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Climate change “deniers” and “skeptics”: What’s the difference?

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"Angry hot planet" (Image: Green Party)

This post is really a question. Over the past few years, ever since the climate change debate, well, heated up, the words “skeptic” and “denier” have been thrown around on countless websites and blogs, usually accompanied by much frothing at the mouth. This has left me wondering; is there anything bordering on a consensus among the climaterati that recognizes a difference between the two?

Now I understand of course that the words lie on an often too slippery continuum. I also realize that true deniers often conveniently cloak themselves with a veneer of polite skepticism. But it strikes me that my own perception of both groups is akin to Potter Stewart’s famous take on pornography; I can’t (and won’t) always define them, but I can usually recognize bonafide cases, at least extreme ones. So for instance, in my dictionary Senator James Inhofe  is squarely in the “denier” camp but Freeman Dyson is squarely in the “skeptic” camp.

In addition I firmly believe that being a skeptic is not just a good thing but a great thing; skepticism is what all of science is founded on after all. So I respect true skeptics as much as I detest true deniers. I am still undecided on someone like Bjorn Lomborg who seems to have started out as a firm denier but gradually gravitated toward the skeptic camp. There’s the additional problem that people like Lomborg sometimes pitch a mix of denial and bonafide skepticism and it can be hard to distinguish between the two.

I also seem to have developed my own rough, somewhat well-defined compass for recognizing members of each group. As far as I can tell there are three central premises of the science of climate change, stated in my opinion in increasing order of uncertainty:

1. The climate is warming.

2. This warming is unprecedented and is almost certainly because of human influence.

3. This unprecedented warming is going to do some very bad (or at least unpredictable) things.

To me it appears that almost nobody except the most rabid fundamentalist denier would have a problem with the first point. Personally I would also call someone who disagrees with the second point as at least leaning toward being a denier; to me there’s really no other good explanation for the warming that we have seen except human activity.

The third point is where it gets more interesting. There are people who agree that humans are warming the planet, but then wonder about the exact details of the effects: How much will it exactly warm? Will it warm equally everywhere? And most importantly – and this is something Bjorn Lomborg has often asked – would the favorable effects of the warming outweigh the unfavorable ones? Many of these questions involve prediction and they ask if the science and art of climate change is predictive enough. I have to say that in most cases I place people who ask these kinds of questions in the “skeptic” camp, although there are sometimes exceptions. It’s also not escaped my notice that the difference between denial and skepticism sometimes simply comes down to whether someone is just throwing around opinions or actually sweating the details.

But that’s enough of what I think. What do readers think? Who in your opinion is a “skeptic” and who is a “denier”? And let’s also involve the other side, the one which thinks that the whole thing is a giant communist scam or misguided science or whatever. What kinds of terms do you have for the moderate and extreme varieties in your sworn enemies and how do you define them?

Friendly housekeeping note: More than for other posts I am going to have the comments on this post on a tight leash since I don’t want the comments section to morph into a mudfest. Strong disagreement and criticism are fine, strenuous arguments are ok, interpretive dance videos are especially welcome; unhinged rants are not. What we are looking for is a spectrum of opinion on definitions. Maybe something approaching a consensus will emerge from the comments or maybe opinion will be as diverse as species of beetles. In either case with enough commenters it should be interesting.

Ashutosh Jogalekar About the Author: Ashutosh (Ash) Jogalekar is a chemist interested in the history and philosophy of science. He considers science to be a seamless and all-encompassing part of the human experience. Follow on Twitter @curiouswavefn.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. aimee w 9:44 pm 05/8/2013

    This is going to be a very interesting conversation.

    From my perspective, deniers say ‘no, it’s not happening’, or ‘not, it’s not humanity’s fault’.

    Skeptics as ‘IS it really happening/our fault?’.

    I think, though, that climate skepticism shouldn’t be included in skepticism as a whole. Certainly, many of the people I know who’re firmly in the skeptic camp, are very upset that the word’s been, in their view, hijacked by the anti-AGW people.

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  2. 2. aimee w 9:45 pm 05/8/2013

    ‘ask’, apologies, not ‘as’. Sigh.

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  3. 3. jplatt 10:23 pm 05/8/2013

    Skeptics aren’t sure about all or some of the science. Deniers think there is a vast conspiracy to make people believe in global warming so someone (mostly Al Gore and grant-earning scientists) can profit off the fear.

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  4. 4. Agesilaus 10:51 pm 05/8/2013

    It is quite simple. Denier is a pejorative term used by Warmists. Skeptic is what we call ourselves.

