RealClimate logo

On attribution

Filed under: — gavin @ 26 May 2010

How do we know what caused climate to change – or even if anything did?

This is a central question with respect to recent temperature trends, but of course it is much more general and applies to a whole range of climate changes over all time scales. Judging from comments we receive here and discussions elsewhere on the web, there is a fair amount of confusion about how this process works and what can (and cannot) be said with confidence. For instance, many people appear to (incorrectly) think that attribution is just based on a naive correlation of the global mean temperature, or that it is impossible to do unless a change is ‘unprecedented’ or that the answers are based on our lack of imagination about other causes.

In fact the process is more sophisticated than these misconceptions imply and I’ll go over the main issues below. But the executive summary is this:

  • You can’t do attribution based only on statistics
  • Attribution has nothing to do with something being “unprecedented”
  • You always need a model of some sort
  • The more distinct the fingerprint of a particular cause is, the easier it is to detect

Note that it helps enormously to think about attribution in contexts that don’t have anything to do with anthropogenic causes. For some reason that allows people to think a little bit more clearly about the problem.

First off, think about the difference between attribution in an observational science like climatology (or cosmology etc.) compared to a lab-based science (microbiology or materials science). In a laboratory, it’s relatively easy to demonstrate cause and effect: you set up the experiments – and if what you expect is a real phenomenon, you should be able to replicate it over and over again and get enough examples to demonstrate convincingly that a particular cause has a particular effect. Note that you can’t demonstrate that a particular effect can have only that cause, but should you see that effect in the real world and suspect that your cause is also present, then you can make a pretty good (though not 100%) case that a specific cause is to blame.

Why do you need a laboratory to do this? It is because the real world is always noisy – there is always something else going on that makes our (reductionist) theories less applicable than we’d like. Outside, we don’t get to perfectly stabilise the temperature and pressure, we don’t control the turbulence in the initial state, and we can’t shield the apparatus from cosmic rays etc. In the lab, we can do all of those things and ensure that (hopefully) we can boil the experiment down to its essentials. There is of course still ‘noise’ – imprecision in measuring instruments etc. and so you need to do it many times under slightly different conditions to be sure that your cause really does give the effect you are looking for.

The key to this kind of attribution is repetition, and this is where it should become obvious that for observational sciences, you are generally going to have to find a different way forward, since we don’t generally get to rerun the Holocene, or the Big Bang or the 20th Century (thankfully).

Repetition can be useful when you have repeating events in Nature – the ice age cycles, tides, volcanic eruptions, the seasons etc. These give you a chance to integrate over any unrelated confounding effects to get at the signal. For the impacts of volcanic eruptions in general, this has definitely been a useful technique (from Robock and Mao (1992) to Shindell et al (2004)). But many of the events that have occurred in geologic history are singular, or perhaps they’ve occurred more frequently but we only have good observations from one manifestation – the Paleocene-Eocene Thermal Maximum, the KT impact event, the 8.2 kyr event, the Little Ice Age etc. – and so another approach is required.

In the real world we attribute singular events all the time – in court cases for instance – and so we do have practical experience of this. If the evidence linking specific bank-robbers to a robbery is strong, prosecutors can get a conviction without the crimes needing to have been ‘unprecedented’, and without having to specifically prove that everyone else was innocent. What happens instead is that prosecutors (ideally) create a narrative for what they think happened (lets call that a ‘model’ for want of a better word), work out the consequences of that narrative (the suspect should have been seen by that camera at that moment, the DNA at the scene will match a suspect’s sample, the money will be found in the freezer etc.), and they then try and find those consequences in the evidence. It’s obviously important to make sure that the narrative isn’t simply a ‘just-so’ story, in which circumstances are strung together to suggest guilt, but which no further evidence is found to back up that particular story. Indeed these narratives are much more convincing when there is ‘out of sample’ confirmation.

We can generalise this: what is a required is a model of some sort that makes predictions for what should and should not have happened depending on some specific cause, combined with ‘out of sample’ validation of the model of events or phenomena that were not known about or used in the construction of the model.

Models come in many shapes and sizes. They can be statistical, empirical, physical, numerical or conceptual. Their utility is predicated on how specific they are, how clearly they distinguish their predictions from those of other models, and the avoidance of unnecessary complications (“Occam’s Razor”). If all else is equal, a more parsimonious explanation is generally preferred as a working hypothesis.

The overriding requirement however is that the model must be predictive. It can’t just be a fit to the observations. For instance, one can fit a Fourier series to a data set that is purely random, but however accurate the fit is, it won’t give good predictions. Similarly a linear or quadratic fit to a time series can be useful form of descriptive statistics, but without any reason to think that there is an underlying basis for such a trend, it has very little predictive value. In fact, any statistical fit to the data is necessarily trying to match observations using a mathematical constraint (ie. trying to minimise the mean square residual, or the gradient, using sinusoids, or wavelets, etc.) and since there is no physical reason to assume that any of these constraints apply to the real world, no purely statistical approach is going to be that useful in attribution (despite it being attempted all the time).

To be clear, defining any externally forced climate signal as simply the linear, quadratic, polynomial or spline fit to the data is not sufficient. The corollary which defines ‘internal climate variability’ as the residual from that fit doesn’t work either.

