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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. 101
    Completely Fed Up says:

    “The arguments of yours and people like you seem to amount to: There is lots of evidence for our view- you don’t accept it- you’re wrong-”

    Your argument seems to be “I have no evidence, but I don’t believe you, therefore you’re wrong”.

  2. 102
    Completely Fed Up says:

    “1) The warming is not as severe as AGW folks say it is – that historical record again…”

    But you said these other hypotheses fitted the evidence. Now you’re saying that you have to change the evidence first…?

    “2) Even if it is, we don’t know it will continue…”

    Yes we do: CO2 will retain it’s IR absorption characteristics until the atom is torn apart.

    “3) Just because we can’t prove another explanation for the alleged warming doesn’t mean it doesn’t exist and is no reason to accept a weak explanation, except as a temporary aid to further investigation, perhaps.”

    Begging the question “Climate science is a weak theory”…

    It isn’t. So #3 doesn’t exist.

    “4) Adopt the null hypothesis…”

    The null hypothesis is that since we’re adding a lot of CO2 and that CO2 retains IR radiation which comes mostly from the earth rather than the sun, we will be warming the earth because of our actions.

    AGW IS the null hypothesis.

  3. 103
    Completely Fed Up says:

    “Such campaigns did certainly exist when AGW was first proposed in the 1980s.”

    Don’t you mean the 1880′s?

    http://www.aip.org/history/climate/#L000

  4. 104
    Doug Bostrom says:

    Ok, let’s skip over Dr. Weart and try something else. How about the National Research Council of the U.S.?

    Lichanos, try reading <a href="http://books.nap.edu/openbook.php?record_id=12782&page=R1"this just-released NRC report, commissioned by Pres. Bush, and then assess if you still disagree w/the NRC’s conclusion regarding uncertainty about climate change research:

    Some scientific conclusions or theories have been so thoroughly examined and tested, and supported by so many independent observations and results, that their likelihood of subsequently being found to be wrong is vanishingly small. Such conclusions and theories are then regarded as settled facts. This is the case for the conclusions that the Earth system is warming and that much of this warming is very likely due to human activities.

    Ask yourself, “At what point does my personal opinion bow to the weight of scientifically derived knowledge?”

    Or seize on “very likely” and put that phrase through dynamic range expansion so as to maintain your set of beliefs. The probability of your core beliefs changing is probably very slight.

  5. 105

    #87 J. Bob

    Re. Lichanos

    Hang in there with what? Non relevant hypothesis about how climate models are not good predictors.

    Rather don’t you think he should bring some relevance to the discussion?

    Lichanos has of course revealed bias in his statements that have not scientific foundation. From my view that translates to a lack of reasonability.

    I do have a bias. Maybe you can point out how my bias is incorrect? I tend to go with the most robust conclusions based on the physical evidence and models that achieve relevance based on the evidence.

    The radiative went form the thermal equilibrium average of the Holocene to 3.6 W/m2 all since we started changing dramatically how humans do things with energy and in larger and larger amounts, not to mention land use changes, etc.

    So my bias is toward evidence, observations, models that describe the situation well and are robust as well as reasonable based on the quantifiable changes and the coincident changes along with the presented maths and physics, and yes I even include the scientific consensus of a body of scientists and collected works that all point the finger at an anthropogenic origin, that works through the scientific method to reduce bias, not to mention that this all came form multiple fields of science (biology, sediment cores, geology, atmosphere, etc.).

    Can you actually find a hole here? I meant the only two opposing theories are unable to find ground (from Lindzen and Svensmark) because they are not supported by the body of the science, maths or physics when weighed in with the rest of the system/evidence?

    Where are the undue or uncalled for ‘bias elements’ from the science? How is the body of evidence refutable to produce doubt or point the finger elsewhere? Please do enlighten all.

    Besides, one does not need to have an in depth understanding of thermodynamic modeling to see the many holes in the presented arguments by Lichanos, especially since his arguments revolve around opinion rather than thermodynamic modeling.


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  6. 106
    Lichanos says:

    @104 Doug B:

    I have read many similar statements. It’s important to attend to what they actually say.

    This one begins with a general statement regarding scientific hypotheses and their establishment as accepted explanations. Okay.

    It then asserts that AGW fits this bill. Now, does the fact that this statement exists prove anything? No. Does it reflect the views of all scientists? No. Do we know how many would accept this statement? No.

    What is this then? It’s simply an editorial. Maybe you know the people at the NRC who wrote it, and you respect them, and you defer to their opinion, but that’s all it is. I don’t dismiss it as trivial, but it doesn’t prove anything.

    Consider the last sentence:

    The earth is warming. Since when? How much? How fast? I am willing to accept that the earth is warming – does that mean I agree with the NRC?

    Will it continue? For how long? At what rate?

    Much of this warming is due to human activities. I’ve already stated that whatever climatic warming exists is due, in part, to human activities. I will also state that CO2 in the air may very well contribute to that. 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?”

    So all these statements that get trumpeted about as evidence of a rock solid consensus don’t amount to much, especially since I would have no trouble agreeing with a lot of what many of them say! In context, of course…

    You should worry less about my internal coginitive processes and think more about how to construct logical arguments.