    As for your points:
    1) The climate has not warmed for the last 15 to 20 years, depending on which data set you look at. Even the Hadley center has admitted as much.
    2) The warming is by no means unprecedented. We had a warmer period around the year 1000 and it was even warmer than that during the Roman Warming period. Furthermore the data is being manipulated to show warming. They call it adjusting the data but it always makes the temperature go up.
    3) A degree or two of warming is beneficial, almost no one dies of a warm spring. Polar bears survived many warming cycles with no human intervention in their history. People do die from cold weather tho and that may be what we are headed for now.

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  5. 5. GoldenEagle 11:40 pm 05/8/2013

    Hi Ashutosh. Good question! What strikes me is that the word denier was historically used in reference to Holocaust deniers. I don’t recall ever seeing the word “denier” used in any other context prior to the anthropogenic climate change debate.

    So I’ve always felt the application of the denier label to ACC skeptics is inappropriate — it feels like a cheap and nasty polemic trick meant to stifle dissent and marginalize dissenters.

    Also, the science around climate and ACC is far too new and hazy to expect everyone to be on board in just a few years. I’m not an ACC skeptic myself, but I’m very interested in their arguments. Related to the “denier” issue is how skeptics are equated to creationists. In my mind, there’s no excuse for that — the science around evolution is settled, and has been for what, a century? There are mountains of evidence on that issue. The science around ACC is not remotely in that ballpark — it’s fresh and new, and focuses on projections based on statistical models with substantial error bands. There are still a lot of things we don’t know about climate, and about the impact of human activities. For example, there’s been a lot of “missing” warming in recent years. The consensus now seems to be that it went into the deep oceans (which may not be a good thing). I don’t think anyone saw that coming — it wasn’t in the models. We were supposed to see more warming on the surface than we have. There are probably going to be many surprises in years to come, because we simply don’t have it all locked down yet.

    Given all that, we can’t justifiably call skeptics deniers.

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  6. 6. MojoMojo 11:42 pm 05/8/2013

    #2 Unprecedented?
    What an absurd question.
    Only a fool would answer that todays warming is unprecedented.
    Examine the ice core graphs for evidence of a precedent.
    This publication continues to reach new lows of intelligence.

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  7. 7. northernguy 12:45 am 05/9/2013

    Three central premises of warmists.

    1. Projected temperature and C.O.2 levels (based on available evidence) are extreme in geological terms.

    2. That current temperature levels are unique to human history.

    3. That not only are all the effects of temperature increase negative but even a small increase will destroy civilization and permanently damage the Earth.

    4. Anyone who expresses even the slightest skepticism about the first three is at the very best an ignorant, ill educated, semi-literate fool but most likely is in the pay of a vast conspiracy.

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  8. 8. rkipling 1:06 am 05/9/2013

    I looked up “Geologic temperature record” on Wikipedia. I won’t bother with the link it is easy to find. The five million year graph shows over a 10 0C variation and looks like guilty person’s polygraph. The biggest lies seem to be told in the last million years with three other maxima similar to now in the last 500,000 years.

    The 65 million year graph shows a delta T of about 20 0C. A least squares regression of that graph shows a cooling tread over that time with much wider variation from a rolling average. (That means lots more up and down to you and me.) I haven’t tried to overlay oxygen or CO2 concentration to look for correlations.

    So, it seems there has been lots of climate change going on here on the third rock way before our ancestors were little rat looking thingies. (Okay maybe they were just my ancestors. But in my case it would explain a lot.)

    Going by the author’s denier-dar:

    1. The climate is warming. – Over the last 100 years it seems to be.

    2. Warming unprecedented and we did it. – Well we probably did most of the CO2 increase in the last 100 years, but there were times when the earth was colder than now with higher CO2 concentration than now. Why that was? Will warming continue? I don’t know?

    3. It’s the end of the world as we know it! – It seems fairly arrogant for someone to say they understand enough of how the planet works to predict what WILL happen. Guess we will have to wait and see? If doubling the atmospheric CO2 concentration is going to cause very bad things, we better shop for “Ark Building for Dummies” because we probably won’t turn it around before that happens.

    My guess is that it will turn out that the earth will adapt much faster and better than some expect to higher CO2 levels. But that’s just a guess. In a few generations we will know for sure.

    I’ve seen people here calling each other “deniers” and “warmists”. Since there appears to be an almost religious element to both, I would prefer to call myself an AGW and CAGW agnostic. And looking at the Wikipedia graphs I will need another few thousand years to be 100% sure of question (1).