So what can you do? The first thing to do is to get away from the idea that you can only be using single-valued metrics like the global temperature. We have much more information than that – patterns of changes across the surface, through the vertical extent of the atmosphere, and in the oceans. Complex spatial fingerprints of change can do a much better job at discriminating between competing hypotheses than simple multiple linear regression with a single time-series. For instance, a big difference between solar forced changes compared to those driven by CO2 is that the stratosphere changes in tandem with the lower atmosphere for solar changes, but they are opposed for CO2-driven change. Aerosol changes often have specific regional patterns change that can be distinguished from changes from well-mixed greenhouse gases.

The expected patterns for any particular driver (the ‘fingerprints’) can be estimated from a climate model, or even a suite of climate models with the differences between them serving as an estimate of the structural uncertainty. If these patterns are robust, then one can have confidence that they are a good reflection of the underlying assumptions that went into building the models. Given these fingerprints for multiple hypothesised drivers (solar, aerosols, land-use/land cover change, greenhouse gases etc.), we can than examine the real world to see if the changes we see can be explained by a combination of them. One important point to note is that it is easy to account for some model imperfections – for instance, if the solar pattern is underestimated in strength we can test for whether a multiplicative factor would improve the match. We can also apply some independent tests on the models to try and make sure that only the ‘good’ ones are used, or at least demonstrate that the conclusions are not sensitive to those choices.

These techniques of course, make some assumptions. Firstly, that the spatio-temporal pattern associated with a particular forcing is reasonably accurate (though the magnitude of the pattern can be too large or small without causing a problem). To a large extent this is the case – the stratospheric cooling/tropospheric warming pattern associated with CO2 increases is well understood, as are the qualitative land vs ocean/Northern vs. southern/Arctic amplification features. The exact value of polar amplification though is quite uncertain, though this affects all the response patterns and so is not a crucial factor. More problematic are results that indicate that specific forcings might impact existing regional patterns of variability, like the Arctic Oscillation or El Niño. In those cases, clearly distinguishing internal natural variability from the forced change is more difficult.

In all of the above, estimates are required of the magnitude and patterns of internal variability. These can be derived from model simulations (for instance in their pre-industrial control runs with no forcings), or estimated from the observational record. The latter is problematic because there is no ‘clean’ period where there was only internal variability occurring – volcanoes, solar variability etc. have been affecting the record even prior to the 20th Century. Thus the most straightforward estimates come from the GCMs. Each model has a different expression of the internal variability – some have too much ENSO activity for instance while some have too little, or, the timescale for multi-decadal variability in the North Atlantic might vary from 20 to 60 years for instance. Conclusions about the magnitude of the forced changes need to be robust to these different estimates.

So how might this work in practice? Take the impact of the Pinatubo eruption in 1991. Examination of the temperature record over this period shows a slight cooling, peaking in 1992-1993, but these temperatures were certainly not ‘unprecedented’, nor did they exceed the bounds of observed variability, yet it is well accepted that the cooling was attributable to the eruption. Why? First off, there was a well-observed change in the atmospheric composition (a layer of sulphate aerosols in the lower stratosphere). Models ranging from 1-dimensional radiative transfer models to full GCMs all suggest that these aerosols were sufficient to alter the planetary energy balance and cause global cooling in the annual mean surface temperatures. They also suggest that there would be complex spatial patterns of response – local warming in the lower stratosphere, increases in reflected solar radiation, decreases in outgoing longwave radiation, dynamical changes in the northern hemisphere winter circulation, decreases in tropical precipitation etc. These changes were observed in the real world too, and with very similar magnitudes to those predicted. Indeed many of these changes were predicted by GCMs before they were observed.

I’ll leave it as an exercise for the reader to apply the same reasoning to the changes related to increasing greenhouse gases, but for those interested the relevant chapter in the IPCC report is well worth reading, as are a couple of recent papers by Santer and colleagues.

559 Responses to “On attribution”

  1. 201
    Completely Fed Up says:

    Where’s the ad hom in #109?

    Or is this the eternal problem of denialist blindness to the meaning of ad hom?

    109 says, effectively, “your idea is dumb, therefore I conclude you are dumb” which is not an ad hom, it’s a conclusion based on evidence.

    It’s not a NICE conclusion, but the evidence doesn’t leave much room for anything else.

    If the conclusion is not liked, maybe Lichanos should try not showing evidence of narcissism and idiocy.

    Except it is someone appropriating victimhood so they can concern troll. And getting the victimisation wrong too…

  2. 202
    CM says:

    CFU #187, Hank #189, right.

    Mark #170, just in case you are laboring under the misapprehension that the relationship you referred to might show the rising trend in global temperatures, rather than human activities, to be driving the rise in CO2: no, it might not. You just need to keep in mind that we’re emitting roughly twice as much CO2 as is being added to the atmosphere. We’re the source, nature’s the (net) sink.

  3. 203
    dhogaza says:

    But simply assuming that any attribution must be false because it comes from a politician, while perhaps a good guess, cannot be justified in general.

    Gavin, she wasn’t a politician when she first made such claims, she was still a working scientist.

    The upwelling stuff is part of her research, as indicated by her being on this abstract.

    I could google more, but she wasn’t simply speculating, I don’t know how much work OSU and UW have done on modeling the response of upwelling patterns to warming, but it’s certainly an area of concern out here.

    My memory of the press coverage of the event, and quotes of her and other researchers, was that uncertainty was certainly highlighted, and no positive attribution of that event to global warming was made.