  7. 107

    #90 ccpo

    Full agreement. Lichanos is showing definitive bias of the media hype type in the contrarian vein, based on his opinion rather than reason.

    The work of Spencer Weart is solid and steeped in well understood history and scientific discovery. I find it hard to read into his work any egregious sensationalism.


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  8. 108
    John says:

    Gavin, can you confirm that GISS’ dataset is in fact not just CRU’s re-hased? Ie- is it independent, compiled etc by yourselves?

    [Response: Yes of course. The code and URLs for the raw data (GHCN mostly) are all provided on the GISTEMP page. There is no connection to CRU's analysis at all - any statement to the contrary is simply not true (except perhaps in Chris Horner's fevered imagination). - gavin]

  9. 109
    Doug Bostrom says:

    Lichanos says: 27 May 2010 at 1:59 PM

    …think more about how to construct logical arguments.

    As opposed to “I doubt it” which is your “argument.” As a logician, would you say an almost perfect absence of logic is impervious to attacks on logic?

    I’m all done w/you, Lichanos, but you’ve served nicely as an example of neurotic intractability bordering (since as a pseudonymous non-person an ad hominem attack on you is essentially impossible) on psychosis.

    Just for the record, here’s Lichanos’ original objection:

    “AGW posits small and precisely calibrated changes as the result of very complex interactions. The ‘narrative’ tries to tie up the mounds of circumstantial evidence that is consistent with the hypothesis into an explanation that presents logical necessity. That is, it tries to show that not only are the supposed bits of evidence [some are controversial in themselves] consistent with the hypothesis, but that that they demonstrate the superior plausibility of the hypothesis.

    Lichanos has the opportunity but refuses to read the NRC report I mention, instead (predictably) remaining all tangled up on personal metrics of reliability useless for addressing his stated concern or for that matter consistent with numerous analogous examples of the human condition improving in the face of similar levels of uncertainty. I am quite certain Lichanos does not arrange his entire life and work around such mental pitfalls, which is what leads me to think of the word “psychosis”; intractable erroneous belief flying in the face of obvious controverting evidence commonly accepted as part of our reality is a diagnostic of psychosis.

  10. 110
    Hank Roberts says:

    > CO2 in the air may very well contribute

    Attribution should inform you better than that; “very well” is an understatement; the forcing from CO2 is calculated using the same physics behind the lasers you use every day, as you know from Weart’s book.

    Why choose such vague language about something so well understood?

    http://www.ipcc.ch/publications_and_data/ar4/wg1/en/fig/faq-9-2-figure-1.jpeg (“Red indicates simulations that include natural and human factors, while blue indicates simulations that include only natural factors”)

  11. 111
    John says:

    54
    SecularAnimist says:
    26 May 2010 at 4:03 PM

    Lichanos wrote: “It also doesn’t mean we know what you seem to think we know about AGW.”

    Exactly and specifically what is it about AGW that you think we think we know, that you think we don’t know?

    We know that CO2 is a greenhouse gas.
    -YES AGREED. BUT HOW EFFICIENT ETC IT IS AT ITS CURRENT AND PROJECTED LEVELS IN OUR CLIMATE SYSTEM IS STILL NOT ACTUALLY KNOWN IS IT.

    We know that human activities over the last century and a half, principally the burning of fossil fuels, have released huge amounts of previously sequestered carbon into the atmosphere as CO2.
    -DEFINE “HUGE” FROM THE PERSPECTIVE OF YOUR STATEMENT. IS OUR OUTPUT HUGE WITHIN THE CONTEXT?

    We know that this anthropogenic excess of atmospheric CO2 is causing the Earth system to retain more of the Sun’s energy, causing rapid and extreme warming (and in addition is rapidly acidifying the oceans as they absorb the excess CO2, which may be an even worse problem than the warming itself).
    -RAPID AND EXTREME WARMING? AGAIN DEFINE THIS. HOW IS IT RAPID AND EXTREME WITHIN THE LONG TERM RECORD – I WOULD SUGGEST IT ACTUALLY IS NOT.

    We know that this anthropogenic warming is already causing rapid and extreme changes in the Earth’s climate, hydrosphere, cryosphere and biosphere.

    IS IT? NAME THESE “EXTREME”, DEFINITELY BEYOND NATURAL VARIATION, EXTREMITIES.

    We know that there is even more warming in store from the CO2 that we have already emitted.
    DO WE? EVEN IF KATLA GOES UP WHILE WE HAVE NEGATIVE AO, LA NINA, AND OF COURSE ACCEPTING THAT ANY EFFECT WE ARE HAVING IS ENOUGH TO STOP THE JERK BACK INTO THE NEXT ICE AGE – WHICH HAS NEVER HAPPENED BEFORE.

    We know that we are continuing to release more and more CO2 and that as a result CO2 concentrations are rising, at an accelerating rate, which guarantees even more rapid and extreme warming than we are already seeing.
    YOU MEAN THE MASSIVE SHORT TERM EXTREME OF LESS THAN A DEGREE?

    What exactly do you think we don’t know?

