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  1. Nice post, Gavin. I had not heard of this issue before. It does seem to be very similar to the MSU satellite data issue. I still run into people who argue that satellite data shows no warming, at which point I have to go into my monologue about the corrections to Christy’s data. Was the Lyman paper a deliberate attempt to discredit AGW like M&M, or honest research that was subsequently pounced on by skeptics like Caillon’s ice core paper?

    [Response: Definitely the latter. As I stated above, they couldn't have been aware of the sensor problem and they updated their analysis as soon as it was discovered. -gavin]

    Comment by Reasic — 18 Apr 2007 @ 2:43 PM

  2. This is great news Gavin. The Lyman et al paper has been a bit of a stumbling block, something that flew in the face of what we would expect to happen, and I’m glad that it has turned out to be something as simple as faulty equipment. With this one now sorted, the contrarians will have to find something else to hang their hat on.

    Comment by Joe White — 18 Apr 2007 @ 2:58 PM

  3. How likely is it that we’ll be able to correct for the mistaken depth estimates?

    When the Hipparcos satellite was launched, it had severe orbit problems, and this was big trouble for its onboard photometers. But by comparing the satellite photometry to ground-based observations, it was possible to “calibrate” the satellite photometers, finally yielding very high-quality results (I was part of that effort). Any chance a similar strategy might recover good data from Argo?

    Comment by tamino — 18 Apr 2007 @ 3:29 PM

  4. Thanks for the quick posting of this. I’ve been waiting for a simple explanation to Lyman’s report (something zealously promoted by some skeptics) for a while. Instrumentation (especially new equipment) should always be suspect when results seem counterintuitive.

    Comment by Ken Winters — 18 Apr 2007 @ 3:30 PM

  5. More info available; first hit is from the Argo site on this subject.

    I wonder who else may have bought from the bad batch and installed them in even less accessible or more life-critical equipment.

    Posting just the Google search since many hits are PDFs; people may prefer to look at Google’s HTML versions.
    http://www.google.com/search?q=Argo+float+pressure+transducer+error&start=0

    Comment by Hank Roberts — 18 Apr 2007 @ 3:44 PM

  6. Thanks gavin,

    When I started to look at the global warming issue my initial inclination was to look at Ocean data, since it’s such a huge heat sink, relatively constant backscatter, and potentially the source one would want to measure with as much accuracy as possible.,Also, Seemed to me like it was a “natural” filter of noisy data.( does that make sense?).

    The sea level response to heating looks nearly linear over the past century . The air/land temp record looked to be rather noisy. Having both signals is nice, but from one perspective focusing on the sea level/temp metrics is much less susceptible to local chaotic distruptions ( hey it was cold this month in New york).

    Compared to air temps. the signal from the ocean appears to be much cleaner. Although, from a publicity standpoint, it air temp that gets people interested.

    I read about the Laymen report on Pielke’s site. The simultaneous cooling and sea level increase made no sense, from a physics standpoint, prima facia. So one would expect some kind of instrumentation correction. ( no hypothesis faces disconfirmintion in isolation).

    Anyways, if you had a $1 dollar to spend on instrumentation. would you spend it on an ocean temp sensor, sea level sensor? or air temp sensor?

    Comment by steven mosher — 18 Apr 2007 @ 4:00 PM

  7. Gavin

    You fail to mention that the corrected data show no temperature increase, still a problem for the models, no?

    [Response: Not really, having flat trends for a couple of years at a time is neither unprecedented nor unusual. Natural variability hasn't been banished after all. But, I think it's better to wait for the definitive time series (which we don't yet have). Right now all analyses show significant long term warming, just like the models suggested they would. -gavin]

    Comment by B Buckner — 18 Apr 2007 @ 4:07 PM

  8. Gavin, I think it would be worth adding to the post 1) the main reason why there was so much doubt about the Lyman et al results (the unphysical melt amounts for 2003-5), 2) the expected role of GRACE in obtaining a reliable result, 3) the fact that the ARGOs don’t measure the deep oceans, and 4) that it’s inappropriate to take the remaining ARGO data (shown in the Lyman et al correction to be essentially flat for the last two years) and draw any conclusions about ocean heat content trends for that period. This latter point is especially important since the usual suspects are already spreading the idea that the correction is somehow additional confirmation of lack of warming.

    Comment by Steve Bloom — 18 Apr 2007 @ 4:10 PM

  9. Should not the climatologist’s (and RC’s) response to the question, “Are the oceans warming?” be: “Likely, but we don’t know for sure.” Or, “maybe; maybe not.”?

    [Response: No. There is good evidence that the oceans warming on the long term. Look at the Ingleby and Palmer presentation linked to above - it doesn't matter if don't use the XBTs or the ARGO data. I would say that it's 'very likely' (on the IPCC scale) the oceans are warming. - gavin]

    Comment by Rod B. — 18 Apr 2007 @ 4:23 PM

  10. Re #3: Tamino, let me first state how excited I am to find a climate subject about which I know more than you, however temporary past experience would seem to indicate that condition is likely to be. :) The ARGO folks seem to think their data is correctable, but according to the Lyman et al correction the XBTs (which are needed for any sort of long-term trend analysis) are a different story. Even the corrected ARGO data will have potential remaining problems, the obvious one being the lack of coverage of the deep oceans, plus of course additional calibration problems may remain. It appears that any definitive results will have to rely on GRACE (which as I understand it, being a new instrument itself will require another couple of years of data in order to make sure its results are self-consistent).

    Re #6: There was a reconciling hypothesis. The problem was that it called for an “unphysical” amount of recent melt (in direct conflict with other obs). To be fair, Lyman et al did note that this was a shaky idea, and looked forward to GRACE resolving all in a couple of years.

    Re #7: Et voila.

    [Response: I'm not sure about your statements re: GRACE. Those instruments measure gravity anomalies (and hence mass) and so are will be great at measuring the loss of ice from the ice sheets etc. Combined with the altimeter data you should be able to back out the component of sea level rise associated with thermal expansion. However, while this is an important check on the ocean heat content data, it isn't a substitute for it and GRACE will not 'resolve it all' in a couple of years time. -gavin]

    Comment by Steve Bloom — 18 Apr 2007 @ 4:33 PM

  11. RE 2

    You wrote:

    “This is great news Gavin. The Lyman et al paper has been a bit of a stumbling block, something that flew in the face of what we would expect to happen, and I’m glad that it has turned out to be something as simple as faulty equipment. With this one now sorted, the contrarians will have to find something else to hang their hat on. ”

    When people write things like this I think of two words: confirmation bias.

    ” The Lyman et al paper has been a bit of a stumbling block, something that flew in the face of what we would expect to happen”

    An observation is NOT a stumbling block unless you have an agenda. A scientist puts up a hypothesis. The task is then to CONFIRM/DISCONFIRM the hypothesis. One does not profess an interest in certain outcomes. It’s
    objective. It’s science. Not religion. not politics. Just the facts maam. From one perspective( popper, you can wiki him) Science seeks observations to prove theories wrong. theories are made STRONGER by facing tough tests. I’ll explain a bit more..

    2+2=4 is not a scientific hypothesis. Do any experiement you like, I won’t give up that knowledge/power. This sentence is observationally vacant. Let’s take another extreme.

    For the religious, “god created the world” cannot be disconfirmed. Everything tells them their belief is true. Evidence to the contrary is a test of faith. stumbling block.

    So the scientist is not interesting in things that are observationally vacant ( 3+3 =6) or in things that cannot be DISCONFIRMED by observation ( an invisible non measureable force made the world). They are intersted in things that can be Proven wrong. They are intersted in things that fly in the face of expectation.

    Then you wrote:

    “and I’m glad that it has turned out to be something as simple as faulty equipment.”

    Well, you cannot be glad of that. Let me reframe this. These scientists spend millions of dollars to take the temp of the ocean. And look. THEY SCREWED UP. Now, they ask me to trust the temp from land systems?
    Now they ask me to trust computer models. The scientist must master the job of being the fallible priest.
    Pointing out the errors of another scientist, while claiming infallibility for yourself, does not work from a rhetorical standpoint.

    See how that works. The issue is science progresses by continual failure. by a belief in the falibility of human intellegence. Retest, duplicate the results, open source, don’t pre judge, be willing to throw your theory to the winds. If you are not open to being wrong, then you are wrong.

    Finally:
    “With this one now sorted, the contrarians will have to find something else to hang their hat on”

    Yes, this is a GOOD THING. You want them pounding and questioning and improving the grounding of the belief. The contrarians are GOOD for the theory, good for the science.

    So the sceptics will pound on ocean temp and then that will drive a better understanding of that area. And they will pound on land use,and that will drive a better understanding of that. And they will pound on the lack of understanding clouds, and that will drive…..

    YOU SEE? the DISBELIEVER drives the science. Science needs the disbeleivers. Otherwise it’s just scholasticism.

    [Response: It's generally not the contrarians who drive better understandings of the science, because most of the contrarian points are completely irrelevant and are used as rhetorical, not scientific, points. If, however, you go to scientific meetings like AGU and you sit in on a session where there is some conflict (real or apparent), what you'll see is not contrarians vs establishment, but a whole bunch of skeptical individuals trying all sorts of ways to reconcile the different data. This is certainly the case for the ocean heat content discussion, and the GW/hurricane links, the aerosol issues etc. The 'contrarians' as you see them generally play the role of Greek chorus - just adding to the background noise. They are (with a couple of exceptions, Lindzen having been one in the past) completely irrelevant to the actual practice of science. - gavin]

    Comment by steven mosher — 18 Apr 2007 @ 4:52 PM

  12. hi gavin

    you wrote:

    “It’s generally not the contrarians who drive better understandings of the science, because most of the contrarian points are completely irrelevant and are used as rhetorical, not scientific, points. If, however, you go to scientific meetings like AGU and you sit in on a session where there is some conflict (real or apparent), what you’ll see is not contrarians vs establishment, but a whole bunch of skeptical individuals trying all sorts of ways to reconcile the different data. ”

    I think you misunderstood. we are talking about the same thing. Scepticism has always been percieved in these two modes. one mode is merely rhetorical. the other pragmatic. I’m talking about the pragmatic mode. Namely, people looking at ARGO data. characterizing them as contraians ( the polite version of denier) isn’t really factual now.

    you go on:

    “This is certainly the case for the ocean heat content discussion, and the GW/hurricane links, the aerosol issues etc. The ‘contrarians’ as you see them generally play the role of Greek chorus – just adding to the background noise. ”

    Is there some new issue on GW and huricanes? Is somebody somewhere claiming that GW will lead to fewer or less strong hurricanes? WHAT? Utter nonsense! It is not logicaly possible. the link between GW and hurricanes is settled science. it’s like the laws of newton, it’s like F=ma. Nobody could argue that GW leads to fewer hurricanes. don’t they know that 2+2 =4? these sceptical greek chorus idiots; are they talking about wind shear, or long term cycles. Hmm is there a test we could set up.. maybe a hypothesis.. a prediction.. and then test, yes test the theory?

    Dang, they should shut up and get on with the program. ( called normal science). We have code to write.

    You went on:

    “They are (with a couple of exceptions, Lindzen having been one in the past) completely irrelevant to the actual practice of science.”

    The great OZ would not appreciate the irony of the following.

    “Thomas Kuhn is most famous for his book The Structure of Scientific Revolutions (SSR) (1962) wherein he argued that science does not progress via a linear accumulation of new knowledge, but undergoes periodic revolutions that he called “paradigm shifts”, in which the nature of scientific inquiry within a particular field is abruptly transformed. In general, science is broken up into three distinct stages. Prescience, which lacks a central paradigm, comes first. This is followed by “normal science”, when scientists attempt to enlarge the central paradigm by “puzzle-solving”. Thus, the failure of a result to conform to the paradigm is seen not as refuting the paradigm, but as the mistake of the researcher, contra Popper’s refutability criterion. As anomalous results build up, science reaches a crisis, at which point a new paradigm, which subsumes the old results along with the anomalous results into one framework, is accepted. This is termed revolutionary science. In SSR, Kuhn also argues that rival paradigms are incommensurableâ??that is, it is not possible to understand one paradigm through the conceptual framework and terminology of another rival paradigm. For many critics, this thesis seemed to entail that theory choice is fundamentally irrational: if rival theories cannot be directly compared, then one cannot make a rational choice as to which one is better.”

    RELEVANCE is a social/politocal determination. Predictive power is what matters. So when you say irrelevant that merely recapitulates a social structure

    [Response: I specifically make a distinction between skepticism - which every good scientist has in spades, and contrarianism which has been the mainstay of people like Singer, Crichton, Carter, and now Lindzen. The former is vital to the scientific enterprise, the latter is about as useful as promoters of perpetual motion machines to the understanding of particle physics. Who ever called the people looking at the ARGO data contrarians? We're not talking about paradigms here, we're talking about rhetorical devices. With respect to GW and hurricanes, I'd ask you to point out anything I've ever written that said that that issue was settled. If you want to converse seriously here, drop the snark. -gavin]

    Comment by steven mosher — 18 Apr 2007 @ 5:52 PM

  13. This is not just a lesson about changes in ocean temperature. It is also about the scientific process and how well it is working.

    1) A paper was published in a peer reviewed journal with data that was viewed by AGW denialists as proof of their viewpoint.

    Data contrary to the consensus does make it to print. AGW denialists, please, stop arguing it doesn’t.

    2) The self correcting nature of scientific research is apparent in this story. The process works and it is not corrupt as the denialists falsely report.

    Thanks for a great post.

    Comment by Petewsh61 — 18 Apr 2007 @ 5:54 PM

  14. http://oceans.pmel.noaa.gov/Pdf/heat_2006.pdf

    “The OCHA estimate made using all data (thick solid line), including spurious float profiles, shows an apparent cooling of about 48 Ã� 10^21
    J (48 zeta joules) from 2004 through 2006. This erroneous cooling arises because of the increasing fraction of spurious profiles in the Argo data stream produced by the WHOI SOLO floats. Another estimate using all data except the spurious float data (thick dashed line) suggests much less cooling, only about 25 zeta joules.”

    Much less cooling, but cooling none the less.

    Also, how does this new information change the point made in the discussion from the original paper?

    “This work has several implications. First, the updated time series of ocean heat content presented here (Figure 1) and the newly estimated confidence limits (Figure 3) support the significance of previously reported large inter annual variability in globally integrated upper-ocean heat content [Levitus et al., 2005]. However, the physical causes
    for this type of variability are not yet well understood. Furthermore, this variability is not adequately simulated in the current generation of coupled climate models used to study the impact of anthropogenic influences on climate [Gregory et al., 2004; Barnett et al.
    2005; Church et al. 2005; and Hansen et al., 2005]. Although these models do simulate the long-term rates of ocean warming, this lack of inter annual variability represents a shortcoming that may complicate detection and attribution of human-induced climate influences.”

    Comment by Ellis — 18 Apr 2007 @ 7:12 PM

  15. Re #13 — definitely agree. Although it clearly shows that the study of global climate is a very young science. Given the data failures in both the satellite and now oceanic data, I would not trust any predictions at this time. Need a lot more of (2) “correcting nature of scientific research.” This “oceans cooling – not” is terrible news for the credibility of AGW.

    It’s great that this work is being done, but it’s going to be years (if not a decade or two) before definitive conclusions can be made.

    Comment by Ian Rae — 18 Apr 2007 @ 7:24 PM

  16. I’d like to extend Steven Mosher’s point, but goes further. When looking at data phenominologists are at a severe disadvantage because they only look at the numbers. Scientist, on the other hand, compare the data to their theoretical model. When there are major differences, before shooting wildly, we (yes, even the fuzzy took classes) look for consistency. A good scientist is extremely reluctant to accept data that does not conform to her understanding of reality and will test such non-conforming information because the alternative is that the model, built and tested on a large body of data has much more support than a single set of measurements.

    Comment by Eli Rabett — 18 Apr 2007 @ 7:33 PM

  17. gavin> “But that intuition is also very good at detecting results that just don’t fit. When that happens, scientists spend a lot of time thinking about what might be wrong – with the data, the analysis, the model or the interpretation.”

    That implies that ‘scientists _do not_ spend a lot of time thinking about what might be wrong – with the data, the analysis, the model or the interpretation’ if those fit their intuition. While that is probably natural, it seems like a potential trap to avoid.

    Is anyone looking for what might be wrong with the data that does fit the current model?

    Comment by Steve Reynolds — 18 Apr 2007 @ 8:00 PM

  18. re 14:

    Eli it’s actually a bit more complicated than that. because science is not math, because it is not true by definition, there is ALWAYS some tension between “theory” ( a dubious term) and observation. In the face of this tension humans have several coping mechanisms.

    1. Accept the prevailing socially accepted norms, follow current theory and engage in behavior to make the non conforming data go away.

    2. Accept the data, but work to make it consistent with accepted theory by introucing ancillary hypotheses.

    3. Accept the data, reject the theory and suggest a replacement paradigm.

    4. Withhold judgement and do so more study.

    Throughout the history of science one could probably find examples of each of these behaviors being successful. None is inherently more rational than another. But you could submit a proof.

    Comment by steven mosher — 18 Apr 2007 @ 8:26 PM

  19. Since this paper was heavily trumpeted by Pielke et al as ‘proof’ of the failings of climate models, it’s worth reviewing their comments:

    “The recent dramatic cooling of the average heat content of the upper oceans, and thus a significant negative radiative imbalance of the climate system for at least a two year period, that was mentioned in the Climate Science weblog posting of July 27, 2006, should be a wake-up call to the climate community that the focus on predictive modeling as the framework to communicate to policymakers on climate policy has serious issues as to its ability to accurately predict the behavior of the climate system.

    No climate model that we are aware of has anticipated such a significant cooling, nor is able to reproduce such a significant negative radiative imbalance. “Meaningless distinctions between “projections” and “predictions” will be unlikely to convince consumers of climate models to overlook experience that does not jibe with modeled output.”

    Roger Pielke also claimed that the IPCC should have modified their report to include the results.

    The list of ‘climate skeptics’ who widely claimed that the paper was proof that the models were wrong is long: Patrick J. Michaels (American Spectator), Dennis Avery (Orange County Register). The conclusion so far? Despite long searches for ‘fatal flaws’ in modern climate models, a handful of contrarians still have no supporting evidence.

    Will Pielke&Pielke now write an article about the success of climate models in predicting ocean warming over the past few decades? Will they even write a retraction of their previous claims?

    Comment by Ike Solem — 18 Apr 2007 @ 8:37 PM

  20. “There is good evidence that the oceans warming on the long term. ….. I would say that it’s ‘very likely’ (on the IPCC scale) the oceans are warming. – gavin]”

    Well, that’s pretty much what I said, with a little wiggle with emphasis. My point is that all of the anamolies with measurements showing an increase are all rationalized away with almost a wave of the hand. The anamolies with measurements showing cooling are highlighted and patently justified. Maybe in reality it all might be true. But on the surface it sounds way too pat, and borders on incredulous — at least in scientific circles. (Might work just fine in political circles.)

    Comment by Rod B. — 18 Apr 2007 @ 9:23 PM

  21. I blogged on this here. My main point is similar to yours about how new papers must stand the test of time. I said that one must view “revolutionary” results suspiciously, esp. if they overturn a claim that is accepted with high confidence by the scientific community. Such results will be retested by the scientific community, and if they are right, such retests will verify the results.

    Comment by Andrew Dessler — 18 Apr 2007 @ 10:03 PM

  22. Re: Steve Reynolds,
    You remarked that “Is anyone looking for what might be wrong with the data that does fit the current model?”

    Clearly many are, as there is a damn good paper (and reputation) in store for the individual(s) who brings the AGW house of cards crashing down. However, I imagine you will find its foundations are a tad stronger than you seem to think.

    Comment by Zeke Hausfather — 18 Apr 2007 @ 11:22 PM

  23. Gavin, thanks for this post, it is really helpful in understanding this specific point.

    I’m sure it’s not lost on you that you are describing here a textbook example of a paradigm leading scientists to the rejection and reinterpretation of an anomaly that appears to contradict the paradigm.

    I am reminded very strongly of the first scientific paper I ever wrote while a UROP student at MIT on “apparent super-luminal motion”, which is to say astronomical observations that seemed to indicate that two celestial objects were moving apart faster than the speed of light. The astrophysics community was loath to accept this result, since overturning Special Relativity would have required either going back to the Newtonian mechanics that had many unexplained anomalies that led to relativity theory in the first place or else developing a better framework than Einstein had (not real likely).

    Eventually, of course, the mystery was solved and the observations were reconciled with the paradigm – rest assured relativity is safe. The big difference (admittedly of degree) is that Special Relativity had already passed many rigorous falsification tests of a kind that climate models have not (readers of my prior posts will know this is a monomaniacal obsession of mine)

    The practical question that I think this leads to is how do we develop confidence that we have found all of the material measurement error and properly eliminated it? If a measurement error of this severity has escaped notice up until now, how do we know that there are not other undiscovered errors of similar or greater import? If our stopping condition is conformance with the model-driven paradigm, and the models have not been subject to sufficiently rigorous falsification tests, this becomes circular.

    Clearly there is no absolute answer to this question – there is always some philosophical possibility of error in any measurement – but I’m asking it in a spirit of practicality. That is, this seems like a pretty huge set of adjustments that in retrospect look kind of obvious, and we are conforming to a set of models that I think any fair-minded observer would agree are not at the stage of maturity of, say, Special Relativity.

    Thanks,
    Dana

    [Response: As you say, there always remains the possibility that any and all measurements are contaminated in some way. So you need to look at a wide range of indicators all of which have independent sources of error (for instance, errors in satellites are not likely to be correlated with errors in weather stations or ocean buoys) and see if your understanding matches all of the different aspects that you expect from the theory (stratospheric cooling, ocean warming, Arctic melt, poleward and upward expansion of biomes etc...). There is never going to be an absolute proof in the mathematical sense, and frankly we are never going to get to the confidence that we have in QED for instance. But the level of confidence we do have (having passed a whole bunch of tests) is enough to allow to project pretty confidently a lot of what's going to happen. - gavin]

    Comment by Dana — 19 Apr 2007 @ 12:11 AM

  24. re: #15
    “Given the data failures in both the satellite and now oceanic data, I would not trust any predictions at this time…. This “oceans cooling – not” is terrible news for the credibility of AGW…..but it’s going to be years (if not a decade or two) before definitive conclusions can be made.”

    This is throwing out the baby with the (ocean) water.

    1) Science doesn’t instantly discard huge masses of data, just because a few new results (especially new types of measurements):
    - disagree
    - disagree, then get changed, and converge into consistency with older data

    2) Surely, anyone who reads RC understands that it is easy to have jiggles in climate time series, and not just measurement errors, and it takes more than 3 years to yield a strong long-term conclusion in any direction.

    It is *really* exciting when new data contradicts older data, and turns out to be right, and leads to radical new hypotheses that evolve into strong theories (i.e., like Michaelson-Morley … Special Relativity). That’s a dream case!

    But it just happens far less than when new data that confirms old data, maybe filling in holes, or getting another decimal point. Most science works by successive approximations, not flying leaps.

    Comment by John Mashey — 19 Apr 2007 @ 12:28 AM

  25. Re #2. I don’t understand why one should one be glad about this correction – why should warming of the oceans be something to celebrate? Apparently, your Schadenfreude towards the contrarians is stronger than your concern about global warming. Wouldn’t it be best to keep your emotions out of the debate and try to avoid liking some results and disliking others? Like Gavin explained, it is very likely that science will correct itself.

    Comment by Matti Virtanen — 19 Apr 2007 @ 3:16 AM

  26. Gavin, I know this is only tangential to this thread but do you have any comment on the new paper by Vecchi and Soden in GRL, which Chris Landsea is promoting as evidence both that the recent increase in Atlantic hurricane activity is due to the AMO, and that global warming should reduce activity (because it increases windshear)?

    [Response: I have no knowledge of what Chris Landsea may be saying about the paper, but I don't see this paper as changing the picture significantly. Two points are relevant here, (1) our modeling of future changes in TC remains an uncertain area of the science. Nonetheless, predictions of increased potential intensity due to rising SST which rest on fairly fundamental thermodynamic arguments, remain robust, and I would refer you back to our discussion of this previously. Climate model predictions of changes in ENSO and the Walker circulation, upon which the conclusions of this paper with regard to possible changes in wind shear rest, remain far from robust for reasons we discussed here previously. In short, the Emanuel (2005) study continues to stand on its merit, and I don't see where this paper puts even a dent in it. We may have more to say about this paper in the near future. -mike]

    Comment by Bob Ward — 19 Apr 2007 @ 4:35 AM

  27. Great news this, eh! Another rotten apple thrown out of the barrel. As the satellite data’s errors get sorted, as the Argo float’s errors get sorted, as we recognise with increasing clarity the changes happening underfoot on the Antarctic ice sheets and elsewhere the picture does become clearer.

    I think (unlike some here) that we ARE able to place increasing trust in the models. Finding an error means it can be allowed for. It’s knowing nothing, or denying everything that are the dangerous positions to assume. It’s sad (but I guess inevitable) to see those with their heads in the sand (or in this case in a thermos flask!) using this correction as a reason to toss the baby out with the bath water. But I guess when they assume that posture they do make a nice target for the rest of us to expend our ammunition upon, eh!

    Comment by Nigel Williams — 19 Apr 2007 @ 5:32 AM

  28. I think it is a bit premature to hope that GRACE will help solve this issue; I have written about this here: http://fergusbrown.wordpress.com/
    and am taking the opportunity to shamelessly promote my own new blog on climate and similar matters.
    Sorry. *blush*
    I’d also be very interested to know what proper scientists think about the material on ocean circulation in the same article.
    Regards,

    Comment by Fergus Brown — 19 Apr 2007 @ 5:41 AM

  29. “Given the data failures in both the satellite and now oceanic data, I would not trust any predictions at this time….

    Why? In both cases, the predictions (models) were claimed to be shown to be bogus, while in reality it was the instrumentation that was broken.

    This makes me tend to be skeptical of new data which contradicts our current understanding of how climate works, rather than make me question that understanding.

    Comment by dhogaza — 19 Apr 2007 @ 6:56 AM

  30. Re #25. Matti, the celebration is not that the oceans are warming, but that the models are working. The models and paleoclimate data are the only handles we have on the potential effects of climate change–and the models are much better understood than paleoclimate. Thus, we may be able to bound risk at some reasonable level and that will be invaluable in deciding how we allocate resources toward mitigating the effects of warming. The contrarians may be objects of wrath from climate scientists, but they are also increasingly irrelevant. Does this make sense to you?

    Comment by Ray Ladbury — 19 Apr 2007 @ 9:11 AM

  31. re: #25

    No offense, but I find your comment somewhat counter-intuitive, a bit of a disconnect, if you will.

    The inference you seem to be making is that someone is happy data points to reinforcing the body of evidence regarding Global Warming. I would be willing to wager hard cash that there are few, if any, people that are concerned about Global Warming and the potential for harm it presents who would like nothing better than to have solid, irrefutable evidence it won’t be a problem.

    Comment by J.S. McIntyre — 19 Apr 2007 @ 10:00 AM

  32. Re # 17 Is anyone looking for what might be wrong with the data that does fit the current model?

    They should be. Competent, credible scientists are usually very self-critical, and always scrutinizing their data. And even if they aren’t as self-critical as they should be, their collaborators, post docs, graduate students, and technicians will likely also be scrutining the data – they all know that experimental results should be repeatable, both internally (in the lab that generated them) and externally (in labs that try to replicate them). And even if no one actually replicates the original experiment (which may be too costly or expensive), predictions generated from those results will likely be tested (esp. if the original results are important) and the new results should be consistent with the original results.

    And any scientist who works with electronic instruments knows that spurious results often arise (due to electronic noise, baseline drift, etc), so careful calibration and close analysis of the data is crucial. This point was driven home to me as a graduate student using a data recorder powered by rechargeable batteries. Half way through the experiment I kept getting a sudden sharp deflection of the recorder thermal pen, suggesting some previously unknown and dramatic physiological response by my experimental animals. My excitement was tempered by my skeptical graduate advisor who assured me that my results were “very unlikely.” Sure enough, the batteries in the recorder were not holding a full charge, and were dying in the middle of my experiment.