    [Response: I should have also said that, assuming that a claim about an attribution on a blog comment without a cite is accurate, is also not a good idea. Thanks for the ref. – gavin]

  4. 204
    Rod B says:

    ccpo, you seem to think that gathering the homogeneous student body around the bonfire at the pep rally and yelling out the cheers that everyone knows by heart is somehow “getting on to the business of dealing with AGW.” Curious. (Though I can maybe see some tangential help to your cause there…)

  5. 205

    #173 Lichanos the anonymous

    You have not been attacked. Your arguments have been attacked for lacking evidence. You think that because you think something, that makes your thoughts better than a body of evidence that is truly massive.

    That’s just pathetic.

    You say you are trained in science and math. That means nothing to me I’ve met PhD’s that had a hard time getting their brain past a particular line of study. Luckily, few. SO having training is not the holy grail either. Lindzen has training too. So does Svensmark. They still can’t quite open their eyes wide enough to see past their confirmation bias.

    If you were truly a humanist you would and should serious consider the ramifications of your mistake. A lot of people are going to die because you and many others are getting this all wrong. The UN estimates that the number will be around 1.8 billion dead and dying by 2080. I think on a BAU course, that is a low number. but there are many sociopolitical economies of thought that must also be considered.

    If you are trained in logic, then one of two things have happened. You were trained improperly, or you misunderstood and reinterpreted the information into your own construct that appears simply to be wholly illogical.

    Main Entry: log·ic
    Pronunciation: \ˈlä-jik\
    Function: noun
    Etymology: Middle English logik, from Anglo-French, from Latin logica, from Greek logikē, from feminine of logikos of reason, from logos reason — more at legend
    Date: 12th century
    1 a (1) : a science that deals with the principles and criteria of validity of inference and demonstration : the science of the formal principles of reasoning (2) : a branch or variety of logic (3) : a branch of semiotic; especially : syntactics (4) : the formal principles of a branch of knowledge b (1) : a particular mode of reasoning viewed as valid or faulty (2) : relevance, propriety c : interrelation or sequence of facts or events when seen as inevitable or predictable d : the arrangement of circuit elements (as in a computer) needed for computation; also : the circuits themselves
2 : something that forces a decision apart from or in opposition to reason
    — lo·gi·cian \lō-ˈji-shən\ noun

    you have also demonstrated that you are illogical

    Main Entry: log·i·cal
    Pronunciation: \ˈlä-ji-kəl\
    Function: adjective
    Date: 15th century
    1 a (1) : of, relating to, involving, or being in accordance with logic (2) : skilled in logic b : formally true or valid : analytic, deductive
2 : capable of reasoning or of using reason in an orderly cogent fashion

    You are also have shown that you are not willing to put your real name on your words in this thread, which indicates you are a man of low integrity, at least in this thread.

    You’re great with red herring and straw-man arguments. You rely on imagination and ignore science. In this case, on this subject, you are performing the actions of stupidity.

    You should not find this conclusion as an attack however. It is merely the reasonable conclusion based on your assertions, claims, imaginations as clearly illustrated in your posts on the subject of anthropogenic global warming.

    To reiteration: You have clearly demonstrated that you have no clue about the science, but have actually determined by direct and indirect statement and inference as well as evidence in your own words that that you believe your imagination overrules the well established science.

    There is a word that describes this:


    You have also clearly demonstrated that you are not very smart. Sure you can construct sentences that have words in them. But you’re not very good at making sense. This is evidenced in your ignoring the actual science.

    You are not being attacked here. Your ideas are. If you feel insulted then maybe you need to examine your feelings. Just because some says your arguments are illogical is not a personal attack on you. You just imagine it that way.

    And I must admit, you have quite an imagination. You stated above that you would explain your position and sign off. That sounds good. But if and or when you actually gain the capacity to bring logic to the table, please do come back.

    A Climate Minute The Greenhouse EffectHistory of Climate ScienceArctic Ice Melt

    ‘Fee & Dividend’ Our best chance for a better future –
    Learn the Issue & Sign the Petition

  6. 206
    Rick Brown says:

    Since my previous comment regarding Jane Lubchenco (following Howard’s mis-attribution about what she’s had to say about dead zones) was probably missed by most due to the turn of the page, here’s the reference again, with a link.

    Chan, F., Barth, J.A., Lubchenco, J., Kirincich, A., Weeks, H., Peterson, W.T., Menge, B.A. (2008). Emergence of Anoxia in the California Current Large Marine Ecosystem. Science, 319(5865), 920. | DOI: 10.1126/science.114901

  7. 207

    #173 Lichanos the anonymous

    Re: “I don’t need evidence to dismiss your hypothesis”

    You can’t show that the AGW argument is illogical if you ignore the science of climate.

    Gavin is right. You fail the logic. Straw-man arguments dont’ pass muster.

    Re. “Each bit has to be proven independently of the other”

    Each bit points to the “very likely” (interpreted scientifically as highly certain) reality that the global warming event is human caused. Multiple lines of evidence merely give3 you multiple support lines to aid in the confirmation of each line of evidence.

    Again, on logic, you fail.

    Re. “unless you can totally disprove AGW outright, nothing you say matters”

    Do you have one single line of scientifically sound reasoning, hypothesis, or theory that shows this global warming event is not human caused? And please don’t use the ‘it’s been warmer in the past’ argument. That’s just too lame. Example: If two people shoot you, they can both have have pulled the trigger for entirely different reasons. The dynamics of earths thermal equilibrium have been different at different times. We are referring to recent patterns:

    Wow, every time I look at that picture, I think what a crazy ‘fad’ this global warming ‘hypothesis’ is. I know you think I have no sense of irony as you have stated, or humor for that matter, but isn’t that a humorous irony in my sentence structure :)

    Re. “when reviewing a scientific hypothesis”

    You continue to confuse hypothesis with theory. Human caused climate change is now well established theory, not hypothesis. Are you unable to parse the relevant connotative definitions?

