Last week in Science there was an article on why the CO2 levels of the atmosphere rose as the world deglaciated. The article and the comment upon it illustrates how climatologists interpret data always in their favor. Any critic is in the position of betting with a guy who says, 'heads I win; tails you lose'. While we all like to think that scientists are simply looking for the truth, sometimes it is that a scientist is simply looking for confirmation of his belief system.
It has generally been agreed that solar insolation changes cause the rise and fall of glaciers. CO2 doesn't actually cause glaciation because the periodicity of the glacial ages matches what Milutin Milankovic calculated almost a hundred years ago. Their periodicities are predicted by the earth's orbital parameters and the distribution of sun over the earth's surface. These periodicities are about 100,000 years in duration, 41,000 years in duration, 23,000 years in duration and 19,000 years in duration. These periods are set by fundamental physics and the laws of Newton.
As with most issues in science, there was controversy about Milankovitch's theory but in 1976, Hays, Imbrie and Shackleton published "Variations in the Earth's Orbit: Pacemaker of the Ice Ages" in Science magazine, 194(1976): p. 1121 ff. They performed spectral analyses of oceanic cores which showed patterns of temperature variation exactly as Milankovitch calculated. That work, which has stood the test of time, pretty much settled the fact that solar insolation variations had to play at least the role of trigger to the glacial rhythms. The climate system is very complex and there might be other causes which amplify the insolation effect, but they can't be the causal trigger. Thus, any claim that CO2 is the cause of glaciation or deglaciation should be highly suspect. I say this for a reason.
CO2 does not have a periodicity, it just is. Earth's orbital parameters do have a periodicity. Remember this as we go further into this interesting article and comments upon it.
The article abstract says it all, almost
"Wind-driven upwelling in the ocean around Antarctica helps regulate the exchange of carbon dioxide (CO2) between the deep sea and the atmosphere, as well as the supply of dissolved silicon to the euphotic zone of the Southern Ocean. Diatom productivity south of the Antarctic Polar Front and the subsequent burial of biogenic opal in underlying sediments are limited by this silicon supply. We show that opal burial rates, and thus upwelling, were enhanced during the termination of the last ice age in each sector of the Southern Ocean. In the record with the greatest temporal resolution, we find evidence for two intervals of enhanced upwelling concurrent with the two intervals of rising atmospheric CO2 during deglaciation. These results directly link increased ventilation of deep water to the deglacial rise in atmospheric CO2." R. F. Anderson,et al " Wind-Driven Upwelling in the Southern Ocean and the Deglacial Rise in Atmospheric CO2," Science, 323(2009), p. 1443
What is happening at the end of a glacial period is that as the insolation changes, it causes the westerly winds move south, causing the ocean to upwell and those deeper waters give off lots of CO2 to the atmosphere. That is why CO2 lags temperature change. In other words, the initial slight temperature rise causes then the rise in CO2 which acts as a positive feedback loop, further increasing the temperature.
This article, and the commentary upon it, though, don't bother to mention poor old Milutin Milankovitch. One can only wonder why, but ascribing other causes to earth's temperature rises might be counterproductive if one wants to blame everything on CO2.
Interstingly, the commentary on this article says the following, which is why I said some of the things I said above. The commentary says two things which Anderson et al, do not say. First, Toggweiler says that the westerlies shifted before the temperature rise or the CO2 rise:
"Data reported by Anderson et al. on page 1443 of this issue suggest that the shift 17,000 years ago occurred before the warming and that it caused the CO2 increase."J. R. Toggweiler, "Shifting Westerlies," Science, 323(2009, March 13, 2009, p. 1434
"Something similar appears to have happened 17,000 years ago at the end of the last ice age: Earth warmed, atmospheric CO2 increased, and the Southern Hemisphere westerlies seem to have shifted toward Antarctica (5, 6). Data reported by Anderson et al. on page 1443 of this issue suggest that the shift 17,000 years ago occurred before the warming and that it caused the CO2 increase. The CO2 that appeared in the atmosphere 17,000 years ago came from the oceans rather than from anthropogenic emissions. It was vented from the deep ocean up to the atmosphere in the vicinity of Antarctica. The southern westerlies are important in this context because they can alter the oceanic circulation in a way that vents CO2 from the ocean interior up to the atmosphere. The prevailing view has been that the westerlies shifted 17,000 years ago as part of a feedback: A small CO2 increase or small warming initiated a shift of the westerlies toward Antarctica; the shifted westerlies then caused more CO2 to be vented up to the atmosphere, which led to more warming, a greater poleward shift of the westerlies, more CO2, and still more warming (5). But Anderson et al. show that the westerlies did not shift in response to an initial CO2 increase; rather, they shifted early in the climate transition and were probably the main cause of the initial CO2 increase." J. R. Toggweiler, "Shifting Westerlies," Science, 323(2009, March 13, 2009, p. 1434
I bolded this last part of the statement because for the life of me, I can't find where Anderson et al say what Toggweiler says they say. No where in the Anderson et al article does it say that the winds shifted before the temperature rise-at least I can't find it anywhere.