    Comment by Chuck Booth — 19 Apr 2007 @ 10:08 AM

  33. Re: data reliability

    Even statistical analysts like me have to be constantly alert to this. I can often prove that a statistically significant change has occured in the data. But this doesn’t mean there’s a significant change in the physical signal — it could be, or there may be a significant deviation between reality and measurement. This emphasizes the need to take a long, hard look at the data to establish its reliability and consistency.

    Comment by tamino — 19 Apr 2007 @ 10:39 AM

  34. Re # 9 Should not the climatologist’s (and RC’s) response to the question, “Are the oceans warming?” be: “Likely, but we don’t know for sure.” Or, “maybe; maybe not.”?

    For an issue of such importance, do you really think that response would be accepted by the press, or politicians, or the general public? I seem to recall a controversy in California years ago dealing with an earthquake prediction; if I remember correctly, seismologists predicted an earthquake that never occurred, and were severly chastized for being alarmist and scaring the public. Surely, any seismologist who detects rumblings deep in the earth and refuses to speculate on the likelihood of an earthquake in the very near futue would be severely criticized, as well?

    So, what ethical obligation do scientists have when it comes to informing the public (or not) about a possible natural disaster, be it global warming, an earthquake, flood, hurricane, disease outbreak, etc? Should they maintain a conservative, scientific skepticism and just shrug their shoulders and say, “We don’t know for sure if the disaster will strike…any prediction is just a guess…we’ll just have to wait and see”? Or should they give their best professional assessment, describing the threat and assigning a degree of confidence in their prediction?

    It seems to me the climatologist community has adopted the latter position.

    Comment by Chuck Booth — 19 Apr 2007 @ 10:54 AM

  35. “But that intuition is also very good at detecting results that just don’t fit. When that happens, scientists spend a lot of time thinking about what might be wrong – with the data, the analysis, the model or the interpretation. It generally pays to withhold judgment until that process is finished.”

    I think -just my opinion, no pun intended- that’s a very simplistic approach to scientists work. Sometimes, the results that do not fit are discarded, because they are not considered representative, because they do not follow other data collection standards, because they provide from other sources, etc. Sometimes, new hypothesis and conditions are added to the original theory to make that results fit. And sometimes, the results are just ignored because they don’t fit.

    Scientists are people, they make mistakes and sometimes, it’s hard to recognize your work might be walking on the wrong direction. And usually theere is a mass of followers that are ready to deny any objection made to the theory. There are indeed plenty of examples in Philosophy and History of Science.

    Not that this applies to GW research -or the rest of the psot-, but I don’t think reflects exactly how scientists work.

    Comment by SebastianDell — 19 Apr 2007 @ 12:09 PM

  36. Chuck:

    http://eqint.cr.usgs.gov/eq/html/eqprob.html

    Comment by Hank Roberts — 19 Apr 2007 @ 12:13 PM

  37. Something like that happen to me yesterday when I figured grades. I was multiplying .9 x total points for the A cut-off, etc., & came up with a odd-looking cut-off for the Bs. It caught my eye, and I redid the calc & got a number that looked right. Then I turned to my students and said, it’s very important to eyeball results to see if they look right, and also recalculate to see if they jive.

    The point is (Re #11), nn observation is NOT a stumbling block unless it looks wrong, based on what you know and expect. It has nothing to do with an agenda.

    GW believers would love nothing more than to find out they are entirely wrong. I keep thinking, when will I wake up from this unpleasant dream (made more unpleasant by GW-deniers — that really demoralizes me), and find out GW is not at all an issue in the real world.

    The people with an agenda are those who would deny facts and probabilities of harm from GW. But I have a hard time understanding that agenda. ? They want the world to be destroyed & want people to do nothing to reduce the harm ? That doesn’t make sense. They desire to live in pleasant dreamland. They want to stay hooked up to the matrix? Doesn’t make sense either.

    Bottom line, THEY DON’T WANT AGW TO BE TRUE. But that’s just how the believers in AGW feel. No one wants it to be true.

    Comment by Lynn Vincentnathan — 19 Apr 2007 @ 12:25 PM

  38. Re: #24 “(especially new types of measurements)”

    Exactly. No one (on either side of the debate) should be making hay (let alone predictions) off such new information. As Gavin said, ARGO “has offered the potential to dramatically increase the sampling density in the ocean and provide, pretty much for the first time” data. As just happened, the initial version of the information was somewhat incorrect.

    Question: The CO2-T lag suggests that it takes hundreds of years for the ocean mass to warm. Does that mean we need to wait a long time (say 25 years) to see non-surface heating?

    Comment by Ian Rae — 19 Apr 2007 @ 1:29 PM

  39. There was an article in the recent issue of Spektrum der Wissenschaft, the German version of Scientific American, about shortcomings of climate models. It says that the study of Gouretski and Koltermann (2007, GRL 34) has reduced the 1957-1997 increase in ocean heat content (0-3000m) by about 38% and that this would be a big problem for climate models. Looking at the paper of Levitus et al. (2005, GRL 32) I find that the 1955 to 1998 ocean heat increase was 14.5*10^22 J. The corresponding value from the paper of Gouretski and Koltermann is 12.8*10^22 J for a slightly shorter interval (1957-1966 to 1987-1996). Considering the different time periods the two values are in fact identical within error. So where is the 38% reduction? Why should there be a problem for climate model verification? Can anybody explain that to me?

    Comment by Florian Boehm — 19 Apr 2007 @ 1:34 PM

  40. I am very curious about another glaring error in the making, which is the continuance of MSU graphs not showing 2005 as the warmest year in history at all, if there is a scandal in atmospheric science that’s the biggest one I know of at this time. Rather you have to read the fine print that MSU mixes lower stratospheric temperatures (usually quite cold) with the mid troposphere.
    Has there been a theory , from proponents confident in MSU data, which limits the warming of the atmosphere strictly near the surface? No, not like a Chrichton Urban warming error proposal blunder, the world is not one paved big city yet.

    Comment by wayne davidson — 19 Apr 2007 @ 1:40 PM

  41. re 34: As I mentioned in a follow-up post my suggestion might not be good for political situations. In the dilemmas you present there is no best answer: there is exactly a 50% chance the person will be hailed and a 50% chance of being creamed. The response should be “we don’t know for sure” but also include a learned opinion with a degree of certainty. I had a minor concern in how, in scientific circles like RC, the level of confidence is drawn, like (exaggerating a bit): “Bad measurements that show warming? NO PROBLEM! Bad measurements that show cooling? SEE? NO GOOD!”

    Comment by Rod B. — 19 Apr 2007 @ 2:14 PM

  42. Lynn (37): If AGW proves to be wrong, some of the proponents will be apoplectic, some angry, some depressed and some disappointed — for a while. This does not make them nefarious (except maybe the first two groups who probably do have strong secondary agendas.) To presume they’d be happy is naive; maybe accepting and redirecting a year or two down the road, but not happy

    Comment by Rod B. — 19 Apr 2007 @ 2:30 PM

  43. Guys (re: #26),

    Emanuel (2005) finds that the increase in potential intensity during his study period (~10%) far exceeds the increase in potential intensity resulting from rising SST (that he estimates as ~2-3%). So thermodynamical goings-on besides SST can (and apparently do) have a large impact on the potential intensity. Emanuel explains, the observed atmospheric temperature does not keep pace with SST which leads to a decrease in vertical stability and an increase in potential intensity. This result, decreasing atmospheric stability, is confirmed by Hoyos et al. (2006). Knutson and Tuleya (2004) show that climate models run with increasing CO2 project that in the tropics the atmosphere should become more stable as there is more warming aloft than at the surface. Thus, I think we all should be able to agree, that unless the upper-air observations are wrong, the observed trend in atmospheric stability over the tropical Atlantic is in a sense opposite to direction that models suggest it will be, at least into the future. As Gavin pointed out over at ClimateScience, perhaps it is not so much that the observations are wrong, just that the observed forcings over the past 30 years or so, have been different from the simplified set of forcings used by Knutson and Tuleya, and that when the observed forcings are used as input, climate models do a better job at handling the evolution of the Atlantic tropical atmosphere. I would be very interested in seeing climate model simulations of the evolution of the atmospheric stability in the Atlantic (both with and without CO2 changes) during the past 30 years to see if they do indeed replicate the observed trend and to what degree CO2 increases were involved in the match.

    The same goes for vertical wind shear trends. As Vecchi and Soden report, there is a robust increase in vertical wind shear over a good deal of the tropical Atlantic in the collection of the 18 climate model results they examined (running SRES A1B). Again, there is a good deal of evidence that vertical wind shear has generally declined over the past 30 years in the Atlantic (e.g. Hoyos et a., 2006). Again, I think we can agree that the trend in observed vertical wind shear is opposite that projected to occur under SRES A1B. Agreeing with Gavin, A1B is not what happened during the past 30 years. If someone actually does know how the models simulated the evolution of vertical wind shear over the Atlantic during the past 30 years, it would be very worthwhile to share that information.

    However, even without the actual results from the models for the past 30 years, I think we can surmise that driven by changes in anthropogenic forcings alone, the models simulations of the past 30 years would be trending in a similar direction as the model projections for the future, that is, vertical stability and wind shear should be increasing, at least over the tropical Atlantic. Adding non-anthropogenic forcings to the mix may, or may not, overwhelm these trends (they will if the models are getting things right, they wont if things in the models are still amiss). But assuming the case that the models aren’t horribly wrong, non-anthropogenic influences must be largely responsible for the observed trends being in the direction that they area which is towards producing a more hospitable environment (that works along with SST increases) for tropical cyclone development and intensification.

    The only problem I have with Emanuel (2005) is that his results are overplayed to infer that the observed trend in tropical cyclone activity is largely anthropogenic in nature. The results in his paper, coupled with the results of Knutson and Tuleya (2004) and Vecchi and Soden (2007) argue otherwise. So [edited] I think that the results of Vecchi and Soden do put a dent in the hypothesis that human industrial emissions are largely responsible for the observed increase in Atlantic tropical cyclones and that they will have a larger impact into the future [edited]
    -Chip Knappenberger
    to some degree, funded by the fossil fuels industry since 1992

    [Response: Chip, we'll permit this one comment, but since this is obviously not supposed to be the topic of this thread, we'll limit it at that. You seem to have missed the central point here. Emanuel (2005) shows that the warming SSTs are behind the increased TC intensity in the Atlantic. No impartial reading of that paper could come to any other conclusion. Independent studies, such as the Santer et al PNAS paper, show that this warming is inconsistent with natural variability, i.e. it is likely only explainable in terms of anthropogenic forcing. That basically closes the loop on the argument that anthropogenic forcing is likely behind increased tropical Atlantic Hurricane intensity. Future predictions of shear changes are interesting, but they have no bearing on this fairly simple logic. -mike]

    Comment by Chip Knappenberger — 19 Apr 2007 @ 2:42 PM

  44. Joe White: “This is great news Gavin. The Lyman et al paper…”

    Yes! Great news. Now the prediction still is that the world goes into the global warming inferno! Good news. You CO2 devoted are so funny. :D

    Comment by Magnus — 19 Apr 2007 @ 3:02 PM

  45. Let me be blunter: Without a theoretical framework one wanders in ignorance. The more quantitative and basic the framework the better (Gray vs. Trenberth).

    Models (aka theory) provide a bullsh*t test for observations as much as data is a bullsh*t test for observations.

    You ain’t Einstein and you ain’t Gallileo either.

    Comment by Eli Rabett — 19 Apr 2007 @ 3:17 PM

  46. Re: #41

    No, it’s not great news because the world is going into inferno. It’s great news because our understanding of climate, and therefore our ability to deal with the problems it presents, is more likely to be sound.

    The objection you raise was already raised on this thread, and already addressed.

    You delusionists are most definitely not funny.

    Comment by tamino — 19 Apr 2007 @ 3:23 PM

  47. [[Joe White: "This is great news Gavin. The Lyman et al paper..."
    Yes! Great news. Now the prediction still is that the world goes into the global warming inferno! Good news. You CO2 devoted are so funny.
    ]]

    Obviously it’s bad news for human well-being. But it’s good news in cutting the feet out from under the deniers who are trying to stop us from doing anything about the problem.

    Comment by Barton Paul Levenson — 19 Apr 2007 @ 3:37 PM

  48. Re: 41.
    1. There won’t be a global warming inferno if people finally start to react (and start quickly because some may need a little longer to realize they have to act). 2. It definitely is good news for those people who try to understand how climate works. It is probably bad news for those who try to make people think it is impossible to understand how climate works. 3. Three years of ocean cooling would certainly not have saved the world from warming.

    Comment by Florian Boehm — 19 Apr 2007 @ 4:29 PM

  49. Environmentalism is no longer a popular movement like it was at the time of the first Earth Day in 1971. It’s become a very esoteric academic discipline that only a few select “experts” in an elite priesthood can understand and participate in. Much like in the humanities and literary studies. And the inferior common folk are to be derided and excluded for their gauche taste in reading Michael Crichton and so on. The result of one is “reading at risk” and the dissolution of the American publishing industry, the result of the other is slow but steady enviromental degradation.

    Comment by Richard Atley — 19 Apr 2007 @ 4:51 PM

  50. Re 45.

    Yes, that’s what I meant with my comment. Thanks to all the others, special mentions to 44 & 46, who have gone in to bat on my behalf.

    http://joewhiteleftfield.blogspot.com/

    Comment by Joe White — 19 Apr 2007 @ 5:55 PM

  51. Mike-

    You are simply incorrect when you assert: “Emanuel (2005) shows that the warming SSTs are behind the increased TC intensity in the Atlantic. No impartial reading of that paper could come to any other conclusion.”

    [edited]

    [Response: Roger, we're not about cherry-picking sentences and out of context quotations here at RC, so you should take that somewhere else. Anybody who has studied the scientific issues involved well knows that SSTs in this context are a proxy for a more complex set of interconnected atmospheric environmental variables which tend to covary with it. We hardly need you to quote Emanuel for us. Figure 1 in Emanuel (2005) comparing SST and TC Power Dissipation in the tropical Atlantic speaks for itself, you might want to take another look. If we do an article on Hurricanes in the near future, you're free to engage in the discussion. But that's not the topic of this post, so we're going to close it out with this. -mike]

    Comment by Roger Pielke, Jr. — 19 Apr 2007 @ 7:03 PM

  52. Re: Kuhn, paradigms, and the neutrality of scientists. Yes, I also see this as an example of paradigm-driven revolutionary science, and gavin (and co.) shouldn’t apologize for it. As he says, scientists are skeptics trying to make sense out of data. It is eminently satisfying when they do! That is an intellectual and emotional attachment to what they do. Scientists are not robots: they *enjoy it* when they solve a problem. They don’t simply spit out “fits theory” “doesn’t fit theory”. No scientist should apologize for this commitment. Just so, when a scientist or group of scientists think they have solved a problem, and then new data suggests they were wrong, there is nothing wrong with feeling frustrated about it! (In fact, there’s really nothing wrong with favoring one theory over another for whatever reason one wants; as long as you follow the data, you can think whatever you want about the theory.)

    Also I want to comment on this snippet from one of gavin’s replies to a comment on this thread:

    “But the level of confidence we do have (having passed a whole bunch of tests) is enough to allow to project pretty confidently a lot of what’s going to happen.”

    Yes–in fact I’m about to post on ClimateAudit on this very point to see how they react. This gets to the heart of the debate about “consensus”–Kuhn even writes on this subject in SSR (I forget exactly where: it’s at the very end of one of the middle chapters…I can look it up). When two paradigms are competing–or simply during a revolutionary period when one paradigm is supplanting an earlier normal science tradition (I get the sense that all this HPS/STS talk makes gavin a little nervous…) then it eventually becomes clear when one paradigm is becoming ascendant. You can almost always bet that it will ultimately be triumphant, i.e. its theory will eventually become accepted as fact, *without* appeal to consensus at all (because everyone will think that way; no proofs will be necessary, though there will be plenty on hand). The alternative paradigm (that anthro ggs play no significant role in current warming) is currently losing the battle; although they are still alive and kicking (and will probably continue to score points here and there) they are not making progress towards convincing the relevant community. It would take a seriously revolutionary set of data (a “counter-revolutionary” set of data?) to put a halt to agw theory right now–undeniable proof that cosmic rays are behind everything, for example, or maybe evidence that an immense cloud feedback is kicking in as we speak (though that latter might not really count as evidence against agw theory…hard to say). And, of course, it remains possible that even if agw theory ultimately triumphs and becomes accepted as fact, it could still be *wrong*–but again, it would take another revolutionary finding to show that.

    If agw is wrong, why does it keep succeeding among the scientific community? (As measured, for example, by the number of scientific organizations that support it:

    http://en.wikipedia.org/wiki/Scientific_opinion_on_climate_change

    I also bet that the citation index shows similiar levels of support, though to my knowledge no one has investigated this in detail.)

    Sorry for the windy lecture; I just wanted to weigh in. And of course, this could all be totally wrong :) But regardless, scientists still don’t need to apologize for having strong feelings about being wedded to one theory or another.

    Comment by mzed — 19 Apr 2007 @ 7:04 PM

  53. I think it is now clear (after the warming of the oceans has now been proven) that if we do not stop adding GHGs to the atmosphere, the entire human race might go extinct along with thousands of other species wihtin a few decades.

    We must stop this catastophe from happening as soon as possible.

    Comment by John N — 19 Apr 2007 @ 9:08 PM

  54. I’d like to comment simply that I agree with the first part of #11 (Mosher) — it is important to be unbiased in our interrogation of observational data. Yes, data that don’t fit the common theory should be scrutized. Data that do fit should be scrutinized equally. Probably everyone could agree with that.

    On another matter, what have the ATOC results contributed to understanding oceanic heat content? http://en.wikipedia.org/wiki/Acoustic_Thermometry_of_Ocean_Climate
    It looks like “nothing” is the answer, but given a decade of data I’m surprised not to see a graph of some sort.

    Comment by Steve Latham — 19 Apr 2007 @ 9:34 PM

  55. And since the new analysis agrees with you, it should be taken the final word and not subjected to the same skepticism with which the previous study was treated, as per usual.

    Comment by DaveS — 19 Apr 2007 @ 9:51 PM

  56. RE #53, “entire human race might go extinct along with thousands of other species wihtin a few decades”

    I think the possible danger is not so much that the worst will happen in a few decades or even in a hundred years, but that what we’re doing now may cause the earth system to rearch a point (maybe in years or decades, or we may have passed it already) at which it may be nearly impossible to slow or halt dangerous warming & great future harms, which could go on for hundreds, thousands, even hundreds of thousands, of years.

    And re #42, I can’t imagine anyone who would want AGW to happen (except some suicidal mass murders). That’s why so many good people are becoming climate scientists and environmentalists. Because they want to warn people and help us solve this problem.

    Seriously, are there GW believers on this site, who would be unhappy if tomorrow we found out that, oops, we forgot to square-root some calculation (or something) and GW is not happening afterall? Some may be red as beets for having claimed it was happening, they may be jumping hoops to show how any reasonable & smart scientist could have made that mistake, but surely their ecstasy in knowing it wasn’t happening, would far outweigh any embarrasment or even temporary unemployment (the guys here are smart, they’d get some other job; in fact I’ve read the many climate scientists started out in other fields). Many people have children and love them. Don’t you think they would be happy to know their children will have a good, sustainable world? Again, it is the denialists who are truly perplexing in their thinking and motives.

    And as for the environmentalists and do-gooders, there’s no shortage of other harms & evils in the world to combat, or one could just stop and smell the flowers along the way. Plenty of other things to do.

    Comment by Lynn Vincentnathan — 19 Apr 2007 @ 10:30 PM

  57. Measurement error, calculation error and reporting errors occur in every field – not just climate science. A significant portion of every professional’s time is spent investigating or fixing problems resulting from these kinds of errors. This is particularly painful in areas such as this – where decisions affecting potentially millions of lives is based on what can turn out to be faulty data or misapplication of data to theory. If it turns out that we can avoid the coming AGW disaster but we failed to act quickly enough because of faulty data – life in fubar. [NOTE: I think we're fubar already, but I'm hoping I'm really wrong about that.]

    Often I believe this drives the deniers – everyone knows that data is wrong, theories are wrong, etc and so they insist that its a data problem or theory problem. As long as the possibility exists that the data or theories are wrong – they reach for the elixir of “it could be bad data/theory” to avoid changing their reality. It’s natural. Human nature basically. In stable times, a high quality survival strategy. In unstable times, not so good.

    Comment by Robin Johnson — 19 Apr 2007 @ 11:56 PM

  58. DaveS the denialist says:

    And since the new analysis agrees with you, it should be taken the final word and not subjected to the same skepticism with which the previous study was treated, as per usual.

    The original post says:

    Are we done then? Unfortunately no.

    Seems that DaveS didn’t bother to read the post, which goes on to say:

    Because of the paucity of measurements, assessments of ocean heat content need to use a wide variety of sensors, each with their own quirks and problems. Combined with switches in data sources over the years, there is a significant potential for non-climatic trends to creep in. In particular, the eXpendable BathyThermographs (XBTs – sensors that are essentially just thrown off the side of the ship) have a known problem in that they didn’t fall as quickly as they were originally assumed to. This gives a warm bias

    In other words, that bias due to sensor problems has in one case been shown to run in the direction of warming.

    Gosh. Maybe it’s just about getting more accurate data and understanding the science after all, DaveS.

    Comment by dhogaza — 20 Apr 2007 @ 2:52 AM

  59. Can anyboy here please show me someone explaining the 800 year lag of co2? Any place where I can read about it?
    The explanation given on this site is not very intelligent.
    Thank you.

    Comment by Marian — 20 Apr 2007 @ 4:45 AM

  60. Re #56, As we came out of the last Ice Age there was a large amount of warming and as the oceans warmed there was a net large release of CO2 from them, however the warming attributed to this period lagged some 800 years behind the initial warming and did not cause it but it was responsible for its own warming and that is the point. It was not a driver for this ending of the ice age but it is a driver for warming as we are experiencing it today.

    I believe that some climate denialists have used the CO2 is not a driver for past climate argument which is incorrect.

    Comment by pete best — 20 Apr 2007 @ 5:12 AM

  61. Re 56: explaining the 800 year lag of CO2

    There is a good explanation here. In a nutshell: 1) wobbles in the Earth’s orbit (the Milankovich cycles) have a warming and cooling effect. 2) Warming causes CO2 to be released – e.g. by thawing the permafrost and drying wetlands, soils and forests thereby allowing organic matter to breakdown, and warming the oceans which causes dissolved CO2 to outgas and methane (which breaks down to CO2) to be liberated from clathrates etc. 3) the extra CO2 (and methane) causes warming that is significantly greater than would otherwise result from the wobbles alone. 4) There is a delay because the various processes such as thawing of permafrost and breakdown of organic matter, warming of the oceans etc. take a certain amount of time to kick in after the wobble mediated warming starts.

    This time around we are not see a warming kick-started by a Milankovich wobble. Instead we are in an already warm period and are initiating extra warming by injecting even more CO2 into the atmosphere. The 64 million dollar question is: how much extra CO2 will now be liberated by those various CO2 liberating processes. And given that we seem to be kick-starting it all much faster than a wobble would, and are doing it on top of an already warm interglacial climate; how fast will that liberation occur, and how much CO2 will it add?.

    Comment by Craig Allen — 20 Apr 2007 @ 5:55 AM

  62. Re: 85

    Thank you Dr. Schmidt. Both links were very helpful. I also read some of Hansen’s work on the subject.

    A few more questions for the forum on climate sensitivity to greenhouse gases:

    1. Doesn’t measurement of climate sensitivity rely on historic data?

    2. Are ice core temperature and gas composition data applicable to the entire globe or just Antartica?

    3. Hasn’t the climate changed dramatically over the last 400k years and thus how can we know how the earth will respond to forcings today if there are different processes at work?

    4. Hansen believes we can avert certain disaster if we keep warming under 1 degrees celsius. Isn’t this hypothesis built on the assumption that the earth will respond in a similar fashion to forcings that occured tens of thousand of years ago?

    Thanks again for taking the time to explain this to a non-scientist.

    Comment by Tim — 20 Apr 2007 @ 6:29 AM

  63. [[I think it is now clear (after the warming of the oceans has now been proven) that if we do not stop adding GHGs to the atmosphere, the entire human race might go extinct along with thousands of other species wihtin a few decades.]]

    I doubt that. There will be great economic disruption and many people will suffer, but I don’t think the species is in danger of extinction. Let’s try to keep some perspective here.

    Comment by Barton Paul Levenson — 20 Apr 2007 @ 7:10 AM

  64. So you say that the sun coming in at a different angle due to wobble of the earth is what previously caused global warming? But now it is the increase by 80 ppmv of CO2 that is the cause? Where in the Milankovic cycle are we now? Will that (M-cycle) have any effect on global warming this time?

    Trying my best to understand.
    Thanks for replying

    Comment by Marian — 20 Apr 2007 @ 7:33 AM

  65. Re #64

    Where in the Milankovic cycle are we now?

    See Present Conditions on this linked page. You might well like to read the whole page, too.

    Comment by P. Lewis — 20 Apr 2007 @ 8:35 AM

  66. Can anyboy here please show me someone explaining the 800 year lag of co2?

    A natural 800-year lagging increase in atmospheric CO2 in response to rising temperatures does not somehow preclude an increase due to anthropogenic emissions… what’s to explain?

    Comment by DaveS — 20 Apr 2007 @ 8:58 AM

  67. Ha, I love that I’m a “denialist” because I point out the somewhat immature tone with which Gavin consistently addresses these things…. he’s made up his mind and has his biases as much as the “deniers” he derides. Even in this post, he said “[sea surface cooling] was going to be hard to reconcile with continued increases in sea level rise (driven in large part by thermal expansion effects)”. That’s called “begging the question”… if you presuppose that increases in measured sea-levels are due in large part to thermal expansion and that there is no “inertia” involved–whereby sea-level rise due to 350 years of warming may not necessarily stop on a dime with sea surface warming–then of course it’s difficult to reconcile. To a more objective observer, thermal expansion might be equally hard to reconcile with cooling waters.

    I’m no climate scientist, but I have a decent science background and I’m something of a lurker here… I’m just saying that it has been obvious to me from day one that Gavin is not exactly an objective source of information… he provides very good information from a perspective, and he does it in an intelligent–but slightly snarky–way. I like this blog and find it informative.

    Don’t project your biased, politicized view of this onto me, please.

    Comment by DaveS — 20 Apr 2007 @ 9:12 AM

  68. #66, “Can anyboy here please show me someone explaining the 800 year lag of co2?

    A natural 800-year lagging increase in atmospheric CO2 in response to rising temperatures does not somehow preclude an increase due to anthropogenic emissions… what’s to explain?

    When you put these together, it’s a really bad scenario…much worse than simply CO2 causes warming.

    Watch out, world, for CO2 causes warming, which causes more CO2, which causes more warming, which causes more CO2, which cause a hellava lot more warming, which causes a hellava lot more CO2, which causes….(no one left to write about it).

    Comment by Lynn Vincentnathan — 20 Apr 2007 @ 9:16 AM

  69. Re #67: On ‘Gavin is not exactly an objective source of information’…
    On the list of people who I would trust to be a straight as possible on the subject and likely to know WTF they were talking about, Gavin is near the top of my list. Maybe this is because I, too, am prejudiced, or maybe it’s because I like the fact that he’s taking time , along with all the other experts here, to educate the likes of us.