    Re. “it’s okay to use tree ring data that does appear to match instrumental records, and when it doesn’t match it, we throw it out”

    I know you likely won’t understand this sentence due to your clear lack of understanding of the body of science but here goes. . . so, your saying that just because one set of trees in one region shows one thing, all sets of trees should show the same thing?

    To illuminate, we have to be at least open to the idea that a region, can have a different behavior that another region or multiple regions. The real ‘trick’ is to find out why. Such is the endeavor of science as Gavin pointed out.

    A Climate Minute The Greenhouse EffectHistory of Climate ScienceArctic Ice Melt

    ‘Fee & Dividend’ Our best chance for a better future –
    Learn the Issue & Sign the Petition

  8. 208

    #174 Bart Verheggen

    Yes, ‘Lichanos the anonymous’ is using the old I brought the truth of my very own shiny logic to them and they all insulted me.

    Those people are meanies. And now I can prove it. I’m going to take this evidence that they are meanies and show it to my teachers and get them in trouble.

    They’re meanies (cry, cry, boohoo, blah, blah, blah)

    Of course, we have seen these guys come and go. And of course he will never step up to the plate and give us his real name. Honor and integrity seems to be a dying way of life.

    A Climate Minute The Greenhouse EffectHistory of Climate ScienceArctic Ice Melt

    ‘Fee & Dividend’ Our best chance for a better future –
    Learn the Issue & Sign the Petition

  9. 209
    Hank Roberts says:

    John, there’s an old Berkeley street saying — if you get in shouting matches with crazy people, nobody passing by will be able to tell which of you is crazy.

    Remember the audience and new readers here. You write:

    > megalomaniac … You are not being attacked here. Your ideas are.
    > If you feel insulted then maybe you need to examine your feelings.
    > … You just imagine it that way.

    Education is what matters. Not your pride. You may feel a personal victory writing that stuff. You’re up on a very high horse though.

    Please stop. The collateral damage to RC isn’t trivial when smart people with much to offer get into competing with trolls for excessive language. You get no credit because the other guy did it first.

    The real clue someone’s trolling effectively?
    You feel like yelling and calling names instead of reasoning and citing scientific sources for what you believe.

    Watch for it. I’m not immune, but when I’m not hooked I can see it more easily in others. I need you to keep me clear here. I hope I can help you when it starts getting muddy.

  10. 210

    191 (Alan Millar),

    Now why should I start to believe that these combinations are now suddenly going to result in a positive response trend in the future.

    I need convincing since I see a billion year trend which says different. My request is for someone to explain why this is so and to back it up with figures.

    Others have pointed out major flaws in your numbered assumptions (not facts, but false assumptions), but even if you were right on those points…

    You are right in saying that the system will return to equilibrium. Either climate change will kill off a large portion of the human race, or we’ll smarten up and avoid causing too much damage, or we’ll just plain run out of oil, but one way or the other we’ll stop dumping CO2 into the atmosphere. So the human race will have caused itself a lot of short term suffering (short in a geologic time sense), and within a few hundred or a thousand years the CO2 will settle out and temperatures will return to normal.

    A billion years from now an alien scientist evaluating the climate history of our planet will see a nice, smooth cooling trend (or whatever else you want to believe), and probably won’t even be able to detect the climate event which proved to be disastrous for the members of the human race living at the end of this century and the next.

    Your entire assumption that a long term (billions of years) record demonstrates the existence of powerful, fast acting negative feedbacks is fatally flawed. Powerful, maybe, fast acting, definitely not. It is more than possible that the planet will heat dangerously in the short term, in response to a once-in-a-planet’s-lifetime event of a sentient species mining/burning/releasing carbon that has taken eons to sequester. Then, in a geologic blink, it will be over. No long term change to the trend.

    So yes, you are right. Very long term we see a nice, stable trend. Over a period short enough to cause havoc among the human race, we will see a very dangerous blip in the long term trend.

  11. 211

    #178 Alan Millar

    Unless you can demonstrate how the actual physics and maths are wrong on the radiative forcing increase and associated error bars, then your incorrect claims that, first, increased forcing is based on GCM’s, and that the forcing is positive, are unsubstantial i.e. unsupportable.

    If you ignore the evidence without any reasonable evidence to the contrary, then you are illogical and unreasonable.

    Feel free to prove me wrong.

    A Climate Minute The Greenhouse EffectHistory of Climate ScienceArctic Ice Melt

    ‘Fee & Dividend’ Our best chance for a better future –
    Learn the Issue & Sign the Petition

  12. 212
    Ray Ladbury says:

    Lichanos, the point is that the computer models are not necessary for attribution–they merely allow you to refine the calculation. That is more important for bounding the temperature increase than it is for attribution. See for example:

  13. 213

    #191 Alan Millar

    Context is Key.

    You are using the last 500 million years, or billion years, as a measure. But the human reality is much more recent. And the modern human reality is just the last 10,000 years where agriculture and modern tools were developed leading to our even more recent industrial age.

    In context we need to understand human adaptive capacity to the changes we have imposed on the system.

    That is why understanding the cause and expected results of ‘this’ global warming event is very important.

    The ‘this climate is not so different from the past argument, to show how unimportant ‘this’ event is, is purely a red herring argument that is often used to confuse people on the real importance of ‘this’ event.

