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CO2 lags temperature - what does it mean?

What the science says...

Select a level... Basic Intermediate Advanced

CO2 didn't initiate warming from past ice ages but it did amplify the warming.  In fact, about 90% of the global warming followed the CO2 increase.

Climate Myth...

CO2 lags temperature

"An article in Science magazine illustrated that a rise in carbon dioxide did not precede a rise in temperatures, but actually lagged behind temperature rises by 200 to 1000 years.  A rise in carbon dioxide levels could not have caused a rise in temperature if it followed the temperature." (Joe Barton, US House of Representatives (Texas) 1985-2019) - Full Statement

At a glance

Antarctic ice-core data today provide a continuous record on temperature and atmospheric composition that goes back for some 800,000 years. The data track the last few glacial periods and their abrupt endings, with rapid transitions into mild interglacials. But in some of the ice-cores, temperature rises first and is followed, a few hundred years later, by rising carbon dioxide (CO2) levels.

Certain purveyors of climate-myths seized on this observation, claiming it to be “proof” that carbon dioxide doesn't cause climate change. Wrong, wrong, wrong. But how? The answer lies in a beer-can.

In fact, you can do this one yourself. You need two cans of any fizzy beer. On a nice summer's day, take one out of the fridge and place it outside in direct sunshine for a few hours. Leave the other where it is. Then open the two at the same time. The warm one will froth like mad, half-emptying the can and making a mess. What is left in the can will be horrible and flat. Conversely, the one straight from the fridge will just give a “pfft” noise and will be pleasant to drink, being cool and fizzy.

What's that got to do with this myth? Well, you have just demonstrated an important point about the solubility of CO2 in water. CO2 gives fizzy drinks their fizz and it is far more soluble in colder water. As the water warms, it cannot hold onto as much CO2 and it starts to degas. Hence that flat lager.

Exactly the same principle applies to the oceans. When global warming is initiated, both land and the oceans start to warm up. On land, permafrost starts to thaw out, over vast areas. Carbon dioxide (and methane) are released, having been trapped in that permafrost deep-freeze for thousands of years. At sea, that “warm beer effect” kicks in. Thanks to both processes, atmospheric CO2 levels rise in earnest, amplifying and maintaining the warmth. That rise in CO2 thereby caused more of the gas to be released, warming things up yet more in a vicious cycle, known as a positive feedback. Other feedbacks kick in too: for example as the ice-sheets shrink, their ability to reflect Solar energy back out to space likewise decreases, so that heat is instead absorbed by Earth’s surface.

The trigger for the initial warming at the end of an ice-age is a favourable combination of cyclic patterns in Earth's orbit around the Sun, leading to a significant increase in the solar energy received by Earth's Northern Hemisphere. That's no secret. Glacial-interglacial transitions are caused by several factors working in combination – triggers and feedbacks. We've understood that for a long time.

And when you think about it, saying CO2 lagged temperature during glacial-interglacial transitions so cannot possibly be causing modern warming is a bit like saying, “chickens do not lay eggs, because they have been observed to hatch from them".

Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!

Further details

That CO2 can lag behind but amplify temperature during a glacial-interglacial transition was in fact predicted as long ago as 1990. In the paper The Ice-Core Record: Climate Sensitivity and Future Greenhouse Warming by Claude Lorius and colleagues published in the journal Nature in 1990, a key passage reads:

"The discovery of significant changes in climate forcing linked with the composition of the atmosphere has led to the idea that changes in the CO2 and CH4 content have played a significant part in the glacial-interglacial climate changes by amplifying, together with the growth and decay of the Northern Hemisphere ice sheets, the relatively weak orbital forcing and by constituting a link between the Northern and Southern Hemisphere climates."

This was published over a decade before ice core records were accurate enough to confirm a CO2 lag. We now know that CO2 did not initiate the warming from past ice ages but it did amplify the warming. In fact, about 90% of the global warming followed the CO2 increase.

Antarctic ice cores reveal an interesting story, now going back for around 800,000 years. During this period, changes in CO2 levels tend to follow changes in temperatures by about 600 to 1000 years, as illustrated in Figure 1 below. This has led some to disingenuously claim that CO2 simply cannot be responsible for the current global warming. Unsurprisingly, such a claim does not tell the whole story.

Figure 1: Vostok ice core records for carbon dioxide concentration and temperature change.