  12. 112
    Ibrahim says:

    “Pinatubo showed a slight cooling.”
    With an El Niño that lasted from end 1991 to mid 1995?
    Wouldn’t the global temperatures have been (at least) flat or higher from 1990 to 1995 without the Pinatubo?

    http://pubs.usgs.gov/pinatubo/self/index.html

    Hansen in 1992: “The simulations indicate that Pinatubo occurred too late in the year to prevent 1991 from becoming one of the warmest years in instrumental records”

    from http://www.agu.org/pubs/crossref/1992/91GL02788.shtml

  13. 113
    Lichanos says:

    I am quite certain Lichanos does not arrange his entire life and work around such mental pitfalls, which is what leads me to think of the word “psychosis”…

    This reminds me of a class I took in Theory of Knowledge in which we discussed a book presenting a radical argument for skepticism, Ignorance, by Peter Unger, Oxford Univ. Press. (I was unconvinced…) Anyway, my professor remarked that despite the fact that Unger argued that we didn’t know anything, couldn’t know anything, and had no logical reason to accept any theory of ethics or knowledge, he was still a pleasant dinner guest, and you didn’t even have to count your silverware after he left!

    Uhh…we operate by different standards in day-to-day life, science, and philosophical disputation.

    Similarly, this bit, numerous analogous examples of the human condition improving in the face of similar levels of uncertainty, is totally irrelevant. I don’t dispute it, it’s just not germane. I thought we were trying to resolve a dispute about a scientific hypothesis. If we are trying to develop a policies to improve the human condition, there’s plenty we can do before we even have to consider scientific controversy. Distributing mosquito nets and building lots of latrines would be a good start.

    Anyway, policy is driven by a different standard of proof than science. Unfortunately, despite my initial opinion to the contrary, I now think it doesn’t even met the relaxed standards for policy making. I’m sure it will surprise you, however, that I support all sorts of AGW-favoried energy policies, but for other reasons, of course.

  14. 114

    #92 Lichanos

    “just deal with my arguments, and leave my person out of it.”

    Then why do you use your real name at the New York Times and on National Public Radio? I would like to know it because I would like to see what you are writing at the New York Times. Don’t be so coy and show some mettle here. Also, I don’t care who you vote for, that has nothing to do with your understanding capacity on this issue. I’m a conservative. Does that mean I don’t understand climate?

    So that I may look at your writing on NYT, what is the name I should look for, since you have nothing to hide.

    “Quite true, but I don’t know why it applies to me. I’m just arguing about hypotheses.”

    Because you said “This statement can hide a multitude of sins!”

    “The general question of how to evaluate models and when to rely on them, and for what, remains.”

    Maybe you should reread the article above again. And then start digging deeper into the RC index page re. models http://www.realclimate.org/index.php/archives/2004/12/index/

    http://www.ossfoundation.us/projects/environment/global-warming/models
    http://www.ossfoundation.us/projects/environment/global-warming/myths/models-can-be-wrong

    “You are extremely vehement, seem to lack a sense of humor or irony, and certainly have no knowledge of philosophy”

    Truly an arrogant statement on your part. Your concern of the nuance of meaning is duly noted. But to claim I have no knowledge or a sense of humor or irony is quite ironic. As to “greatest philosopher” vs. “completely ignorant”, what happened to your sense of nuance you were bragging about above? BTW, you might want to look into Zoroaster for some truly brilliant philosophy.

    “How about: AGW is plausible, but I think it’s not sufficiently demonstrated,”

    Just because you can’t figure it out does not overturn the well established science. It just means you are obviously myopic on this issue, sufficiently so as to preclude your ability to see clearly the reality that the science reveals.

    “so I think those scientists are wrong”

    Is this based on something more than your naive opinion?

    “What is scientifically insupportable with doubting the relevance and claimed certainty of individual scientific claims?”

    The mistake here on your part it it is not done by individual scientific claims, it is done by the body of science and evidence that has passed muster through the scientific method to arrive at reasonable conclusions.

    –Generally speaking, you’re looking at the argument, not the science.
    “What the heck does this mean??”

    This is an interesting example of you contradicting yourself and specifically the ‘pot calling the kettle black’; As per above “If you think you can settle the meaning of ‘to know’ and ‘certainty’ by consulting Webster,”. You mean you can’t parse the nuance of the usage id est argument (opinion) vs. science?

    “I think the temperature record is extremely problematic.”

    Problems are dealt with methodologically with the scientific method produce results and error bars.

    I think use of proxies is very problematic.”

    Problems are dealt with methodologically with the scientific method produce results and error bars.

    “I think many arguments presented to the general public to support AGW are utter garbage, e.g., glaciers are melting and migration patterns are changing, ergo, AGW is true.”

    Add to that ‘Attribution’ (see above article and http://www.ossfoundation.us/projects/environment/global-warming/attribution and http://www.ossfoundation.us/projects/environment/global-warming/natural-variability and especially:

    http://www.ncar.ucar.edu/research/climate/now.php

    Evidence, plus attribution = plausibility conclusions. Or do you have another theory to explain why the global glacial ice mass is dropping so rapidly?

    “but that does not prove it in any way because it is consistent with other views as well.”