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  9. 9. stargene 1:52 am 05/9/2013

    First, there is the quaint notion that vast numbers
    of scientists from virtually all relevant fields,
    all over the planet, are actively colluding in a
    stable massive hoax pretending that global warming
    caused by humanity is real, and a towering danger
    for the world (already pretty shaky and battered,
    due to, how shall I put it… politicians and their
    rich suzerains always looking out for our very best
    interests, so we shouldn’t worry our pretty little
    heads about anything beyond the next reality shows.)
    And we know that these politicians and their sainted
    friends on Wall Street would never lie to us, create
    an environment which allowed millions of trusting
    families to go into staggering debt based on faulty
    yet ‘gold-plated!’ ‘financial instruments’, and
    would never allow idiocy like Sequestration to occur,
    exactly like shooting ourselves in both feet with
    shotguns. And who would never, never award them-
    selves obscene multimillion dollar bonuses while
    the nation they turned into a car wreck will be
    in deepening pain for at least a generation.

    Truly, any “denier” insisting in the above is in
    some sense undergoing a sort of lunaticastrophe. A
    huge cabal of many scientists plotting a great
    lie would have a tiny half-life rivaling that of
    the free neutron, about eleven minutes. Max.
    Simply by the very nature of scientists and science.
    They are simply one of the most unruly, skeptical
    and truth-seeking missiles around. Kind of like
    herding cats. Only worse.

    But can someone be a legitimate skeptic about some
    the details. Of course. In the sense that at
    present, we only know many, though not all, of the
    broader strokes of anthropogenic global climate
    change. However, a supposed skeptic (~Lomborg?)
    asking rather coyly whether all temperatures
    everywhere would increase by the same amount
    actually betrays someone with no feel for the
    inherent chaos of super complex systems, and who
    perhaps does not truly deserve yet the name of
    Skeptic. To put it kindly.

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  10. 10. Benfun 1:58 am 05/9/2013

    Denier exists in this category because there is a concerted, well funded effort to explicitly sow doubt about the science.

    Former tobacco PR firms teamed up with Oil PR firms and used the exact same playbook the tobacco industry used to sow doubt about cigarettes and cancer. The fact that we live in a hyper partisan media landscape means a lot of ideologically aligned people regurgitate the same inaccurate and fabricated talking points as evidenced by some of the comments already added to this article.

    On the side of AGW is EVERY science academy in the world, EVERY professional scientific and engineering body in world, and 33,000+ scientists of universities and government agencies. They do the science, they place the instruments, they debate the measurements and causes amongst equally trained experts and work towards a better understanding of the way our planet is behaving and changing.

    From 1991 to 2013 the number of articles in the peer reviewed literature that support an AGW interpretation: 13,926, the number that don’t 24. Of those that don’t they all subsequently failed to make their case and have been shown to have flawed premise or data.

    Then, of course, there is a list of common lies or misunderstandings that are pushed out repetitively from a small group of PR shops and non profits (like for instance that it hasn’t warmed in the past 10 years) and that get repeated ad nausea when there’s ample sources all over the web that completely refute the point and put it in its proper context.

    Denier is anyone merely repeats something that can be traced back to one of these fake sources. A skeptic is someone who engages with the ever evolving science and pushes for greater clarity and a more nuanced understanding.

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  11. 11. Climate Chris 5:43 am 05/9/2013

    David Rose seems to be a good exemplar of just how sceptical the deniers are. He writes in the Daily Mail many falsehoods about climate change, and defends himself as being a sceptic, and that being so is a healthy thing. I am sceptical in my approach to policy narratives. Hence I didn’t believe claims that Iraq had WMD. I believe the science of anthropogenic climate change, but am sceptical about claims that climate change will not become dangerous until 2 degrees of warming. David Rose, despite his claims to being sceptical, swallowed the Iraq WMD lies hook line and sinker. So his scepticism is not indicative of his attitude to reality, but is a device he uses to promote right wing policies. I think this is true of most deniers who call themselves sceptics.

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  12. 12. curiouswavefunction 7:57 am 05/9/2013

    Thanks all for your comments. I should have made one point clear before and I am glad GoldenEagle brought it up. I don’t want this discussion to even remotely turn into one comparing climate change denial to Holocaust denial; in my book there’s no comparison whatever, and any person who does this will have their comment removed. That being said, “denier” has a legitimate place in the English language, you can find it in most dictionaries independent of the vile context in which it’s used today, and it did exist before it was hijacked by Holocaust deniers. Personally I use it precisely because in my dictionary it has nothing to do with Holocaust denial. If the word makes you uncomfortable feel free to replace it with “denialist”. In any case, I hope this is the last time we discuss this particular topic in the comment thread.