    I like to pretend my judgement of other’s reliability is based on an assessment of their rationality and fairness, but who gives a damn about such archaic notions these days? I think there’s an important distinction to be made between being biased and having a clear point of view based on substantial knowledge and experience. But hey, that’s just me…

    Comment by Fergus Brown — 20 Apr 2007 @ 9:30 AM

  70. I think you make an important point regarding the “test of time” for research papers. In my studies I have found a number of papers which become widely accepted in a short period of time and shortly after we find stronger studies rebutting these initial findings. This applies to both sides of the controversy. After all, this is what science is all about, the problem is that some researchers, journalists and even the public get deeply attached to the first set of data they encounter and disregard subsequent arguments against those claims. That is why we should keep a critical eye on research papers concerning climate change, whether they support our personal beliefs or not.

    It is important to recognize that some data sources, such as the ARGO floats, can provide instantaneous data, but the overall trends may require more time to be determined. Some of the arguments I have encountered against global warming are based on a quick glance at these data, which may be displaying only short term trends, rather than continuous global cooling patterns. At the same time we also have some researchers supporting their claims on global warming in a similar fashion. This calls for caution on the part of the audience to which these claims may be directed. Neither proponents nor opponents should knowingly make strong claims based on faulty, incomplete or adjusted data due to the implications these factors may have on their conclusions.

    It is also alarming the fact that some of the probes may be producing anomalous data, and some researchers may be using it to back up previously construed arguments, instead of analyzing it, taking into consideration its flaws, to provide an objective study of climatic trends. With the increasing number of debates over this issue, my personal recommendation for the public is to understand data sources presented by both proponents and opponents before following either sideâ??s conclusion.

    Comment by Ingrid Tobar - Dept. Geosciences UMKC — 20 Apr 2007 @ 9:56 AM

  71. I am so happy that finally oceans get the attention they diserve, as I have strongly stated in varoius ways that we should consider more that the oceans are linked to the climate and influence the climate almos as much as the son does.

    Comment by Adrianne — 20 Apr 2007 @ 9:59 AM

  72. Don’t project your biased, politicized view of this onto me, please

    Is anybody forcing you to participate here? Nobody is projecting anything on you here, if anything, by choosing to participate, you are projecting yourself onto us.

    This website belongs to its creators. They are free to project anything they want here, and you are free to ‘turn the channel’.

    Comment by Thomas Lee Elifritz — 20 Apr 2007 @ 10:00 AM

  73. DaveS:

    As the Buddha said in a different context, “The pollution is in your mind.”

    Gavin’s statement that ocean cooling was going to be hard to reconcile with rising sea levels is simply fact, not attitude. Given that we know that sea level is rising several millimeters per year, the observed net contribution of melting glaciers and ice caps is not enough to explain current sea level rise, and water shrinks as it cools, how would you explain the current rate of sea level rise? You have to come up with a completely new source of water, a source of heat in the deap ocean, or show that water expands as it cools.

    If you don’t have an answer handy, then I submit that you demonstrate the simple truth of Gavin’s statement that such a reconciliation is hard.

    Comment by Tim McDermott — 20 Apr 2007 @ 10:33 AM

  74. Dave S., Gavin does indeed have a perspective. We all do. The difference is that Gavin’s perspective is supported by the evidence and so reflects the scientific consensus on matters of climate. And lo and behold, because his perspective is consistent with the scientific consensus, he is, far more often than not, right.
    A scientist may support the scientific consensus. A scientist may be skeptical of the scientific consensus. In either case, they must do so based on the evidence. As soon as they lose sight of this fact, they leave the realm of science and, if they are experts, become contrarians (e.g. Lindzen), or if they are not experts, denialists, (e.g. you). In either case, you make yourself irrelevant to the process of science–quite unlike the true skeptic.
    Look, we know the climate is changing–that is beyond question. We have a very probable mechanism–anthropogenic greenhouse gas emissions. Those who say, “It’s natural” have absolutely no mechanism to propose to explain the changes we are seeing. As a physicist, I get uncomfortable when people seem to suggest that the energy in a system (e.g. the climate) can just increase with no cause. So until you have a mechanism to suggest, you are not part of the scientific process–skeptical or otherwise.

    Comment by Ray Ladbury — 20 Apr 2007 @ 10:38 AM

  75. RE# 68
    On the good side, we have 800 years to prepare before this supercharged co2 feedback begins?

    Comment by Keith Rogstad — 20 Apr 2007 @ 11:56 AM

  76. Re: #75

    On the good side, we have 800 years to prepare before this supercharged co2 feedback begins?

    Not necessarily. One of the reasons the lag of CO2 behind temperature in deglaciations is so long is that warming during deglaciations is so slow. The rate of warming during a reasonably rapid deglaciation is about 0.1 deg.C/century, the rate today is about 1.8 deg.C/century.

    Also, the ice core records from Antarctica give a good measure of global CO2 concentration (it’s a well-mixed gas), but give a more local measure of temperature. Milankovitch cycles don’t actually cause warming globally, they redistribute incoming solar energy to more polar latitudes, so that they trigger ice melt. This causes the temperature in polar regions to warm even before the global temperature warms, but it’s the global warming that triggers CO2 release from the oceans. But the modern warming is global, so we can expect ocean-solubility influence to happen sooner.

    There is, however, the factor of CO2 released from melting ice masses, which one would expect to be “prompt” in relation to ice mass wasting. Anybody know the relative contribution to CO2 increase from oceans versus ice melt, during a deglaciation?

    Comment by tamino — 20 Apr 2007 @ 12:24 PM

  77. Hmm, for whatever reason, my reply hasn’t showed up after two postings over the course of a couple of hours.

    I guess I’ll ask again and hope for the best…

    Gavin’s statement that ocean cooling was going to be hard to reconcile with rising sea levels is simply fact

    Since we know that the oceans expand and release CO2 over hundreds of years in response to surface warming, how is a few years of surface cooling hard to reconcile with continuing thermal expansion? The expansion is occurring in the depths of the oceans, in response to ongoing warming that has been occurring going back 300+ years, is it not?

    The “irreconcilability” seems to be an unfounded assertion. It seems to me that the thermal expansion wouldn’t stop on a dime in response to what amounts at this point to an insignificant blip of a few years of recent cooling (assuming, for the sake of argument, that cooling has occurred). If you take a longer-term moving average, any recent cooling wouldn’t even show up.

    Comment by DaveS — 20 Apr 2007 @ 12:29 PM

  78. Re 75. Actually, no. The feedback is temperature, rather than time dependent, so once we reach the temperature where the feedback kicks in, it will be too late–be that in 800 years or next year.

    That is one of the reasons why having working models is so important–it allows us to explore feedback mechanisms under various scenarios. This post is neither crowing over success, nor rejoicing at the demise of yet another denialist argument. Rather, it is saying that the models are working well, and that means that we will not be flying blind as we confront the likely effects of climate change.

    Comment by Ray Ladbury — 20 Apr 2007 @ 12:34 PM

  79. Look, we know the climate is changing–that is beyond question. We have a very probable mechanism–anthropogenic greenhouse gas emissions. Those who say, “It’s natural” have absolutely no mechanism to propose to explain the changes we are seeing. As a physicist, I get uncomfortable when people seem to suggest that the energy in a system (e.g. the climate) can just increase with no cause. So until you have a mechanism to suggest, you are not part of the scientific process–skeptical or otherwise.

    You are arguing with a straw man. You also seem to be unaware, incredibly, that noone denies that the climate varies naturally and always has… in other words, it is certainly true that “the energy in a system (e.g. the climate) can just increase with no cause”–of course, noone is arguing that there is “no cause” aside from your straw man. To claim such is nothing less than an intentional misrepresentation of people with whom you disagree.

    The difference is that Gavin’s perspective is supported by the evidence…

    What evidence is there that a few years of surface cooling would immediately stop the thermal expansion that is occurring in response to 300-400 years of warming? That was the statement I originally inquired about. There may be an answer, and that’s why I asked.

    I’m not a climate scientist, but common sense tells me that his assertion there was 100% unfounded. I’m simply asking, for the 4th time now, for someone to explain to me why it is founded. That’s all. What’s with the super-defensive reaction to a simple question?

    [Response: You are confusing surface warming (which can be checked directly with satellites) and upper ocean heat content (top 700m). Both the sea level change and the numbers reported here are sensitive to the latter, not the former. - gavin]

    Comment by DaveS — 20 Apr 2007 @ 12:40 PM

  80. So you’re saying that warming causes CO2 increases, which causes warming, which causes CO2 increases, etc? Why has this perpetual feedback cycle not caused our planet to be uninhabitable prior to this point?

    Once again, asking because I want an answer, not to be contrarian.

    Comment by DaveS — 20 Apr 2007 @ 12:52 PM

  81. It seems to me that the thermal expansion wouldn’t stop on a dime in response to what amounts at this point to an insignificant blip of a few years of recent cooling (assuming, for the sake of argument, that cooling has occurred)

    That just the point. Since sea level continues to rise, any observed cooling is likely to be insignificant in the long run. There are clear mechanisms for observed local cooling, which are not incompatible with local warming. A large volume of ocean is very cool. The ice sheets are melting into the oceans. Get the picture now?

    As long as sea level continues to rise, then there is no way to repudiate global warming. Sea level rise is clear evidence that warming is continuing, and there is no evidence to date to indicate that trend is reversing, or likely to reverse. Everything we see is in accord with our expectations. When the paper indicated anomalous cooling, we fully expected to see correction to the data to appear, because we understand sea level is rising via thermal expansion, and thermal expansion is nearly instantaneous on geological timescales. The analogy is neutrinos from the solar interior, they give us a nearly instantaneous picture of stellar processes which are otherwise obscured from our direct view.

    Comment by Thomas Lee Elifritz — 20 Apr 2007 @ 1:01 PM

  82. Re: 77: DaveS: Why wouldn’t thermal expansion stop on a dime? If there is no additional heat going into the ocean (and it is hard to imagine a way that additional heat could enter while the surface is cooling), then we are just moving heat around in the deep. And if we’re doing that… any increase of temperature and therefore expansion in one place will be balanced by a cooling and therefore contraction in another… There isn’t (as far as I understand it) “inertia” in thermal expansion: the water molecules respond pretty much instantly to the new temperature. The inertia comes in with the transfer of heat from atmosphere to ocean, and that’s why it takes hundreds of years to cause the expansion.

    Comment by Marcus — 20 Apr 2007 @ 1:02 PM

  83. Re: the continuing saga of CO2-lagging indicator

    Going back 400,000 years, the maximum CO2 concentrations surrounding the warming and cooling pulses are all lower than current levels. (And the heating associated with those spikes is around +4C. )

    Comment by Jeffrey Davis — 20 Apr 2007 @ 1:12 PM

  84. There isn’t (as far as I understand it) “inertia” in thermal expansion: the water molecules respond pretty much instantly to the new temperature.

    Hmm, that makes sense to me. However, the amount of expansion in response to new energy wouldn’t be uniform. That heat near the surface will move deeper over time, which will certainly have some sort of “lagging” effect. The density of the water is a function of temperature and pressure, right?

    Admittedly–off the top of my head–I suspect that this would actually exaggerate short-term sea-level changes, since the response would probably be smaller in colder, deeper waters under higher pressure. In other words, a complete halt in surface warming would probably cause a slow decline in sea levels, as surface heat mixed downward.

    That assumes, of course, that I’m remembering my physics correctly.

    Comment by DaveS — 20 Apr 2007 @ 1:29 PM

  85. Re #76: tamino — While but an amateur, it seems that the oceans store vast quantities of carbon in various forms and are much more extensive than the LGM ice sheets were. So I’ll hazard the guess that the contribution of carbon dioxide stored in the ice is negligible…

    Comment by David B. Benson — 20 Apr 2007 @ 2:41 PM

  86. >thermal expansion
    I have no idea how pressure depth relates to thermal expansion — anyone got a pointer? I’m sure the submariners have charts for how density changes with temperature and with depth.

    Comment by Hank Roberts — 20 Apr 2007 @ 3:16 PM

  87. Re: #83, DaveS: Huh. Yeah. The differences in density between deep water and surface water might mean that moving heat around could cause changes in sea level without new heat inputs. Also, the density to heat content relationship is probably non-linear, so that could also cause discrepancies.

    I’d still think that these would be 2nd order effects, and not large enough to account for the sea level changes being observed… but I acknowledge that I could be wrong.

    Comment by Marcus — 20 Apr 2007 @ 4:12 PM

  88. RE: 62
    Still struggling with the concept of climate sensitivity. Questions above. Can anybody summarize the fundamental assumptions being made to estimate current climate sensitivity. I cannot seem to get past the idea that we can only make assumptions about today’s climate’s reaction to forcings based on the earth’s reaction to forcings from tens of thousands of years ago. Is it not reasonable to assume that many climate systems (ocean circulation patterns, cloud dynamics, etc.) are likely very different and thus past behavior cannot really give us an accurate sense of climate sensitivity today?

    Sorry if I am overlooking something obvious.

    Comment by Tim — 20 Apr 2007 @ 4:30 PM

  89. Lyman’s assert on observed ocean cooling last year was an interesting attempt on understanding ocean changes. Discussing therefore whether the ocean heat contents changes is a quiet sensible consequence. But wondering should be permitted. The oceans water masses are quite a massive body, with 1000 times the “heat capacity” of the entire atmosphere, and last not least are only +3,5 degree Celsius warm. Who will be able to tell that the ocean heat content has changed?

    Comment by Adrianne — 20 Apr 2007 @ 5:14 PM

  90. Responding to 14 (I know this was a long way back, but I haven’t seen a specific response): “Also, how does this new information change the point made in the discussion from the original paper? This work has several implications. First, the updated time series of ocean heat content presented here (Figure 1) and the newly estimated confidence limits (Figure 3) support the significance of previously reported large inter annual variability in globally integrated upper-ocean heat content [Levitus et al., 2005]…”

    You’ve got to understand that none of the numbers here is known with a high degree of confidence, because the ocean is very poorly sampled. (Until ARGO, that is, but unfortunately that data is still new.) There have been suggestions for a while that the global ocean heat content has higher interannual variability than simulated by the models (ie by the ocean component of coupled climate models). With the latest revision the evidence for *really* high interannual variability has melted away. Still, it’s an interesting subject and one that should be revisited when we have, say, a decade of ARGO data.

    I wouldn’t be at all surprised if the ocean component of coupled climate models *did* show lower than observed levels of interannual heat flux variability. For one thing, the models in question have rather coarse spatial resolution and so the flow in them is very “syrupy”. (How that would affect interannual variability in heat content I don’t know, but you’ve got to wonder.) For another, there could be greater interannual variability in the radiative forcing at the ocean surface than we know about. But I don’t think any of this provides evidence of serious problems with the climate models, ones that would make their projections invalid.

    Comment by Mark Hadfield — 20 Apr 2007 @ 5:23 PM

  91. re 69: I’m a skeptic and on opposite sides of the table from Gavin. I think he sometimes goes over the top and sometimes shows his bias too much (though bias is kinda O.K as opposed to prejudice). But, IMO, I’m very impressed with his efforts and scientific demeanor and consider him extremely reliable. I’ve critized him sometimes and questioned him a number of times but think he is top-notch and does a helluva job.

    Comment by Rod B. — 20 Apr 2007 @ 5:39 PM

  92. re 73 et al: This is a latent sandbox1 concern that’s been bugging me for some time. Beyond the spin and assertions of the sensor designers (designers always contend their design works exactly) how can we tell if ocean(s) rise a couple of millimeters? All the oceans? An average of all of the oceans? Particular oceanic “hot spots”? El Niño changes the surface about 500 mm; can we detect a variation of 1-2 mm “because of AGW”???

    Comment by Rod B. — 20 Apr 2007 @ 5:57 PM

  93. No-one has answered 79 from DaveS yet: “So you’re saying that warming causes CO2 increases, which causes warming, which causes CO2 increases, etc? Why has this perpetual feedback cycle not caused our planet to be uninhabitable prior to this point?”

    I haven’t been able to found any good answers elsewhere yet. I assume that during the interglacials, various carbon sequestration processes kick in or are enhanced, and that these lower the CO2 concentration enough to bring the temperature back down. Does anyone have information on the specifics of this? What are the candidate processes and how well do we understand them? This explanation prompts the opposite question though. What prevents the CO2 concentration from continuing to drop until we freeze over?

    Comment by Craig Allen — 20 Apr 2007 @ 9:00 PM

  94. Re 85 Hank,
    If I understood your question correctly:
    Water is nearly incompressible, so its density doesn’t change significantly with depth – any density differences are almost entirely due to differences in temperature and salinity. Any good oceanography textbook (e.g., Sverdrup, Johnson, and Fleming,1942, The Oceans Their Physics, Chemistry, and General Biology; see Chapter IV, http://ark.cdlib.org/ark:/13030/kt167nb66r/) have tables or nomagrams relating temperature/salinty/density, and tables or figures showing temperature and salinity as a function of depth. Another, more recent, source is:
    Emery, W.J. and L.J. Dewar, 1982: Mean temperature-salinity, salinity-depth and temperature-depth curves in the North Atlantic and North Pacific. Pergamon Press, Oxford, England, 91 pp.

    Comment by Chuck Booth — 20 Apr 2007 @ 10:44 PM

  95. Re #92 Sea level changes

    Basically, tide gauges and satellite altimetry:
    http://sealevel.colorado.edu/
    http://www.pol.ac.uk/psmsl/manuals/
    http://www.csr.utexas.edu/gmsl/main.html
    http://science.howstuffworks.com/question356.htm

    Comment by Chuck Booth — 20 Apr 2007 @ 11:01 PM

  96. This was a very informative post. The details of the ocean temperature data are important.The wider lessons at the end are even more important. One of the things that the general public needs to know when they are trying to understanding global warming is how science works.

    It also shows how politics have become a part of the public debate of the science. If someone submits a paper, like Lyman et al, that might cast doubt on AGW people wonder if there is a contrarian/political motive involved. In my own idealistic way, I think its unfortunate that that the clean scientific method is being drawn into the dirty world of politics.

    Comment by Joseph O'Sullivan — 21 Apr 2007 @ 1:02 AM

  97. re 92

    I agree that we seem to be extrapolating global trends from a limited number of data sets and therefore these global sea level rise figures have to be viewed with a healthy dose of skepticism. I think the same can be said of Antartic ice core data and their utility for determining temperature for the rest of the planet.

    Still learning a lot reading the contributions at this exceptional site, but it is my impression that the scientists still lack sufficient knowledge to be able to categorically state that the earth is on the verge of catatrophe.

    Comment by Tim — 21 Apr 2007 @ 6:28 AM

  98. Re: #87: Marcus-*The differences in density between deep water and surface water might mean that moving heat around could cause changes in sea level without new heat inputs. Also, the density to heat content relationship is probably non-linear, so that could also cause discrepancies.*

    When a water molecule warms it vibrates more. This causes it to occupy more space amongst the molecules surrounding it. As it mixes with cooler molecules it warms them and they cool it, causing the extra space that it occupied on warming to diminish; however, the original extra space is not lost but merely acquired by the molecules that it warmed.

    The net effect is no additional thermal expansion or contraction due to mixing with other molecules. Additional heat must be added to the water molecules to cause more expansion.

    Comment by Henry Molvar — 21 Apr 2007 @ 8:22 AM

  99. Re: #92, #97 (sea level trend)

    Indeed the rate of sea level rise is slow by comparison to changes brought about by tide and wind. I don’t know whether or not there is a limited number of data sets, but let’s assume, for the sake of argument, that indeed it’s true.

    The limited amount of data does not invalidate in any way the detection of a trend. When we study data looking for a trend, we apply statistical tests which are tried-and-true, confirmed by literally millions of cases, and more important, can be *proved* in the only way that true proof exists: mathematically. If the statistical test shows overwhelming likelihood of a trend, then it’s overwhelmingly likely to be there — regardless of whether we have a limited number of data sets.

    Of course, more data sets are better, because that increases the sensitivity of the trend analysis; it enables us to separate ever-smaller trends from the noise with statistical confidence. So, more is better.

    The “catch” is that statistical tests can detect and quantify trends in the data. But if the data don’t match the physical system, as is the case for the Argo floats, then we’ve only detected a trend in a bunch of numbers, not in the physical quantity we tried — and failed — to measure.

    Therefore a larger number of data sets is doubly helpful: not only does it increase the sensitivity of statistical tests, to identify even smaller trends if present, it also decreases the likelihood that we’ll be fooled by bad data, since it’s unlikely that multiple data sets will all be affected by errors that go in the same direction, giving false detection of a trend (opposite errors will cancel in a trend analysis, and give the false impression of the absence of a trend).

    Comment by tamino — 21 Apr 2007 @ 8:35 AM

  100. [[if you presuppose that increases in measured sea-levels are due in large part to thermal expansion and that there is no "inertia" involved--whereby sea-level rise due to 350 years of warming may not necessarily stop on a dime with sea surface warming--then of course it's difficult to reconcile.]]

    How in God’s name does inertia tie into it? You’re saying the ocean had momentum upward which took decades to dissipate? I don’t think that ties in with what we’ve known about physics for the last 300 years or so.

    As the ocean warms, it has to expand. Period. Do you want the equations? You can probably look the figures up in the CRC Handbook. If they don’t have the values for seawater, the NOAA might. But previous expansion will have no effect at all. There is something called “thermal inertia,” but it has nothing to do with expansion.

    Comment by Barton Paul Levenson — 21 Apr 2007 @ 9:45 AM

  101. [[It seems to me that the thermal expansion wouldn't stop on a dime in response to what amounts at this point to an insignificant blip of a few years of recent cooling (assuming, for the sake of argument, that cooling has occurred). If you take a longer-term moving average, any recent cooling wouldn't even show up. ]]

    It will stop on a dime if the ocean temperature stops rising. And if the ocean cools, expansion will become contraction. There is no “inertia” to thermal expansion, or if there is, it’s measured in seconds, not years. Conduction of heat may be a slow process, but it’s not that slow. Nothing is. Look up figures for the thermal conductivity of seawater.

    Comment by Barton Paul Levenson — 21 Apr 2007 @ 9:52 AM

  102. [[So you're saying that warming causes CO2 increases, which causes warming, which causes CO2 increases, etc? Why has this perpetual feedback cycle not caused our planet to be uninhabitable prior to this point?

    Once again, asking because I want an answer, not to be contrarian. ]]

    It’s a converging series. Not all infinite series diverge. For example, 1 + 1/2 + 1/4… converges to 2 no matter how many terms you add.

    Comment by Barton Paul Levenson — 21 Apr 2007 @ 9:54 AM

  103. RE #93, I suppose one mechanism that halts carbon increasing in the atmosphere (& concomitant warming increase) is that a large amount of fauna die off (there was a 90% die-off of life during the end-Permian extinction some 251 mya). And once the methane from their carcasses is all released, that’s it. Carbon releases plummet. Then eventually plants uptake that atmospheric carbon & we get back to a lower CO2 level & a cooler climate (assuming “we” as a species are around to see that day, which could come some 100,000 years into the future).

    The climate scientists hate my use of “venus effect” or “runaway warming” precisely because Venus has permanent runaway warming, while there is nothing at this time re earth that would put it into permanent runaway warming. Not until the sun turns into a very hot red ball some billions of years from now.

    Until then we have the possibility of hysteresis, in which natural (volcanic, etc) or human causes trigger such an amount of warming that nature is induced to release its vast (but finite) store of sequestered (frozen) carbon.

    So let’s not push our luck by pushing into this hysteresis scenario. Regular non-hysteresis global warming is bad enough.

    Re ocean warming, and new findings that methane clathrates are closer to the surface than heretofore thought, it seems to me if the ocean warming happens fast enough (in geological terms) and vast stores of methane are released (along with the permafrost methane also being released), we could enter a hysteresis scenario. Atmospheric methane (which is 23 times more potent a GHG than CO2) has about a 10 year lifetime, before it breaks down into CO2, etc, unlike CO2, part of which can stay thousands of years in the atmosphere. So if a huge amount of methane is released within 10 year timeframes that would compound to create a really bad case of warming.

    Which is why it is so very important that we slow our release of GHGs into the atmosphere & slow the rate of warming (which, I believe, is faster now than it ever has been in geological history).

    We are entering into a dark, unexplored forest here with beasts known and unknown. There is already momentum & we’re headed into the outskirts of the forest, like it or not. But we need at least to slow down (that is, drastically reduce GHGs), if not halt altogether (go to zero emissions — which would be impossible).

    Comment by Lynn Vincentnathan — 21 Apr 2007 @ 9:56 AM

  104. RE #42, re climate scientists & environmentalists being unhappy if GW is proven false, I sorta understand your point from your perspective. My husband thinks the same way, that GW believers (like myself) are somehow happier when evidence is pointing to GW.

    I do feel very happy today, after seeing yesterday that 20/20, Oprah, and Nightline had very good programs on GW (& not in the pro-con format). I used to watch them regularly in the early 90s, expecting them to adress GW. Also the televangelist programs, since AGW is a big moral failing, not just an inconvenient truth. But nada, nada, nada over the years, over the decade+. But yesterday, they (except the televangelists) finally came around.

    But I’m not gloating (despite what my husband & you might think); I’m just happy that the message is getting out, and perhaps NOW enough people will start doing something to solve this problem.

    I was also ecstatic 17 years ago around Earth Day, after learning about lots of things to do to reduce my GHGs (after spending a torturous lent after learning about AGW and that I was responsible, but having no idea how to mitigate it). Again to the outsider it may have appeared I was happy that there were awful environmental problems.

    However, I felt very sad — I cried actually — when the recent IPCC report came out. That surprised me, since I already suspected way in advance (actually from the time of TAR) they would say things are worse than they had thought & that they were more certain. Also bec I consider IPCC to be somewhat conservative.

    First of all science is conservative, requiring 90 & 95% certainty that a big problem is happening before claiming it so. And second, because the IPCC requires some level of consensus among a lot of nit-picking conservative scientists, so it’s even more conservative than a single scientific study (one of which BTW found 95% confidence AGW was happening back in 1995).

    So I cried, because if these conservatives can say it’s happening with 90%+ certainty, that’s it. Near nil chance of waking up from this really bad dream, because it’s not a dream.

    But today I’m happy, bec the world seems to be catching on, and maybe this problem can be mitigated enough to avoid the worst.

    Comment by Lynn Vincentnathan — 21 Apr 2007 @ 10:25 AM

  105. Re: #98: Henry Molvar: Well, to take one example, water is densest at 4 degrees Celsius. If you take a mass of water at 4 degrees, and use Maxwell’s demons to move heat around such that half of the water is at 2 degrees and half is at 6 degrees your new volume will be larger than the old one, even though you have added no heat to the system (we’ll ignore the entropy laws this violates). This is an example of what I meant by non-linear density to heat content relationship.

    I have no idea what effect pressure might have on this relationship.

    However, if you read my full post, you will also note that I doubt that these sorts of 2nd order effects can matter on the large scale.

    Comment by Marcus — 21 Apr 2007 @ 11:01 AM

  106. Re [So you're saying that warming causes CO2 increases, which causes warming, which causes CO2 increases, etc? Why has this perpetual feedback cycle not caused our planet to be uninhabitable prior to this point?]

    I’d think that a big part of the reason this hasn’t happened in the past is that there’s only so much CO2 dissolved in the oceans, and even if you got it all into the atmosphere, the amount just isn’t enough to cause such a runaway warming.

    That’s the point to keep in mind: basically all of the increase in CO2 over the last century comes from carbon that was taken out of the system (as coal & oil) over many hundreds of millions of years, and is now being dumped back in all at once.

    Comment by James — 21 Apr 2007 @ 11:12 AM

  107. Re 42 and subsequent discussions among Lynn and Rod.
    Rod, why do you assume we WANT the climate to change. What we want is irrelevant–it’s what the evidence tells us that matters. As a technophile and science geek, I strongly regret that much of the next century’s greatest minds will be distracted from fundamental science, by a need to adapt and survive. I also realize that some of the lifestyle changes that may be needed will not be easy. Nonetheless, if humans cannot anticipate and adapt to a challenge, then the mass of neurons on the end of our spinal columns seems to serve little adaptive purpose. Yeast cells can do as well–growing until they render their environment uninhabitable to themselves.
    On the other hand, as I have pointed out, I am happy when the models work–as that at least provides us with some guidance as to what to expect and means we are not flying blind. A working model is always better than a nonworking model–even when you don’t like what the model is telling you.