    What other views? Are the peer reviewed and peer responded. Are they based on or have achieved the status of well established science? Or some guys opinion on a blog because he says so and uses equations that the public does not understand?

    “Human beings certainly change local and regional climate. This idea has been around at least since George Perkins Marsh published Man and Nature in the 19th century.”

    http://www.ossfoundation.us/projects/environment/global-warming/climate-science-history

    “If “highly likely” means 90% certainty, and “most” means more than 50%, what are we left with?”

    From what i’ve seen, the science has advanced in relevant areas of understand ing to 95% to 99.99% virtual certainty on the change in radiative forcing that is causing the global temperature to rise.

    “If my concerns about the data record and proxies are only partly correct, then the part of the rise that is AGW is not very big at all.”

    The only thing that leads you to believe your concerns are valid is your own opinion. To achieve that, you have to actually ignore the relevant science ant the contexts. That implies you choose ignorance over understanding.

    “crystal ball”

    You don’t need a crystal ball. More GHG’s means more warming. More warming means warmer oceans. Warmer oceans means more evaporation. More evaporation means more GHG”s. . . or are you implying that warmer oceans will not evaporate more moisture?

    “Should we really have confidence that they can predict the future to such a degree of precision over such a time scale when such positive feedbacks have never been observed before on this scale? When we have so little knowledge about many of the physical systems involved? When the models are calibrated against the historical record which is itself in doubt?
    I remain unconvinced. I don’t think it’s a hoax. I think it’s a fad. We’ll know for sure in fifteen or twenty years.”

    Your confirmation bias is showing. “fad”, “know for sure in . . .

    Ignoring science to favor your opinion is both naive and ignorant. Or do you just prefer ‘cautious consideration without proper consideration of the evidence at hand in context’. Would you bet your life on your opinion on this matter, that being it is not human caused and merely a “fad”?

    You’re reliance on ambiguity in your argument is quite telling. Try science instead.


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  15. 115
    Daniel Goodwin says:

    It’s nice to see the plaudits here for Weart’s fine historical work. Naomi Oreskes’ work is equally uncontroversial. Her primary thrust seems to be that the best oceanographers in the world were raising the red flag way back in the 50′s. Where in that you can find anything questionable, with regard to the historian’s craft, is beyond me.

    When smears such as “triumphant” or “celebratory” are attached to painstaking work such as Weart’s, it’s clear that a game-playing mindset – my side versus your side – is engaged.

    On the other hand, RC would be a lot less interesting without the irritants to generate so many pearls!

  16. 116
  17. 117

    #106 Lichanos the anonymous

    “It then asserts that AGW fits this bill. Now, does the fact that this statement exists prove anything?”

    If your assumptions are correct it actually indicates or even proves something very frightening!

    Since we know that CO2 absorbs IR. And since we know that adding more GHG’s will increase the effect (CH4, N2O and the resultant H2O), it rather clearly shows an entirely new conclusion. That being:

    If current warming is natural, and not AGW, then the AGW effect has still yet to kick in.

    Now there is a scary proposition.

    Thanks for that one, even if you didn’t mean to sound so alarming!!!

    But I have to call foul. I don’t approve of you being so unduly alarming. It is not scientifically appropriate without evidence.

    Got any?


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  18. 118
    Jim Eager says:

    Re Lichanos @92: “[AGW] is based on two foundations: the temperature record and the GCMs.”

    Oh, look, yet another engineer shows up to tell us that the scientists have got it all wrong but ends up just showing us how much he thinks he knows just isn’t so.

    Lets take this one step at a time.

    The number of people that have shown up here at RC to assert that one of the foundations of AGW is GCMs is not measured in dozens, but in hundreds, perhaps thousands. And every single one of them has been as flat out wrong as engineer Lichanos.

    No, dear engineer Lichanos, the foundation of the greenhouse theory, AGW being just a specific example of that theory, is based on the radiative physics of the so-called greenhouse gases, a phenomenon that has been observed and measured in both the lab and the atmosphere for 150 years now.

    There simply is no escaping the physical reality that increasing the amount of CO2 in the atmosphere, by what ever means — natural or anthropogenic, will cause more outgoing radiated long wave energy to be absorbed and emitted back down towards the surface, thus retaining more energy within the surface-atmosphere system, thereby warming it.

    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.

    There is nothing at all controversial about this, except in the minds of those simply without the education needed to understand it, and those suffering from the Dunning-Kruger effect, which prevents them from understanding much of anything.

    The only thing anthropogenic about AGW is the source of the additional CO2, that mainly being humans turning fossil carbon into CO2 by burning fossil carbon fuels.

    Do we have a problem with any of this so far before we move on to your assertions about the temperature record?

  19. 119
    Lichanos says:

    @114 JPR & 115 DG:

    Would you bet your life on your opinion on this matter, that being it is not human caused and merely a “fad”?

    I wouldn’t bet my life on anything. Would you?

    I would, however, bet money on it. Not with you, but with people I know personally. Actually, 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. Under my rules, the other guy gets to decide who wins! See, that’s why I will only do it with people I know and trust. No takers yet.

    When smears such as “triumphant” or “celebratory” are attached…

    Whoaa! If you think that’s a smear, you must lead a pretty sheltered life!