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  13. 13. markhoofnagle 8:54 am 05/9/2013

    I think you must be self-trolling your own blog to create a topic like this. For one, the answer is a google search away. And for another, the tactics of denialism are quite well known, and denialism even has it’s own wikipedia entry. This has also been called the demarcation problem.

    The main difference is between skepticism and denial is not on a point of fact. It’s about methods. Skepticism vs pseudoscience and anti-science are defined far more by their methods than by the positions they take, and I think that’s the mistake your making by trying to find a consensus point that would exclude a “denier”.

    Denialists use some combination of five general tactics to make their pseudoscientific arguments.

    First, to explain why they believe something so different, without adequate data to back it up, they usually have to rely on some form of conspiracy theory. Hence, those that make the relatively insane argument that thousands of scientists worldwide are participating in a “hoax”, essentially requiring them to coordinate, fabricate data, trick journals and editors and peer reviewers etc. Anyone who believes such a thing is possible is probably already lost to reason.

    Second, cherry-picking is critical to create the appearance of some evidenciary basis for their belief, but their is no need for the denialist to incorporate all the data, all the facts etc., into their alternate reality. They just need to create the appearance that there is a debate to be had, even though there is not.

    Fake experts are frequently relied upon. In global warming denialism world, these include Christopher Monckton, Richard Lindzen, the Pielkes. They may or may not have expertise in climate change (the classic fake expert is usually in a completely unrelated field), but more importantly, they misrepresent the current literature and state of knowledge of the field, and only lend credibility by virtue of whatever credentials they hold.

    Denialists also continually move goalposts – that is as their arguments are answered or satisfied they continually adjust what needs to be done to convince them. This is because they are fundamentally dishonest brokers in a debate. They are not interested in science or finding an observable truth. They are only interested in protecting a belief critical to their ideology. In climate change denialism, the ideology is usually free-market fundamentalism.

    Finally, various logical fallacies are usually employed, from argument from analogy to petty insults about Al Gore being fat.

    I also have to disagree with you that climate change denial and holocaust denial are completely unrelated. You will find that all denialists rely on these methods no matter what they are debating. That is not meant to imply a moral equivalence between the two. Instead it’s a matter of some study into what is being called “motivated reasoning”. When the facts don’t fit a strongly-held or overvalued belief, people engage in motivated reasoning to try to protect those beliefs from the encroaching facts. The methods are the same and common to all people, it’s just the overvalued belief being protected that is different. On the one hand, anti-Semitism, on the other free market fundamentalism. Don’t be distracted by the global warming denialists crying foul over the comparison, it’s part of their tactics of deflecting criticism via the classic logical fallacy of a straw man argument.

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  14. 14. DoubtfulNews 10:11 am 05/9/2013

    A committee of skeptical thinkers put this document together in part to deal with just this issue. I’d like to get it around to more journalists.
    Media Guide to Skepticism

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  15. 15. Chryses 10:15 am 05/9/2013


    It might be best to use your post as a common point of reference.

    “1. The climate is warming.
    2. This warming is unprecedented and is almost certainly because of human influence.
    3. This unprecedented warming is going to do some very bad things.”

    Only denialists would disagree with the first claim; it is well documented.

    If what you mean by the current warming being unprecedented is that the current average global surface temperature is higher now than it has been in the past (unprecedented high), then I must disagree with you, as both long and short term data fails to support your claim ( ). If instead what you mean by the current warming being unprecedented is that it is the first to have a component composed of human produced GHGs (unprecedentedly constituted), then I’ll agree with you, but with the comment that this is the first time that was possible.

    As there have been prior climate warmings with no significant human contribution ( ), it cannot reasonably be argued that because there is a human component to this warming, this warming is due only to the human component, unless the components of the prior warmings have been shown to be not present in the current warming. To my knowledge, such exclusion has not yet occurred.

    This is the point I find interesting (thanks for your patience): not that the current warming has no human component (it does), but what portion of the recorded warming can reasonably be attributed to human activity? I doubt, for reasons given above, that 100% of the recorded current warming is due to human activity. If the portion of the current warming due to human activity is less than 100%, then what might be the optimal – not ideal, but optimal – response? What mixture of accommodation to the inevitable and prophylaxis of the manageable should be attempted?

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  16. 16. DuFarle 10:33 am 05/9/2013

    #3 Bad things will happen. In historical record the times there was cooling e.g.6th century and 14th century can be viewed as bad things but they were most certainly part of social, political and economic human evolution. So “bad” is only if one wants to remain the same (in power or control) or go back to what was.