    Id est: “It’s the economy stupid”, to quote an oft used phrase.

    A Climate Minute The Greenhouse EffectHistory of Climate ScienceArctic Ice Melt

    ‘Fee & Dividend’ Our best chance for a better future –
    Learn the Issue & Sign the Petition

  14. 214
    Rod B says:

    CFU, against my better judgment: “your idea is dumb” is not an ad hominem as you say; “you are dumb” is; ‘you are dumb, neurotic, psychotic, NUTS’ really is.

  15. 215
    Alan Millar says:

    #211 John ReismannUnless you can demonstrate how the actual physics and maths are wrong on the radiative forcing increase and associated error bars, then your incorrect claims that, first, increased forcing is based on GCM’s, and that the forcing is positive, are unsubstantial i.e. unsupportable.

    If you ignore the evidence without any reasonable evidence to the contrary, then you are illogical and unreasonable.

    Feel free to prove me wrong.”

    Mr Reismann

    I am not ‘denying’ Physics.

    It is you who does not have an understanding of the import of my comments.

    If the Earth was a closed non-dynamic system then the effect of an increase of radiative forcing would be easy to calculate. The Earth is a dynamic system however.

    As an example of dynamic and non dynamic systems put one end of an iron bar in a bowl of hot water together with your feet and wait for your head to warm up just like the iron bar. Same physics, different effect!

    The fact is that taking all factors into account the Earth has not warmed in the last billion years not withstanding a huge increase in direct radiative forcing.

    My point is that climate science is far from settled there are a huge number of uncertainties.

    For instance the consensus is that in the next billion years the Suns 10% increased output will make the Earth uninhabitable. However the Earth was hotter than now a billion years ago and since that time the Sun indeed has increased its output by 10% and yet it is cooler, not uninhabitable!

    Perhaps you can explain how this happened and why it wont happen in the next billion years!


  16. 216

    #209 Hank Roberts

    Thanks Hank. Point taken. I was just pointing out that his adherence to the argument to authority claiming that ‘his’ logic and ‘his’ imagination were enough to falsify the body of evidence is in dead indicative of a megalomaniacal perspective, if not the actual disorder.

    1 : a mania for great or grandiose performance
    2 : a delusional mental disorder that is marked by feelings of personal omnipotence and grandeur

    I don’t think it is fair to call it a high horse though, but that’s just my opinion. My intention is to pick away at his straw-men. Behavioral science and human behavior and psychology are a part of this argument though. As long as Gavin et al let’s them post, due responses are in order. I don’t think we should let them just spew without attacking the actual argument as well as the construct. I’m not saying I don’t push the edge once in a while to test the fence either. I am perfectly comfortable with RC editing or even declining my posts as they deem appropriate.

    I’m not confident it hurts RC, though I may be wrong? There are many ways to attack an argument that is in base fallacious. I do my best to address reasonability, but am human after all. I do believe you are quite correct about the feeling of yelling. But a lot of the denialism seen in RC fits the bill for trolling then. You and I and others have often extended the olive branch when the truth later is revealed that it was a trolling string of posts, not sincere questions re. logic and science.

    Once in a while we do see a sincere question that is interested in learning though. Refreshing and rare.

    A Climate Minute The Greenhouse EffectHistory of Climate ScienceArctic Ice Melt

    ‘Fee & Dividend’ Our best chance for a better future –
    Learn the Issue & Sign the Petition

  17. 217
    Completely Fed Up says:

    “[Response: I love this. But one question first – how do you manage to type when you are spinning so fast? – gavin]”

    I can answer that:

  18. 218
    Nick Gotts says:

    I understood that return to pre-industrial levels of CO2 would take on the order of tens of thousands of years, and would occur because both higher CO2 levels and higher temperatures (and hence rainfall) speed up erosion, increasing the rate at which CO2 leaves the atmosphere. Maybe someone more knowledgeable can confirm or deny this – wikipedia on the carbonate-silicate cycle suggests a longer timescale.

  19. 219

    #211 John P. Reisman

    Re. #178 Alan Millar

    My mistake. I meant that middle sentence to read: If you ignore the evidence without any reasonable evidence to the contrary, then you being are illogical and unreasonable on this subject.

    Sometimes I don’t reread what I wrote before posting.

    Such as my mistake in #214 para. 1, where I wrote ‘in dead’, meaning ‘indeed’.

  20. 220
    Lichanos says:

    #214 JPR

    Behavioral science and human behavior and psychology are a part of this argument though…

    Ah, beware the sword of the Dunning–Kruger effect, for it cuts both ways!

  21. 221
    Nick Gotts says:

    – of course, my previous comment assumes we don’t push the system past a really nasty threshold and get runaway warming, as Hansen believes we would if we burned all recoverable fossil fuels.

  22. 222
    Hank Roberts says:

    Thanks John, good calm reply, appreciated. And I remind myself that one of the victories trolls aim for is, uh, exactly what I did: getting people in their target group to criticize each other’s replies to the trolling.

    Um, does anyone have a ladder? I need to get down off my horse now.

  23. 223

    #219 Hank Roberts

    Most welcome. Please know I have great respect for your perspectives.

    I must admit also that I have ridden high horses in the past and hope to again in the future (I’m thinking Montana these days ;). I remember one in particular. His name was Jake. Quite a thrill going down a steep grade. From the saddle it looked like going over a cliff.