  20. 120
    Jim Eager says:

    And I see John has joined in with his caps key locked.

    John: “BUT HOW EFFICIENT ETC IT IS…”

    Actually, we have a pretty good idea from lab benchmarks and from the paleo record for times when CO2 has been at or near 392 ppmv how efficient CO2 is at causing energy to be retained in the atmosphere: between 2.5C and 4.5C, or around 3C per doubling.

    John: “DEFINE “HUGE”

    Around 320 Gt of carbon, enough to increase CO2 in the atmosphere by 38%, even with roughly half of that 320Gt being absorbed by the ocean and biosphere.

    John: “RAPID AND EXTREME WARMING? AGAIN DEFINE THIS.”

    Simple: compare the current rate of temperature increase with rates demonstrated in the long term paleorecord.

    John: “EVEN IF KATLA GOES UP…”

    Even if Katla goes up, it’s effect will largely be limited to the northern hemisphere since it’s so far from the equator, and its effects will last for only a few years at most. After it’s effects are gone elevated CO2 will still be there.

    John: “DO WE?”

    Why yes, we do, because CO2 is not going down and so far most of the warming has gone into heating the surface of the ocean. There’s a lot of ocean to warm before it reaches equilibrium with the atmosphere.

    John: “STOP THE JERK BACK INTO THE NEXT ICE AGE”

    Which isn’t due for another 40,000 years or so, because it has happened before, John. Look at the Milankovitch cycle insolation matrix and the interglacial of 425,000 to 400,000 years ago compared to present.

  21. 121
    J. Bob says:

    #105 John, have you ever figured out the difference between confidence levels and accuracy yet? Anyway here is a item for you on a legal twist on relying to much on math modeling and no enough on physical models.

    http://machinedesign.com/article/toys-aid-accident-investigation-0520

    That’s why they still test cars and trucks in wind tunnels, besides A/C. If you have ever worked with fluids and thermal systems, you would understand.

  22. 122
    Phil Scadden says:

    Lichanos – you claim AGW is based on temperature record and GCMs and find both unconvincing. Then claim that UHI is insuffuciently accounted for etc.

    I think it would make for a better conversation if you were more informed about the science that you are criticizing. Please at least browse the IPCC AR4 WG1 – it would obviously present no barriers to someone with your background. No one is asking you to believe it – but then points of disagreement like the basis of the argument, UHI, reliability of GCMs can start from a informed base.

    For starters, how about the energy imbalance as measured at TOA? AGW is rested in physics not paleoclimate.

  23. 123
    Hank Roberts says:

    A correction to my reply above to this post:
    http://www.realclimate.org/?comments_popup=2348#comment-175757
    Dr. Ornstein has a website, not a blog; he has published other interesting ideas he mentions there, worth a look:
    http://www.springerlink.com/content/55436u2122u77525/
    Irrigated afforestation of the Sahara and Australian Outback to end global warming
    Climatic Change Volume 97, Numbers 3-4 / December, 2009
    DOI 10.1007/s10584-009-9626-y
    – Leonard Ornstein, Igor Aleinov and David Rind

    Rereading his post, perhaps the key point about statistics isn’t that people don’t understand that a trend isn’t proof of causation, but rather that when combining work done with different statistical tests the combined result is hard to weigh, statistics doesn’t answer that problem very well. I think Gavin’s answer is that statistics doesn’t perhaps bring in the solid physical mechanisms we know are operating either, and knowing the physics adds some assurance, if not some statistical strength, to evaluating what’s going on.

    On taking dead old growth as fuel and returning the ashes, I’ve still got severe doubts; in the Western European forests, people have harvested every stick that falls for centuries and that’s suspect in the overall decline there. Besides we’d see industry sending sewage sludge to dump in the old growth forest as “equivalent” material rather than returning only the clean ash from burning old growth trees — which probably would be valuable because it has little natural or anthropogenic heavy metal or fallout contamination in it, ya know? Probably clean wood ash would be diverted to rich people’s secure shelters for hydroponics if they could get it. Or maybe I’m too cynical?

    On comparing that to taking the whales, well, they were already mostly before science had a baseline
    http://www.pnas.org/content/100/21/12223.full
    but those remaining plankton harvesters are still getting a lot of study along the edge of the Arctic sea ice for example as it changes:
    http://www.onr.navy.mil/en/Science-Technology/Departments/Code-32/All-Programs/Atmosphere-Research-322/~/media/3EB2D1066E954AE8972609637D8BF351.ashx

  24. 124
    Lichanos says:

    There simply is no escaping the physical reality that increasing the amount of CO2 …more outgoing radiated long wave energy to be absorbed and emitted back down … thus retaining more energy within the surface-atmosphere system, thereby warming it.

    Absolutely agree, assuming that over the long-term nothing compensates by removing the CO2 from the atmosphere, like rampant kudzu growth, or something like that…

    Of course, your statement implies a very simple model of the earth-atmosphere system, sort of like an inert billiard ball surrounded by air, perfect for a lab experiment!!