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  17. 17. markhoofnagle 10:39 am 05/9/2013

    @Doubtful news, one suggestion. No guide to skepticism is complete without a big glaring warning about conspiracy theories. Once you hear someone alleging a conspiracy all your alarm bells should go off, flags raised, and you should subject the subsequent claims to the highest degree of scrutiny. I’m not talking about criminal conspiracy either, which is rather ordinary and common, but the type of non-parsimonious conspiracy theory that suggests hundreds or even tens of thousands of people are acting in concert to hide the truth (as global warming hoaxers would suggest).

    Such conspiracy theories aren’t used by deniers to explain the data, they’re used to explain the absence of or conflicts with existing data.

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  18. 18. RSchmidt 11:37 am 05/9/2013

    Don’t think this is a big question. A skeptic is unsure and open to the evidence. A denier denies the evidence and the conclusions drawn from it. Skeptics are scientists, deniers are sociopaths.

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  19. 19. Agesilaus 11:53 am 05/9/2013

    No conspiracy theory is needed to explain Warmism. The proponents make a fine living off of scaremongering. Gore has accumulated more than $200,000,000. The scientists get grants.

    I’d like to point out that not one of the defenders of Warmism in this thread have used a data based defense. Whereas skeptics are almost always willing to base their argument on real data and usually leave links and references to that data.

    And not one of the Warmists here has addressed the fact that CO2 continues to climb but temperature has not for 15 t0 20 years. Indeed then period of static temperatures is just as long as the sharp increase that ignited this issue in the first place. There is not cause and effect link between CO2 and temperature.

    And here is a list of a 1000 peer reviewed papers by scientists who do not support Warmism:

    And even the IPCC admits that solar forcing is important:

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  20. 20. rkipling 12:23 pm 05/9/2013

    Since you brought up definitions, I did a quick search for “denier” and “denialist”. The vast majority of the hits actually did associate those terms with denying the Holocaust, HIV causes aids, etc. So, it doesn’t seem to have a value neutral meaning in the common usage. Maybe that wasn’t what you were trying to argue?

    If we define “denier”/“denialist” as someone holding a position on blind faith, then they certainly wouldn’t make very good scientists. Anyone claiming a priori knowledge of the truth on any side of a scientific issue can’t really be a scientist.

    I’m absolutely not defending deniers as defined above. I have no use for them. I have seen comments from those with a religious belief in CAGW who appear to me equally intractable in their beliefs. I see no value to the arguments of either group. But, members of the last group don’t seem to take as much heat in the main body of environment related blogs.

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  21. 21. M Tucker 1:09 pm 05/9/2013

    With regard to your three points I ONLY pay attention to respected climate scientists who are actually doing research in the field and whose work is peer reviewed. So Dyson fails that test and Lomborg is so far removed from being a scientist that he isn’t even remotely relevant. Then I pay attention to what the major national and international science organizations have to say and I cannot find any skepticism. There will always be outliers and Dyson is one of them…the man actually talks about “super-trees” that will save us.

    Climate science is a broad field but that would include paleontologists who study past periods when Earth went through large climate fluctuations and paleoclimatologists who are actively doing research. For me, because I am greatly influenced by geology, reconstructions of the climate during the PETM, mid-Miocene and mid-Pliocene have more influence than computer models. Further back than the PETM doesn’t have much importance for what we can expect because the tectonic plates are further away from current positions. The climate has always changed, always due to some forcing, humans are doing the forcing now.

    Next, we already have seen remarkable changes and impacts from the climate change that has already happened and continues to happen. We already know warming is not the same everywhere. We already know that to reduce CO2 concentrations we will need to nearly end all emissions, otherwise you simply slow the increase, you will not get a decrease. If we don’t start now we risk very difficult problems like prolonged droughts and heat waves and it will be much more difficult and expensive to make the necessary transition later. Agriculture in Southern California and in the Central Valley is threatened. The Colorado River is and has been threatened and impacted. We risk very big problems in the next 20 to 50 years and severe problems in the next 90 to 100 years.

    I understand why some politicians say the stupid conspiracy theory things they do. They want to keep those campaign funds flowing from fossil fuel supported PACs. I understand why those who oppose taking any action to eventually end emissions don’t want to be labeled deniers. They want to be called skeptics. Beyond that I don’t give them much thought and I only vote for those who will protect the environment and will work to reduce GHG emissions.

    I always keep TR in mind. He worked to protect the environment and he spent a lot of time writing about the danger of corporate influence in government.