    Comment by Ray Ladbury — 21 Apr 2007 @ 12:34 PM

  108. Re: #105 Marcus: *…water is densest at 4 degrees Celsius. If you take a mass of water at 4 degrees, and use Maxwell’s demons to move heat around such that half of the water is at 2 degrees and half is at 6 degrees your new volume will be larger than the old one, even though you have added no heat to the system (we’ll ignore the entropy laws this violates). This is an example of what I meant by non-linear density to heat content relationship.
    However, if you read my full post, you will also note that I doubt that these sorts of 2nd order effects can matter on the large scale.*

    Your insight is well noted.

    Any water, e.g. Arctic, that is between 0C and 4C will contract and get denser as it warms until it reaches 4C. This will reduce the volume of the oceans by some amount during warming periods counteracting the warming and expansion that occurs above 4C.

    To what extent this retarding effect is happening now I don’t know.

    Anyone?

    Comment by Henry Molvar — 21 Apr 2007 @ 2:18 PM

  109. Bit off topic but have seen comments before about bets. Leading Irish bookie Paddy Power will give you 7/2 for this to be hottest year on record in the UK and 5 to one that Ireland has its hottest year on record. Now, let´s see who has the courage of their convictions!?

    Comment by gerard mc aree — 21 Apr 2007 @ 2:19 PM

  110. [[But yesterday, they (except the televangelists) finally came around.]]

    Actually, Pat Robertson, of all people, recently said he believes it’s really happening. I’m not a big Robertson fan, but at least he’s got this issue right.

    Comment by Barton Paul Levenson — 21 Apr 2007 @ 4:48 PM

  111. According to Wikipedia, because of the salinity of seawater, it does not expand at temperatures below 4 deg.C. However, the density variations with temperature are much less at low temperatures than at higher temperatures, so the upper layers of the ocean have a much greater expansion due to warming than the lower levels, on a per-kilogram basis.

    This means that we can expect the thermal expansion of deep-ocean water to depend on heat permeating to massive volumes of the deep ocean. There’s plenty of deep-ocean water, so the effect can be sizeable — but it will take a long time to accumulate the necessary thermal energy. Therefore it would seem that on short timescales, thermal changes in the upper ocean will dominate those of the deep ocean.

    This makes it even more incongruous that upper-ocean cooling would coincide with sea level rise.

    Comment by tamino — 21 Apr 2007 @ 6:16 PM

  112. What is inherently wrong with this whole situation is with the “flattening of the world” economywise and the concurrent climate change there needs to be international cooperation for success. This is possible, but I see one huge issue that could spell disaster for the world and humanity in general. To say it nicely, some countries may try to control space, and others might not like it too much. Get the picture?. The next decades or so should be ones of cooperation, and if we don’t work together civilized human existence could be highly problematic. I also see the ice sheets falling off, but to combat those problems we need the world to work together. Humanity has one chance here, are we going to screw this up?

    Comment by Paul M — 21 Apr 2007 @ 7:00 PM

  113. Ocean Warming. Yes, but is it Really CO2?

    1. Earth orbital geometry is currently approaching coincidence of perihelion and solstice. In fact, this will occur roughly within next thousand years, i.e. coincidence at opposite phase every half-precessional cycle. Precessional cycles are in turn modulated by orbital eccentricity, i.e. the envelope of precession.

    2. Current phase is perihelion close to summer solstice in southern hemisphere, and perihelion close to winter solstice in northern hemisphere. Seasonal effect of current perihelion-solstice approach is hotter summers in southern hemisphere, and also warmer winters in northern hemisphere. This seasonal effect will reach a maximum at coincidence.

    3. Usual Milankovitch analysis of insolation at high-latitude is much too simplistic for understanding current warming climate situation which is being forced by increased oceanic summer heat absorbtion in mostly oceanic southern hemisphere, and also by decreased oceanic winter heat loss in northern hemisphere.

    4. Effect of southern hemispheric perihelion-solstice approach is gradual global oceanic warming with corresponding adjustment of current and air flows, oceanic thermal expansion with gradual shift in oceanic-atmospheric CO2 balance (with more CO2 being released on top of anthropogenic addition), increased polar melting, particularly at the margins where ice is most affected by nearby warming oceanic temperature, and of course corresponding sea level rise.

    5. This climatic effect is exacerbated when eccentricity is very low, as is currently the case, and as was the case 400,000 years ago during the long MIS-11 Interglacial. At that time, the evidence indicates that sea levels were 15-20 meters (50+ feet) higher than today! This too, was “Real Climate”, and with CO2 levels under 300 ppm, suggesting that CO2 did not cause that period of “Global Warming”.

    6. MIS-11 was a period of much warmer climate in Europe, given that we have fossils of Hippopotamus amphibius (hippos), Elephas antiquus (elephants), and Bubalus murrenis (water buffalos) in Northern Germany, Northern France and also England, all dated from this period. Clearly, Europe was then a much warmer place than it is today, and without the benefit of anthropogenic CO2.

    7. While some more anthropogenic CO2, per the IPCC, will increase sea levels by a few centimeters, I strongly suggest that if you are really interested in understanding the scope of future climate change, then you should all carefully read:

    Earth’s Climate and Orbital Eccentricity, The Marine Isotope State 11 Question. Droxler, Poore, Burckle. AGU Geophysical Monograph 137, 2003.

    The Climate of Past Interglacials. Sorocko, Claussen, Sanchez Goni, Litt. Developments in Quaternary Science 7, Elsevier, 2007
    Particularly the following articles:
    - Eustatic sea levels during past interglacials, Siddall
    - Mammalian faunas from the interglacial periods …, Koenigswald

    After reading these volumes, one of clear mind might question the IPCC’s current obsession with anthropogenic CO2, and its resultant recommendations and priorities, given the implications of accepted paleoclimate research and scientific evidence.

    But then again, people have often been known to ignore the lessons of the past many times before. I commented on this previously under – IPCC Sea Levels .. #49.

    Comment by Dan Fregeau — 21 Apr 2007 @ 7:08 PM

  114. Didn’t the latest research fine that the Oceans were neither cooling nor warming? If the ocean is not warming and the troposphere according to RSS and UAH is not warming like the surface, we have some major problems with the models.

    Comment by Craig Truglia — 21 Apr 2007 @ 7:34 PM

  115. Re #68: I think you miss the point. The 800 year lag between rising temperatures and increasing CO2 is used by some anti AGM people as “proof” that carbon dioxide levels have nothing to do with the earth’s temperature. This may be hard for us scientists to imagine, but I have met people (some of whom are highly educated) who argued exactly that. So I have to go back to basic chemistry and an explanation of how a greenhouse actually works, which some people still can’t imagine being applicable to something on the scale of the earth’s climate.

    Comment by Richard Vineski — 21 Apr 2007 @ 8:43 PM

  116. “I’m just happy that the message is getting out, and perhaps NOW enough people will start doing something to solve this problem.”

    Boy Howdy, Lynn. That’s what I thought last night watching the ABC line-up. Good deal. It’s a shame some folks just don’t want to know the truth about anything and hold fast to ideas that just aren’t true only becasuse they have them. That’s a failure to adapt which, is terminal.

    Comment by Mark A. York — 21 Apr 2007 @ 10:23 PM

  117. Re. #111: tamino: *According to Wikipedia, because of the salinity of seawater, it does not expand at temperatures below 4 deg.C. However, the density variations with temperature are much less at low temperatures than at higher temperatures, so the upper layers of the ocean have a much greater expansion due to warming than the lower levels, on a per-kilogram basis.*

    Thanks for the adjustment regarding the temp at which expansion of cold seawater starts to commence. I take it that your view is that this effect is negligible in the grand scheme of things?

    Comment by Henry Molvar — 21 Apr 2007 @ 11:14 PM

  118. > try to control space

    Already too late, according to the models of, again, basic physics; even before China added 10% to the space debris, there was already enough junk to expect a cascade of collisions to start eventually, producing more, and leading to loss of use of low earth orbit for satellites. I’m not sure if geosync is also expected to become a debris belt or not.

    Although the official website for the joint intergovernmental group on space debris still says China’s hosting this year’s meeting right about how:

    http://www.iadc-online.org/index.cgi?item=home

    News sources say China suddenly cancelled the meeting. Perhaps proof they’re capable of embarassment, or simply don’t want to admit they were capable of being so uncoordinated as to make an already marginal situation utterly disastrous.

    China Junks Space Debris Meeting=April 20, 2007
    http://www.livescience.com/blogs/author/leonarddavid
    “China has canceled the hosting of the 25th meeting of the Inter-Agency Space Debris Coordination Committee (IADC). The China National Space Administration was slated to host the IADC April 23-26 at the China Academy of Space Technology in Beijing.”

    Commentary here: http://onemansblog.com/2007/02/11/china-destroys-satellite-adds-10-more-debris-to-orbit/
    quoting a NYT article:

    “Today, next year or next decade, some piece of whirling debris will start the cascade, experts say.

    �It�s inevitable,� said Nicholas L. Johnson, chief scientist for orbital debris at the National Aeronautics and Space Administration. �A significant piece of debris will run into an old rocket body, and that will create more debris. It�s a bad situation.�

    Those old enough to remember the Cuban Missile Crisis will recall both the US and the USSR “tested” nuclear weapons in space during those critical days, supposedly as mutual threat
    http://www.vce.com/crisis.html
    apparently the results (widespread EMP, damage to satellites, whatever else) convinced both governments that actually using a larger number would be an utterly stupid move —- the long-delayed treaty banning nuclear tests above ground finally was signed shortly thereafter.

    They moved to killing satellites by throwing rocks. That should be safe, duh?

    “Take the machine gun aboard Salyut-3…. It weighed about 40 kg, was 2 meters long, and fired 200 gram projectiles at rate of 900 rounds per minute and a velocity of 780 m/se…… the USSR sowed the spacelanes with a dozen clouds of shrapnel from killer satellite tests in the late 1960′s which were lingering threats to navigation for decades. These small fragments were too small to track and too numerous to dodge, so important vehicles were just armored against them.

    “This was the preferred kill mechanism for many anti-satellite (ASAT) weapons, from the Soviet space-to-space â��killer satelliteâ�� of the 1960â��s and 1970â��s which used a shrapnel charge aimed at its target to the air-launched U.S. ASAT missile of the 1980â��s, which used precise guidance to directly ram the target.”
    —- excerpted from: http://www.jamesoberg.com/06122001pearlharbor_pol.html

    Well, now _that’s_ proven utterly stupid, as we’ve already exceeded the amount of garbage in orbit to predict more collisions, leading to more garbage …. it’s another chicken-and-egg argument. Too damn many, can’t stop them from multiplying.

    This is the outcome of attempting to control anything by being best at breaking it. Mutually assured destruction works as a threat, not as an incremental, ongoing strategy applied tactically.

    Imagine their surprise:

    “What? We can _share_ it but we can’t _own_ it or _control_ it??? That’s politically unacceptable ….”

    “But, Mr. Administrator, it’s basic physics ….”

    “Guards! …..”

    Comment by Hank Roberts — 22 Apr 2007 @ 7:08 AM

  119. Much of the discussion on this thread relates to Gavin’s statement that sea levels would not continue to be rising if in fact the sea temperatures have stopped rising or fallen slightly. The time period referenced in the Willis el al paper is mid 2004 to mid 2006. A look at the actual sea level data points in the data provided in post #95(ignoring the time related smoothing curve) during this period, with all of their scatter, does in fact suggest sea levels have not risen in this time period. With that said and has Gavin has stated, the time period is too short as yet to come to any conclusions as the data remain firmly in the long term upward trend. So the descrepancy between the sea temperatures and levels may not in fact exist.

    Comment by B Buckner — 22 Apr 2007 @ 8:32 AM

  120. Re: #113 (Dan Fregeau)

    Consider how slowly the astronomical cycles act. The fastest of them (the precession cycle) has a period which varies between 19000 and 23000 years.

    Consider how slowly climate changes during the natural warmings and coolings of glacial cycles. A reasonably rapid deglaciation warms the planet by about 5 deg.C in 5000 years. That’s a rate of 0.1 deg.C/century, while the warming rate during the modern global warming era is about 1.8 deg.C/century — 18 times faster.

    The extremely rapid climate change we’re experiencing now cannot be due to the cycles of eccentricity, obliquity, or precession. After reading your post, one of clear mind must doubt your clarity of mind.

    Comment by tamino — 22 Apr 2007 @ 8:52 AM

  121. Re: #117 (Henry Molvar)

    I misspoke; the sources I’ve seen indicate that seawater continues to contract as temperature is lowered, all the way to the freezing point, but the rate of contraction is much smaller at low temperatures than it is at near-surface temperatures.

    I don’t think the effect (heating of deep ocean water) is negligible in the grand scheme of things, but it seems clear to me that the effect is dramatically slower than the effect of heating upper-ocean water. So, long-term (many centuries) projections of sea level rise may be strongly influenced by the deep ocean, but short-term (the next 50 years) are likely to be dominated by the upper ocean.

    Comment by tamino — 22 Apr 2007 @ 8:57 AM

  122. Re: #119 (B Buckner)

    My analysis of the data referenced in post #95 indicates that during the period 1993 through most of 2006, the average rate of sea level rise was 3.1 +/- 0.2 mm/yr. Using just the data from mid-2004 to mid-2006 gives a rate of 5 +/- 2 mm/yr, and that result is most assuredly statistically significant.

    So your statement that “sea levels have not risen in this time period” is mistaken.

    Comment by tamino — 22 Apr 2007 @ 9:21 AM

  123. Re #120 (tamino) and #113 (Dan Fregeau): tamino has shown that the long time scale of orbital changes make them largely irrelevant for understanding present climate change or ocean temperature. I would argue further that Dan has the effect backwards. The northern hemisphere is more sensitive to changes in insolation because it has more land mass and sea ice cover. The paleoclimate record shows that the northern hemisphere drives global climate, which was warmer 8 thousand years ago (when northern summer occurred while the Earth was closest to the sun) in spite of the presence of continental ice remaining from the previous ice age.

    So the influence of orbital cycles for the past few thousand years has been in the direction of global cooling. This has been offset by anthropogenic changes, which if you believe William Ruddiman, has been happening for up to eight thousand years.

    Comment by Blair Dowden — 22 Apr 2007 @ 10:49 AM

  124. Re: #113 (Dan Fregeau)

    Countless Forest Fires have historically been caused by natural means. Does that mean humans shouldn’t be considered the cause of any Forest Fires? Of course not. But that’s the basic logical flaw many skeptics use. Just because a previous climate change was caused by natural causes doesn’t mean the current one is. And since the current one is happening much more rapidly than any detected in the historic record, it seems quite reasonable to look beyond natural causes for the explanation. That’s what’s been done the past 30 years and the evidence indicates a human let a campfire run astray causing the current forest fire (to further my analogy).

    Comment by Ken Winters — 22 Apr 2007 @ 10:53 AM

  125. Re #113 & following arguments re orbital cycles, CO2-temperature lag, etc: It seems that everyone is discussing this from the point of view that global warming is an observed phenomenon (or possibly observed, for the skeptics), and the task is to find an explanation – CO2, solar variation, orbital changes, cosmic rays, or little green men – that best fits the observations. That’s taking things exactly backwards: AGW is a prediction which was first made IIRC half a century or so before there was data to confirm it.

    To continue the analogy of #124, we know this forest fire was caused by careless humans, and are now using computer modelling to predict how the fire will spread. (Which is something that is actually being worked on, BTW.)

    Comment by James — 22 Apr 2007 @ 11:35 AM

  126. Re. #120 (Tamino)

    “A reasonably rapid deglaciation warms the planet by about 5 deg.C in 5000 years. That’s a rate of 0.1 deg.C/century, while the warming rate during the modern global warming era is about 1.8 deg.C/century — 18 times faster.”

    - This is a rather uniformitarian view of the global climate process.

    Please consider the Younger Dryas termination/transition to Pre-Boreal, when the northern hemisphere was similarly close to perihelion-solstice coincidence. Then, per the original work of Dansgaard (The Abrupt Termination of the Younger Dryas event, Nature 339, 1989), and since further refined, the temperature drop in the North Atlantic region was around 7 deg in 50 years, with the bulk of the temperature change occuring in just 2 decades. Of course, this was also accompanied by a massive reorganization of Atlantic currents.

    Comment by Dan Fregeau — 22 Apr 2007 @ 12:42 PM

  127. Re. #124

    Dear Ken, I am not skeptical about global warming, nor that some level of anthropogenic GHG forcing is contributing to the warming process.

    But what I dispute is the conclusion that CO2 is the main causal of this current warming phase, on the basis of the reality of the MIS-11 Interglacial when CO2 was quite normal, but sea levels were much higher due to extensive deglaciation well beyond what has occured so far, or projected to occur by the IPCC.

    The fact that the current Holocene is quite similar to MIS-11 from an orbital geometry standpoint should alert one to the possibility that there may be other significant factors at work, and with forcing potential well beyond that of anthropogenic CO2.
    Dan

    Comment by Dan Fregeau — 22 Apr 2007 @ 12:55 PM

  128. The 800 year lag between rising temperatures and increasing CO2 is used by some anti AGM people as “proof” that carbon dioxide levels have nothing to do with the earth’s temperature.

    Well… no. Most people who cite the fact that CO2 naturally lags warming are responding to the unsubstantiated insinuation popularized by Al Gore’s movie, by which an ancient correlation is subtely passed off as evidence that CO2 *causes* the warming. The mythology here didn’t start on the “skeptical” side.

    It is also often cited in response to the assertion that increasing CO2 will triger an infinite feedback cycle (which has already been brought up in this thread)–where CO2 causes warming, which causes more CO2, which causes more warming, etc. It is actually an excellent demonstration of the fact that such a thing only exists in the virtual world described by computer models, and that CO2 has naturally increased in response to warming in the past without ever actually triggering runaway warming.

    [Response: No models predict 'runaway warming' and positive feedback in the climate sense of the term does not lead to unbounded solutions. See here for a discussion: http://www.realclimate.org/index.php/archives/2006/07/runaway-tipping-points-of-no-return/ -gavin]

    Comment by DaveS — 22 Apr 2007 @ 12:58 PM

  129. Re. #123 (Blair Dowden)

    Yes, you are quite correct that the northern hemisphere was closest to the sun (perihelion) at summer solstice around 10,000 years ago. This caused much warmer summers in the north as well as significant and abrupt climate change including the advent of the Holocene, i.e. this interglacial.

    Today, the opposite is true – the southern hemisphere has much warmer summers instead of the northern. But what you fail to realize is that the northern hemisphere is now also closer to the sun (perihelion) at winter solstice, which makes for warmer northern winters in addition to somewhat less warm summers, but still more warm overall.

    Therefore, when the earth is near perihelion-solstice coincidence, now or 10,000 ago, both polar regions are warmer on a seasonal basis. This is why polar deglaciation is synchronous in both hemisphere.

    With respect to having it “backwards” – please note that water aborbs (and retains) heat quite well, because it has very low albedo. Oceanic albedo is below 5%, whereas most land albedo is 10-40%, and ice and snow from 40 to 90%. Since the southern hemisphere is mostly water, do you not think that it would absorb heat far more efficiently than the northern hemisphere?

    Comment by Dan Fregeau — 22 Apr 2007 @ 1:22 PM

  130. So, Dan, what might those “other significant factors” be? Until you have real candidates, you don’t even have what mounts to a scientific hypothesis. What is more, if your candidate mechnanisms turned out to be important, there would be the additional problem of explaining why a greenhouse gas should not behave like a greenhouse gas.
    After all, we can measure insolation–and that doesn’t come close to explaining things. What else would you propose?

    Comment by Ray Ladbury — 22 Apr 2007 @ 1:36 PM

  131. Re: #126 (Dan Fregeau)

    per the original work of Dansgaard … the temperature drop in the North Atlantic region was around 7 deg in 50 years, with the bulk of the temperature change occuring in just 2 decades…

    Dansgaard’s paper claims a 7 deg. temperature drop in south Greenland. That’s not the north Atlantic region, it’s nowhere near as big as (nor does it have the thermal inertia of) the ocean, and it’s certainly not the world.

    Frankly, your contention that the global average ocean temperature changes are being driven by orbital changes just doesn’t hold water.

    Comment by tamino — 22 Apr 2007 @ 1:37 PM

  132. Re. #125 (James)

    I agree with you AGW was theorized a while back, and forces climate to an extent, and that modelling future climate change due to AGW makes very good sense. Go for it.

    However, I also think that modelling future climate change on the basis of well-measured past climate change makes even more sense, particularly if past climate change analog (MIS-11) was significantly greater than current AGW climate change, per the geological record, i.e. the prehistoric Real Climate.

    Otherwise, modelling future climate change on the basis of AGW alone might be largely inconsequential, might it not?

    Comment by Dan Fregeau — 22 Apr 2007 @ 1:43 PM

  133. So why aren’t the experts saying this is Milkanovichian this time around? Just wanted to overlook it? One has to wonder why it is CO2 defenders try so hard to blame something else, the oldest of which is it happened before and thus is natural. That strikes me as simplistic as well.

    Comment by Mark A. York — 22 Apr 2007 @ 1:57 PM

  134. Re #127

    Take a look at this graph. Even the Antartic experts are telling us that its CO2.

    http://home.btconnect.com:80/objectcomx/IPCCAnt_small.jpg

    If we get to 550 ppmv then all current ice sheets will be in danger and remember it is not just CO2 but methane and others contribute to.

    Comment by pete best — 22 Apr 2007 @ 2:19 PM

  135. Lynn, a minor quibble with a small part of 104. I don’t see the IPCC as a bunch of conservative scientists. Nor is it correct to say because there is a big bunch per se, conservative or otherwise (ignoring the large mass of politicos), the answer is going to be either more conservative or “better.” To paraphrase an old saw, with a half-dozen or so good scientists you might get a good scientific theory/law; with 1000 good scientists you can have some grapes stomped and get some good wine.

    Comment by Rod B. — 22 Apr 2007 @ 2:27 PM

  136. Dan, you’d need to identify _two_ unknown significant factors, wouldn’t you?
    One unknown to subtract from the known CO2 forcing, to zero it out (since CO2 is enough to explain current warming).
    Plus another unknown equal to the known CO2 forcing, to explain current warming.

    Why do you think sea levels were much higher? What source are you relying on, can you give us your cite and why you consider it good info?

    I looked for recent articles
    http://scholar.google.com/scholar?q=%22MIS-11+interglacial%22&hl=en&lr=&scoring=r&as_ylo=2002

    I found references to an older idea that sea levels were higher during that period, a known paradox being studied.

    More common recently are a series of refutations—-for examples from that search, one area formerly considered evidence of a sea level change has apparently been uplifted,
    http://www.agu.org/cgi-bin/SFgate/SFgate?&listenv=table&multiple=1&range=1&directget=1&application=fm06&database=%2Fdata%2Fepubs%2Fwais%2Findexes%2Ffm06%2Ffm06&maxhits=200&=%22PP51B%22
    another site referred to, when restudied, appears to be evidence of a major tsunami,
    http://www.agu.org/cgi-bin/SFgate/SFgate?&listenv=table&multiple=1&range=1&directget=1&application=fm06&database=%2Fdata%2Fepubs%2Fwais%2Findexes%2Ffm06%2Ffm06&maxhits=200&=%22OS33E-06%22

    Where are you finding the info you rely on? I’m always _very_ interested in sources, and very few people ever reply by giving their cites, so I’d much appreciate knowing where you got yours. I’d like to look into it further; I’m just another casual reader here, but I dearly love footnotes (grin).

    Comment by Hank Roberts — 22 Apr 2007 @ 2:31 PM

  137. Re:122 (tamino)

    Perhaps you used a different starting point, but from the second half of 2004 through the end of the data series I get a trend of -0.002mm/yr +/-5mm. There is a lot of scatter in the data and I am not sure how you came up with a standard deviation of only +/- 2mm.

    Comment by B Buckner — 22 Apr 2007 @ 2:37 PM

  138. But what I dispute is the conclusion that CO2 is the main causal of this current warming phase, on the basis of the reality of the MIS-11 Interglacial when CO2 was quite normal, but sea levels were much higher due to extensive deglaciation well beyond what has occurred so far, or projected to occur by the IPCC.

    Gosh, I don’t know where to begin here. First of all, if the present warming continues, on the timescales that you are referring to, all of the ice is going to melt, not just Greenland and the West Antarctic – presumed 20 meter or so rise to which you refer. So we can establish easily that natural forcing, left to it’s own over geological time, can melt Greenland and/or West Antarctica. Clearly then 383 ppm rising at 2 ppm/year will melt all the ice. Are you with me so far?

    Now, clearly a 100 ppm per century (on average) rise of carbon dioxide concentration is not natural, and we have good evidence that humanity is perturbing the carbon cycle on a grand scale. We know that carbon dioxide traps heat. We’ve quantified that carbon cycle to approximately first order, constructed sophisticated mathematical models running on sophisticated computational systems of our own design, using a fairly sophisticated second order set of physical principles derived over several hundred years, and we have achieved a moderate amount of empirical success with the technological systems that we have.

    What particular processes do you think we have missed? New physics?

    Comment by Thomas Lee Elifritz — 22 Apr 2007 @ 3:15 PM

  139. Re #127: Dan Fregeau — I encourage you to read

    David Archer & Andrey Ganopolski
    A moveable trigger: Fossil fuel CO2 and the onset of the next glaciation
    Geochemistry, Geophysics, Geosystems. v. 6 #5 (2005 May 5)

    The paper is easy to find via web trawling, but there is also a link in a comment in the What triggers ice ages thread.

    The similarities between MIS-11 and the Holocene are not directly discussed in this paper, but it will help you to understand the magnitudes of the natural and anthropogenic effects…

    Comment by David B. Benson — 22 Apr 2007 @ 3:59 PM

  140. Re: #133 (B Buckner)

    I got the data from the link provided in the post you referred to (http://sealevel.colorado.edu/). There are four data sets: with or without “inverted barometer” correction (to correct for the effect of air pressure), and with or without the seasonal trend removed. Analyzing data from 2004.5 to 2006.5 by linear regression, I get a statistically significant trend for all four datasets.

    The scatter in the data itself is around 5mm, but it’s generally true that the uncertainty in the result of a trend analysis will be far less than the raw data scatter. I even allowed for the effect of auto-correlation in the data, to be sure the results were statistically significant.

    Comment by tamino — 22 Apr 2007 @ 5:03 PM

  141. Regarding the role of orbital variations, carbon dioxide and ice sheets in the glacial cycles, it still seems that CO2 variations are a primary driver in the glacial cycle, and that the ice sheet dynamics lag behind changes in CO2. It also seems clear that CH4 and N2O can play important roles in short-term variability. See Ice, Mud Point to CO2 Role in Glacial Cycle by Richard A. Kerr and The 100,000-Year Ice-Age Cycle Identified and Found to Lag Temperature, Carbon Dioxide, and Orbital Eccentricity, Shackleton 1999

    “Shackleton sees the lockstep of eccentricity, greenhouse gas, and temperature as a sign of cause and effect. In his view, at the beginning of glaciation changes in eccentricity–presumably by shifting the distribution of sunlight across the globe–could have decreased atmospheric carbon dioxide, weakening the greenhouse and cooling the ocean and atmosphere. At the end of an ice age, the changes are in the opposite sense. Those changes are relatively rapid and would appear to coincide; the sluggish ice volume would lag behind. That delay rules out ice as a prime mover, Shackleton says; it’s only a follower….

    Shackleton’s results impress many researchers who specialize in sorting out the cause of the ice ages. The paper “is really well argued,” says geophysicist Richard Peltier of the University of Toronto. “It has inevitable drawbacks because of the short record,” but it would appear that “carbon dioxide is a primary driver, not just a weak feedback.”