The initial change in temperature as an ice-age comes to an end is triggered by cyclic changes in Earth’s orbit around the sun, affecting the amount of seasonal sunlight reaching Earth’s surface in the Northern Hemisphere. The cycles are lengthy: all of them take tens of thousands of years to complete.As both land and oceans start to warm up, they both release large amounts of CO2 into the atmosphere, from melting permafrost and from warming ocean water, since CO2 solubility in water is greater in cold conditions. That release enhances the greenhouse effect, amplifying the warming trend and leading to yet more CO2 being degassed. In other words, increasing CO2 levels become both the cause and effect of further warming. Once started, it’s a vicious, self-reinforcing cycle - an excellent example of what science refers to as a positive climate feedback.

Indeed, such positive feedbacks are necessary to complete the shifts from glacial to interglacial conditions, since the effect of orbital changes alone are too weak to fully drive such variations. Additional positive feedbacks which play an important role in this process include other greenhouse gases like methane - you may have seen videos of that gas bubbling up through icy lakes in permafrost country and being ignited. Changes in ice sheet cover and vegetation patterns determine the amount of Solar energy getting absorbed by Earth’s surface or being reflected back out to space: decrease an ice-sheet’s area and warming will thereby increase.

The detailed mechanisms for the above general pattern have of course been investigated. In a 2012 study, published in the journal Nature (Shakun et al. 2012), Jeremy Shakun and colleagues looked at global temperature changes at the commencement of the last glacial-interglacial transition. This work added a lot of vital detail to our understanding of the CO2-temperature change relationship. They found that:

1) The Earth's orbital cycles triggered warming in the Arctic approximately 19,000 years ago, causing large amounts of ice to melt, flooding the oceans with fresh water.

2) This influx of fresh water then disrupted ocean current circulation, in turn causing a seesawing of heat between the hemispheres.

3) The Southern Hemisphere and its oceans warmed first, starting about 18,000 years ago. As the Southern Ocean warms, the solubility of CO2 in water falls. This causes the oceans to give up more CO2, releasing it into the atmosphere.

4) Finally, CO2 levels may lag temperature in some ice-core records from Antarctica, but in some other parts of the world the reverse was the case: temperature and CO2 either rose in pace or temperature lagged CO2. Figure 2 demonstrates this graphically and shows how things are never as simplistic as purveyors of misinformation would wish.

Shakun Fig 2a 

Figure 2: Average global temperature (blue), Antarctic temperature (red), and atmospheric CO2 concentration (yellow dots). Source.

Last updated on 14 February 2023 by John Mason. View Archives

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Further reading

That CO2 lags and amplifies temperature was actually predicted in 1990 in a paper The ice-core record: climate sensitivity and future greenhouse warming by Claude Lorius (co-authored by James Hansen):

"Changes in the CO2 and CH4 content have played a significant part in the glacial-interglacial climate changes by amplifying, together with the growth and decay of the Northern Hemisphere ice sheets, the relatively weak orbital forcing"

The paper also notes that orbital changes are one initial cause for ice ages. This was published over a decade before ice core records were accurate enough to confirm a CO2 lag (thanks to John Mashey for the tip).

Also, gotta love this quote from Deltoid in answer to the CO2 lag argument: See also my forthcoming paper: "Chickens do not lay eggs, because they have been observed to hatch from them".

Further viewing

Denial101x video

Myth Deconstruction

Related resource: Myth Deconstruction as animated GIF

MD Lag

Please check the related blog post for background information about this graphics resource.


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Comments 1 to 25 out of 451:

  1. Nice correlation between T and CO2 level. However, given a correlation between two variables one has still to clarify which is doing what. One might of course notice that in the most recent "burst" CO2 gets well above the temperature curve, unlike the previous cases. Does anyone know what in the past produced the "fast" T and CO2 growths? Marco
  2. It is reasonable that warming of the oceans is in fact causing CO2 increase in the paleo record. What I wonder about is how anyone can turn this into evidence that CO2 causes warming? When I first saw this at an ACS function nearly 20 years ago these curves were presented as proof of CO2 caused warming; despite the obvious fact that the graphs, even then, showed that the temperature change was not following but rather was leading the CO2 change. Now we are trying to explain away T changing first invoking creative models. It appears the fundamental premise that CO2 causes warming is simply not supported by the paleo record. It may still be true, but what evidence do we have in the climate record that supports this hypothesis? Here is another question: If ice ages are on 100,000 year cycles because the Earth's orbit is more elongated on 100,000 year cycles why is the Earth's orbit so round now? Shouldn't it be nearing maximum excentricity?
    Response: The paleo record shows that Antarctic temperatures rise about ~800 years before CO2 and Greenland temperatures rise after the CO2 rise. The CO2 warming effect is necessary to explain both how weak orbital forcing can get us out of an ice age and also how an orbital forcing that affects only southern areas can spread through the globe. The paleo record also enables us to compare Co2 forcing with temperature change to calculate climate sensitivity.
  3. Provide error bars for the reconstructions, they tell quite a different story. Error bars are always necessary for meaningful interpreration of graphs like this.
    Response: Not sure what your point is - are you disputing that CO2 lags temperature? Monnin 2001 doesn't display error bars but quantifies the lag as around 800 ± 600 years:

    Caillon 2003 constrains the CO2 lag to 800 ± 200 years (but again, no error bars):


    Stott 2007 finds similar results - a CO2 lag of 1000 ± 300 years. Stott does include 200 year uncertainty on the benthic ages (in fact, Stott's graph includes everything but the kitchen sink):

  4. RE: response Are we sure about that? I am sure the original data from way back then was actually from Greenland ice cores, showing that temperature was rising before CO2, there as well as in the Antarctic. The Antarctic data was not yet around. If CO2 is rising first in Greenland than your hypothesis may be correct. I know CO2 is supposed to cause warming, and I think I understand why. But, the data still seems to scream corelation does not equal cause and effect.
    Response: The "original data from way back then" was probably Monnin 2001 which used the Dome Concordia ice core or Caillon 2003 which used the Vostok core - both are from Antarctica. Caillon concludes "The sequence of events during Termination III suggests that the CO2 increase lagged Antarctic deglacial warming by 800 ± 200 years and preceded the Northern Hemisphere deglaciation." More recently, Stott 2007 found that tropical temperatures lag southern warming by ~1000 years. I agree with you - correlation does not necessarily imply causation. But the ice core record is consistent with the warming effect of CO2 and explains both the degree of deglaciation and how a localised warming (increased insolation in the south) spread across the globe.
  5. No, the American Chemical Society Conference at which I noted this discrepency in a presented paper was in 1989 because I was in Grad Chemistry courses at the time, so I much doubt that it was 2001 or 2003 data. Other than that I hope you're right because otherwise 1)we are being led down the primrose path and 2) I am freezing my butt off up here. The presenter after having this error spotted by a lowly physics type grad student was not well recieved in the question session by the roomful of chemistry PhD's that were present. None the less his hypothesis that CO2 causes global warming is still widely discussed. :)
    Response: I would be surprised if ice core records were of sufficient resolution back in 1989 to clarify CO2 was lagging temperature - it's only been more recent ice core records that have been of high enough resolution to clarify the CO2 lag. Spencer Weart has published a great online history of ice core measurements that is well worth a read.