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  22. 22. SilverTusk 1:42 pm 05/9/2013


    “a lot of ideologically aligned people regurgitate the same inaccurate and fabricated talking points as evidenced by some of the comments already added to this article.”

    For that claim to be true, more than one of the comments preceding your post (#10, 1:58 am 05/9/2013) must fall into that category.

    Are you willing to identify those comments? Post 1, 2, 3, 4, 5, 6, 7, 8, or 9 are where they must be found. Can you quote them and explain why you believe they are “inaccurate and fabricated talking points”?

    Is it post #6 by MojoMojo (11:42 pm 05/8/2013)?
    “#2 Unprecedented?
    What an absurd question.
    Only a fool would answer that todays warming is
    That’s pretty hard core; do you believe it is one of those “inaccurate and fabricated talking points”?

    You made the claim; can you warrant it?

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  23. 23. markhoofnagle 1:42 pm 05/9/2013

    Since you brought up definitions, I did a quick search for “denier” and “denialist”. The vast majority of the hits actually did associate those terms with denying the Holocaust, HIV causes aids, etc. So, it doesn’t seem to have a value neutral meaning in the common usage. Maybe that wasn’t what you were trying to argue?

    Ultimately, it’s hard to be value-neutral when you’re trying to describe unreasonable people who deny reality. The question is how much baggage does any given word carry. Denier probably carries more than denialist, but in the end it’s besides the point. No matter what, no pseudoscientist will never be happy about being called a pseudoscientist, no matter how you describe it, because the behavior isn’t value neutral. People will tend not to like bullshit and those that spread it. The labels will become insults even if appropriately applied.

    The reason pseudoscientists make these types of arguments is that they crave the validity that scientific legitimacy confers. They don’t hate science, they know full well that scientific fact is the ultimate authority in the modern world, and all their arguments are ultimately a false appeal to this authority. When you point out they’re doing it wrong they’ll always cry foul, say you’re name calling, whatever. Just ignore it, or you’ll get hopelessly off-topic (which is their goal).

    This is their classic “ad hominem” defense, which is actually a misunderstanding of what an ad hominem is. An ad hominem argument would be, “you’re wrong because you’re a dishonest, lying idiot”. A perfectly valid, non-adhom argument is, “you’re wrong because you don’t understand the facts, you misrepresented the science, you fabricated your data, and are therefore a dishonest lying idiot.” The denialist only pays attention to the dishonest, lying, idiot part.

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  24. 24. CarefulReview 2:13 pm 05/9/2013

    @20 M Tucker

    “…We already know that to reduce CO2 concentrations we will need to nearly end all emissions, otherwise you simply slow the increase, you will not get a decrease …”

    What do you mean by that? Do you advocate shutting down fossil fuel powered electrical generating facilities in China, the U.S., Europe, and India immediately? Do you advocate banning the use of internal combustion engines throughout the world immediately?

    Alternatively, do you suggest replacing fossil fuel powered electrical generating facilities in China, the U.S., Europe, and India with nuclear capacity immediately? That, of course, is just another way of putting off the “fix” for several years while the new generating facilities are built.

    It is easy to post from your electrically powered computer over the electrically powered internet onto the electrically powered Sci Am web site “… we will need to nearly end all emissions, otherwise you simply slow the increase, you will not get a decrease …”, but what do you propose actually be done to achieve your goal of “nearly end all emissions”?

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  25. 25. CarefulReview 2:16 pm 05/9/2013

    @22 markhoofnagle

    “An ad hominem argument would be, “you’re wrong because you’re a dishonest, lying idiot”.”

    Yup! We’ve certainly seen that on this blog on this topic!

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  26. 26. billfalls 3:28 pm 05/9/2013

    As a mathematician long ago I would have considered it important to define “deniers” and “skeptics” precisely. But I soon switched course to linguistics, and now find the author’s quest for precision Quixotic. People use words for their own ends, and words in modern politics are often swords.

    People like me who are concerned about climate change and think it’s our responsibility to our grandchildren to do something about it are likely to use “deniers” to describe folks who, like one commenter above, are content to “wait and see” how it all turns out without changing course.

    Those on the other side of the debate are likely to claim the more respectable label “skeptics.”

    Neither use is wrong; that’s just how language works.

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  27. 27. donfit 3:34 pm 05/9/2013

    So, based on his “Rational Optimist”, is Matt Ridley a skeptic?

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  28. 28. rkipling 3:35 pm 05/9/2013

    It’s not a matter of being content to wait and see. It’s that I don’t think it is realistic to believe anything will change until there is absolutely no choice. If you can talk the deciders into making the change, it’s perfectly fine with me. I don’t care how much it costs to keep the ac/heat and lights on. Many do care and won’t vote for it until salt water is coming in their front door.