    Peltier says his own computer models reinforce that conclusion. Hoping to show that ice sheets themselves were crucial to glacial cycles, he developed a model that included not only orbital forcing and carbon dioxide variations but also the way ice sheets grow and decay. The ice turned out to be essential for the distinctively abrupt end of an ice age, but not crucial the way carbon dioxide seems to be. “The model only works because it includes the forcing from carbon dioxide,” Peltier says. “If we exclude that, we get no glacial cycle. The ice dynamics just doesn’t do it for you at all without carbon dioxide.”

    We’ve strengthened the greenhouse effect through the use of fossil fuels; now we’re wondering how the oceans and ice sheets and hydrologic cycle (and the biosphere) will respond. Sort-of-trustworthy data says that currently, the oceans aren’t warming at their earlier rate, and are not cooling either.. but the Earth is still in energy imbalance of 0.85 +/- 15 Watts/m^2 ; where is that energy going, if not into the ocean? (over 10,000 years, that’s enough to melt enough ice to raise sea level ~1 km). If only one could measure the planetary energy imbalance directly… but the Deep Space Climate Observatory has been grounded. The satellite has already been built, but won’t be launched, due to NASA’s “competing priorities”. Why? “Four hundred million dollars have been cut to pay for shuttle flights to the International Space Station and to return astronauts to the Moon.” Maybe NASA should rethink priorities?

    Comment by Ike Solem — 22 Apr 2007 @ 5:43 PM

  142. Re 128> Ray: “Until you have real candidates, you don’t even have what mounts to a scientific hypothesis.”

    How about this hypothesis (for discussion, I’m not necessarily claiming it is correct):

    Actual climate sensitivity to CO2 is 1.0C (GHG positive feedbacks are effectively canceled by negative feedback from clouds), not the 3C calculated mostly from insolation changes (including volcanic solar dimming).

    The higher positive feedback with insolation change is due to previously unconsidered effects that may only respond to insolation. A possible example is ocean emissivity changes with wind:
    http://aerosols.lanl.gov/conf2006/talks/files/Volz.pdf

    Any discrepancy with 1C sensitivity and current measured temperature increase is a combination of natural variation and measurement error (including UHI effects not properly accounted for).

    Comment by Steve Reynolds — 22 Apr 2007 @ 6:23 PM

  143. Re #129: (Dan Fregeau): The precession cycle does not change total insolation over the course of a year. So the ocean in the southern hemisphere may well absorb the increased summer insolation, but it will lose the same amount of energy from the decreased winter insolation. Therefore no net change. The same is true in the northern hemisphere, except for the large amount of sea ice. Here the timing is critical; the summer warmth may melt more ice (thus reduce albedo and absorb more energy) than the winter cooling will cause it to freeze. That is why global temperature is driven mainly by changes in the northern hemisphere.

    You are incorrect to assume the precession cycle changes the amount of energy received over the course of a year. Because of the seasonal effects, our present position in the precession cycle is one of slight global cooling, not warming as you claim. And the magnitude of this change is very small compared with anthropogenic greenhouse gases over the century timescale that we are concerned with.

    So while the precession cycle is important for understanding past climate, it is not having much influence over the present climate changes. Anthropogenic changes are the main driver at this time.

    Comment by Blair Dowden — 22 Apr 2007 @ 7:27 PM

  144. Re #142: Steve, the problem with a climate sensitivity of one, as you suggest, is that it is hard to explain how the large changes in climate occurred during the ice ages when the forcings caused by the orbital cycles are relatively small. For example, it is hard to understand how the large temperature swings during the Younger Dryas period could happen without a significant feedback from somewhere. If changes in cloud cover canceled the feedbacks, the climate would be much more stable than it actually is.

    Comment by Blair Dowden — 22 Apr 2007 @ 7:36 PM

  145. The ice sheets at antarctica slipping off and creating catastrophe, or most marine life dying off, or plants and insect relationships failing, or permafrost thawing, we need to work together to tackle this. Sputnick spurred competition, the initial catastrophe will spur cooperation. Poor Bangledesh. We created the bomb because Hitler was allegedly working on it, now we need to save the planet. The initial catasrophe will change everything.

    Comment by Paul M — 22 Apr 2007 @ 8:07 PM

  146. Re #128: The “CO2 has naturally lagged warming amd the same must be true now” argument predates the Gore movie considerably. IIRC it was raised by the usual fossil fuel-funded suspects (e.g. Pat Michaels, Steve Milloy) just as soon as the first ice core papers came out. It’s fallaciousness was pointed out immediately, but since it is sometimes effective in fooling the ignorant it has become one of the stock denialist arguments. BTW, Gore did not get this point wrong.

    Comment by Steve Bloom — 22 Apr 2007 @ 9:25 PM

  147. the forcings caused by the orbital cycles are relatively small.

    Do you honestly expect us to believe that?

    Comment by Thomas Lee Elifritz — 22 Apr 2007 @ 10:08 PM

  148. Re: orbital forcing

    The obliquity and precession cycles alter the latitudinal and seasonal distribution of incoming solar energy, but have no effect on the solar energy intercepted by earth averaged over the entire year. Only the eccentricity cycle alters this, but its effect is small; the eccentricity-induced change in average insolation generally amounts to less than 0.5 W/m^2, and the cycle takes about 100,000 years.

    Comment by tamino — 22 Apr 2007 @ 10:16 PM

  149. Re #147: Thomas, the orbital forcings aren’t large enough by themselves to drive the glacial cycles. Feedbacks are required to make things work.

    Comment by Steve Bloom — 22 Apr 2007 @ 10:34 PM

  150. Clearly orbital forcing is the pacing element. Carbon dioxide forcing and other feedbacks are measured in Watts (per square meter), whereas the integrated solar forcing from orbital variations is measured in tenths of Watts (per square meter), but insolation at latitude varies by tens of Watts (per square meter). Clearly orbital forcings are neither insignificant nor even ‘small’, since they drive the oscillations. That’s why orbital variations drive the processes, and feedbacks do the amplification. I hope that clarifies a hopelessly naive statement.

    Please don’t tell me that carbon dioxide is driving orbital variation. I suppose things would be a lot simpler if the ice caps where at the equator, but I can’t imagine trying to live on a planet like that.

    Comment by Thomas Lee Elifritz — 23 Apr 2007 @ 12:38 AM

  151. Thomas, your first word is “clearly” — so you appear to be reading from a study you can cite for us that supports your statement. What is your source? How old is it?

    When I look, I find recent references to small changes from astronomical variation, which require amplification to change the climate. The recent science is focusing on finding out what provided the amplification. For example:

    http://journals.hil.unb.ca/index.php/GC/article/view/1241/1621
    “positive feedbacks to small changes in climate induced by Milankovitch changes in radiative forcing.”

    Another example: http://www.aos.princeton.edu/WWWPUBLIC/alexey/publications/philander.fedorov.ice.aug8.pdf

    “Although the Milankovich variations in sunlight are only on the order of 10% in high latitudes, they are now capable of inducing dramatic global climate changes associated with recurrent Ice Ages.
    Apparently the drifting of continents altered conditions on land, and in the atmosphere and oceans in such a manner as to introduce processes capable of amplifying and changing the response to Milankovich forcing. …. This paper explores entirely different feedbacks involving interactions
    between the ocean and atmosphere in low latitudes.”

    Comment by Hank Roberts — 23 Apr 2007 @ 1:38 AM

  152. And, this has all rather been gone over just recently:
    http://www.realclimate.org/index.php/archives/2007/02/what-triggers-ice-ages/

    Comment by Hank Roberts — 23 Apr 2007 @ 1:40 AM

  153. [[Effect of southern hemispheric perihelion-solstice approach is gradual global oceanic warming with corresponding adjustment of current and air flows, oceanic thermal expansion with gradual shift in oceanic-atmospheric CO2 balance (with more CO2 being released on top of anthropogenic addition), ]]

    At the moment the oceans are a net sink for carbon dioxide, not a net source of it. The oceans lose about 90 petagrams of carbon per year, but take in 92.

    Comment by Barton Paul Levenson — 23 Apr 2007 @ 7:05 AM

  154. [[But what I dispute is the conclusion that CO2 is the main causal of this current warming phase, on the basis of the reality of the MIS-11 Interglacial when CO2 was quite normal, but sea levels were much higher due to extensive deglaciation well beyond what has occured so far, or projected to occur by the IPCC. ]]

    Nobody ever said CO2 was the only thing that affected climate. Climatologists are well aware of the course of the ice ages. It has been a major focus of climatological study since the 19th century.

    If you study the carbonate-silicate cycle which keeps Earth habitable, you will find that during a glaciation, weathering decreases, and so volcanic and metamorphic CO2 build up in the air. It takes a while for the high CO2 level to melt the ice again. So if you merely sample the period well into a deglaciation, you may find an ice age coexisting with high CO2 levels. You have to look at the whole process.

    CO2 is a greenhouse gas. Adding more to the atmosphere heats the ground. That’s physics, not climate correlation.

    Comment by Barton Paul Levenson — 23 Apr 2007 @ 7:13 AM

  155. Am I wrong in this statement?
    Temperature can increase for 800 years regardless of CO2, the later rising of CO2 does not further increase temperature ( possibly only keeping temperature stable).

    So in this particular case, CO2 levels are NOT responsible for Global warming?

    Right?
    Wrong?
    Don’t know?

    Marian

    Comment by Marian — 23 Apr 2007 @ 7:34 AM

  156. As just another reader here, I’d say all three statements look wrong to me.
    I’d suggest you read some of the links here — and that you discount most everything other websites say you’ll find on RealClimate. Go to the source, use the search box at the top of the page.

    You can look that up; much of the 2nd and 3rd hand stuff is bogus in a variety of ways (misrepresentation, oversimplification, flat out wrong).

    When you read the RC articles, look for the text in _green_ from the climatologist Contributors, not the text in black, which is from all the rest of us kibitzers hanging around, some trying to make sense of it all.
    http://www.google.com/search?q=%2Brealclimate+%2B%22800+years%22

    Text in black (wry grin); my opinion of the three statements you propose:

    Temperature isn’t going to increase for 800 years without anything else happening, anything else that happens is likely going to affect CO2 with life as it is on this planet nowadays.

    There’s nothing magic about ’800 years later’ — look at the ‘ice age’ threads.

    Nothing is 100% responsible; many forcings combine.

    As I recall, at present, it looks like in the absence of human activity the planet would have been slowly cooling from the peak temperature about 11,000 years ago. That’s s-l-o-w-l-y as in very, very slow. In that sense human activity may be responsible for more than 100%; offsetting cooling to zero and pushing climate the other direction. But that’s only looking at each previous ice age with the exception of the PETM event, the one most similar (albeit much slower) than the current human CO2 increase.

    Comment by Hank Roberts — 23 Apr 2007 @ 9:09 AM

  157. Re: #155 (Marian)

    Temperature can increase for 800 years regardless of CO2

    Temperature can increase for a lot of reasons.

    Deglaciation begins because changes in earth’s orbital configuration redistribute incoming solar energy, so that more of it hits the polar regions, less the equatorial regions. This brings the heat to the ice, and starts wasting away the ice sheets.

    Wasting away the ice sheets reduces the overall reflectivity of the planet (ice is highly reflective, land and open ocean are not). This causes more of the incoming solar energy to be absorbed rather than reflected back to space, and that warms the planet as a whole.

    Warming causes the oceans to hold less CO2, which they release to the atmosphere. So at first, it’s temperature that causes CO2 change.

    the later rising of CO2 does not further increase temperature (possibly only keeping temperature stable).

    False. CO2 does absorb longwave radiation — the “greenhouse effect.” This does warm the climate. So after the initial “temperature causes CO2 change” event, the CO2 causes further warming. It’s important to realize that both factors are both cause and effect.

    What we have is “warming causes CO2 increase causes further warming…” — a classic feedback mechanism.

    One of the dangers of modern global warming, is that warming will further increase CO2 (and other greenhouse gases); the feedback works both ways.

    Comment by tamino — 23 Apr 2007 @ 9:43 AM

  158. Marian, Actually, if you look at the Vostok Ice Core data, there is clearly a spike in temperature after the CO2 spike starts, and the temperature starts to fall after the CO2 fall starts. So it looks like the CO2 exacerbates and maintains the warming epoch.

    Comment by Ray Ladbury — 23 Apr 2007 @ 9:48 AM

  159. [[Am I wrong in this statement?
    Temperature can increase for 800 years regardless of CO2, the later rising of CO2 does not further increase temperature ( possibly only keeping temperature stable).
    ]]

    Yes, the statement is wrong. Increased CO2 does increase the temperature further. It’s a greenhouse gas.

    Comment by Barton Paul Levenson — 23 Apr 2007 @ 9:51 AM

  160. Steve R. # 142, well, your hypothesis might qualify as a hypothesis, but not as a scientific hypothesis. First, what would be your basis for choosing 1 degree rather than 3? Second, your putative mechanism might be physically plausible, but there’s no evidence to suggest it’s acutally operating. On the other hand, we know CO2 is increasing. We know CO2 is a ghg. We know the added forcing due to the added CO2 is adequate to account for observed effects. What I don’t understand is the motivation for rejecting a theory that matches results very well in favor of vague ideas that aren’t even worked out. The physical world doesn’t much care whether we like the physics or not.

    Comment by Ray Ladbury — 23 Apr 2007 @ 9:53 AM

  161. Re. #130 (Ray Ladbury) – What are other mechanisms?
    I think that boiling down Milankovitch/Astronomical forcing to July 65N insolation curve is a gross oversimplification of the overall process, which is regional (large-scale) vs. global in nature. As with our annual seasons, the long-term changes in insolation are most pronounced at the polar regions and higher altitudes in both hemispheres, and this reaches a maximum at the intersection of perihelion and solstices, roughly every 10,000 years, a zone that we are currently approaching.

    Likewise, boiling down the effect of the resultant increased/decreased regional insolation to +/- energy, is also greatly oversimplified. Albedo modulation is particularly critical, including that due to large changes in cloud cover, as well as major changes in the biosphere. If Svensmark is correct in his hypothesis that cloud cover is modulated by cosmic ray flux, which is in turn modulated by solar wind, then that could become a major factor in the equation, since astronomical orbital variation would in effect drive large-scale regional cloud cover and resultant albedo variation. The results of CLOUD at CERN should provide more insight on that.

    With respect to biosphere changes, the best proxies are those found in previous interglacials, particularly MIS-11, which it why it is critical to understand exactly what happened then.

    Re. #131 (Tamino) – Greenland vs. North Atlantic
    There are several other locations with good YD termination proxies. The fact that the temperature change was that high in Greenland actually supports the notion that the effect is most pronounced at the poles and higher latitudes, does it not?

    Re. #136 (Hank Roberts) – MIS-11 Sea Levels
    Thanks for the references. Yes, decoupling eustatic sea level rise from uplift is quite difficult, particularly that far back. But irrespective of that, there is now general agreement, including from the IPCC, that Eemian sea levels were higher by ~5m, and those are generally the basis for estimating the MIS-11 sea levels. Given the increased length of that interglacial, which is no longer disputed, and the faunal fossil evidence for this period in northern latitude, one can argue that it was probably higher than the Eemian, but I agree that much more research is required on this critical point.

    #138 (Thomas Lee Elifrtiz) – Higher CO2 ppm will melt all of the ice.
    A recent paper in Nature – Continental Ice in Greenland during the Eocene and Oligocene, Eldrettt, etal. 2007 – suggests that there was glaciation during periods when CO2 levels were well above today, perhaps even higher than 1000 ppm. While I don’t dispute the Greenhouse Effect, the degree to which it directly impacts atmospheric temperature at different concentration levels is perhaps more debatable. Likewise, the optimal global temperature distribution to stimulate glaciation or glacial melting, i.e. changes in mass balance, is also perhaps debatable.

    #143 (Blair Dowden) Precession does not affect insolation.
    While you are right that global insolation is the same, the real climate issue is what the insolation distribution is on a large-scale regional basis, and this is in turn affected by the envelope of precession – the degree to which eccentricity places the orbit closer or farther away from the sun at perihelion and aphelion. Changes in axial tilt, and changes in orbital plane inclination I might add, also affect the degree to which the polar regions face more directly into or away from the sun at the solstices, with climatic implications. We are currently in a summer southern hemisphere forcing configuration and therefore the notion that this can be analyzed via July 65N insolation curve appears to be the root of the problem.

    #154 (Barton Paul Levinson) – CO2 heats the ground
    I don’t dispute the fact that GHG trap heat. But there is also a long chain of inorganic and organic processes/feedbacks that take place once CO2 is in the atmosphere, or in the ocean, many of which we are just beginning to understand.

    Comment by Dan Fregeau — 23 Apr 2007 @ 10:06 AM

  162. re 155.
    [So in this particular case, CO2 levels are NOT responsible for Global warming?]

    Here is the real climate moderators response to your question from the listed thread:

    http://www.realclimate.org/index.php?p=13

    “In other words, CO2 does not initiate the warmings, but acts as an amplifier once they are underway. From model estimates, CO2 (along with other greenhouse gases CH4 and N2O) causes about half of the full glacial-to-interglacial warming.

    Some (currently unknown) process causes Antarctica and the surrounding ocean to warm. This process also causes CO2 to start rising, about 800 years later. Then CO2 further warms the whole planet, because of its heat-trapping properties. This leads to even further CO2 release. So CO2 during ice ages should be thought of as a “feedback”, much like the feedback that results from putting a microphone too near to a loudspeaker.”

    Comment by Richard Ordway — 23 Apr 2007 @ 10:20 AM

  163. Although the Milankovich variations in sunlight are only on the order of 10% in high latitudes

    ONLY 10%. I rest my case. Heaven forbid if there were 100% changes in solar insolation. You guys need to start looking for another planet. That requires that you start looking AT other planets.

    Comment by Thomas Lee Elifritz — 23 Apr 2007 @ 10:47 AM

  164. Dan, the main problem with Svensmark’s ideas are that his cause happens to be absent–that is, GCR fluxes are not changing. Moreover, there is no real evidence that cloud cover is changing significantly–that ought to be easy to document from weather reports. Finally, the fact the Svensmark shows a rough correlation of cloud cover to the 11 year solar cycle is not significant in the absence of a statistical measure of that variation, and even then, it is not necessarily causal–a lot of things correlate to the 11-year cycle. Moreover, don’t forget that clouds can warm as well as cool. As any amateur astronomer knows, the best nights for star gazing are often the coldest.
    Likewise, it doesn’t matter how you package it, dice it, slice it or mangle it, insolation by itself is not adequate to explain the level of warming seen. It requires an amplification, and you have not proposed anything credible. CO2 is a working theory that explains the results–why are you anxious to discard it? Of course if you do come up with a credible mechanism, it will be very exciting, because it would mean that we would have to understand why CO2 was suddenly not acting like a greenhouse gas. I don’t think that is very likely, though.

    Comment by Ray Ladbury — 23 Apr 2007 @ 10:55 AM

  165. Re #s 142/160: “Actual climate sensitivity to CO2 is 1.0C (GHG positive feedbacks are effectively canceled by negative feedback from clouds), not the 3C calculated mostly from insolation changes (including volcanic solar dimming).”

    What Steve R. suggests is essentially the same as Lindzen’s discredited “iris effect.” If it was correct, there would be evidence of it now (in the form of an increase in clouds to counteract the recent warming). That evidence has been looked for and found to not be there. It also fails to explain the PETM. Underlying the “iris effect” and similar arguments seems to be the idea that our present climate (Pleistocene glacial cycles) is inherently stable. What paleohistory shows is quite the reverse. The present climate epoch is 1) very recent as these things go (just the last 3 million years or so) and 2) a cold extreme that is very unusual relative to the climate history of the last half-billion years. For more than 80% of that period there weren’t even permanent ice caps. Also, the glacial cycles don’t even have internal stability — about 700,000 years ago, some very subtle change (meaning not at all obvious in the geologic record) shifted the length of the cycles from about 40,000 years to about 100,000 years. Given this and the association between CO2 levels and temperature before and during the course of the glacial cycles, it seems very obvious that a seemingly small push from anthropogenic CO2 could result in a rather drastic climate shift.

    Comment by Steve Bloom — 23 Apr 2007 @ 11:09 AM

  166. Dan Fregeau is trying to claim that fossil fuel-sourced CO2 and anthropogenically-sourced CH4 and N2O increases in the atmosphere aren’t causing the oceans to warm, based on the fact that sea levels were once higher than they are now when CO2 levels were lower.

    Timescales, Dan, timescales. We are currently increasing CO2 at rates ~30X greater than anything observed in the ice core records. A slow transition from a glacial period to an interglacial over six thousand years is a bit different from a transition from an interglacial period to some unknown future state due to rapid increases in the greenhouse effect over the course of a single century.

    The response time of ocean warming to anthropogenic increases in the greenhouse effect is slow due to the thermal inertia of the oceans – but that also means that the oceans will continue to warm for centuries even if CO2 levels are stabilized at the current ~380 ppm. The Titanic analogy fits; the ship was too big and moving too fast to respond to the rudder in time.

    The fact that atmospheric CO2 continues to increase at an accelerating rate (1.4 ppm/yr over 1960-2005; to 1.9 ppm/yr over 1990-2005, to ?) could be attributed to several things: an increase in the rate of fossil fuel CO2 production as well as a decrease in the ability of the biosphere and oceans to absorb CO2. Theroretical arguments indicate that the biosphere and the oceans will actually release CO2 to the atmosphere as the oceans warm and as the biosphere becomes more stressed; at the very least they will not be able to absorb fossil CO2 at the current rate, and this might already be happening.

    Comment by Ike Solem — 23 Apr 2007 @ 11:10 AM

  167. Re #161: Dan, you provided no link for the Eldrett paper, but I had a look at the abstract. It concludes “our data suggest the existence of (at least) isolated glaciers on Greenland about 20 million years earlier than previously documented, at a time when temperatures and atmospheric carbon dioxide concentrations were substantially higher.” You kind of didn’t mention the bit about temperatures being *substantially* higher. Also, note that isolated glaciers do not a continental ice sheet make. This paper does not support your argument.

    Comment by Steve Bloom — 23 Apr 2007 @ 11:29 AM

  168. >> “Although the Milankovich variations in sunlight are only on
    >> the order of 10% in high latitudes…”
    >
    > ONLY 10%. I rest my case.

    Could you be persuaded to show your reference, or your work if you’re doing this calculation yourself? You’re asserting the opposite of the published science, starting from the same facts.

    Rest assured many of us believe there are good reasons to get our descendants off this one planet. You don’t need to believe the climatologists are wrong about insolation and climate.

    Do we need a reason to hurry to get humanity spread out more broadly?
    I’d say the precautionary principle suffices: there may be a truly scary explanation for the Fermi Paradox! We’ve advertised the bullseye we live on; we should send some of the grandchildren elsewhere as soon as possible. Just, you know, in case it’s a wise precaution.

    Comment by Hank Roberts — 23 Apr 2007 @ 12:32 PM

  169. Let’s see . Temperatures rise, and 800 years later CO2 levels rise. Both temperatures and CO2 then continue to rise.

    Can somebody explain how that proves causation??

    Comment by tom — 23 Apr 2007 @ 12:41 PM

  170. Tom, how much physics have you had? You understand what science does, and how it differs from “proof” in math?

    Do you know how solubility changes with temperature (the common example is, run cold tap water into a glass; let it warm to room temperature; notice the bubbles coming out).

    Have you read Arrhenius’s basic work, and the followups?

    Assuming you’re asking a serious question, it’d help if you’d give some idea what you know now, as a place to start answering you.

    Comment by Hank Roberts — 23 Apr 2007 @ 1:24 PM

  171. Re #166, I am still trying to figure out how measurements of CO2 (or temperature proxies) taken from ice cores hundreds or thousands of years apart can be said to be 30x lower than the present rises in CO2. Is it physically impossible for CO2 to fluctuate naturally at today’s rate? Ice core measurements that span centuries could easily hide such fluctuations.

    Comment by Eric (skeptic) — 23 Apr 2007 @ 2:20 PM

  172. Eric, there is better information available than you are looking at. You seem to be making the mistake Lindzen makes in public. For example:

    “… Greenland cores (GRIP, GISP2) and Antarctic cores (EPICA DML) have sub-annual resolution in many cases for the isotope (temperature) records, and at least decadal resolution (Law Dome, Siple Dome) for the greenhouse gases (CO2, CH4). It’s true that the very longest records (Vostok and Dome-C) have coarser resolution ….”
    http://www.realclimate.org/index.php/archives/2007/02/quick-pre-spm-round-up/

    Comment by Hank Roberts — 23 Apr 2007 @ 2:25 PM

  173. [[Is it physically impossible for CO2 to fluctuate naturally at today's rate? Ice core measurements that span centuries could easily hide such fluctuations.]]

    Could be, Eric. Although absence of evidence for a phenomenon hardly proves the presence of that phenomenon. But in the case of the present warming, the radioisotope signature of the new CO2 shows that it’s coming largely from fossil-fuel burning. So speculating about its coming from a natural source is out of court from the beginning. You’re explaining something that doesn’t need to be explained.

    Comment by Barton Paul Levenson — 23 Apr 2007 @ 2:33 PM

  174. Re 169, 171

    Why don’t you start by taking the time to read the peer-reviewed literature cited in the IPCC reports?
    You are spending a lot of time trying to pick holes in the conclusions of mainstream climatology, with the result that your ignorance of the science quite evident. Do you spend as much time and energy picking hole in the skeptics “alternative theories,” such as they are?

    Comment by Chuck Booth — 23 Apr 2007 @ 2:38 PM

  175. Re 160: Ray>well, your hypothesis might qualify as a hypothesis, but not as a scientific hypothesis.

    What is unscientific about it? It is testable given good quality data.

    Ray> First, what would be your basis for choosing 1 degree rather than 3?

    Clarity of discussion. The same argument can be made about almost any number between 0 and 3.

    Ray> Second, your putative mechanism might be physically plausible, but there’s no evidence to suggest it’s acutally operating.

    There is some evidence (non-conclusive) in the referenced info.

    Ray> On the other hand, we know CO2 is increasing. We know CO2 is a ghg. We know the added forcing due to the added CO2 is adequate to account for observed effects.

    While we have considerable evidence that feedback effects could imply a 3C sensitivity, that depends on feedback from ghg forcing being the same as from insolation forcing. Do we know that is the case? They clearly have a very different distribution of warming effects.

    Ray> What I don’t understand is the motivation for rejecting a theory that matches results very well in favor of vague ideas that aren’t even worked out.

    My motivation is understanding reality and avoiding making important decisions on a mis-understanding of reality. I am not rejecting the standard theory, just looking to see if there are alternatives. After all, epicycles also fit the data at one time.

    Ray> The physical world doesn’t much care whether we like the physics or not.

    I agree. So why be afraid of looking closely at all possibilities?

    Comment by Steve Reynolds — 23 Apr 2007 @ 2:49 PM

  176. 165:Steve Bloom >…there would be evidence of it now (in the form of an increase in clouds to counteract the recent warming). That evidence has been looked for and found to not be there.

    I am interested in seeing that data. Can you provide a reference?

    Comment by Steve Reynolds — 23 Apr 2007 @ 2:56 PM

  177. Could you be persuaded to show your reference, or your work if you’re doing this calculation yourself? You’re asserting the opposite of the published science, starting from the same facts.

    I’m not disagreeing with you or published science, I just find it amusing that someone would find a 10 percent variation of solar insolation at 65 degrees latitude, a variation which demonstrably paces the ice ages, to be ‘small’, as in trivial. My audio signal is also a very tiny voltage, but it amplifies to high fidelity and high power just fine. The ice and ocean cores yield very high fidelity signals in the paleoclimate record, and that’s so weird, because those isotopes, and diatoms and foraminifera are so darn tiny, it’s no wonder nobody but scientists can take them seriously. I’m pulling your chains here.

    This is what I think is happening, a brief glance at the record makes it fairly obvious. As natural background carbon dioxide slowly settled below a critical threshold of around 300 ppm or so, who knows why, but clearly Earth’s biosphere is slowly winding down, geological processes have become relatively stabilized, whatever the case, with the continental distributions being what they are, the climate begins to oscillate, triggered by orbital variations. Are you with me? I’m simplifying this a great deal. Milankovitch forcing theory as THE PRIMARY TRIGGER, the gate signal if you will, has withstood the test of time, no matter what geological and climatic circumstances are amplifying it and altering it. Get over it.