In fact, Anderson specifically say this:
"During the interval between 30 and 60 ka, when we have the best constraints on the age model of TN057-14PC (see Supporting Online Material), the opal flux record provides evidence for increased upwelling associated with each period of elevated CO2. Uncertainties in the age model for TN057-14PC do not allow for meaningful assessments of apparent lead-lag relationships between upwelling and CO2." R. F. Anderson,et al " Wind-Driven Upwelling in the Southern Ocean and the Deglacial Rise in Atmospheric CO2," Science, 323(2009), p. 1447
If you can't do lead lag between upwelling and CO2 you also can't do it between CO2 and temperature from this data.
Anderson et al, also show a chart trying to correlate various events from the southern to the Northern Hemisphere.
Note the last sentence in their caption--at the bottom of their core, the age uncertainty is 5000 years plus or minus. Yet, Toggweiler assured us that this work showed that CO2 leads temperature. That means that Toggweiler has implicitly dismissed the Milankovitch trigger for glaciation (without having any explanation then for why CO2 varies with precisely the Milankovitch periodicities of 100,000 year, 41,000 year, 23,000 year and 19,000 year periods.
Because we must play a game of 'heads the anthropogenic global warming believer wins; tails the anthropogenic global warming skeptic loses,' Toggweiler can assure us that CO2 leads temperature AND therefore implicitly, Milankovitch is wrong and CO2 miraculously varies with the same periodicities.
One other issue, which I am not going to push hard concerns the source of today's CO2. This article at least makes one want to take another look at the rational for blaming mankind
"Climate variability in the high-latitude Southern Hemisphere (SH) is dominated by the SH annular mode, a large-scale pattern of variability characterized by fluctuations in the strength of the circumpolar vortex. . . .During the summer-fall season, the trend toward stronger circumpolar flow has contributed substantially to the observed warming over the Antarctic Peninsula and Patagonia and to the cooling over eastern Antarctica and the Antarctic plateau. David W. J. Thompson and Susan Solomon,"Interpretation of Recent Southern Hemisphere Climate Change", Science 296(2002):895
The data they study is for the past 30 years, and they say that the winds have been strengthening over that period--and at the same time Antarctica is warming, and thus, even more CO2 has been sent into the Atmosphere by the upwelling gases caused by the stronger winds.
How much CO2 comes from this source? I don't know. I do know that it weakens one argument that is used to say that no natural phenomenon can explain the isotopic composition of CO2 in the atmosphere.
"Are the Increases in Atmospheric Carbon Dioxide and Other Greenhouse Gases During the Industrial Era Caused by Human Activities?"
" The relative amount of the carbon-13 isotope in the atmosphere has been declining, showing that the added carbon comes from fossil fu¬els and vegetation. Carbon also has a rare radioactive isotope, carbon-14, which is present in atmospheric CO2 but absent in fossil fuels. Prior to atmospheric testing of nuclear weapons, decreases in the relative amount of carbon-14 showed that fossil fuel carbon was being added to the atmosphere." IPCC, 2007: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA." http://oceanservice.noaa.gov/education/pd/climate/factsheets/areincrease.pdf
The thing that strikes me is that the deep oceanic water will be depleted in C13 and C14 and then CO2 made from them enters the atmosphere, they will at least in part, mimic the signature of some fossil fuel burning. Burned petroleum and CO2 from the deep water will have the same CO2 signature and water not in the North American Deep Water circulation, water which upwells off Antarctica may have been away from the surface for 10,000 years or more, and thus would also be depleted in C14, which would mimic anthropogenic carbon.
So, what is the 'age' of the deep waters off of Antarctica? Well, Marchitto et al report on a study they did of the age of the C14 in deep ocean waters.
"Ages of up to 5000 years have been reported for glacial deep waters near New Zealand (41), but more northerly sites in the Pacific show little difference from today, at least at depths shallower than ~2 km (40). We infer that the greatest 14C depletion of the glacial deep ocean was probably concentrated in the Southern Ocean region (and deepest Pacific), coincident with the highest densities (22) and lowest d13C values (24)." Thomas M. Marchitto, et al."Marine Radiocarbon Evidence for the Mechanism of Deglacial Atmospheric CO 2 Rise,"Science 316, (2007) p. 1459;
While 5000 years does not represent total depletion of C14 from the deep upwelling waters reported by Anderson et al, it does mean that nearly half of it is gone via decay and so, the CO2 sent into the atmosphere, this deep invading CO2, is old CO2.
Thus this article raises some interesting questions with regard to the global carbon cycle. Because of this article there might have been more CO2 sent into the atmosphere than is currently believed, and correspondingly more removed. How can this be? The current atmospheric CO2 level is nothing but the difference between input and output--even if both input and output are larger, the current CO2 level would be the same.
As one friend always says, the climate is so complex that no one will be able to understand all its feedback loops, which means that man's control of the climate and the ability to predict what will happen is poor.