    For the record, I’m rarely actually angry, though my words might assume that appearance. My goal is to shoot at the foundations of such false arguments to illustrate that they truly are built with straw and/or herring.

    I fully admit to frustration though.

    A Climate Minute The Greenhouse EffectHistory of Climate ScienceArctic Ice Melt

    ‘Fee & Dividend’ Our best chance for a better future –
    Learn the Issue & Sign the Petition

  24. 224
    Anonymous Coward says:

    Mark (#170) has asked for papers and I don’t see any answers (I’ve not read every posts). I’m mostly ignorant of the litterature so I can’t give a good answer but here’s a starting point for Mark: google “Frank carbon cycle” (without the quotes). It’s not exactly what Mark wants but it adresses the general issue and there may be something more relevant in the papers it cites.

  25. 225

    #216 Nick Gotts

    David Archer did a nice paper on the subject of recovery times, though I don’t recall if it addressed that specific issue.

    I think it was: “Millennial Atmospheric Lifetime of Anthropogenic CO2”

    A Climate Minute The Greenhouse EffectHistory of Climate ScienceArctic Ice Melt

    ‘Fee & Dividend’ Our best chance for a better future –
    Learn the Issue & Sign the Petition

  26. 226
    David B. Benson says:

    Alan Millar — You need to learn some geology. For example, there is evidence of lifeforms as early as 3.4 billion years ago with definite evidence from somewhat later. Please go learn about it.

  27. 227
    CM says:

    Lichanos #173,

    > And yes, I ask that you read Weart just as you have suggested. Isn’t
    > that appropriate when reviewing a scientific hypothesis?

    Did I say it wasn’t? If you mean we should read Weart with the attitude “Show me the evidence”, sure, that’s the scientific approach.

    If you mean we should try to get into the heads of people who are shown the evidence and just continually shift to some new sloppy excuse for denying reality, without so much as an “oops” when their bloopers are pointed out to them… that’s hard to do. The irrationality I can handle, it’s the lack of shame I don’t get.

  28. 228

    A general cry for help!

    I’m looking for a specific image from a PDF file that I recall was from Jim Hansen. I have searched all my documents from Hansen and can not find this image. I checked with the source that originally sent it to me and he suggested it may have been the ‘Target CO2’ paper. It was not there though.

    I have inquired with several obvious sources, no one seems to recall where it is? It may have been from 2004 or 2005 but I’m not sure? Could be earlier?

    Here is the link to the image:

    My goal is to use it in my next video but I really need a HiRes shot to make it look good. If anyone can help or recalls this image, please let me know here, or through oss site

    A Climate Minute The Greenhouse EffectHistory of Climate ScienceArctic Ice Melt

    ‘Fee & Dividend’ Our best chance for a better future –
    Learn the Issue & Sign the Petition

  29. 229
    Geoff Wexler says:

    Re #183

    The only problem is that the people who should understand its contents, don’t read articles this long.

    Some of the people who need to understand such articles are perfectly capapable of reading and following them.

    43 out of 1314 Fellows of the Royal Society may have succeeded in their campaign to have a rewrite of the Society’s pages on global warming. Their real goal is a bit unclear, as is their knowledge of the subject. We just don’t know from this report. It is not always the case that strongly held opinions of an FRS are supported by deep reading.

  30. 230
    Ken Coffman says:

    Oh boy, I sure like this earth energy budget analysis a lot more than I like Dr. Trenberth’s.

  31. 231
    Jacob Mack says:

    AC # 221 there are discussions here at RC regarding that very topic as well as on Google Scholar. There are some misconceptions regarding temperature and C02 that be remedied through careful reading of the literature and here at RC.

  32. 232
    Doug Bostrom says:

    So, bluster but no bet. A disappointment. I guess that’s one of the benefits of adopting a disposable persona.

    Not to criticize everybody using a pseudonym or otherwise trying to maintain anonymity, mind, which can happen for good reason. Surprisingly few so doing make embarrassing asses of themselves by being hermetically and conspicuously ignorant; I suppose our egos normally invade even our pseudonyms, don’t enjoy taking even a proxy beating.

  33. 233
    ralphieGM says:

    Doug Bostrom: “We’re digging or pumping a significant fraction millions of years’ storage of C02 out of the ground and releasing it in the course of a couple of dozen decades.”

    If it took a billion years to accumulate fossil hydrocarbons how is it possible to release the CO2 in that mass in “a couple of dozen decades”? You’re just guessing at the rate of re-entrance.

    But in terms of a mass balance – we are only returning to the atmosphere what was here before – regardless of the speed at which it is reflowed. It seems to me we are just re-distributing CO2 rather than creating it – and I can’t see cause for alarm.

    [Response: Well, I’m glad that the prospect of re-establishing early Cretaceous levels of CO2 in the atmosphere on timescales of a century or two (rather than, say, 100 million years), causes you no loss of sleep. Oddly enough, some other people do worry about that. — mike]

  34. 234
    trrll says:

    I find it interesting that so many “skeptics” imagine that the use of models is some kind of a weakness of climate theory. From my perspective, modeling is a scientific discipline, like statistics or “blinding” of data, that scientists use to avoid self-deception, because everybody is subject to bias. The main source of bias in science is not grant funding (as some clearly would like to believe) but merely the fact that everybody likes to be right. It is natural to favor your own hypotheses over others. As Feynman famously said, “Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.”