    You can go ahead and try and refute it, but it doesn’t matter one whit what the comparative signal levels are, the climatic oscillations demonstrably exist, the oscillating signal is clearly being amplified, and the paleoclimate records verify that every which way but naught. If you’ve got a better theory, I will patiently await reading your peer reviewed publication.

    So the initial claim to have a hard time understanding how a weak signal can be amplified, was just too amusing for me to pass by. Sorry for the misunderstanding.

    What we have here is a climatic oscillator and amplifier that is just about on the verge of shorting out and going up in smoke. So get your tools together, Dr. Spock, this is going to take some work. Edith Keeler must die.

    Comment by Thomas Lee Elifritz — 23 Apr 2007 @ 3:03 PM

  178. Thanks Hank, from what I can see in the links, the annual layers are good to about 11k years and there’s some close approximation to that for “tens of thousands” of years before that. But they don’t talk about the sources of smoothing and the number of years of data that would be incorporated (by diffusion mostly) into one measurement. Barton, the radioisotope argument is good evidence for the current CO2, but doesn’t preclude natural fluctuations whatsoever. The lack of evidence from prehistorical ice cores doesn’t imply lack of CO2 fluctuations, only the inability to measure them. Other proxies can provide that evidence, or physical models that preclude any realistic chance of rapid CO2 fluctuations. I believe there is work in the former, the latter is probably still too difficult.

    Comment by Eric (skeptic) — 23 Apr 2007 @ 3:07 PM

  179. Re 161; “If Svensmark is correct in his hypothesis that cloud cover is modulated by cosmic ray flux, which is in turn modulated by solar wind, then that could become a major factor in the equation, since astronomical orbital variation would in effect drive large-scale regional cloud cover and resultant albedo variation.”
    Dan, what are you trying to say here? Surely not that astronomical orbital variation affects the solar wind.

    Comment by Pat Cassen — 23 Apr 2007 @ 3:17 PM

  180. [[Barton, the radioisotope argument is good evidence for the current CO2, but doesn't preclude natural fluctuations whatsoever.]]

    Nor does it preclude the existence of leprechauns. Why are you advancing a theory for which there is zero evidence? And if “the radioisotope argument is good evidence for the current CO2,” what is the point of arguing that natural fluctuations are possible? Possible or not, they’re not happening now. I can’t understand what you’re trying to achieve here.

    Comment by Barton Paul Levenson — 23 Apr 2007 @ 3:37 PM

  181. Re: #178 (Eric)

    The lack of evidence from prehistorical ice cores doesn’t imply lack of CO2 fluctuations, only the inability to measure them.

    On the contrary, the lack of CO2 fluctuations in ice cores, even at grainy resolution, is strong evidence (but not proof) of the lack of fluctuations in the physical system.

    Grainy resolution means we’re unlikely to detect a single fluctuation. But if there are many fluctuations, and we have thousands of measurements, then the probability we’ll fail to catch any of them is very small.

    Furthermore, there are plausible (albeit unlikely) physical processes that can dramatically increase atmospheric CO2 on very short timescales. But I know of no physical process that can dramatically decrease atmospheric CO2 on very short timescales. That’s one of the dangers of CO2: even when removed by natural processes, it tends to stay in the atmosphere for a very long time.

    So, on statistical and on physical grounds, it’s overwhelmingly unlikely that we’ve “missed” large-scale fluctuations due to low time resolution of ice core data.

    Comment by tamino — 23 Apr 2007 @ 3:45 PM

  182. Ray: re. 30 [The models and paleoclimate data are the only handles we have on the potential effects of climate change--]

    I’d like to niggle with you and say that physics is a third way to help indicate what climate change might have in store for us.

    With physics, you can calculate the energy inbalance that we humans are causing by adding CO2 into the atmosphere and test against model results and paleoclimate data.

    This is just a niggle, but it helps the public understand that this is not “handwaving”.

    http://www.realclimate.org/index.php/archives/2005/02/why-looking-for-global-warming-in-the-oceans-is-a-good-idea/

    Comment by richard ordway — 23 Apr 2007 @ 3:55 PM

  183. This comment from 166: “We are currently increasing CO2 at rates ~30X greater
    than anything observed in the ice core records.” The ice core records can’t be compared to today’s fluctuations due to resolution problems. Similar fluctuations could have occured with isotope ratios as well with similar measurement problems. I realize this isn’t much evidence (i.e. a physical process explanation), but the measurements in this paper http://www.holivar2006.org/abstracts/pdf/T3-032.pdf suggest that isotope ratios rose well before the industrial revolution (and well before the significant emissions: http://cdiac.ornl.gov/ftp/ndp030/global.1751_2003.ems)

    [Response: There is no support for such a statement in the linked poster. The ice core records show a sharper decrease in d13C because the mixing time is relatively short and thus the trend from ~1750 on is very clear. In ocean sediment, bioturbation (mixing of the sediment by bottom dwelling beasties) will cause more significant smoothing. Given those constraints, the match between the ocean d13C and the ice core d13C is impressive, not contradictory. - gavin]

    Comment by Eric (skeptic) — 23 Apr 2007 @ 4:17 PM

  184. Tamino, I don’t think that it is physically possible to randomly capture a CO2 spike in the ice core measurements since the measurements are smoothed from centuries (in the 100k and older cores) of actual CO2 values. A smallish spike of CO2 would reduce to 40% in 50 years (see figure 4 in http://isam.atmos.uiuc.edu/atuljain/publications/WuebblesEtAl.pdf) but how that impulse response scales to larger spikes is uncertain due to a large amount of nonlinearity in the carbon cycle. Obviously there would still need to be a physical explanation for a “spike” in the first place.

    Comment by Eric (skeptic) — 23 Apr 2007 @ 4:22 PM

  185. Re #166, “The Titanic analogy fits; the ship was too big and moving too fast to respond to the rudder in time.”

    The Titanic analogy fits in many other ways, as well. (I saw the movie again recently.) The lookout crew didn’t have binoculars bec the rich had taken all of them, but were partying inside — similar to the gov trying to silence the scientists, then fiddling while the world burns. They didn’t have enough lifeboats bec the rich wanted more room on deck without those ugly ?wind generators? and bec of arrogance that the ship couldn’t sink (the denialist stance). The poor were left to last, most to die, while a few rich escaped in life boats; the poor of the world, who contribute least to GW, will disproportionately suffer GW harms.

    The movie theme was about arrogance, wealth, & selfishness v. good human values, including love and sacrifice.

    Comment by Lynn Vincentnathan — 23 Apr 2007 @ 4:25 PM

  186. Eric, let’s say you continue to ignore the high resolution ice cores and focus solely on the low-resolution ones. How about looking at the sediment cores, then? Just one example, as a way to search. What puzzles me is you’re arguing your opinion but haven’t documented any publication that supports it.

    So look at a different source for higher resolution info, sediments instead of ice; you know diatoms build their shells out of dissolved CO2, you know there’s a level coming by 2100 at which that process stops because the shells dissolve; that’s happened before, though the species change dramatically over time so you have to really focus on the details to know what’s a good indicator.

    But the layers are quite precise and shells aren’t going to go migrating after they’re laid down in an annual layer.
    http://www.journals.royalsoc.ac.uk/(b1ot4izzfj1qg3vjcld0xifx)/app/home/contribution.asp?referrer=parent&backto=issue,3,14;journal,47,153;linkingpublicationresults,1:102021,1

    Comment by Hank Roberts — 23 Apr 2007 @ 4:52 PM

  187. Wups, Gavin already covered that in his comment about the poster study a few back, I missed it. So, good for you, you’re getting the data and an explanation for it.

    ‘Bioturbation’ is bottom dwelling worms and clams and whatever else stirs up the surface layers; it’s understood (we know what animals did what to the bottom) and can be tested against known specific layers from say volcanic eruptions — how much does that layer get spread through the mud by the animal life, that’s a good way to estimate how accurate the rest of the layers are).

    Comment by Hank Roberts — 23 Apr 2007 @ 4:59 PM

  188. Re #176: Steve R., search this blog for “ISCCP” and “iris” (separately).

    Re #184: And explanations for why they were all too small to leave any trace, why they don’t show up in the more finely-gradated recent record, and why they don’t seem to have happened during the present interglacial. Eric, I’m afraid it’s starting to sound like “low sensitivity in the gaps.”

    Comment by Steve Bloom — 23 Apr 2007 @ 5:43 PM

  189. Re #157: tamino, you said

    Deglaciation begins because changes in earth’s orbital configuration redistribute incoming solar energy, so that more of it hits the polar regions, less the equatorial regions. This brings the heat to the ice, and starts wasting away the ice sheets.

    This is not how I understand it.

    The net annual insolation at any latitude (not just 65N) does not change much. So while under certain condition the high latitudes can get up to 80 W/m2 extra insolation (a lot more than 10%), six months later the Earth will be on the other side of the sun, and the same region will get 80 W/m2 less. Correct me if I am wrong, but I don’t think there is any redistribution of incoming insolation between polar regions and the equator.

    I also think that Dan Fregeau in #161 is wrong about the effect of eccentricity. Today at summer solstice the southern hemisphere does receive more insolation because the Earth is closer to the sun at that time. But in the southern winter the Earth is further away, so the winter is relatively colder. The energy gained in summer is lost in winter.

    The only difference the orbital cycles make is the timing of seasonal warming and cooling, not the net amount. Locally as well as globally. This paper in Science shows the large seasonal variations in insolation in the polar regions.

    Comment by Blair Dowden — 23 Apr 2007 @ 7:01 PM

  190. Steve Bloom >…search this blog for “ISCCP” and “iris” (separately).

    I tried that, saw lots of discussion about clouds, but nothing that looked like reliable data showing no change in cloud cover.

    Comment by Steve Reynolds — 23 Apr 2007 @ 8:34 PM

  191. Re: Comment 164 (Ray Ladbury) “the main problem with Svensmark’s ideas are that his cause happens to be absent–that is, GCR fluxes are not changing.”

    Ray, there is evidence that the GCR changed in the 20 th century.

    http://hesperia.gsfc.nasa.gov/sspvse…ntergreen1.pdf

    Quote from the above link.

    In The Modern Era (Since 1954)

    ( 1 ) The galactic cosmic ray intensity near earth has been one of the lowest in the past 1150 years.

    ( 2 ) The frequency of occurrence of large solar particle events has been low compared to the long term average.

    For A Period Similar To 1889 – 1901

    ( 3 ) The galactic cosmic ray intensity was higher compared to the modern era by factors of:

    - 7.0 AT 100 MeV
    - 3.5 AT 300 MeV
    - 2.25 AT 1.0 GeV.

    Comment by William Astley — 23 Apr 2007 @ 9:19 PM

  192. Re #189: Blair, the key is that summer melt then exceeds winter accumulation. Note that there’s nothing about colder winters that tends to increase accumulation.

    Comment by Steve Bloom — 23 Apr 2007 @ 9:47 PM

  193. Re: #189 (Blair Dowden)

    It’s true that the primary ice-melting mechanism appears to be the change in the seasonal distribution of insolation. But it’s not correct that “The only difference the orbital cycles make is the timing of seasonal warming and cooling.”

    The precession cycle has no effect on annual average insolation at any location. But the obliquity cycle does; a change in obliquity from 22 deg. to 24.5 deg. increases annual average insolation at latitude 65 deg. by 5 W/m^2, and at the pole by 17 W/m^2, while insolation at the equator decreases by about 3.5 W/m^2.

    Comment by tamino — 23 Apr 2007 @ 10:23 PM

  194. Re: #191 (William Astley)

    The link you gave doesn’t work.

    Comment by tamino — 23 Apr 2007 @ 10:27 PM

  195. Reply to Comment 164 (Ray Ladbury) “Moreover, there is no real evidence that cloud cover is changing significantly–that ought to be easy to document from weather reports… Moreover, don’t forget that clouds can warm as well as cool. As any amateur astronomer knows, the best nights for star gazing are often the coldest.”

    Overall, clouds reflect more solar radiation than they trap, leading to a net cooling of ~27.7 W/m2 from the mean global cloud cover of ~63.3% [Hartmann, 1993].

    According to Tinsley and Yu’s paper (see link below), an increase in GCR results in an increase in low level clouds and a decrease in high level clouds. There are papers that ostensibly provide some support for a link between GCR and low level clouds, however, the papers in question are disputed by others. (See Palle, satellite data and earthshine data.)

    Svensmark’s satellite data and analysis was disputed as others thought satellite data could not show whether the clouds were low or high and disputed detailed aspects of Svenmark’s analysis. Palle used a different analytical technique than Svensmark, which Palle thought resolved some of the analytical issues. I did not find any papers disputing Palle’s earthshine data and analysis, however, there probably were some.

    Atmospheric Ionization and Clouds as Links between Solar Activity and Climate
    By Brian Tinsley and Fangqun Yu

    http://www.utdallas.edu/physics/pdf/Atmos_060302.pdf

    The solar cycle appears, based on the data I have seen, to be moving towards a sever minimum. If Tinsely and Yu’s theory is correct and Palle’s back of the envelope estimate of the forcing is correct there should be a cooling of around 5 W/m^2, over the next four years. (Solar large scale magnetic field takes about four years to dissipate if the solar cycle is interrupted.)

    There is no need to speculate, however, if the change is significant there will be a need to relook at the fundamentals. If not, then the issue should be resolved.

    Comment:
    The data did not support T & Y’s, theorized reduction in high level clouds with increasing GCR. Maybe the theorized high cloud mechanism requires higher energy GCR. According to T & Y low level clouds result in net cooling and high level clouds net warming. Mid level clouds about neutral. See their paper for details.

    Comment by William Astley — 23 Apr 2007 @ 10:37 PM

  196. Re #190: Steve R., see this discussion. Per Gavin the ISCCP team think these papers are correct (that the long-term cloud trends are more or less flat). This RC post is also somewhat relevant.

    Comment by Steve Bloom — 24 Apr 2007 @ 2:54 AM

  197. Re #193: Thank you, tamino, for correcting my misconception that obliquity does not affect the distribution of insolation. But I did get it right that the position in the precession cycle referred to by Dan Fregeau does not change the amount of insolation received in any region, and will not affect sea surface temperature in the way he claims.

    Comment by Blair Dowden — 24 Apr 2007 @ 5:49 AM

  198. Gavin and Hank (#186,#187), thanks, the biological proxies are worth more studying. My thoughts might have been backwards, the isotope ratio in forminifera may be related to CO2 concentration rather than solely to CO2 source (anthropogenic or natural methane) although this is apparantly controversial (see http://www.shef.ac.uk/aps/apsrtp/humphreys-claire/masters-dissertation.pdf p. 4). Also for Steve B (#188), it’s not so much “gaps” as comparing 1000′s of data points in the current interglacial to about two dozen in the previous interglacial to maybe 3-5 in the ones prior to the previous one (ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/vostok/co2nat.txt)

    Comment by Eric (skeptic) — 24 Apr 2007 @ 5:55 AM

  199. Agree with the removal of bias from the float data as the NOAA paper outlines. Not sure the bias was real bias or actual areal temperature anomalies, my random continous sampling of inflight air temperatures and pressures at various levels indicates pools of instability outside of the normal range. I have a suspicious that there was a cooling for the period as there does not seem to be an acknowledgment of the inflows of melt water into the ocean circulatory systems, cold water can be quite diffuse. If there is a suppressing northern and southern melt water temperature effect then the proof will be rising but behind the model temperature increase estimates over the next decadal period.

    Comment by Mike Hart — 24 Apr 2007 @ 6:31 AM

  200. I note that when people talk about CO2 levels in the distant past to today they compare the CO2 in the ice to the atmospheric levels of today. When I have looked at the Ice core record there is a difference between the age of the ice and the air trapped within. My question, are there any ice core records that can be compared to the atmospheric record of CO2 since the late 1950′s. My concern is that without actually being able to compare known atmospheric CO2 trends to trapped CO2 in ice, any information obtained about past CO2 levels may be dubious at best.

    Comment by Ellis — 24 Apr 2007 @ 7:54 AM

  201. William, the problem with a GCR driven mechanism is that it has to be operative at the time of the effect it tries to explain–and GCR fluxes simply are not changing–based on either satellite observations or neutron monitoring. Moreover, I would characterize the latter half of the 19th century to be a time of exceptionally high solar activity, rather than the present being low. The 1854 Carrington flare was the biggest on record–generating auroral displays as far south as Havana. The proton fluxes for the solar cycles of that era were significantly higher than the present–but also higher than past solar cycles.
    I really don’t trust estimates of GCR fluxes prior to our ability to measure neutron fluxes and especially GCRs themselves. And I especially don’t trust such estimates for energys lower than 1 GeV. Hell, solar protons have energies up to about 300 MeV, and at fluences higher than GCR over a solar cycle. I’m afraid the whole GCR theory is a house of cards–just one last straw for skeptics to grasp. I just don’t understand why people believe in such a mish-mash when there is a perfectly credible theory based on well known physics with mountains of evidence in favor.

    Comment by Ray Ladbury — 24 Apr 2007 @ 7:59 AM

  202. Ellis (#200)–they can and do look at trapped gasses in ice as soon as forms (about 10 years, I think). They also correlate well with other measures. Ice physics is pretty well understood. Also, what would you expect to be the effect if the gas content did correlate with time? Would you expect the warming to line up with CO2 content as we see it, or would you expect no correlation? Systematic errors generally do not give rise to order.

    Comment by Ray Ladbury — 24 Apr 2007 @ 8:29 AM

  203. Re: #201 (Ray Ladbury)

    Do you have a link to GCR data, both space-based and ground-based measurements?

    Comment by tamino — 24 Apr 2007 @ 9:08 AM

  204. Re196: Steve Bloom> Per Gavin the ISCCP team think these papers are correct (that the long-term cloud trends are more or less flat).

    That is not what I see at your link. The conclusion seems to be that there is currently no reliable data on long term cloud trends.

    From Evan et al.:
    “Our results suggest that in its current form, the ISCCP data may not be appropriate for certain long-term global studies, especially those focused on trends.”

    Comment by Steve Reynolds — 24 Apr 2007 @ 9:54 AM

  205. The issue of cosmic rays affecting climate really comes down to whether there is a trend in cosmic rays or not, and people don’t seem to agree on that. Nir Shaviv shows cosmic ray data from ion chambers (ie high energy GCR) on his website http://www.sciencebits.com/CO2orSolar (Fig 6. note that the graph has an inverted y-scale), claiming that these high energy rays are more relevant for atmospheric ionization than low energy GCR’s as measured by neutron counters. The trend is different for different energies, for which he doesn’t have an explanation. Which measurements should we trust more, and why?

    [Response: There is a perfectly sensible explanation. The figure Shaviv uses to demonstrate a trend is a splice between two individual stations with different means (Cheltenham/Fredricksburg and Yakutsk) - neither of which have a trend - but as you go from one to the other (C/F in the early years, Y later on), you get an apparent shift. No single detector of any GCR related quantity shows a trend over this period. - gavin]

    Comment by Darrel — 24 Apr 2007 @ 9:55 AM

  206. Hi Tamino,
    I looked at the space based data (GOES and other satellites) myself as part of a study we were doing. It fluctuates of course, but I didn’t see any trend in the mean.
    The terrestrial stuff is here:

    http://ulysses.sr.unh.edu/NeutronMonitor/Misc/neutron2.html

    More recently, Clive Dyer et al. have been doing research using neutron monitors on airliners.
    All of this data says to me that there is no clear trend–certainly not one sufficient to see the level of warming we are seeing.

    A caveat about the GOES data–it just looks at particle fluxes–so you have to confine yourself to times of solar quiet–either solar min or between events during solar max.

    Comment by Ray Ladbury — 24 Apr 2007 @ 10:48 AM

  207. Re: #206

    Thanks for the link and the info! I don’t doubt the absence of a trend (although I’m sure to run the numbers anyway), I just have a blog reader who keeps asking.

    Comment by tamino — 24 Apr 2007 @ 11:06 AM

  208. Scientists have a love for discovering, and sometimes will go to great lengths to keep on doing what they love, which is scientific inquiry and discovery. They need funding, so they develop a relationship with the government similar to a trophy wife who marries for money. This relationship works out well, at least it used to. Unfortunately scientists are at the whims of the funding source, and this is the paradigm that has to change. That is why science and politics mix. The new science has to discover for the cause without the money having a say.

    Comment by Paul M — 24 Apr 2007 @ 11:12 AM

  209. Paul M. (#207) Like most scientists, I really hate writing grant proposals. However, I view it as a necessary evil because I have questions that I need to answer if I’m to be able to do my job (making satellites fly in a radiation environment). I make my living as a physicist–that means somebody has to pay my salary–in my case about 330 million somebodies (thanks, y’all, by the way). Ultimately, I am answerable to them for the quality of my work, and they or their representatives have to decide whether the work I do is worth the investment. I am, however, hardly a trophy wife–not nearly ornamental enough for one thing. My salary does not buy my complicity in producing bad science that supports policy. As a scientist, part of my job description is: “Tell the truth.” That is true no matter who signs my paycheck, and if my employer does not understand that, then they might want to think again about employing a scientist. Despite the tendency of the current administration to try to control the flow of information, scientists have insisted on speaking out–not because they necessarily oppose the administration, but because it is their job.
    In the past, I have worked for industry, and the tendency of scientists to bluntly state the truth was alarming to customers. The solution in business was to create layers of management between the scientist and the customer to sugar coat the bad news. Now that I am a customer of these same businesses, I insist on talking to the scientists.

    Comment by Ray Ladbury — 24 Apr 2007 @ 11:30 AM

  210. Re #294: Possibly I was imprecise. The papers throw into question what had been thought by some to be a long-term trend, while the ISCCP team believe that there is no significant trend (i.e., there won’t be one after the correction is made).

    Comment by Steve Bloom — 24 Apr 2007 @ 2:58 PM

  211. I was surprised by your edit of Roger Pielke’s comment. I am also surprised that I am not allowed to express my surprise. Is this RealClimate or RealCensorship?

    Comment by Richard Tol — 24 Apr 2007 @ 3:41 PM

  212. Re: #209 (Ray Ladbury)

    I have worked for industry, and the tendency of scientists to bluntly state the truth was alarming to customers.

    Boy howdy, I hear that! I used to do mathematical analysis for astrophysicists, and they wanted the straight story good or bad. I’m now in industry, and although the pay is a lot better, it surprises me how often management will wince when I try to give it to ‘em straight.

    And they don’t let me near customers.

    Comment by tamino — 24 Apr 2007 @ 4:49 PM

  213. Hi Ray, in reply to your comment:

    “William, the problem with a GCR driven mechanism is that it has to be operative at the time of the effect it tries to explain–and GCR fluxes simply are not changing–based on either satellite observations or neutron monitoring.”

    It is hypothesized that planetary cloud cover can be reduced without a drop in GCR. The high speed solar winds which occurred at the end of cycle 21 and 22 it is hypothesized energized the global electric circuit (see Tinsley and Yu’s paper in my comment above for a discussion of the mechanism). It is hyphothesized the increase in the global electric circuit current, through the process of electroscavenging removes cloud forming ions. The effect is greatest over the oceans. Palle’s paper references Tinsley and Yu’s electroscavenging mechanism and states he believes his data supports, that planetary cloud cover has reduced over the oceans due to that mechanism.

    Due to the sun’s hypothesized affect on the global electric circuit, the sun’s overall affect on cloud cover and climate is not a simple linear relationship of number of sunspots. I can see why other researchers who only looked at number of sunspots could not find a simple relationship between sunspot number and climate. Cycle length is also important as is the large planet’s cyclic gravitation change of solar position, which appears to affect the radiative zone to convection zone boundary. Based on this most recent solar change.

    In reply to your second comment that solar activity was high around 1854.

    Ken McCracken’s data and analysis (see attached below) compared current solar activity and GCR to that at the end of the 1900 century (not mid 19th century) At the end of 1900 century solar activity has low and the climate was coincidently cold.

    K.G. McCracken’s “Long Term Trends in the Intensity of GCR and Frequency of occurrence of Solar Particle Events.”

    http://hesperia.gsfc.nasa.gov/sspvse/oral/Ken_McCracken/wintergreen1.pdf

    Your comment that there was a strong solar flare in 1854 does not necessarily mean solar activity was strong during that period. (This is more an aside, I have been reviewing what papers I can find concerning the solar cycle mechanism, what causes a Maunder minimum, and Super solar flares.)

    The following is Hathaway’s comment from the attached link, which notes that super flares can and have occurred at solar minimums. (The attached link notes that the sun was at a minimum February 2006. It is again at minimum April 2007. As to what to expect for solar cycle 24, there is not agreement. Both high and low predictions. Cycle 23 was predicted to end sometime between December 2006 and October 2007.)

    “But not absolutely quiet,” adds Hathaway. “During solar minimum we can have occasional sunspots and solar flares.” Indeed there was at least one monster spot and one X-class solar flare (the most powerful kind) during each of the last three minima in 1976, 1986 and 1996.

    http://science.nasa.gov/headlines/y2006/06mar_solarminimum.htm

    Comment by William Astley — 24 Apr 2007 @ 9:31 PM

  214. Ray, Tamino, et al: I was (in part) on the marketing and product management side in industry (big ticket computer systems and telecommunications). I found customers once in a while demanded direct interface with the scientists/engineers/techies; I was all in favor. Every now and then the techie would perceive a non-problem as an upcoming disaster and I’d have to patch that up, but a small price to pay for the credibility gained. If you’re trying to sell a $50 milllion system or network you can forget it if 1) you have poor credibility with the customer, or 2) you leave some strongly-felt technical questions go unanswered. And if the scientist describes a really dirty truth (hopefully before a customer meet…) you’d damn-well better know it long before the day after the system install.

    Comment by Rod B. — 24 Apr 2007 @ 9:45 PM

  215. William, I guess we need to define what we mean by solar activity–I’m looking at solar particle event frequencies, which correlate with sunspot activity. By my definition, the solar cycles in the latter half of the 19th century were quite active compared to today. And the Carrington event was about 4x larger than any other SPE we know of. What is your definition?
    The solar cycle is actually 22 years, but we really only see a sort of absolute value reflected in solar activity. Solar max is roughly 7 years long, while solar min is roughly 4 years long. GCR oscillates on the same 11 year cycle, but is max during solar min and vice versa. What is more, if you’re saying that the fin de siecle solar activity was low, how does that square with the fact that climate has been warming since the end of the 18th century? Indeed, the basic mechanisms of greenhouse warming were developed to explain this trend.
    Finally, there is zero evidence that gcr fluxes are changing significantly. They fluctuate–hell there are only 6 particles per cm2/sec, they’re bound to fluctuate. But mean fluxes are not changing. And unlike CO2, if fluxes aren’t changing your driver is gone–there’s no persistence.

    Comment by Ray Ladbury — 25 Apr 2007 @ 8:01 AM

  216. Re: #186. Diatoms are made out of silica; coccolithophorids and foraminifera are made out of CaCO3.

    Comment by Jack — 25 Apr 2007 @ 8:56 AM

  217. Hi Ray,

    Ak is my parameter of choice, to measure the solar affect on planetary temperature. Ak is a measure of the sun’s affect on the geomagnetic field. (The are a number of solar changes that affect Ak. i.e. In addition to energy of particle such as strength of the solar large scale magnetic field) There is an interesting paper that shows there is close correlation of 20th planetary temperature changes and changes in Ak.

    Some believe there is evidence for an increase in the solar large scale magnetic field in the 20th century. (See below.) Do dispute that evidence or conclusion?

    Evolution of the Sun’s large-scale magnetic field since the Maunder minimum

    http://www.nature.com/nature/journal/v408/n6811/abs/408445a0.html

    “A part of the Sun’s magnetic field reaches out from the surface into interplanetary space, and it was recently discovered3 that the average strength of this interplanetary field has doubled in the past 100 years. There has hitherto been no clear explanation for this doubling. Here we present a model describing the long-term evolution of the Sun’s large-scale magnetic field, which reproduces the doubling of the interplanetary field. The model indicates that there is a direct connection between the length of the sunspot cycle and the secular variations.”