    Without knowing which older studies you're talking about, the most recent studies with up to date (and dare I say the most accurate) data (Monnin 2001, Caillon 2003) paint a similar picture of Southern warming -> CO2 rise -> Northern warming. But if you do know of any pertinent older papers, it'd be great if you could post the links here. And kudos for sticking it to the man :-)
  6. First of all, John, thanks for spending the time to create and maintain this site. I do realize it must be quite substantial time commitment. Although, it is not exactly neutral and is somewhat driven by your current opinion that GW is mostly due to anthropogenic CO2 emissions, the forums on the site are still one of the few places where we can have some more meaningful debates based on some scientific thinking and facts. So, in some respect the website is just like Churchill's quote on democracy (I think, he is the right man to quote since as you've correctly noticed many things in the GW debates on both sides are politically motivated consciously or not): "It has been said that democracy is the worst form of government except all the others that have been tried. " Of course there are another two quotes from him that I think very much apply to the GW debate: "The best argument against democracy is a five-minute conversation with the average voter. " & "A lie gets halfway around the world before the truth has a chance to get its pants on." Well, enogh quotes. On a more serious note, sadly enough, the whole field of Climate Science and Global Warming has become just like Finance. There is so much easy money flowing around that there is a great number of people with all sorts of backgrounds and levels of knowledge that have no relation to climate/physics or anything distinctly related (although by all means I am not saying we should only used established scientists' work as a guideline) that would make most outrageous claims/predictions with arbitrary certainty backed up many low-quality science booklets/papers/reports, posh presentations and heavy media support to streer more funds their way. In general, what I'm refering to is the so-called "press release science", unfortunately endemic to so many other fields besides climate. And finally, refering to the following quote from your bio section: "I'm still yet to meet a skeptic argument that is even vaguely convincing." I would suggest looking at some arguments that come from people that don't exactly fit the typical skeptic stereotype you describe, for example take a look at this list and the following scorecard on the same website
    Response: Love those quotes from Churchill. I must confess, I'm not particularly impressed with Warwich Hughes' climate change page which reads a lot like my Skeptic Arguments page (except mine is more comprehensive :-) His scorecard is interesting - if I have more time after maintaining this site (and responding to your comments), I'll give it a closer look.
  7. All of the conclusions you make in your rebuttal of the skeptics argument are valid only if the Milankovitch cycles (which as you note provide relatively weak forcing) are indeed the sole cause for this whole process. This seems like a big assumption to me and I don't think the science behind that has been settled. Most of people sort of automatically assume it, but there are number of scientists starting with John Imbrie (the guy who led the whole CLIMAP effort and published the infamous Ice Ages: Solving the Mystery) that say Milankovich cycles (Earth's orbital variations and such) seem to explain only 50-60% of the whole insolation variance. So, adjusting one's model only using insulation curves generated by orbital modeling as they do in the papers you mention seems unjustified to me. In essence, the authors of the above papers precondition themselves to look only for models that fits their believes (that are only limited to Milankovich cycles as a driver). There are many other additional hypothesis that also make sense even though their quantification is not as simple as just writing an orbital mechanics models which is all nice and simple with nice math functions. A major examples for additional forcings on these time scales include changes in the solar irradiation due to the long-term manifestations of the solar activity that are ought to be much bigger that what we've observed with satellites for the past 20 years (I refer to the TSI measurements) and are not only related to the TSI, but to things like the solar diameter, the solar wind and its interactions with Earth's magnetic field and many other process on the Sun and inside the Earth's core. Many things in the Solar System seem to work in synergy. So, that many cycles and superpositions of cycles of completely different physical processes external or internal to the Earth's climate have similar length and appear as if only one factor is at work when in fact there are several. I acknowledge that there is the Occam's razor that advocates simplicity, but I don't necesesarily think it is the best approach when we are considering Earth's climate and the near-Earth environment. So, I wasn't really asking about the lags, but whether we can even begin to consider that these lags mean anything. As far as the error bars, I was asking for the errors of the reconstruction models that create those curves on the graphs you show. The lines only follow the positions of the 50% quantile of each model output point but tell us nothing about its possible range (due to original measurement errors and other uncertainties).
    Response: There's still a lot to be worked out re the whole mechanism of deglaciations. For example, there are various theories on what causes the CO2 increase after temperature increase, the most accepted theory being degassing from the deep ocean. I've read of theories that the 100,000 year cycle is caused by solar variations rather than orbital changes although the Milankovitch theory seems to be more established and confirmed by at least several papers I've read. But the main point of this page is to answer the argument that "the CO2 lag debunks anthropogenic global warming". The current scientific understanding of the CO2 record (and the papers quoted in citing CO2 lag) state that the CO2 lag confirms the warming effect of well mixed atmospheric CO2.