    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? Because it couldn’t happen another way, obviously, is that it? How much will it happen? Might anything slow down or negate this process? Everyone here seems to agree that the processes by which clouds are formed and unformed is one of the more mysterious elements of the system. And, as you point out, water vapor is a GHG, the most important one of course, so this is quite an important area of uncertainty. And, again, when we are considering relatively small physical changes of state to the system – remember that Kelvin scale – my dear James this uncertainty is rather troubling.

  25. 125

    #119 Lichanos the anonymous

    “I wouldn’t bet my life on anything. Would you?”

    I would bet my life on many things and in fact have taken various degrees of risk for the sake of justice and truth. I am confident enough in the evidence right now (re. AGW) to bet my life that the major shift in radiative forcing since the beginning of the industrial age is human caused.

    Not unlike the soldiers of our armed forces that take that risk for the freedom of our country and others to maintain relative global stability when able (politics aside). Or those that felt freedom was so worthwhile in the Revolutionary war. Or that the United States was more important in the Civil war. I would have sided with the North to protect the union.

    I’ll bet you $10,000. And let’s say we don’t decide, but let the well established body of evidence and science speak for the reality of AGW, rather than anyone’s opinion. Also, if I make more money and can afford to add to the bet in the future, let’s say we up it to $100,000.

    How about if confidence is still above, or between, 90% and 99.99% and it’s fad status has not faded do to countervailing established science, you pay me $10k. If not, I pay you. Agreed?

    As to:

    When smears such as “triumphant” or “celebratory” are attached…
    Whoaa! If you think that’s a smear, you must lead a pretty sheltered life!

    As in all such things, context is key! In your usage, in the context of the demeanor of Spencer Weart and your inferred bias confirmation upon his work, yes, that is pretty much a smear. You don’t know enough about Spencer or the Science to understand just how much of a smear it is though.

    But I’d suppose that is why you tend to rely on ambiguity rather than specificity based on the evidence. It gives you room to say, ‘I didn’t mean what you think I mean’. But what you don’t realize is that most people in here are not left handed when it comes to the science of global warming.

    Oops, I’m sorry. I forgot I’m supposed to have a sense of humor.


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  26. 126

    #121 J. Bob

    I have some very interesting material from Jim Maslanik, that I have unfortunately not had time to digest yet. I hope to get to it soon.

    I’m terribly behind on my analysis lately.


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  27. 127
    dhogaza says:

    Lichanos displays his ignorance …

    Re Lichanos @92: “[AGW] is based on two foundations: the temperature record and the GCMs.”

    Jim Eager gave you a detailed answer, but really, people are wasting far too much time on you.

    Neither the temperature record nor GCMs (or the computers on which they run) were around when the foundations of greenhouse gas warming of the climate were laid down. Nor were the huge increase in CO2 emissions of the last century being imagined by those doing the work.

    If you’re this ignorant of climate science, why should anyone pay any attention to anything you say?

  28. 128
    dhogaza says:

    #119 Lichanos

    “I wouldn’t bet my life on anything. Would you?”

    I bet my life on science and technology every time I step on an airplane.

    I must admit that I very, very rarely bet my life on ignoring science and technology, particularly a scientific field that goes back 150 years and which has roots in physics going back much longer.

  29. 129
    Completely Fed Up says:

    “I wouldn’t bet my life on anything. Would you?”

    You’re betting your life on thousands of experts who studied the climate for nearly two centuries are wrong and that you’re right.

    You’re also betting OUR lives.

  30. 130
    Completely Fed Up says:

    I reckon lychanos is running over here to make dumb statements so he can go back to the herd and tell them that “those AGW believers” are sooooo closed minded.

  31. 131
    Doug Bostrom says:

    John P. Reisman (OSS Foundation) says:
    27 May 2010 at 4:11 PM

    I’ll bet [Lichanos] $10,000.

    Oh, boy. It’s about time something like this happened. Twang, plonk. Will the strings break?

  32. 132
    Completely Fed Up says:

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

    Because we’ve been able to do the experiments for hundreds of years.

    “Because it couldn’t happen another way, obviously, is that it?”

    What other way could it happen? Freeze when you warm the ocean???

  33. 133
    Ray Ladbury says:

    Lichanos,
    Your entire position is based on ignorance of the scientific method. As you show no inclination to actually learn how science is done, I see no point in discussing things with you.

    Should you decide at some point that you actually want to learn the science, I and many others here would be more than happy to help, but when all is said and done, a man cannot be reasoned out of an opinion he did not arrive at by reason to begin with.

  34. 134
    Jim Eager says:

    Lichanos: Absolutely agree, assuming that over the long-term nothing compensates by removing the CO2 from the atmosphere, like rampant kudzu growth, or something like that…

    It’d take an awful lot of Kudzu, don’t you think? Moreover, kudzu that wouldn’t just die and rot and thus return its carbon to the atmosphere.
    Got anything more substantive?

    Over the long term we won’t have to worry about it, though, since eventually enough calcium carbonate shells will rain down to the ocean floor, assuming ocean pH doesn’t fall faster than carbonate shelled marine life can adapt, and enough silicate rock will weather by absorbing CO2, but take a look at how long it took after the Indian subcontinent collided with Asia and uplifted the Himalayas and Tibetan Plateau 50 mya to geologically draw down enough CO2 to cause temperature to fall enough for Antarctica to form a permanent ice cap 34 mya.