    Comment by William Astley — 25 Apr 2007 @ 1:45 PM

  218. When I see the word “correlation” in an abstract, alarm bells go off in my head. Solanki’s a good researcher, but he is sometimes off in the weeds. If heliomagnetic field has doubled, that would affect primarily the low-energy end of the GCR spectrum–and those particles probably won’t contribute to cloud formation at low altitudes in any case. What is more, there does not seem to be ANY indication that GCR fluxes are changing over the last, say 60 years, and warming has definitely accelerated during this period. That’s one of the problems with this work–if you look at a blow-up of warming and solar activity in recent years, there’s zero correlation. What is more, the reliance on correlations with zero understanding of the physics (why heliomagneitic field correlated with sunspot, how and whether GCR facilitate cloud formation, why the cloud formation should be at low rather than high altitude, and so on) makes the theory rather murky. On the other hand, there is a perfectly well worked out theory with well understood physics that does an excellent job of explaining the observed trends. The anthropogenic ghg theory works. It ain’t broke. There’s no indication that it has any difficulty explaining what we see. And we understand the physics. Pray tell, why would I swap a working theory for a not-quite-half-baked outline?

    Comment by Ray Ladbury — 25 Apr 2007 @ 2:23 PM

  219. Jack corrects me quite properly. Diatoms use silica, and it’s the organisms with calcite and aragonite shells that are at risk. They all show up in the sediment cores, and the variation’s part of the info there.

    Comment by Hank Roberts — 25 Apr 2007 @ 8:38 PM

  220. Speaking of which, here’s an interesting thesis on the oceanic shelled plankton, a good general read with some interesting bits:
    http://www.nioz.nl/public/annual_report/2005/brummer.pdf

    Comment by Hank Roberts — 25 Apr 2007 @ 8:42 PM

  221. Ray, the 20th century temperature increase has not be a linear change. (See the paper below.) There is a hypothesized mechanism and evidence that the forcing function for that mechanism was been active during the 20th century. There is correlation of solar changes and planetary temperature. The question is what is the appropriate weighting of the two forcing functions, GHG and solar?

    I have looked at the abrupt temperature changes in the past. I do not understand how ocean current changes could cause abrupt simultaneous wide spread planetary cooling including tropical oceans or what could cause semiperiodic stoppage of ocean currents. As to insolation changes driving the glacial cycle, besides specific periods when there is not even correlation, I support David’s comment that it is fact that the insolation forcing is balanced if both hemispheres are considered or both seasons are considered. As the planet is 70% covered with water and the thermal capacity of the ocean is 1000 times that of the atmosphere, it seems reasonable the oceans would smooth symmetrical insolation changes.

    As the solar cycle seems to be about to abruptly slow down, we will all have a change to observe what the correct bifurcation of forcing functions is. Have you had a chance to look at recent solar data?

    http://sait.oat.ts.astro.it/MSAIt760405/PDF/2005MmSAI..76..969G.pdf

    CMEs, however, are not the only source of high speed solar wind. Early in the 20th century it was noticed that many geomagnetic storms occur without any visible solar disturbance. Such storms tend to recur every 27 days – the period of solar rotation, therefore they originate from long-living regions on the Sun which come back into geoeffective position rotation after rotation. Only when X-rays telescopes were flown above the atmosphere, it was found out that are large regions of open magnetic field geometry, and sources of high speed solar wind. They are now known as Coronal Holes (CHs) because, due to their lower density and temperature compared to the surrounding corona, they look darker in X-rays.

    In Figure 6 the long-term variations in global temperature are compared to the long-term variations in geomagnetic activity as expressed by the ak-index (Nevanlinna and Kataja 2003). The correlation between the two quantities is 0.85 with p<0.01 for the whole period studied. It could therefore be concluded that both the decreasing correlation between sunspot number and geomagnetic activity, and the deviation of the global temperature long-term trend from solar activity as expressed by sunspot index are due to the increased number of high-speed streams of solar wind on the declining phase and in the minimum of sunspot cycle in the last decades.

    Comment by William Astley — 25 Apr 2007 @ 10:24 PM

  222. [[Ak is my parameter of choice, to measure the solar affect on planetary temperature.]]

    The problem here is in your first phrase above. I don’t think you’re doing it deliberately, but it’s possible you’re looking through all the solar indices to find one that correlates well with temperature, then seeking to figure out a physical explanation for it later. That’s not good science. Look at enough time series and you can nearly always find one that seems to match another series of interest, but that’s not a theory, that’s just the fallacy of the enumeration of favorable circumstances.

    Comment by Barton Paul Levenson — 26 Apr 2007 @ 6:37 AM

  223. #167 (Steve Bloom) – Eldrett paper

    I think that it is an interesting finding that should raise some eyebrows given that current models cannot duplicate the scenario unless you have much lower CO2 levels. It is hard for me to conclude that it does not raise any serious questions about current assumptions regarding expected climate during very-high CO2 periods given that the paper states:

    “Recent palaeoclimate model experiments generate substantial ice sheets in the Northern Hemisphere for the Eocene only in runs where carbon dioxide levels are lower (approaching the pre-anthropogenic level)”

    Furthermore, the degree to which this represents small or large glaciers vs. giant ice-sheets is still unknown, but the paper suggests large ice-sheets for at least a part of this period. Paraphrasing the paper’s conclusion:

    “By inference, our data strengthen the case for … more extensive ice-sheets at the glacial maximum of the Eocene â�� Oligocene transition”

    Given that much of the support for the Greenhouse Theory, including quantifying/bracketing sensitivity, comes from the long-term correlation between glaciation = low CO2 levels, and warm periods = high CO2 levels, as measured during the Phanerozoic (Royer 2004; Berner 2004), this paper seems to be of some significance to the ongoing discussion by pointing to the fact that paleoclimate is still not fully understood (unlike what appears to be the much higher certainty claimed for our modern climate).

    [Response: You were on the right track citing Royer and Berner, but you're out of date. The most recent work by this group shows that the Phanerozoic record of CO2 in fact independently supports a sensitivity to greenhouse gas forcing that is eerily close that estimated by most other methods (just under 3C for 2xCO2). The article requires subscription, but there is a news release summarizing the study here. - mike]

    Comment by Dan Fregeau — 26 Apr 2007 @ 6:59 AM

  224. #179 (Pat Cassen) Svensmark and Solar Wind
    Of course not, although there might be local current variations, but the density/intensity of the solar wind is greater at perihelion than at aphelion. Per Svensmark, greater solar wind would cause more GCR shielding, reducing nucleation and cloud cover, hence increasing atmospheric transparence. Therefore, the season of perihelion (more solar wind = less GCR) would have fewer clouds and therefore be warmer and converserly the season of aphelion (less wind = more GCR) would have more clouds and therefore be cooler. This should vary according to precession, with coincidence of perihelion-solstice representing a maximum seasonal effect of solar wind/cloud cover relationship. Of course, this will also be modulated by eccentricity such that when eccentricity is high, the seasonal solar wind/cloud cover will vary more, but when eccentricity is low as it is today, the seasonal solar wind/cloud cover differential will be less.

    So putting this in the modern context, because we are approaching coincidence of perihelion-solstice at low eccentricity, the solar wind would be greatest in southern hemisphere summers and northern hemisphere winters. This would maximize summer heat absorbtion in the southern oceans, as well as inhibit winter glaciation with increased melting in the northern hemisphere, and this seems to be occuring today.

    Comment by Dan Fregeau — 26 Apr 2007 @ 7:08 AM

  225. #166 (Ike Solem) – Timescales
    Let’s be clearer on this. I do not dispute that burning fossil fuels, large-scale deforestation, various types of agriculture, industrial cement processing, etc. are all increasing atmospheric GHG concentration. I also do not dispute that the resultant GHG increases are warming the earth and will have an impact of the biogeochemistry of the earth, and that therefore we should take appropriate steps to manage our emissions and environmental practices. I think we are all on the same page on these points, i.e. the earth is a great place to live and we should take care of it as best we can.

    But the degree to which GHGs will be warming the earth by comparison to perihelion-solstice approach in the next century or thousand years, is what I am trying to debate. While it is true that changes in annual global insolation, i.e. due to solar variation, by themselves cannot account for significant climate change, it is equally true that large-scale changes in regional insolation due to orbital geometry can cause large regional temperature differences, witness the fact that we have annual seasons, as one obvious example.

    The notion that we might also have much longer term “seasons” at the millenial time scale (to use your term) should not be haphazardly discounted, particularly given the reality of the paleoclimatic record, which suggests just that. Furthermore, the fact that we are approaching a longer-term “seasonal” zone, i.e. perihelion-solstice coincidence in the southern hemisphere during a long low-eccentricity interglacial, warrants a better understanding of the scope of natural vs. anthropogenic forcing within that zone, particularly given the fact that we have evidence that natural forcing during prior MIS-11 interglacial analogue may have been significant based on reported sea levels as well as Northern European fossils of warmer species during that period. Do you disagree?

    Comment by Dan Fregeau — 26 Apr 2007 @ 7:11 AM

  226. Re #222, Barton, it’s also possible to look through anthropogenic factors to pick out a set that correlate with temperature although fitting in the physics is generally easier than with the sun’s effects. William, although there is a natural component to the current warming (and CO2) that must be combined with the human component to get a complete theory.

    Comment by Eric (skeptic) — 26 Apr 2007 @ 7:11 AM

  227. #189 and #197 (Blair Dowden)

    Please clarify why you think that heat gain and heat loss are in balance. This seems like a critical assumption and I would like to understand your reasoning here.

    Unlike the northern landmasses, the southern oceans have greater heat capacity, and the entire system is well insulated by the atmosphere. Heat transport via oceanic currents is very slow, so it’s not clear to me how higher heat gain during southern hemisphere summers would be offset in the winter.

    Comment by Dan Fregeau — 26 Apr 2007 @ 7:23 AM

  228. #223 Response by Mike

    Re. Nature Royer/Berner – yes I read that report and the sensitivity is at least or greater than 1.5 as stated in the abstract (with 2.8 being the best fit currently), but that still does not explain glaciation in Greenland which is what my point was really about.

    If there was no extensive glaciation at very high CO2 ppm levels, then that would support the belief that increased CO2 is responsible for massive deglaciation via global greenhouse warming. But if there was still large glaciation with very high CO2 ppm levels, then it’s not that simple, per the Science paper I referenced. Do you disagree?

    Comment by Dan Fregeau — 26 Apr 2007 @ 7:44 AM

  229. Dan, aren’t you forgetting albedo there? Ice builds up extensively; albedo goes up; while albedo is high, CO2 can increase and stay quite high. It’s a time series of events you have to follow, not a snapshot.

    Comment by Hank Roberts — 26 Apr 2007 @ 8:06 AM

  230. Dan, do the math. The solar wind will decrease as the inverse square of the distance from the Sun–just as insolation does. Thus, both effects are <1%. The effect of the 11 year solar cycle is much larger–roughly a factor of 3x in gcr fluxes.

    Comment by Ray Ladbury — 26 Apr 2007 @ 8:10 AM

  231. #218 (Ray Ladbury) The theory ain’t broke

    “On the other hand, there is a perfectly well worked out theory with well understood physics that does an excellent job of explaining the observed trends. The anthropogenic ghg theory works. It ain’t broke. There’s no indication that it has any difficulty explaining what we see. And we understand the physics. Pray tell, why would I swap a working theory for a not-quite-half-baked outline?”

    I thought that the goal of science was to understand what is really happening, i.e. the reality of Real Climate. Svensmark is not advocating “swapping” anything that I am aware of, nor should his findings be exclusive of any other climate changing factor in any way. GHG is certainly a component of the truth, perhaps even the most important component of today’s climate, as most believe.

    But what if there were other critical components that also merit scientific research – astronomical cycles, cosmic ray flux variability, heliospheric currents, geophysical feedbacks, etc. Are you suggesting that it would be better science to discount researching those altogether, or to attack them by restricting their funding? Please clarify as I don’t really understand your position here.

    Comment by Dan Fregeau — 26 Apr 2007 @ 8:14 AM

  232. William, It doesn’t matter how good your correlation is if GCR fluxes aren’t changing, and they aren’t. BTW, for a “correlation” type study such as this, a correlation of 0.85 is not that great, mainly because the search for a correlation is not constrained by an underlying physical model that tells you what parameters to look at. Thus if p=.01 for an 85% correlation, if you look at 100 different variables, you’re sure to find such a correlation with one of them. In effect, what you are doing is epidemiology here. And while epidemiology comes up with interesting results from time to time, it has a pretty poor track record as a scientific discipline.
    And here’s the thing that I don’t understand. There is LOTS of evidence for a forcing of ~3 degrees C per doubling of CO2–tons of evidence. So it seems to me that if you find that a cosmogenic mechanism is important, you have to explain why a) all of that other evidence needs to be ignored; or b)why the situation is different now and the same forcings no longer apply. The whole system has to stand or fall as a whole, and it is difficult for me to believe that we do as good a job at modeling a complicated system like climate with models making reasonable physical assumption purely by chance. Climate science just doesn’t resemble a nascent field where there are no physical models and the inquiry is dominated by exploration. It is a mature science. So, maybe GCR do contribute to climate–it’s a stretch to believe that a driver with only 5 particles per cm^2/sec is significant, but I’ll suspend disbelief. To think that this mechanism–completely ignored in current models–contributes more significantly than the known sources absolutely strains credulity.

    Comment by Ray Ladbury — 26 Apr 2007 @ 8:58 AM

  233. #230 (Ray Ladbury) Do the math

    But if this seemingly small effect is cumulative because the southern ocean’s larger heat capacity is acting as a long-term heat reservoir, what might that add up to?

    I thought that the Greenhouse Therory was likewise caused by a small cumulative effect, is it not? Why is it that the GHG effect is not discounted on the same ground as this one?

    Comment by Dan Fregeau — 26 Apr 2007 @ 9:02 AM

  234. #229 (Hank Roberts)

    Since the period prior was clearly one of very high CO2, then why did the ice build-up in the first place since the earth should have been plunged in a global greenhouse state, correct?

    Some of the thinking I have seen on this proposes that something caused the CO2 to drop dramatically – can you suggest the mechanism by which this would occur? My understanding is that this is not understood, but maybe I am wrong. Can you send me references that explain the mechanism for that transition.

    Comment by Dan Fregeau — 26 Apr 2007 @ 9:10 AM

  235. Dan, the sun is and will remain the most important energy source for climate. Fortunately, its input is easily measured. After the sun, the greenhouse effect is #2, with H2O being the greatest contributor. That too, is relatively easy to model. CO2 is #2 on the list of ghgs. Other sources are way down the list. If there were other critical components that contributed at the same order as the above components, the climate models would not come even close to getting the answer right. There are mountains of evidence that support the current model, and it’s not as if there are lots of adjustable parameters that we could twiddle to support new physics–the models are pretty well constrained by data; their main uncertainties have to do with the human response. So, it’s not just a matter of coming up with a couple of new phenomena to consider. You’d have to come up with a whole new model.

    Should these other sources be investigated? Certainly. And if they hit the jackpot, they pay off big. However, the probability of a payoff is small, so in the mean time, we have a working theory, physically reasonable and well substantiated by evidence. We should use that to guide policy.

    Comment by Ray Ladbury — 26 Apr 2007 @ 9:11 AM

  236. #232. Well, except that the oceans would then lose the heat to the atmosphere via evaporation and via radiation at aphelion. There’s no mechanism for transfering energy to the deep ocean where it would be somewhat insulated. The thing is that you are not changing the amount of energy incident on Earth. Nor have you proposed a mechanism for Earth to hold onto more of the incident radiation. The greenhouse effect serves as an insulating blanket, preventing some IR from radiation back into space, so it’s holding onto more of the incident energy. As to the climate and past warming and cooling epochs, no climate scientist has ever said that CO2 is only or even the most important factor in climate. If solar radiation decreased due to Milankovitch cycles, then Earth would cool because ultimately all energy in Earth’s climate comes from the sun.
    As to how CO2 could suddenly decrease–biogenic processes are the only process I know of with the right timescale, unless maybe there were a rapid overturning of cold ocean water for which CO2 solubility is high. Anybody else?

    Comment by Ray Ladbury — 26 Apr 2007 @ 9:38 AM

  237. I thought that the goal of science was to understand what is really happening

    Another stunning statement from the audience.

    According to our current perspective of reality, nature and the universe, we can NEVER understand what is really happening, we can only model it to higher and higher precision. What is the exact value of pi? That’s easy, it’s pi. Rather than blindly adopting a denialist position, you need to do a little research about the history of science, and of science itself. Skepticism of science must be backed up with evidence, just as science itself must.

    All things are in principle knowable, but the act of investigating reality itself changes the landscape, just as our pursuit of science on Earth has changed the landscape of Earth. That’s what we are trying to come to grips with here, and you’re flailing about mucking up what we think we know, is not producing any new knowledge. If you think you can break a paradigm, you’re going to have to try a lot harder than simply posting your reservations on an internet blog. I would encourage you to try, but I must point out that it appears that you haven’t even fulfilled the basic educational prerequisites for intelligent discussion yet.

    Search engines are your friend. Use them.

    Comment by Thomas Lee Elifritz — 26 Apr 2007 @ 10:21 AM

  238. Re 224, 230: The flux of galactic cosmic rays is modulated over the entire extent of the heliosphere, so the difference in GCR flux from perihelion to aphelion is probably more like 1%/(size of heliosphere in AU), i.e., zilch.

    Comment by Pat Cassen — 26 Apr 2007 @ 11:37 AM

  239. Science is about transistors, masers, lasers, and moore’s law. Because of Sputnik, the Government got involved and we got some healthy competition going and fufilled Kennedy’s promise of sending a man to the moon (although he did not live to see it). But the NASA glory days are over, and now medicine is the new darling. But just as the science landscape is changing, so is the global landscape, in every facet including economic. In the near future the prospective scientist will be heading to China to do research, maybe at MIT’s new facility there. Scientists love to discover, and they married the Government to do exactly this. In the new landscape scientists need to do research with no restrictions from the money source, ultimately to save the human race. In the WWII years, German scientists could have stayed where they were and could have developed nuclear weapons living a comfortable life. But they made a stand on principle—develop the bomb, but do it before the evil society does it, in a free environment. Climate scientists must make these decisions in an arena that is equally important as the nuclear one. Politics must step aside and pure science needs an environment that will solve this crisis or we cannot call ourselves civilized.

    Comment by Paul M — 26 Apr 2007 @ 11:57 AM

  240. [[Some of the thinking I have seen on this proposes that something caused the CO2 to drop dramatically - can you suggest the mechanism by which this would occur? My understanding is that this is not understood, but maybe I am wrong. Can you send me references that explain the mechanism for that transition.]]

    On a long enough time scale, CO2 is reduced by weathering and deposition in sediments. For more information, try here:

    http://www.geosc.psu.edu/Courses/Geosc320/walker.pdf

    Comment by Barton Paul Levenson — 26 Apr 2007 @ 12:45 PM

  241. Paul, I disagree with your post on several grounds
    First, practical. Science costs money. Where will this money come from if government does not fund science. Business? Not likely–they’ve cut R&D to the bone.
    Second, NASA is hardly dead–there’s a Hubble Servicing Mission planned, a mission to Europa, the James Webb Space Telescope. They are looking at the sky from microwaves to gamma ray bursts and finding new stuff all the time. Hell, just yesterday, we had the announcement of the first Earth-like planet.
    Third, yes many of the scientists who built the bomb for the US were German emigres. They were also Jewish. Had they stayed in Germany, they would have died in the camps. Their stand was personal as well as principled.
    Third, the answer is not for scientists to refuse the coin of the realm. There is the old story of the Texas Legislator who said his ethis code was, “If you can’t take their money, drink their liquor and screw their women and still vote against them, you’re in the wrong place.” Now that’s ethics of a sort, but the lesson applies. Paying my salary buys my efforts, not my honor. Part of the job description of the scientist is to find the truth and to tell the truth. At one point politicians realized that despite the occasional inconvenience of having to face unpleasant truths, ultimately society benefited from supporting science. Problem is that until the people are educated enough to understand that, they won’t be able to teach it to their leaders.

    Comment by Ray Ladbury — 26 Apr 2007 @ 1:03 PM

  242. Barton’s answered you on CO2 reduction; keyword search would be “biogeochemical cycling” and you’ll find it well studied.

    In the (geologically) shorter term, you can also watch an example of evolution in action as life evolved forms (in less than a hundred thousand years) that could make use of the surplus CO2. That’s the “bio-” part of the cycling.

    I recall one good article on that, let’s see if I can find a copy.
    It had a typo corrected later, the length of the hottest time was wrong, you can look that up.

    http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=11001051&itool=pubmed_AbstractPlus

    You may find a readable copy online(if it’s not showing up later, ask your librarian)
    http://72.14.253.104/search?q=cache:YJ3oQ9MTf7AJ:courses.washington.edu/ocean450/Discussion_Topics_Papers/Schmitz_et_al.pdf+%22Plankton+Cooled+a+Greenhouse%25&hl=en&ct=clnk&cd=4&gl=us

    Comment by Hank Roberts — 26 Apr 2007 @ 3:11 PM

  243. Dan, don’t miss Mike’s response inline in your #223.
    Note right hand list, of postings “…With Inline Responses”

    Comment by Hank Roberts — 26 Apr 2007 @ 4:01 PM

  244. RE #161 “As with our annual seasons, the long-term changes in insolation are most pronounced at the polar regions and higher altitudes in both hemispheres, and this reaches a maximum at the intersection of perihelion and solstices, roughly every 10,000 years, a zone that we are currently approaching.”

    Any comment on this?

    http://ams.allenpress.com/perlserv/?request=get-abstract&doi=10.1175%2F1520-0442(2001)014%3C2369%3AAODTSF%3E2.0.CO%3B2

    To quote from it:

    “When the ENSO oscillation is in transition between the two regimes, and is weak and moderately regular, the system can lock to the period of the forcing (1 yr). This gives rise to the abrupt behavior shown in Fig. 1. This behavior recurs on an approximately 11-kyr timescale, when perihelion occurs either during boreal winter or summer.”

    And again:

    “The paleoclimate record shows that the pacing of abrupt climate change could be linked to the solar forcing. Heinrich (1988) found that episodes of major ice
    rafting in the North Atlantic recur on an 11-kyr timescale over the last glacial at times of boreal winter and summer insolation maxima…”

    Comment by Jim Cross — 26 Apr 2007 @ 6:51 PM

  245. Ray,

    Solar changes can affect cloud cover without a change in GCR through the mechanism of electroscavenging, where changes to the global electric current, caused by high speed solar winds, removes cloud forming ions. The negates your argument that as GCR was not trended continually down in the later portion of the 20th century, that a change in cloud cover could not be responsible for a significant portion of the 20th century warming.

    The satellite data and earthshine data (Palle 2003 & 2004) supports at a 99.5% confidence level that planetary clouds track GCR changes 1973 to 1993. 1993 to 2003 planetary clouds continue to track GCR except for a persistent reduction in cloud cover. The reduction in cloud cover is believed to be due to the electroscavenging process. Palle in his earthshine paper estimated the forcing due to the reduction in planetary cloud to be 7.5 W/m2 (for the period in question) as compared to the estimate 2.5 W/m2 for combined GHG.

    See copy of Palle’s satellite paper. (See figure 2. Note low level clouds are reduced by minus 0.065% per year, starting in about 1993.)

    http://solar.njit.edu/preprints/palle1264.pdf

    The high speed solar winds in solar cycle 21 and 22 were caused by coronal holes that moved towards the solar equator. For cycle 23 the cycle time has increased which allowed the coronal holes to dissipate. As I said, it appears the solar radiative to convection zone boundary were it theorized that the magnetic ropes are created, that rise to the solar surface and then create sunspots, has been disturbed by the large planets which move the sun cyclically. It seems reasonable based on paleodata/solar models that this could be a precursor to a Maunder type minimum. Regardless, the solar cycle will return to normal levels which will enable the two forcing function solar GCR/electroscavenging vs GHG to be separated.

    What are your thoughts on Palle�s paper and the solar changes?

    Comment by William Astley — 26 Apr 2007 @ 10:06 PM

  246. Re #227 – Dan Fregeau: One more try at the effect of orbital cycles. My claim about the balance in heat gain/loss between winter and summer did not take the inverse square law into account. In fact, at the present time the southern hemisphere receives 6.7% more radiation averaged over the year than the northern hemisphere.

    As you say, because the southern hemisphere is mostly ocean, which has a lower albedo, this would push global average temperature to be highest at this point in the orbital cycle (southern summer at perihelion). But the paleoclimate data shows the opposite. Maybe someone can explain this.

    But either way, this is an irrelevant influence on global warming in the 20th century. The annual change amounts to 6.7% / 5000 years (one quarter precession cycle), or 0.0013% per year. The key point is time scale – what is significant over a period of thousands of years is much less significant over a century.

    Comment by Blair Dowden — 26 Apr 2007 @ 10:25 PM

  247. Wow, I am allowed to speak on RealClimate!

    Here is what Roger Pielke wrote:

    You are simply incorrect when you assert: “Emanuel (2005) shows that the warming SSTs are behind the increased TC intensity in the Atlantic. No impartial reading of that paper could come to any other conclusion.”

    Here is what Emanuel actually says:

    “Tropical cyclones do not respond directly to SST, however, and the appropriate measure of their thermodynamic environment is the potential intensity, which depends not only on surface temperature but on the whole temperature profile of the troposphere. . . The above discussion suggests that only part of the observed increase in tropical cyclone power dissipation is directly due to increased SSTs; the rest can only be explained by changes in other factors known to influence hurricane intensity, such as vertical wind shear.”

    Misrepresenting Emanuel is bad enough, but for a site that often underscores the importance of consensus, your favoring of one single study (on a thread about not favoring one single study) when consensus perspectives exist (WMO, IPCC) does a disservice to your readers.

    You can compare this to #51 to see the edits of RC.

    Roger posted this sorry story at Prometheus, and not everybody is impressed:
    http://sciencepolicy.colorado.edu/prometheus/archives/climate_change/001180a_little_testy_at_re.html

    [Response: As long as one doesn't violate our comment policy, one is always free to post here. This comment would usually be screened out because it is deeply off topic. We've screened it in to make a point. There is now a full article on the topic in question and a useful discussion thread below. In the context of this fuller discussion, it should be crystal clear why Roger's comments were silly and off the mark (and were indeed edited). By the way, comments that are snarky are typically not admitted, so if you want to post here in the future, watch the snark. - mike]

    Comment by Richard Tol — 27 Apr 2007 @ 12:55 AM

  248. Re 245. I’ll take a stab at that (from a nonexpert). My understanding of the cooler summers South vs. North is the predominance of water in the south–that is water evaporates, taking with it A LOT of latent heat, which then circulates over the globe. There’s a lot of thermal mass in them there oceans. The land masses in the North heat up more. So, experts, did I come even close, or am I full of dingo’s kidneys?

    Comment by Ray Ladbury — 27 Apr 2007 @ 6:55 AM

  249. #238 (Pat Cassen) GCR flux is zilch

    Can you please clarify your statement further.

    The GCR flux in the earth’s atmosphere, which per Svensmark is proposed to be a causal of cloud formation and resultant albedo modulation of (regional) insolation, is modulated by the properties of the earth’s magnetosphere which is itself modulated by the solar wind(s). Together, this represents a localized electromagnetic circuit within the heliosphere that is sensitive to variations in current strength (solar cycles), to coupling distance (orbital variation), as well as other geomagnetic factors such as relative polar angle, upper atmospheric conductance, etc.

    The resultant electromagnetic GCR shielding at the poles and high latitudes takes on a complex field configuration, and the sensitivity or behavior of that shielding/field does not appear to be fully understood at this time. Is this incorrect?