  8. This discussion goes on as if the only evidence we have to decide whether CO2 has a warming effect is the paleoclimate data. That's a very, very narrow perspective. What everyone needs to appreciate is that we have fundamental physics and really, really extensive laboratory analysis of the absorption spectra gases alone and in combination, at all sorts of temperatures and pressures. You can look up the raw data on HITRAN at and you can read the conclusions drawn from this raw data about the greenhouse effect at, e.g. Ray Pierrehumbert's free access draft of his "Climate Book" This is a university level physics textbook, not aimed at the general public. If you need more basic accounts of how GHGs absorb infrared, you can check out where Dr. Pierrehumbert is an active contributor. I'm linking to the academic text just to point out that belief in CO2 being a greenhouse gas, able to *cause* warming as well as respond to warming, is built on over a century of physics and lab analysis, and really, really NOT just on a few graphs taken from ice cores and put up on the screen by Al Gore. Way too much online discussion has treated this as if the whole line of reasoning rested solely on the paleo graphs and nothing else. To sum it up: temperature changes do indeed drive CO2 changes, *and vice versa*. The positive feedback between the two accounts for how ice age terminations get moving so much faster than the very gradual Milankovic forcings. The feedbacks don't run away forever because, for one, the carbon dissolved in the ocean is not infinite, the ice albedo feedback runs out when the glaciers and sea ice have retreated, etc.
    Response: Thanks, very pertinent comment and the link to Pierrehumbert's page is useful, particularly the latest draft of his upcoming Textbook on climate. Down the track, I hope to update this page fleshing out the point that CO2 warming is not dependent on ice core records but on fundamental physics (yet another on the to-do list :-)
  9. I have two questions regarding this "CO2 lags temperature" argument. You say that the Milankovitch cycle is to weak to explain the big temperature difference and that it requires strengthening through energy absorption by means of CO2. How do we know that CO2 is the main cause and not something else, e.g., the change in Earth's albedo due to ice and snowcover ? Also you say that it is not fully understood how oceans give up CO2. What about the reverse, the removal of CO2 from the atmosphere when the Milankovitch cycle drives the temperature down ? Hope you have time to answer these.
  10. This idea that Malinkovitch needs CO2 feedback to do the job is clearly false. Since it relies on a WATTS-PER-SQUARE-METRE model which is a light-and-air-only model. If we allow for the accumulation and decumulation of joules in the planet and the oceans then it is the factor of TIME ALONE that needs to be taken into account and not this sideshow of CO2-feedback. We ought to be looking at a model which relies on STRATA AND HEAT BUDGETS. Not on WPSM. The WPSM model is a first draught that people came up with looking through telescopes. They couldn't see anything else so they imagined the whole thing could be determined by spectroscopy alone. But what we are talking about is the accumulation and decumulation of joules. Another thing that these WPSM models fail to take into account is the distance travelled through the atmosphere. The stratosphere ends about 50km up in the air. But that doesn't mean that a "ray" of light hitting the stratosphere has to travel only 50km. This is only true at the equator and at high noon. And this is important since the climate guys talk as if only greenhouse gas and ozone can attenuate this radiation. But all gasses inhibit radiation and a lot of this radiation has a very long way to go. Not taking into account of this and failing to think about ACCUMULATION and DECUMULATION of joules over many decades and years is a fatal flaw to these climate models.
  11. The problem with your comment birdbrainscan is that its already part of the armchair hypothesis so it can scarcely be included as evidence. The armchair thinking goes like this: If the colour of CO2 is such that it absorbs a little bit of the infrared spectrum then industrial-CO2-release ought to substantially warm things up on a global scale. Now the fact is that there isn't a scrap of evidence for this thesis. One-step inductive armchair inferences don't always turn out to be true. This one has failed all experimental tests. CO2 might well COOL the temperature of the earth in the long run. An armchair inference with billions of dollars behind it is still an armchair inference.
  12. Actually, Milankovitch hypothesis requires much more than WATTS_PER_SQUARE_METRE. The thing is that GLOBAL year-average solar flux does not change more than 0.1% during those cycles. Climatologists like to plot amplitude of "Milankovitch forcing" at one spot on Earth - at latitude 65N, which does not represent in any way or form the GLOBAL change in incoming radiation. I find this very misleading, especially when the whole talk is about GLOBAL warming. For the Milankovitch to have any effect on Earth, climatologists have to use a hidden assumption that Nothern Hemishpere controls the whole climate by having some sort of "rectifier effect". So far this rectifier has not been identified, and ony speculations exist that it has something to do with more land in NH than in SH, and maybe with Arctic ice having contact with land (Greenland etc).
  13. birdbrainscan wrote: "What everyone needs to appreciate is that we have fundamental physics and really, really extensive laboratory analysis of the absorption spectra gases alone and in combination, at all sorts of temperatures and pressures. You can look up the raw data on HITRAN at and you can read the conclusions drawn from this raw data about the greenhouse effect at, e.g. Ray Pierrehumbert's free access draft of his "Climate Book"" I am familiar with this book, it is really a university level physics textbook, under which I mean "entry level". One needs to realize that the explanation of GH effect inherently relies upon so-called "atmospheric lapse rate", to link the height of "effective emission layer" with surface temperatures. One really needs to realize that so-called "lapse rate" must be an average of all atmospheric structures and weather patterns over the whole globe and from ground up to the whole troposphere. One needs to realize that the atmospheric patterns include turbulent boundary layer, global circulation patterns (Hadley, Ferrel, and polar cells), jet streams, hurricanes and other tropical depressions. More importantly, the lapse rate is strongly affected by moisture, which, in turn, is strongly affected by sea temperature. What is more important is that the moisture tends to condense into clouds under certain atmospheric/aerosols conditions. The laps rate ("moisture adiabate") tends to DECREASE with higher moisture content providing a negative feedback. Clouds also provide negative feedback by reducing insolation. Needless to say that all of listed