    True, we’re no where near CO2 levels of the Eocene peak, but the last time atmospheric CO2 was at 392 ppmv was at least 3 mya, before the start of the Quaternary glacial-interglacial cycles, and probably 10-15 mya during the mid-late Miocene, while CO2 was close to 450 ppmv when Antarctica stared to freeze, a level we’ll reach around 2030-2035 at the current rate of emissions.

    Pointing to the long term tends to accentuate the time factor we’re up against, not downplay it.

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

    Ummm, because it has happened that way in the past? Because if the iris effect is as powerful as Lindzen keeps insisting it is he can’t explain how an interglacial comes to be, let alone past long term periods of high temperature.

    Lichanos: remember that Kelvin scale

    Oh, please tell us you are not trying to run the “show the entire scale” argument du jour up the flagpole.

  35. 135
    Aaron Lewis says:

    How do we determine that a predicted effect of AGW has actually happened?

    Consider loss of Arctic sea ice (ASI). When we started building GCM, ASI provided high albedo in the Arctic, helped keep the atmosphere dry so heat could be radiated into space, and provided a breeding platform for marine mammals. Then, ASI was a smooth, fast surface for dog sleds to take seal hunters out the hunting grounds. Moving through the multi-year ice was a job for Class A ice breaking ships.

    Today, ASI is porous and perforated for much of the year so that water vapor from the sea enters the Arctic Atmosphere. During the melt season, a film of water on the surface of the remaining ice reduces albedo. And, both walrus and polar bears have experienced significant loss of young when the ice broke up early. Now, travel over the ice is hampered by cracks and open water. Last summer, a small Class C research vessel was able to cruise through thick ice at speeds near its normal cruise speed for open water.

    Certainly, there is lots of ice left in the Arctic. However, it does not function the same way that ASI functioned 40 or even 10 years ago. Do we say the Arctic Sea Ice gone when it stops acting like Arctic Sea Ice, or when the last bit of slush is gone?

    How, and when do we know that global warming has taken the ASI?

  36. 136
    David B. Benson says:

    Lichanos (92) — We knew enough over 30 years ago.

    Charney et al. 1979 NRC/NAS report:
    http://books.nap.edu/openbook.php?record_id=12181&page=R1

  37. 137
    kevin king says:

    Very funny.

    >>You always need a model of some sort

    I suppose you do. Einstein and Bohr both had models.
    But of course they could verify hypothesis against reality
    very easily. It’s called empirical data.

    If you have to explain your results by hand waving and postulating
    the question

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

    you have a fundamental problem with your approach. You don’t have to
    have a phd in physics to grasp this very simple(emphasis simple) point.

    [Response: Please, at least try to pretend you are paying attention. - gavin]

  38. 138
    Pete Dunkelberg says:

    It’s remarkable how someone can get regulars here wound up with versions of the Argument From Personal Incredulity and sundry sly smarting off. I take it most of you have not been through the sameo-sameo for ten years with creationists.

  39. 139
    wurstendbinder says:

    from my point of view as a biologist, taking “microbiology” as THE example for a lab science gets it pretty bad: the science you are talking of should better be called “molecular microbiology”, biochemistry or the like; whereas the rising sciences of “microbial ecology” and “environmental microbiology” show exactly where the problem is: humans and their means to “observe” are (still!) extremely limited. therefore you have to admit: all the datasets we’re working with are more or less imperfect. scientists may reduce this imperfectness by appropriate statistics and reasonable modelling. but although they try this all the time, they sometimes fail.

  40. 140
    Lichanos says:

    #125 As in all such things, context is key! In your usage … that is pretty much a smear.

    But calling a man a liar and diagnosing me as subject to psychosis is…polite?

    #127 Neither the temperature record nor GCMs (or the computers on which they run) were around when the foundations of greenhouse gas warming of the climate were laid down

    A lot of people make arguments like this. Oreskes proposes a similar non sequitur. In the 19th century, Arrhenius proposed the “green house” effect deriving from burning fossil fuel. This was based on knowledge of the physical characteristics of CO2. Nobody disputes the nature of CO2. That’s not what’s at issue. If it were all so simple and straightforward, why the heck would you need to spend hundreds of millions of dollars on computer models? Obviously, the system is complicated.

    #128 I bet my life on science and technology every time I step on an airplane.

    That’s like saying you take a bet everytime you flush the toilet that the water will go down and not up. Some odds! Just for laughs let me ask you, would you bet your life on something that actually makes for a wager as it’s usually understood, like whether or not the BP “top kill” will work…today…this week?

    #130 I reckon lychanos is running over here … so he can go … tell them that “those AGW believers” are sooooo closed minded.

    You sure give me plenty of evidence for that!

    #132 What other way could it happen?

    Your lack of imagination in the face of nature is astonishing.

    #138 …sameo-sameo for ten years with creationists.

    I’ve been through the “same old” with creationists. The dispiriting thing is, you supporters of AGW sound like THEM. To compare climate science to Darwinian Theory is ridiculous. Just reading Darwin, and how he deals with objections to his theory would make that clear.

