzpatrick gives a good reaction…
There is little doubt that temperature has an influence on CO2 levels: about 3-5 ppmv/°C for short-term variability and not more than 8-10 ppmv/°C for (very) long time variability like the MWP-LIA cooling and the glacial-interglacial-glacial transitions. See for the latter (based on all Vostok data):
http://www.ferdinand-engelbeen.be/klimaat/klim_img/Vostok_trends.gif
That simply means that temperature is not the driving force for the recent increase in CO2 levels: the increase in temperature since the LIA of maximum 1°C would give an increase in CO2 levels of not more than 8 ppmv. The rest of the 100+ ppmv rise is quite certainly of human origin. See:
http://www.ferdinand-engelbeen.be/klimaat/co2_measurements.html
If you look beyond the Mauna Loa period, the discrepancy between temperature and CO2 levels becomes even more clear:
http://www.ferdinand-engelbeen.be/klimaat/klim_img/temp_emiss_increase.jpg
In the 1945-1975 period, SST cooled slightly, but CO2 levels (from high resolution ice cores: Law Dome 8 years) increased in ratio with the emissions…
Ice cores are reliable storages for ancient atmospheres, but their resolution fades with layer thickness, inverse with maximum time span. The most recent period of about a century was covered by three ice cores with very high resolution at Law Dome. The most recent completely closed ice there was from 1980, spanning an overlap of about 20 years with the atmospheric data at the south pole (the ice age – gas age difference is of no interest here, the gas age was measured in firn in this case). The south pole data, are within the borders of the ice core accuracy during the overlap:
http://www.ferdinand-engelbeen.be/klimaat/klim_img/law_dome_overlap.jpg
There is no sign that there is a loss of CO2 levels in ice during burying: CO2 levels in firn and already closed bubbles in ice at closing depth are equal and the glacial/interglacial ratio between temperature (proxy) and CO2 levels doesn’t diminish over 800,000 years of ice layers in the deepest cores, which would happen if there was some (vertical) migration of CO2.
At last: I had a firm discussion with an author of a similar study of stomata index data: there is a bias in the stomata data, as stomata are formed at CO2 levels in spring, which are higher than average, including locally enhanced levels (from rotting vegetation of the previous year). This is more or less compensated by calibrating the SI data (resolution +/- 10 ppmv) with… ice core data of the past century. The main problems is that it is very difficult to know what happened with the local CO2 levels over the centuries (in contrast to CO2 levels at the south pole) when local/regional CO2 sources were added/removed.
Ivan (16:12:25) :
Ivan, the year by year variability of the natural CO2 cycle is +/- 1 ppmv
The emissions are nowadays about 8 GtC/yr or about 4 ppmv/yr
The increase nowadays is about 2 ppmv/yr
Thus nature is a net absorber of CO2 at a rate of about 2 ppmv/yr
See: http://www.ferdinand-engelbeen.be/klimaat/klim_img/dco2_em.jpg
Thus the natural variability of the CO2 cycle is -2 +/- 1 ppmv/yr sink capacity. There was no net addition of CO2 by nature over the past 50 years in average of each year.
It doesn’t matter if 10, 100 or 1,000 GtC is circulating through the atmosphere, absorbed and released by the oceans and vegetation. All what counts is how much the difference is at the end of the cycle: negative in all cases…
About residence time: The residence time is governed by the exchange rate of about 150 GtC on 800 GtC residing in the atmosphere or about 20% per year, hence the about 5 year half life time.
If we should stop emitting any fossil CO2 today, next year, we would see a drop of about 2 ppmv (4 GtC, as the pressure difference between atmospheric CO2 and oceanic CO2 didn’t change, thus the same removal rate as today), the year after that, the drop is only 1.6 ppmv (as the pressure difference now is lower),… Thus the excess CO2 decrease is not governed by the 150/800 ratio, but by the 4/800 ratio of removal which is related to the average partial pressure difference between atmospheric CO2 and oceanic (and alveoles) CO2. See Feely e.a. for a very good explanation of the atmosphere/ocean pressure differences:
http://www.pmel.noaa.gov/pubs/outstand/feel2331/exchange.shtml
So how was Dr. Spencer wrong? Was it just bad math like Drs. Mann & Steig?
Ivan (16:12:25) :
‘Is there any experimental or observational evidence that fossil fuel CO2 have longer time residence than 5 or 10 years, or it is only model “fudge” factor?’
The CO2 from fossil fuels has the same residence time as the radioactive C14 generated by atomic bomb tests, as you said, between 5 and 10 years, no longer. What builds up is the overall level of CO2. The C12/C13 isotope ratio changes over time are completely consistent with a slowly increasing fraction of fossil fuel based CO2 in the atmosphere as the quantity of fossil fuels consumed each year have increased. I know that Dr. Spencer has asked why we do not see shifts in this ratio when there are shifts in the rate of CO2 increase driven by short term ocean temperature variation (like El Nino). I have not researched this, so I can’t respond directly to Dr. Spencer’s question. However, I want to point out that if Dr. Spencer were correct (ie. that ocean temperature increase is the main cause for increases in atmospheric CO2), then his temperature driven model would have given a much better fit to the historical data; the fit was really quite poor. Occam’s razor says the simplest explanation is usually the right one. The fact that the simplest explanation also generates a much better fit to the data only reinforces Occam’s observation.