processes occur under strong non-isotropic turbulent conditions, and are way beyond the reach of any direct computer modeling. As result, either a hand-made parameterizations have to be used, or parameterizations of experimental data. Given the spatio-temporal complexity of atmospheric patterns, data from few weather balloons cannot be seriously considered as a good representation of average atmospheric structure. The reference to HITRAN/MODTRAN serves no purpose for this discussion since the code uses a pre-selected fixed MODEL of atmospheric profile. In MODTRAN, there are 84 different models for atmospheric profiles; each gives different result for amount of OLR and surface temperature. So, what would be your selection of models across the globe to include into a global greenhouse model? How objective or subjective it could be? As you see, the "fundamental physics" of absorption spectra or two-stream Schwarzschild equations are not all the sophistications you need to build a model of GH effect and calculate its amplitude.
  14. Tekhasski, you sure can pile on the jargon but the basic argument is not affected by what you or GMB are saying: sunlight comes in with a small amount of long-wavelength infrared (so does not get absorbed so much by CO2, methane, NO2, etc.), gets absorbed, then tries to head out again as blackbody radiation, which is mostly in the long-infrared range and is strongly absorbed by the accumulating CO2, methane, NO2, etc. in the atmosphere. No matter what the atmosphere is doing, if you add heat you get warming. You don't need a PhD to understand that. The main outcome of the above research is to suggest that heating of the planet causes more carbon dioxide in the atmosphere (with some delay). We already know that increased carbon dioxide causes warming, so this means that the warming will be amplified by increased CO2 emission from the oceans. GMB, everything you are saying has already been taken into account in the current climate models. Climatologists have been out of their armchairs for decades now; where are you sitting?
  15. Nice personal attack Farmer but it added nothing to this discussion. Your Comment "No matter what the atmosphere is doing, if you add heat you get warming. You don't need a PhD to understand that." makes no sense in this context. There is no heat being added unless you are talking about variation in Solar output. The warming is supposed to be the result of Earth holding on to more heat and releasing it more slowly. The Earth is not a Black body radiator, but that doesn't even matter because CO2 isn't a big absorber of black body radiation at this temperature. Or this comment "We already know that increased carbon dioxide causes warming, so this means that the warming will be amplified by increased CO2 emission from the oceans." This is simply not correct. We think it should work this way, we have some theoretical reason to believe it should. But, it has rather badly failed the experimental test so far. In addition if your assertion were true this would be a positive feedback loop that is clearly not present in the Earth's paleo record. If the climate really worked this way the Earth would be vastly warmer than it is and would never have had any ice ages because once the CO2 got high, as it has many times in the past, it would cause a warming spiral. The idea that you can "take into account" in models affects that we simply don't understand is absolutely silly.
  16. What if CO2 is meaningless? The graphs show measured concentrations of CO2 for the past how many years? Modern direct measurement of gases using a bench and means of interpreting past CO2 are not going to give the same results. Even trapped gas pockets in ice suffer from osmotic action. Past climates are mostly guesswork. As Wondering Aloud points out "it would cause a warming spiral." but that did not happen. The graph shows 450K years, ALL of which were within the oscillations of an ice age. We assume that this is an interglacial period. What if it isn't? How do we know that the planet isn't returning to Earth Normal or Earth Mean temperature? The fact is, we don't know.
  17. Quietman 'How do we know that the planet isn't returning to Earth Normal or Earth Mean temperature?' Are you seriously proposing a new theory - that the Earth has a memory? Do you have a mechanism? Or a 'setting' to which this 'memory' is adjusted? Is there any peer-reviewed literature as a source? CO2 clearly cannot be meaningless, it has long been known to be infra-red active and remains resident in the atmosphere for a long time, from memory ~33% remains after one hundred years and 20% after a thousand years, but there is a long tail meaning that some will remain for tens of thousands of years, causing significant warming. Inevitably, this alone will affect the net heat balance of the Earth. Of course CO2 is NOT the only GHG and as temperature increases, so does the water vapour, which acts as a positive feedback amplification. But while water vapour is a stronger GHG than CO2, it does not remain in the atmosphere for long. The source of the excess CO2 is explained by the shifting isotopic ratio of the atmospheric carbon. From this it is known to originate from non-biological sources - i.e. fossil carbon: coal, oil & gas. Regarding CO2, the Mauna Loa CO2 readings overlap ice core data during the period 1959-1978. The CO2 readings obtained match perfectly during the overlap. AFAIK, the oldest ice cores are ~ 1000 ky old. Here's one with the source data and references - so that YOU can check its authenticity! Image:Carbon_History_and_Flux_Rev_png and Image:Carbon_Dioxide_400kyr_Rev_png Sorry, but I couldn't locate a version in the p/r literature. I've seen them before, it's just that I couldn't find any. We are clearly performing a global experiment and no-one can be absolutely certain as to the precise outcome, but if it does all go dreadfully wrong, the trouble is that we are INSIDE the test-tube! It would therefore be a really good idea to heed the scientists and stop trying to light the Bunsen burner! Let's cut-back on the use of fossil-fuels, through improved technology, energy conservation & efficiency and renewable energy generation. The economic argument that carbon taxes will damage the US economy is bogus. “As Congress prepares to debate new legislation to address the threat of climate change, opponents claim that the costs of adopting the leading proposals would be ruinous to the U.S. economy. The world’s leading economists who have studied the issue say that’s wrong” We owe it to the next generation and generations to come to hand over the Earth in the same condition as it was when we received it. Sadly, this will not be the case.