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  29. 29. Chryses 3:38 pm 05/9/2013

    M Tucker (20),

    When I checked Wikipedia for Climate Change External Forcing Mechanisms ( ), I found that Human influences was only one of six listed (Orbital variations, Solar output, Magnetic field strength, Volcanism, Plate tectonics, Human influences).

    My reading of your post “The climate has always changed, always due to some forcing, humans are doing the forcing now.” is that in your opinion the other five are insignificant contributors to this current warming process. Is that true?

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  30. 30. string_beery 3:51 pm 05/9/2013

    denier – no evidence will ever change their opinions
    skeptic – honestly uncertain, but open to evidence

    warming – sure, tough even to deny

    unprecedented warming – i believe this refers to the (very short) timescale over which the recent warming is occuring, and is not intended to include historic (ancient) periods of warming that occured over, typically, many thousands of years

    bad things – likely, but there may be positive outcomes also – living in a cold region, it can be tough to be concerned that the climate may get warmer

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  31. 31. MiltonAnderson 4:06 pm 05/9/2013

    “Accept” or “reject” would be the neutral terms to use regarding whether someone considers climate change to be true or false.

    “Denial” is a term used to describe the rejection of climate change by someone who knows that it is true. It is not a neutral term, since it implies a deliberate falsehood.

    A skeptic would be someone who considers the matter still open and not yet proved one way or the other.

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  32. 32. curiouswavefunction 4:07 pm 05/9/2013

    #31: “unprecedented warming – i believe this refers to the (very short) timescale over which the recent warming is occuring, and is not intended to include historic (ancient) periods of warming that occured over, typically, many thousands of years” – correct.

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  33. 33. rkipling 4:33 pm 05/9/2013


    This may not be exactly on point, but I’m curious what you think is likely to happen and what in your best case could actually be done to reverse or slow AGW? You have obviously thought about it a lot.

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  34. 34. M Tucker 4:41 pm 05/9/2013

    Chryses @29, If you are truly interested in finding out what is causing our current warming you can get that information from many different science based sources. You know it, I know it, everyone knows it. I don’t expect you to agree or to suddenly arrive at the correct answer to your question. I expect you to continue to deny the evidence.

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  35. 35. Chryses 5:58 pm 05/9/2013

    M Tucker (34),

    What are you talking about?

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  36. 36. RFBrownPE 7:35 pm 05/9/2013

    My biggest concern are the ‘certain-ists’ [yes, my word] that is, those who choose to be ‘certain’ they know . . . anything about this topic, at either extreme or anywhere in between. Why? Because we have so little data relative to the magnitude in time and space about the issue, we have such weak methods of considering that data, we have extraordinary conflicts of interest among so-called ‘professionals’ writing on the topic, and so on.
    Mostly because most of the most horrible things ever perpetrated on people by people have been done by those who were absolutely certain they knew what they were doing [Hitler, Stalin, Caligula, Charles Manson, etc].
    Blessed are the confused [poor in spirit, not certain, searching for answers], for theirs is the kingdom of heaven.
    A corollary is that the Law of Unintended Consequences has not been repealed. However, for the reasons mentioned above there is strong motivation to move to a grand conclusion and sell it to humanity, ie governments, in order to fund favored policies, support puffed up egos, or just do what someone thinks is ‘the right thing to do’ for all the rest of us, whether we agree, want it, need it, are willing to pay for it, etc. without regard for what monumental problems may be caused by the ‘cure’ they favor.
    Lets keep gathering data, do our best, avoid the abuses and we will stumble through.

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  37. 37. syzygy 8:11 pm 05/9/2013


    You are a lone voice in this wilderness. Just wait to see how you are welcomed.

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  38. 38. Benfun 12:32 am 05/10/2013

    4,7,8,19 all fit the description of regurgitated talking points. Hence they qualify as deniers. There’s no actual thought process or dialog occurring, they simply state as fact things which are untrue or out of context think that the way science works is that you can spout nonsense with conviction and it will make other’s believe you are right. Since that’s how they were convinced.

    Taking umbrage with a contextually defined term like “unprecedented” and applying a common use interpretation is naive and irrelevantly argumentative but not denial by my definition.

    Citing current edge case disagreements about model sensitivity is more like skepticism as long as the speaker doesn’t seem to be representing that the edge case uncertainty undermines the whole edifice.

    eg. Einstein spent the last 40 years of his life throwing out challenges to quantum mechanics, constantly trying to find an alternative theory that would not depend on some of the premises he didn’t like. He was a true skeptic on this point, and was wrong. He was also self aware enough to see his actions and role in that light.