    Mathematical modeling is a way of testing your ideas, of verifying that your theory actually does what you think it does, so that you don’t fool yourself. This becomes particularly crucial in dealing with theories that involve feedback mechanisms, because intuition is notoriously fallible when it comes to such theories. Often, a hypothesis can be rejected simply on the basis of modeling, when it can be shown to be inconsistent with data. It seems to be an article of faith among critics that mathematical models are infinitely malleable, that they contain adjustable parameters be tweaked to accomodate any kind of observation. This may be true for arbitrary equations, and to some extent for statistical models, but a scientific model has to accomodate itself to physical reality. It cannot violate conservation of energy, for example. Real scientific models tend to be highly constrained, and it is not uncommon to discover that there is no way that a model with a particular structure can be made consistent with observation, even allowing for statistical uncertainty and measurement error.

    A model is a strength, not a weakness–if an idea has survived the process of mathematical modeling and testing against observational data, it has already passed one hurdle. What I see as a weakness is the lack of a model. As a scientist, I will place more weight on the opinion of the guy with the model than the guy whose ideas are still in the hand-waving stage. It is very easy to wave your hands about and assert that there might be some mechanism that will kick in to prevent the rise in temperature due to CO2 from being as large as expected, or that the parameters of existing models can be “tweaked” to achieve this. Fine–show me a model in which this is the case, and which still manages to be consistent with the rather large mass of known information related climate, and I will begin to take you seriously. If you don’t trust the standard models, then show me a better one! Publish the code, let me take it for a spin. Until then, I’m unlikely to take you seriously.

  35. 235
    Radge Havers says:

    Classic troll, someone crippled with low self-esteem and armed with a boat load of down-scale sophistry seeking cheap thrills from negative attention.

    They’d be more pathetic than loathsome if it weren’t for the sneaking suspicion that sooner or later they’re going to exploit weaknesses in the political system and wind up in positions of power.

    One thing you can try is to give way to women who are willing to argue with them. As trolls are typically stunted males who have issues which prevent them from responding to women, gender can sometimes have a deterrent effect on such septic behavior.

    Politically, anger may in fact be a valid and effective response, but it’s a tricky thing. Personally I love the concise dry wit of Gavin et al., the hilarious bursts of blistering (but thoughtfully aimed) fire from CFU, not to mention the beautifully written passages of Ray Ladbury, Doug Bostrom, and others.

    Have to admit though, I’m pretty angry myself, and if you can cut away at the foundations of trolldom, more power to ya.

  36. 236
    David B. Benson says:

    John P. Reisman (OSS Foundation) (255) — I would be interested in the sources for the lower figures. Here is the paper for the first graph:

  37. 237
    Hank Roberts says:

    John, I tried Google Image Search using phrases and words from your image. Got ten pages of results, most clearly wrong
    but this looks possible:

  38. 238

    #220 Lichanos the anonymous

    How obtuse. But weak unsubstantial arguments are apparently your modus operandi, no surprise there.

    Do you have any evidence for any one of the claims you have made? Evidence, other than you opinion I mean?

    #232 Doug Bostrom

    He won’t take the bet. In fact he can’t take the bet, because he wont’ use his real name. I can’t make a bet with a finger, no matter how many times it points spuriously into the ether of ones own argument to self indulgent authority.

    #233 ralphieGM

    “I can’t see cause for alarm”

    Could you provide some context for this claim? Obviously you are not considering modern infrastructure supporting a large population all built around the approximate thermal equilibrium of the Holocene, of which we have now largely departed from.

    Do you have any idea what the latitudinal shift will do that infrastructure?

    I remind you of the obvious: “It’s the economy stupid”.

    A Climate Minute The Greenhouse EffectHistory of Climate ScienceArctic Ice Melt

    ‘Fee & Dividend’ Our best chance for a better future –
    Learn the Issue & Sign the Petition

  39. 239
    Doug Bostrom says:

    ralphieGM says: 28 May 2010 at 4:06 PM

    [yet another fake question]


  40. 240
    David B. Benson says:

    Oops. Here is the paper with that Figure:

  41. 241

    Lichanos 92: How about: AGW is plausible, but I think it’s not sufficiently demonstrated, so I think those scientists are wrong.

    BPL: Here is the argument for AGW.

    1. Increasing the level of a greenhouse gas in a planet’s atmosphere, all else being equal, will raise that planet’s surface temperature.
    2. CO2 is a greenhouse gas (Tyndall 1859).
    3. CO2 is rising (Keeling et al. 1958, 1960, etc.).
    4. Therefore Earth should be warming.
    5. Earth is warming (NASA GISS, Hadley Centre CRU, UAH MSU, RSS TLT, borehole results, melting glaciers and ice caps, etc., etc., etc.).
    6. The warming is moving in close correlation with the carbon dioxide (r = 0.874 for ln CO2 and dT 1880-2008).
    7. The new CO2 is mainly from burning fossil fuels (Suess 1955, Revelle and Suess, 1958).
    8. Therefore the global warming currently occurring is anthropogenic.


    Which of the above points do you dispute, and on what basis?

  42. 242
    Didactylos says:

    Alan Millar said: “Perhaps you can explain how this happened and why it wont happen in the next billion years!”

    Good grief.


    good grief.

    You really think such timescales are relevant here? A clue: they are not. Right now, we are concerned with the century and decadal timescales. We can also glean useful knowledge and make projections for millennial timescales. Trying to go beyond that is a not very clever attempt to distract attention from our very immediate problems, here, now, in this century.

  43. 243

    Lichanos 106: What about the part that doesn’t fall under “Much of..?” And of course, if this means anythig significant, we’re back to the question of “How much?”