‘Do we have any proof or plausible reason to believe that natural flux of about 135 giga tonnes per year is not much more important factor in overall CO2 increase than 6 giga tonnes of human emissions, i.e. that tinny human contribution is not lost in the large natural noise, just like it seems plausible that CO2 greenhouse warming signal is lost in natural climate variability?’
The very big natural fluxes should be close to “in balance” over any period of more than a few years. There is of course natural variation, which is directly linked to temperature changes in the surface of the ocean, driven by a number of different causes, including El Nino and major volcanic eruptions (which dim the sun and cool the ocean for a couple of years). The effect of a continuous relatively small addition of CO2 to the large natural pool will never be evident over the noise of natural variation in the very short term, but it should cause a gradual increase over time. The entire system can only return to a more-or-less equilibrium state when the processes that remove CO2 from the atmosphere increase their rates in response to the slowly increasing concentration of CO2, until the increases in removal balance the rate of addition of CO2. Ocean absorption/neutralization is one of the natural responses to addition of CO2 to the atmosphere, and increased plant growth rates at higher CO2 levels is another. No doubt there are a number of other process that remove CO2 from the atmosphere, such as increased weathering of rock due to higher CO2 dissolved in rain, which also increase when CO2 concentration in the atmosphere rises.
The “Correlation: Model Increase vs. Mauna Loa Increase” graph is shown with a linear fit but to me it looks more like a quadratic fit would be more appropriate. This would indicate an asymptotic effect. Perhaps that means the biosphere can handle more than we give it credit for. But don’t misunderstand me, I am all for reducing human contributions.
I think it would be interesting to see a correlation with the average weight of Americans vs. CO2 emissions (breathing harder due to poor physical consition).
Steve Fitzpatrick (18:08:26)
“The very big natural fluxes should be close to “in balance” over any period of more than a few years. ”
Who is to say what is natural and what is not. Is not man a part of nature. We emit CO2 to live well. Animal and plant respiration releases CO2 by consuming oxygen to produce energy they need to live.
If we did not release CO2 from those so called “fossil fuels” the world would eventually run out of atmospheric CO2 as all of earths CO2 will end up as limestone. There is much less CO2 in the atmosphere today than hundreds of millions of years ago as a result of this process.
Since most of the last 600,000 years has seen man living in an ice age (90%), and with warmer periods during interglacials than today, the alarm over todays CO2 levels, given mans contribution is only 4% of the total being emitted seems baseless, especially at the low level of understanding of most of the processes that drive climate (sun, cloud formation, precipitation, etc).
Not saying CO2 can not cause warming, just saying cold kills more swiftly than warmth does. Less CO2, lower crop yields, less food for humans, cooler temperatures. An ice age would kill 80% of the human population. If mans CO2 helps delay the next one, I am all for it.
If it means that some coastal cities will slowly see property eroded, well, building newer cities inland would be the manner in which man adapts to a warmer climate. In the last ice age, the property where most coastal cities are in today were well inland. The mythical Atlantis may very well have been consumed by rising sea levels as the last ice age ended. Man survived. Climate changes, always has and always will, and man and other species adapt to it. Those that don’t become extinct. That’s evolution.
Thank you for responding TonyB. You are one of the few who do. An interesting article in that the forests ( a huge portion of the South American continent ) can sometimes radiate Co2, rather than just be sinks for Co2. We have a lot more to learn about how these things collectively work together. I believe that nature is far more resilient than anyone gives her credit. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We have the pine beetle currently decimating the forest of south eastern British Colombia. The beetle has been stymied by the colder temperatures this winter (die back occurs when it is colder than ~35C for a couple of days). There is a lot of people who make the claim that the beetle has been successful due to global warming. My question to them is how many times do you think that these types of infestation have occurred over the millennia. Countless times. Is the forest still there? Yes it is. Are ecosystems as fragile as fellows like David Suzuki would have you believe? Forest fires have always cleansed the forest and prepared it for rejuvenation. Certain pine trees will only release their seed from the pinecone in temperatures only achievable in a fire. The forest always grows back. Nature is in a constant state of flux. This is why the term “nature preserve” makes me laugh. Mankind feels that nature should maintain the status quo. Yet her adaptive capabilities are what is so amazing. As Neil Peart said; “Changes aren’t permanent, but change is”.
@Steve Fitzpatrick
It is rather unfortunate the your model does not attempt to encompasse the earlier 20th century warming period between 1910 and 1945, as human CO2 emissions were roughly only 25% of the later warming period (1975 – 1998).
Surely any decent model must reflect this effect.
How does your model cope with the warming between 1910 and 1945. Can anyone else shed any light on this strange effect.