    Comment by Dan Fregeau — 27 Apr 2007 @ 7:56 AM

  250. #244 (Jim Cross) ENSO

    This is a very relevant post.

    Note that some paleoclimatic proxies display a strong signal at half-pressional cycles, whereas other display a strong signal at full-precessional cycles, only. This suggests very different hemispheric effects to precession induced perihelion-soltice coincidence, which is why reducing analysis to insolation variation at July 65N is incomplete/misleading.

    Given the mathematical challenges of his time, I can understand why Milankovitch resorted to this simplification, combined with the fact that he was mostly interested in understanding the behavior of northern glaciation/deglaciation.

    Comment by Dan Fregeau — 27 Apr 2007 @ 8:13 AM

  251. Dan. Satellite measurements of GCR fluxes are not changing–they oscillate, but they are not changing. Neutron fluxes are not changing. So if your putative cause is not changing, how can it produce a change?

    Comment by Ray Ladbury — 27 Apr 2007 @ 8:55 AM

  252. #246 (Blair Dowden) Significance
    Thanks for clarifying cyclical hemispheric insolation differential.

    Opposite data in paleoclimatic record – what data proxy are you looking at? The current models makes critical assumptions between various proxies, glaciation and temperature.

    Re. Irrelevance – small effects are insignificant if they do not cumulate. But if heat from annual insolation increases is being trapped in an oceanic reservoir, then the cumulative effect of that trapping would be more significant than the annual effect, perhaps even on a relatively short timescale, would it not?

    Comment by Dan Fregeau — 27 Apr 2007 @ 8:58 AM

  253. Dan, where do you see this happening?
    http://www.osdpd.noaa.gov/PSB/EPS/SST/climo.html

    Comment by Hank Roberts — 27 Apr 2007 @ 9:17 AM

  254. #235 (Ray Ladbury) Major Climate Factors
    We agree that the sun is most important, and then H20 (in all of its phases) after that. These are the basics.

    Since Svensmark hypothesis specifically addresses how these two may be coupled, via solar wind, to modulate clouds, i.e. H2O vapour, with potential large impact to albedo, then it might be valuable to get to the bottom of this one, not to mention oceanic heat capacity and heat-transporting currents, and their long-term modulation by astronomical cycles. Agree?

    Comment by Dan Fregeau — 27 Apr 2007 @ 9:20 AM

  255. Re: #252 (Dan Fregeau)

    if heat from annual insolation increases is being trapped in an oceanic reservoir, then the cumulative effect of that trapping would be more significant than the annual effect, perhaps even on a relatively short timescale, would it not?

    The important part of this is, “IF.”

    The precession cycle alters the seasonal distribution of insolation, but has NO EFFECT on the annual total. So, the cumulative effect of zero being zero …

    Comment by tamino — 27 Apr 2007 @ 11:02 AM

  256. Re: Comment 246 “In fact, at the present time the southern hemisphere receives 6.7% more radiation averaged over the year than the northern hemisphere.”

    I believe this commment is not correct. The earth’s orbital differences average out over the year. The orbital eccentricity changes whether one season is relatively warmer and the other proportionally relatively colder. The forcing effect is balanced. The total amount of energy received by the earth, from the sun, in both hemispheres is equal. The current affect on planetary temperature due to orbital eccentricity, is that there is less seasonal temperature difference in the Northern Hemisphere than the Southern Hemisphere. (i.e. Earth is closer to the sun during January and farther from the sun in June.) Does this statement make sense?

    Milankovitch’s hypothesis, which I believe based on paleoclimatic evidence is not correct, is that insolation changes at specific critical latitudes triggers the glacial/interglacial cycle. As you stated the insolation changes are gradual, the ocean should smooth out any changes.

    The following are some very basic fundamental questions, which can not be explained by Milnakovitch’s hypothesis.

    Why does the interglacial period occur roughly every 100 kyrs now and prior to 700 kyrs ago occurred every 41 kyr? Why are there semi-periodic abrupt climate changes of 2C and greater? (The glacia/interglacial cycle is 5C. These are very large changes.) Why does the entire planet cool and warm rather than a single hemisphere? Why did the interglacial cycle start at event 11 before the insolation increased at the 60degree N?

    The fundamental explanation of past climate changes is relevant to a discussion of expected future short term changes in the planet’s temperature, as the models have been tuned based on a hypothesis (i.e. Orbital changes cause the glacial/interglacial cycle) that appears to have first order deficiencies. From a model standpoint, an unstable system is required, that is very sensitive to small changes in forcing to create the interglacial/cycle. (i.e. Positive feedback is required to amplify small forcing changes.)

    I believe there is evidence that there are significant damping mechanisms that work together to regulate the planet temperature. (i.e. Ocean, atmosphere, and clouds.) If the hypothesis that there are significant negative forcing functions that resisted change is correct, it has two implications:

    First, a much stronger global forcing function is required to explain the glacial/interglacial cycle and the abrupt climatic changes. The insolation changes and orbital changes cannot have caused the observed changes.

    Second, the will be less change in the earth’s temperature, from increases or decreases in forcing.

    Comment by William Astley — 27 Apr 2007 @ 11:08 AM

  257. Dan, how much of the AIP history have you read?
    I don’t see anything in what you’re raising that isn’t already well studied.
    What do you believe is contributing to current rapid changes, that isn’t being studied?
    Where are you getting what you believe to be true?

    I can’t tell if you’re asking for reassurance, or if you’re raising points you believe nobody has studied, or if you have theories you believe need to be taken seriously that aren’t.

    Can you focus a bit on what your information is, and where it comes from? What do you know now and how?

    Comment by Hank Roberts — 27 Apr 2007 @ 1:02 PM

  258. Ray, the following is in reply to your comment and line of reasoning.

    “William, the problem with a GCR driven mechanism is that it has to be operative at the time of the effect it tries to explain–and GCR fluxes simply are not changing–based on either satellite observations or neutron monitoring.”

    For short term periods (say for example the last 100 years), there is evidence that solar changes can module planet cloud cover by directly affecting GCR or by the electroscavenging mechanism (The jury is still out as to whether the solar changes did cause a significant portion of the 20th century temperature rise, however, as there is not scientific consensus, concerning the supporting data, although the earthshine data in addition to the satellite data helps the case.)

    Your line of reasoning is correct, that over the long term solar changes could not have directly caused long term cloud changes and could not therefore have caused the glacial/interglacial cycle via the GCR mechanism. (Assuming the GCR/electroscavenging mechanism works.) There is an alternative to the insolation hypothesis as to what drives the glacial/interglacial cycle, which I think is relevant to the current climate change discussion.

    This paper hypothesizes that geomagnetic field changes modulate the GCR which causes the glacial/interglacial cycle (The paper below also discusses the problems I mentioned in my comment concerning Milanokovich’s hypothesis.) I find their hypothesis, that GCR modulated by the geomagnetic field, more persuasive as there is evidence that “the geomagnetic intensity drops suddenly by a factor of 5-10 and the local direction changes dramatically ” The ‘normal’ state of the geomagnetic field, dominate by an axial dipole, seems to be interrupted every 30 -100 kyr: it (my comment, the geomagnetic field) may not therefore be as stable as we thought. ” These important results paint a rather different picture of long-long term behaviour of the field from the conventional one of a steady dipole reversing at random intervals instead the field spends up to 20 per cent of its time in a weak, non-dipole state (Lunde et al. 1998)” (Quote from paper is the geomagnetic field unstable?)

    Paper “Glacial Cycle and Cosmic Rays”

    http://arxiv.org/pdf/physics/0407005

    “There is growing evidence for close links between climate changes in the Holocene (approximately the last 10 kyr) and variations of the cosmic ray flux (see, for example, [17, 18, 19]). A high GCR flux is associated with a cold climate, and a low flux with a warm climate. On these 100 yr timescales, variations of the cosmic ray flux are thought to reflect changing solar activity (increased solar magnetic activity reduces the GCR flux). However, recent high-resolution paleomagnetic studies suggest that short-term geomagnetic variability may in fact control a significant fraction of the GCR modulation within the Holocene, even on 100 yr timescales [20]. Moreover, we will present evidence here that shows climate changes are also linked to variations of the cosmic ray flux caused by changes of geomagnetism. This indicates that GCRs directly influence the climate, rather than merely serve as a proxy for solar variability.”

    [Response: FWIW, this paper was rejected after peer review and never resubmitted. -gavin]

    Paper: “Is the geodynamo unstable?”

    http://eprints.whiterose.ac.uk/archive/00000416/01/gubbinsd4.pdf

    I have found other papers that support the assertion that the geomagnetic field is unstable and that it can change extraordinary rapidly (The drop in geomagnetic intensity appears to follow a rapid unsuccessful attempt to reverse, followed by a gradual increase back to normal geomagnetic strength.) For example:

    Oregon rapid field change.

    http://scholar.google.com/url?sa=U&q=http://www.nature.com/nature/journal/v374/n6524/abs/374687a0.html

    Acton’s Near Instantaneous Geomagnetic Reversal

    http://scholar.google.com/url?sa=U&q=http://www.geo.edu.ro/~paleomag/PDF/00-180-225.pdf

    What do you think of the two hypotheses? 1) Large drops in the geomagnetic field intensity have happened. 2) Large drops and a return to normal geomagnetic field strength could have caused the glacial/interglacial cycle.

    [Response: The changes in the geomagnetic field do not correlate to climate. Look up the Laschamp excursion for instance. - gavin]

    Comment by William Astley — 27 Apr 2007 @ 6:47 PM

  259. Ray (248), a minor point/question: I thought there was very little mixing of the atmosphere between the north and south hemisphere’s.

    Comment by Rod B. — 27 Apr 2007 @ 8:39 PM

  260. RE 259 (Rod B)
    I’m no expert on this, but: Winds from the southern and northern hemisphere converge near the equator at the intertopical convergence zone (ITZ). The ITZ oscillates north and south, but is generally north of the equator, esp. in the Northern Hemisphere summer, when it moves up over Asia. In the fall, it moves south, sometimes dipping below the equator.

    Comment by Chuck Booth — 27 Apr 2007 @ 11:57 PM

  261. In reply to “The changes in the geomagnetic field do not correlate to climate. Look up the Laschamp excursion for instance.”

    The Laschamp excursion is the lowest geomagnetic field intensity, in the last 70 kyrs. A lower geomagnetic field will result in higher GCR, however, there is a point where the GCR mechanism saturates so that additional GCR does not cause additional clouds. Also as the planet was very cold, already during the Laschamp excursion (it occurred during glacial part of the cycle) there was less moisture in the atmosphere for the GCR mechanism to create additional clouds.

    As to whether the geomagnetic field changes are cyclic, there is disagreement. There is agreement that the geomagnetic field abruptly and severly drops and that the excursions in the field were cyclic for a period of time, but not for the entire period. See the attached paper. There appears to be correlation with the start and termination of glacial periods with high and low intervals of geomagnetic field intensity.

    http://www.geo.uu.nl/~forth/publications/Langereis99.pdf

    Excerpt from the above paper:

    “Channell et al. therefore concluded that their record provides evidence that the Earthâ��s obliquity influences geomagnetic field intensity, with a period of around 41,000 years. They suggested that this is caused by the effect of obliquity on precessional angular velocity and hence on precessional forces in the Earthâ��s core. Does this hypothesis take us back to the early 1970s? Not according to Guyodo and Valet2. They performed a spectral analysis of Sint-800, comparing every 400,000-yearlong interval, in steps of 100,000 years, over their entire record, and found no evidence of any dominant stable periodicity in palaeomagnetic intensity. This, however, is no doubt a debate that will run for some time.

    Another feature of Sint-800 is the occurrence of many intervals of low geomagnetic intensity. Low intensities of Earthâ��s dipole favour the incidence of geomagnetic excursions, both in direction and intensity, because the non-dipole contribution of the field becomes significant. But it is not clear whether excursions should be considered as increased secular variation or as aborted reversals; and because of the imprecision of published excursion ages, it has even been speculated that excursions correlate with climate, for example with cold periods. (Worm, H.-U. Earth Planet. Sci. Lett. 147, 55â��67 )”

    Summing up what is known. This paper and other papers support the hypothesis that the geomagnetic field suddenly drops and that the drop in the field intensity are sever. The geomagnetic field instablity started 700 kyrs ago, which happens to be when the ice age cycle changed from 41 kyr to 100 kyr.

    There is agreement that say a sudden 70% drop in the geomagnetic field would result in increased GCR. There is evidence that GCR changes affect planetary cloud cover.

    To me there still seems to be a reasonable and defendable hypothesis. I will ask Richard Muller, to see why as you state the paper “Glacial Cycle and Cosmic Rays” was withdrawn and will get back to you.

    Comment by William Astley — 28 Apr 2007 @ 1:13 AM

  262. #253 (Hank Roberts) SST Data shows southern ocean not warming

    Measuring sea surface temperature, which is in constant flux as the graphs clearly show, is not a good measure of increased long-term oceanic heat absorbtion. For that you need to go deeper.

    Gille, Warming of the Southern Ocean since the 1950′s (Science 2002, 295:1275)

    Autonomous Lagrangian Circulation Explorer floats recorded temperatures in depths between 700 and 1100 meters in the Southern Ocean throughout the 1990s. These temperature records are systematically warmer than earlier hydrographic temperature measurements from the region, suggesting that mid-depth Southern Ocean temperatures have risen 0.17°C between the 1950s and the 1980s. This warming is faster than that of the global ocean and is concentrated within the Antarctic Circumpolar Current, where temperature rates of change are comparable to Southern Ocean atmospheric temperature increases.

    Comment by Dan Fregeau — 28 Apr 2007 @ 9:00 AM

  263. #252 (Tamino) Annual global insolation – zero

    Yes, solar variation aside, total annual global insolation remains the same irrespective of orbital variations – but this is irrelevant. The issue is that heat from this relatively constant insolation is not being absorbed and retained/released uniformely, regionally and over time. The heat is being absorbed and retained more efficiently in certain regions during certain periods, due to the variable composition of the earth and its variable heat capacity.

    Comment by Dan Fregeau — 28 Apr 2007 @ 9:59 AM

  264. Re #261: [A lower geomagnetic field will result in higher GCR, however, there is a point where the GCR mechanism saturates so that additional GCR does not cause additional clouds.]

    I hope you realize that what this amounts to is fitting the hypothesis to the desired result. You want to explain climate changes by GCR and geomagnetic field changes, therefore you’re postulating a mechanism that conveniently switches off and on just when it needs to in order to match observations. Seems to me that that’s about half a step away from invoking the benevolent hand of God :-)

    To me the more interesting question is one of psychology: why are some people so obsessed with finding some alternate theory? Surely they can’t all have their entire retirement savings invested in fossil fuel stocks?

    Comment by James — 28 Apr 2007 @ 10:02 AM

  265. #251 (Ray Ladbury) GCR not changing

    As you say, short-term satellite measurements show an oscillation inline with the solar cycle. But this is too short a timeframe to detect the longer-term trend. Be10 and C14 proxies suggest that they are changing, or perhaps even oscillating with longer astronomical cycles, as well. Do you altogether dispute those proxies?

    Comment by Dan Fregeau — 28 Apr 2007 @ 10:15 AM

  266. Dan, where do you find evidence for a mismatch between hemispheres, that you claim should be happening according to your theory differently than what the climatologists have described?

    You seem to be pulling up bits and pieces and claiming they show something, but — like saying “you have to go deeper” and quoting one study — it’s just bits and pieces.

    Of course there’s deep water warming; even the abyssal depths turn out to show a warming signal, earlier than expected, from one Japanese transect I recall. The deep ocean currents don’t stop at the equator!

    So are you arguing there’s a level at which the ocean somehow only goes around the Antarctic, not too deep, and not too shallow, in which somehow this warming you expect will appear unique to the Southern hemisphere? If so how would it get warmed up, if not from deep circulation or insolation?

    I just can’t tell if you’re suggesting you have a theory that others ought to look into, or that there’s a body of work being ignored that you’re revealing one bit at a time, or that there must be an explanation, try this…. now this ….

    Where’s the science here? Do you have it collected on a website somewhere in a focused way?

    Comment by Hank Roberts — 28 Apr 2007 @ 11:38 AM

  267. Is this ‘Dan Fregeau’ the executive vice president of Document Sciences Corporation? Just wondering. An IP associated with Document Sciences Corporation recently hit my website.

    Comment by Thomas Lee Elifritz — 28 Apr 2007 @ 12:18 PM

  268. #266 (Hank Roberts)
    Hank, I am frankly, like you and many others, just trying to better understand our climate change situation, in particular the amount of natural versus anthropogenic warming, which seems to have been the crux of the ongoing (and very confusing) scientific and political debate of the past years.

    If warming was much greater during previous interglacials, when there was no anthropogenic component, which seems to have been the case on the basis of purported sea levels and distribution of fauna (e.g. MIS-11), then I am trying to better understand what might have caused that amount of warming and sea level rise, and whether this might also likewise be occuring today, in addition to the critical GHG forcing component which we all agree on.

    It seems, based on all the responses, that the concensus of this blog and its scientific community is that the GHG forcing is sufficient to account for all currently occuring global warming, and that it is very unlikely that there are any other significant types of natural forcing occuring today based on the scientific research of all other possible warming mechanisms.

    Thus, we should make every effort to focus on reducing global GHG emissions, and such actions if implemented at sufficient levels, should by themselves significantly reduce global warming in the coming decades, centuries, etc.

    Comment by Dan Fregeau — 28 Apr 2007 @ 2:10 PM

  269. Re: Comment 264 (James).

    James you seem skeptical concerning the “Geomagnetic field intensity changes drives the glacial cycle” hypothesis.

    Attached is a review Paper: “Time Variance in Geomagnetic Intensity” by Jean-Pierre Valet. See page 4-24, figure 9, entitled “Field variations during the past 75 kyrs.”

    The Laschamp magnetic field excursion occurred roughly 41 kyr ago, at which time the geomagnetic field intensity dropped to roughly 20% of its current value. As shown in figure 9 a) the geomagnetic field gradually recovered from the Laschamp low point. The high point in the geomagnetic field strength in the last 75 kyr matches the Holocene interglacial period.

    http://ssn.dgf.uchile.cl/home/informe/2001RG000104b.pdf

    The sea floor sediment geomagnetic paleodata for the last 75 kyr can be checked against volcanic data. Note for this short period the low point in the geomagnetic field does occur during minimum orbital obliquity.

    My interest from a scientific standpoint: Is what is causing the abrupt changes in the geomagnetic field? I believe I have found the mechanism and understand the reason for the periodicity of the geomagnetic field changes. I am looking at paleoclimatic data to try to prove the hypothesis. I am also interested in long term variations in the solar cycle. (Maunder type minimums and super solar flares. I am looking at data from stellar studies of other stars which are similar to the sun.)

    Comment by William Astley — 28 Apr 2007 @ 3:58 PM

  270. In my opinion, Dan makes a valid point that the southern hemisphere is mostly covered in ocean, therefore has a lower albedo, and should cause the Earth to warm at points in the precession cycle (like now) when southern summer occurs when the Earth is closest to the sun.

    But paleoclimate evidence shows the mid-Holocene was warmer than today, and as I understand it climate theory predicts that we should be in a period of slight cooling without anthropogenic influences. I can’t explain this contradition. Maybe someone else can help.

    While understanding interglacial periods such as the Eemian or MIS-11 are important for understanding the mechanics of climate, they are less relevant for understanding the impact of the current anthropogenic warming. Different interglacials have different patterns, the current Holocene natural pattern is almost flat, or declining slightly. So my suggestion to Dan is that he is not taking into account the timescales – the timescale of the orbital changes that drive the ice age cycles is much longer than the century or two relevant to global warming.

    Comment by Blair Dowden — 29 Apr 2007 @ 7:36 AM

  271. should cause the Earth to warm at points in the precession cycle (like now) when southern summer occurs when the Earth is closest to the sun

    No, this is not the case. When southern summer coincides with perihelion, the souther hemisphere has a hotter summer and a colder winter. Furthermore, because planets move faster along their orbits when closer the the sun, the southern hemisphere also has a shorter summer and longer winter.

    The effect of the precession cycle is to increase the seasonal contrast, but it has no effect on cumulative insolation at any location on earth.

    Comment by tamino — 29 Apr 2007 @ 8:19 AM

  272. Dan, you keep dropping these statements, like this:

    “… If warming was much greater during previous interglacials …”

    Would you _please_please_please_ say where you are getting your ideas?

    Did you read that somewhere? If so, where, and why do you consider it a reliable source?
    Did you make it up as a hypothetical? If so, there’s no end to what-ifs, but it’s just noise with no data.

    You can look this stuff up. Instead of just doing the endless “what-if” stuff with ideas lacking any cite, lacking any source, lacking any theory —– could you please try to say what you’re thinking and what your sources are?

    Comment by Hank Roberts — 29 Apr 2007 @ 10:16 AM

  273. Re #269: [James you seem skeptical concerning the "Geomagnetic field intensity changes drives the glacial cycle" hypothesis.]

    Skeptical is far too mild a word. I’ve occasionally brought up some of my questions re the whole GCR-climate connection hypothesis. These range from the short term (particle fluxes change considerably during solar flares: shouldn’t we see obvious short-term correlations?) to the long term (many millions of years of geomagnetic data from e.g. mid-Atlantic Ridge spreading, but AFAIK no correlation to climate) to the basic mechanism. If I can ask such obvious questions, and get no better answer than that the effect is modulated just the way it needs to be to match observations… Well, can you see how I’d be skeptical of such a theory, even if it were presented in isolation?

    It’s not presented in isolation, though, but as an alternative to a mechanism which was derived from basic theory, and which predicted the current warming well before evidence of it was available. It seems that the only advantage GCR has as a theory is that it absolves humans from any responsibility for the current changes, and thus any need to change their behavior. That’s why I go beyond skepticism to a very cynical suspicion.

    (I should probably add that this just applies to the invocation GCR/geomagnetic/climate connection, not to basic research into the geomagnetic field and its reversals. I think that’s an interesting area of science, just not relevant to the current climate. And on a quick read-through, I didn’t see anything about climate in the paper you linked.)

    Comment by James — 29 Apr 2007 @ 10:24 AM

  274. Would you _please_please_please_ say where you are getting your ideas?

    We all know where Dan Fregeau is getting his … er … talking points.

    Comment by Thomas Lee Elifritz — 29 Apr 2007 @ 11:10 AM

  275. Re #271: tamino, I think I was misinformed by these lecture notes that say eccentricity causes a temperature imbalance between the hemispheres, which I assumed could only because of eccentricity. I appreciate you correcting my errors, but could you please point me to a reliable reference so I can understand this properly, and not continue to mislead readers of this forum?

    Comment by Blair Dowden — 29 Apr 2007 @ 11:38 AM

  276. Re: #275 (Blair Dowden)

    Alas, the lecture notes you link to are just plain dead wrong on this point. It’s quite clear that the lecturer simply computed the difference in midsummer insolation between the hemispheres, ignoring the change in the length of seasons. Furthermore, even if there was no change in length of seasons, his estimate of the hemispheric difference (7% at present eccentricity) is inflated — you can’t just extrapolate the midsummer value to the entire year. Frankly, this doesn’t bode well for the students.

    Technical expositions can be found in Vernekar (1972, Long-term Global Variations of Incoming Solar Radiation, Meteor. Monogr. No. 34), Vernekar (1977, Variations in Insolation Caused by Changes in Orbital Elements of the Earth, in The Solar Output and its Variation, O.R. White ed., Colorado Associated University Press, pp. 117-130) Berger (1978, Long-term Variations of Caloric Insolation Resulting from the Earth’s Orbital Elements, Quat. Res. 9, 139-167) and Berger (1979, Long-term Variations of Daily Insolation and Quaternary Climate Changes, Jour. Atmos. Sciences, 35, 2362-2367). I’ve computed it myself, and arrived at exactly the same formulae. For a less technical expose, maybe I’ll do a post on the topic on my blog.

    Comment by tamino — 29 Apr 2007 @ 12:47 PM

  277. #272 (Hank Roberts) Sources
    My main sources for the idea that past interglacials may have been warmer than the current Holocene are:

    - The Climate of Past Interglacials. Sorocko, Claussen, Sanchez Goni, Litt. Developments in Quaternary Science 7, Elsevier, 2007
    - Earth’s Climate and Orbital Eccentricity, The Marine Isotope State 11 Question. Droxler, Poore, Burckle. AGU Geophysical Monograph 137, 2003.

    These books contain several papers that seem to suggest a warmer climate (at least in some areas) during some parts of past interglacials based on evidence of higher sea levels and, in the case of the long MIS-11 interglacial, based on recovered fossils of warmer climate-adapted species in Northern Europe.

    As was pointed out, the sea level evidence appears less secure because of other geological factors although I believe the IPCC agrees that sea levels were higher than today during MIS-5. In any case, the latest IPCC report appears to provide a very thorough review on Paleoclimate (Chapter 6), and reading that will hopefully provide more clarity on the relationship between past sea levels and past global temperatures.

    On perihelion-soltice coincidence, I want to clarify that according to Kukla, Gavin (Milankovitch Climate Reinforcements, Global and Planetary Change, 2004), precessional coincidence actually occured around 1250 AD, and so I was incorrect in my earler statement about approach, given that the earth is already past that special orbital point.

    Therefore if there is no long-term oceanic heat retention/accumulation mechanism then it would also be true that southern summers should now be getting cooler on the basis of the natural forcing component, exclusive of any anthropogenic GHG forcing, which I believe is your position based on the feedback provided.

    Comment by Dan Fregeau — 29 Apr 2007 @ 1:45 PM

  278. I suppose there’s some reason to question a file of “old notes” even left publicly available. The latest cite I noticed was “The correlation between cosmic rays and cloudiness was discovered by Svensmark and Friis-Christensen in 1997.”
    These notes may date from a decade ago.

    Comment by Hank Roberts — 29 Apr 2007 @ 1:49 PM

  279. Re #276: Thanks, tamino. I seem to occupy a middle ground where the standard simplified explanations are not good enough, but I am not at a level to understand a full technical book (such as the ones you suggest) intended for a specialist. If you choose to cover it in your blog, that would be great.

    I have a web page of my own on the subject, which I am using as an attempt to collect information to understand the climate change issue. You may recognize a small part of it – I lifted it from one of your helpful responses.

    Comment by Blair Dowden — 29 Apr 2007 @ 8:29 PM

  280. Dan, you wrote — after giving some references saying some areas were warmer during some interglacials:

    > “… Therefore if [X]* then it would also be true that southern summers should now be getting cooler which I believe is your position …”

    I don’t have a “position” — I’m a reader here; I’m trying to understand the science, and where people get what they believe to be true, by asking questions about their sources, checking cites, looking for the science behind what’s being said.
    ________
    * “if there is no long-term oceanic heat retention/accumulation mechanism” (Now, where did this come from? Who said that the ocean _doesn’t_ retain heat over the long term? Earlier you were talking about some separation of heat somehow between the hemispheres, quite a different idea. I think.)

    Comment by Hank Roberts — 29 Apr 2007 @ 9:36 PM

  281. Re #279 — Blair, that is a very nice web page you’ve put together on the Milankovic cycles. The balance between text and graphics is just about perfect, and the writing is clear and to the point.

    Comment by Barton Paul Levenson — 30 Apr 2007 @ 6:23 AM

  282. Re #281: Thanks, Barton. I found this interesting page on The Length of the Seasons” which talks about orbital variations in great detail, so I will be updating my page. It states

    The Northern Hemisphere dominates global weather patterns because it contains most of the land area. With its Summer being the longest season and getting longer, while Winter is the shortest season and getting shorter, for the next several millennia there will be an unavoidable cumulative trend toward global warming.

    The argument was made that the southern hemisphere has more ocean area, with lower albedo, thus absorbs more energy. But I think what drives climate change is the change in albedo, which is greater in the northern hemisphere due to the vulnerability of sea ice and snow cover on land. But this idea is not consistent with the fact that the mid Holocene was a relatively warmer period.

    Comment by Blair Dowden — 1 May 2007 @ 11:27 PM

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