    Note - usually cites his sources if you want to track down the original studies where he get the data from.

  18. Quietman, Another thought: Those graphs in my previous post show a rapid upward acceleration of CO2 in recent decades, one that matches the accelerated warming. If what you suggest were true: namely that Earth is [your hypothesis] 'returning' to 'normal', then one would expect an ever decreasing asymptotic approach. Instead, what is seen in the second graph is a rapid departure upwards from the upper bound historic values - the exact reverse of what is expected. Image:Carbon_Dioxide_400kyr_Rev_png Oops! your theory is shot full of holes!

  19. During a glacial period (between interglacials), the graph shows many changes in temperature direction, trend up, followed by trend down, followed by trend up, followed by trend down and so on for many cycles. If the theory is that a trend up causes atmospheric carbon dioxide to increase which adds to warming, why, with atmospheric carbon dioxide level higher than it had been during the temperature increase, would the temperature stop going up and go down instead?
  20. ScaredAmoeba 1. I said "what IF. (food for thought). There is a CO2 feedback effect and a contribution by AGW regardless. 2. Not one single graph that I have seen matched the rise in CO2 to the rise in temperature without some serious manipulation. Show me a graph of rising surface temperaturs that is based solely on rural weather stations and a chart of CO2 with a matching slope. You won't be able to.
  21. ScaredAmoeba Re: "The economic argument that carbon taxes will damage the US economy is bogus." This is an unknown. It could go either way depending on exactly who is taxed and how much as well as who is hired and how many. If we are heavily taxed to pay for green products made in India we loose. If we are lightly taxed for production within the US by non-illegals we win. Can you assure us that the latter will be the case rather than the former?
  22. Dan Pangburn Very astute observation. Another look at those graphs will also show that temperatures fell dramatically when CO2 was at it's peak.
  23. In johns skeptic of the week article it says "Moreover, the Earth has experienced no discernible temperature increase since 1998, nearly nine years ago. Remember, too, that the atmosphere is approaching CO2 saturation--after which more CO2 will have no added climate forcing power." This I don't understand. Is this at all credible?
  24. lest we forget.
  25. If you are refering to the saturation idea, credible yes, possible yes, right? I just don't know. It does look to me like most of the forcing predicted from a doubling of CO2 should have already occured unless there is a big time lag in the system that is un accounted for. this is why I asked on other threads if there was a lag of perhaps 30 years we didn't have identified. Without it we are down to only those large, but not now apparent, feedback numbers or a relatively small total signal on the order of 1 C.

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