  41. 141
    Hank Roberts says:

    > It then asserts that AGW fits this bill. Now, does the
    > fact that this statement exists prove anything? No.

    > Nobody disputes the nature of CO2.

    What exactly about the subject of attribution do you want to discuss?
    Attribution. That’s what the topic is for.

    You realize proof isn’t available in science, this isn’t mathematics.
    You’ve read Weart; you’ve read the IPCC material; you’ve read the Start Here links at the top of the page.

    Attribution. What do you want to know about it from the climate scientists?

    Ignore anyone who seems just to be anklebiting and eventually they’ll leave you alone. Don’t encourage the distractions from the topic.

  42. 142
    Phil Scadden says:

    Lichanos – I’d take your bet but only with the reassurance that you had read and understood WG1. Otherwise I would have some ethical issues.

  43. 143
    Lichanos says:

    #141 Attribution. What do you want to know about it from the climate scientists?

    Hey, man. I posted a simple comment, way back when, on the argument that Gavin presented. Since then, I’ve just been responding to comments hurled at me by the running dogs. Who’s doing the ankle biting?

  44. 144
  45. 145

    #140 Lichanos the anonymous

    - Did I say you are psychotic? And I’m not calling you a liar, just so it’s clear, I’m saying you are using narrow-minded argument that is largely misguided that relies on opinion while ignoring science. If you are aware of it, then you are a liar. If your just not that bright in this particular area of science then you are merely ignorant and/or naive.
    - The basic science of CO2 is straight forward.
    http://www.realclimate.org/index.php/archives/2007/08/the-co2-problem-in-6-easy-steps/
    - You’re comparing getting on board a complex aircraft that relies on a multitude of manmade systems, repair schedules and complex technology, to gravity. You are kidding, right?
    - If you have evidence that the regular posters here are closed minded, I would love to see it.
    - you highlight lack of imagination, again forgetting that it’s not about opinions, it’s about evidence and science. You can imagine that aliens are heating up the planet, but how is that relevant?
    - then you compare those that look at evidence in science to creationists. Geez, no wonder you are too chicken to tell us your name. Your logic is not merely confused, it’s embarrassing.

    You have successfully managed to answer all not relevant points with your opinion and you have not answered any of the relevant questions I gave you.

    hmmm . . .


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  46. 146
    Jim Eager says:

    Lichanos: Nobody disputes the nature of CO2.

    On the contrary, plenty of half-wits do, they make drive-by comments here all the time.

    Not that I’m saying you do or that you’re a half wit, mind.

    Lichanos: You sure give me plenty of evidence for that!

    Speaking of which, I just reviewed all of your comments in this thread and you have yet to provide a shred of evidence to support your arguments, straw man and otherwise, assertions, hand waving and dismissal of the science and multiple lines evidence.

    Not one single piece.

    You know what they say about glass houses.

  47. 147

    #140 Lichanos the anonymous

    Climate science is much more well established that the Top Kill solution for a multitude of reasons. I would not bet on Top Kill. In fact I have serious doubts about it. I have proposed a different solution that I think has a better chance of working though.

    We will have to wait and see their next move.


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  48. 148
    dhogaza says:

    Attribution. What do you want to know about it from the climate scientists?

    Ignore anyone who seems just to be anklebiting and eventually they’ll leave you alone. Don’t encourage the distractions from the topic.

    You assume he’s serious about learning. It’s hard to anklebite an anklebiter …

  49. 149
    Daniel the Yooper says:

    Re: Lichanos & similar sorts

    To paraphrase Eldridge Cleaver, when it comes to the subject of Anthropogenic Global Warming, one can be part of the solution by becoming familiar with the fundamentals of the subject matter (cf. Weart, IPCC WG1, RC Start Here) or one becomes part of the problem, which is the denial of testably verifiable science (i.e., “Denialism”).

    Or you can be as Lichanos, which is to claim to be educated enough in the science, but apparently not well enough to understand it. It is in in his denying of the science (without any furnished citations) despite his proclaimed understanding of it (cf. Dunning-Kruger) that I stay on-topic & Attribute him as a troll.

    Despite the valiant efforts of Doug Bostrom, John Reisman, Hank Roberts & many others, Lichanos is undeterred in his mission to cause conflict & argument, and to continue to sow the seeds of discord among the sway-able masses reading but not yet commenting on these threads. If Lichanos has substantive, verifiable concerns supported by source citations (cf. virtually any post by any regular commentator here on RC) that can be shown to override over a century of research into atmospheric physics, let him provide them for peer review.

    Until that (far removed future) time, Hank’s suggestion in comment 141 at 27 May 2010 at 6:42 PM would be a wise one to follow:
    “Ignore anyone who seems just to be anklebiting and eventually they’ll leave you alone. Don’t encourage the distractions from the topic.”

    Cheers,

    Daniel the Yooper

  50. 150

    #143 Lichanos the anonymous

    Your simple comment (#22) was largely naive and/or ignorant in the context of the well established climate science.

    Or do you have evidence, other than your opinion, to the contrary? I mean ‘hey man’, opinions don’t count here.


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