    BPL: 76% of the variance of dT 1880-2008.

  44. 244
    Doug Bostrom says:

    Didactylos says: 28 May 2010 at 6:10 PM

    …good grief.

    You may as well argue with your cat.

    I’ve said it before, these discussions remind me of nothing so much as the process of giving my cats their medication for hyperthyroidism. Every day, twice a day, it’s the same boring yet aggravating routine: Pick up the cat, squeeze its jaws open, struggle to get the pill down while the cat gnashes its teeth, does the amazing trick of reversing its upper alimentary tract and causes the pill to mysteriously appear somewhere else, the cat struggling with all its tiny, furry, writhing capacity to escape swallowing the pill it needs to remain living.

    Can’t the the little creature just eat the pill itself? No, the cat won’t eat the pill even if it’s inserted into something tasty, the same way some folks won’t read Spencer Weart’s enjoyable book because the taste of the ideas therein is repugnant to them.

    Does the cat know that without the pill, it will die? No, it does not have the intellectual capacity. And there lies the difference; the people who show up here to argue against reality -do- have the capacity to understand. There’s where my analogy fails miserably.

  45. 245

    Lichanos 119: I’ve been looking for someone who will take me up on it. $2500 says AGW will be generally regarded as a fad in twenty years.

    BPL: I’ll take that bet, with the slight change, “will be regarded as a fad by the scientific consensus.” Regarded as a fad by the public doesn’t count. We can use as a measurement a positive response to “anthropogenic global warming is well-established” by any nationally known polling organization, polling professional climatologists in the year 2030. Not “scientists,” and certainly not “engineers.” Not even “meteorologists.” Climatologists only. Oh, you can add “planetary astronomers,” too, if you like, since we were discussing the greenhouse effect in planetary atmospheres for decades before it became a hot-button political issue.

  46. 246

    Lichanos 124: “Having warmed the ocean surface, more water will be evaporated, and having warmed the atmosphere, it will then be capable of holding more of that evaporated water vapour, which also being a greenhouse gas, will add still more warming as an amplifying feed back.

    This second part is certainly plausible, but how do we know it will really happen that way?

    BPL: Google “Clausius-Clapeyron relation.” Then read these articles:

    Brown, S., Desai, S., Keihm, S., and C. Ruf, 2007. “Ocean water vapor and cloud burden trends derived from the topex microwave radiometer.” Geoscience and Remote Sensing Symposium. Barcelona, Spain: IGARSS 2007, pp. 886-889.

    Dessler AE, Zhang Z, Yang P 2008. “Water-Vapor Climate Feedback Inferred from Climate Variations.” Geophys. Res. Lett. 35, L20704.

    Held, I.M. and B. J. Soden, 2000. “Water vapor feedback and global warming.” Annu. Rev. Energy Environ., 25, 441–475.

    Minschwaner, K., and A. E. Dessler, 2004. “Water vapor feedback in the tropical upper troposphere: Model results and observations.” J. Climate, 17, 1272–1282.

    Oltmans, S.J. and D.J. Hoffman, “Increase in Lower-Stratospheric Water Vapor at Mid-Latitude Northern Hemisphere Site from 1981-1994,” Nature, 374 (1995): 146-149.

    Philipona, R., B. Dürr, A. Ohmura, and C. Ruckstuhl 2005. “Anthropogenic greenhouse forcing and strong water vapor feedback increase temperature in Europe.” Geophys. Res. Lett., 32, L19809.

    Santer, B. D, C. Mears, F. J. Wentz, K. E. Taylor, P. J. Gleckler, T. M. L. Wigley, T. P. Barnett, J. S. Boyle, W. Bruggemann, N. P. Gillett, S. A. Klein, G. A. Meehl, T. Nozawa, D. W. Pierce, P. A. Stott, W. M. Washington, M. F. Wehner, 2007. “Identification of human-induced changes in atmospheric moisture content.” Proc. Natl. Acad. Sci., 104, 15248-15253.

    Soden, B.J., D. L. Jackson, V. Ramaswamy, M. D. Schwarzkopf, and X. Huang, 2005. “The radiative signature of upper tropospheric moistening.” Science, 310, 841–844.

  47. 247

    Mark 170,

    The Granger causality runs from CO2 to dT, not the other way around. I have the numbers if you want them.

  48. 248
    Hank Roberts says:

    > 230 Ken Coffman says: 28 May 2010 at 3:44 PM
    > Oh boy, I sure like this earth energy budget analysis a lot
    > more than I like Dr. Trenberth’s.

    It’s numbered in percentages. It shows 100 percent in equals 100 percent out. The numbers are confusing. It shows some energy going into the atmosphere (missing an orange arrowhead for ground-to-air) and into clouds, but none apparently remaining in earth and ocean. People might mistake that as meaning there’s no warming happening. I think it’s confusing. I’d stick with

  49. 249

    Alan 191,

    Here’s your explanation: Continents moved, the albedo changed, the rise of vascular plants increased the rate of CO2 weathering, and the continued fall in mantle temperatures slowed the outgassing of CO2.

    Does that help? If you want a quantitative, mathematical model, try GEOCARB III (Google it).

  50. 250
    Doug Bostrom says:

    Barton Paul Levenson says: 28 May 2010 at 6:38 PM

    I’ll take that bet…

    Forget it, BPL. John Reisman already stepped forward to take him up on it, offered to up the sum to $10K. No dice; apparently the strength of L.’s conviction is subject to a great degree of natural variability.