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  39. 39. syzygy 1:10 am 05/10/2013


    I’m building a factory that generates renewable energy as a byproduct. I put my own money at risk. My factory will reduce fossil fuel consumption with virtually no waste. So tell me, how are you contributing to a solution?

    Is sitting at a computer slamming out invective accomplishing anything? The AGW problem has been identified. That work is done. I question what the severity of the problem will be. The question you should ask yourself is what contribution can you offer? Attacking people who are part of the solution isn’t going to reduce CO2 concentration a single ppmv.

    Take some time to come up with even one solution. Try to figure out what it will cost, how to build it and make it work, and if it can make enough money to sustain itself. If you can’t do the engineering or math yourself, find someone you trust who can to help you examine the issues.

    Call people “deniers” if you like. I have no interest in name-calling. Taking time to discuss this issue doesn’t make me a single extra dime.

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  40. 40. Chryses 6:11 am 05/10/2013

    M Tucker (34),

    “… I don’t expect you to agree or to suddenly arrive at the correct answer to your question …”

    With whom or what do you expect me to agree to arrive at the correct answer to my question? You posted “humans are doing the forcing now”, which to me appears to say that the other 5 listed forcings are incidental components to the current warming. Please let me know if I’m mistaken; I’m interested in learning what others might think about an issue that you and I agree is important, and why they think that way.

    “… I expect you to continue to deny the evidence.”

    I think I was reasonably explicit at post #15 about how I arrived at the position I take on the AGW topic, and yet you claim I deny the evidence. Would you plese identify the evidence you think I have denied? I think that is a reasonable request.

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  41. 41. SilverTusk 7:02 am 05/10/2013


    “4,7,8,19 all fit the description of regurgitated talking points. Hence they qualify as deniers. There’s no actual thought process or dialog occurring, they simply state as fact things which are untrue or out of context think that the way science works is that you can spout nonsense with conviction and it will make other’s believe you are right. Since that’s how they were convinced.”

    Recall that for your claim “inaccurate and fabricated talking points as evidenced by some of the comments already added to this article” to be substantiated, only the comments preceding your post #10, (1:58 am 05/9/2013) where you made the claim are relevant, so #19 is ineligible for the purpose of warranting it.

    So what was thoughtless, untrue or inaccurate about post #8 (1:06 am 05/9/2013), to arbitrarily select one of the posts you’ve identified as a regurgitated talking point? (sorry rkipling, but I had to select one from Benfun’s list)

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  42. 42. markhoofnagle 9:26 am 05/10/2013

    @36. RFBrownPE

    There are no certainists, this is a straw man. The science is constantly couched with uncertainties, projections with error bars, and tempered predictions. What is then done with this science (alarmism, predictions of doom, whatever) is not in the control of science.

    There is certainly enough data, however, for us to be concerned. The physics of it are plain enough, CO2 is a greenhouse gas. We experiment with our atmosphere at our own peril, and the data so far suggest our contributions have a clear effect.

    We don’t know what the end result of this experiment will be, but we are living in the test tube, and are already seeing it heat up. It’s enough evidence for me to say, we need to slow our effects on climate change, because while might be benefits as well as harms, rapid climate change will be devastating.

    The response to alarmism is to call them on it, not to deny the science. There are denialists who deny the most basic physics to avoid accepting CO2 is a greenhouse gas (the sky dragons). There are denialists who allege outrageous conspiracy theories and viciously attack the scientists gathering data themselves, calling them liars, traitors, monsters, and worse.

    By all means, fight alarmism, fight certainty, but that has nothing to do with whether or not CO2 is a greenhouse gas, that the climate is warming, and humans are contributing to it.

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  43. 43. rkipling 12:36 pm 05/10/2013


    That’s fine no apology needed. I’m a bit curious myself.

    I paid no attention to the CO2 issue until a few years ago. I thought to myself, “Okay, I’ll do the math.” I didn’t approach it with a hope to find a particular result. The first thing I did was to try to satisfy myself that human activity accounts for the increase. Enough independent data is available so that I came fairly quickly to the understanding that yup it looks like we are at least most of the cause.

    Then I looked at estimates of CO2 levels over geologic time vs. temperature (see post 8). I’m not unaccustomed to interpreting graphs and tables, and my interpretation of the data is that other variables in addition to CO2 must be in play because there were times when CO2 was substantially higher than today yet the temperature was cooler. That isn’t denying anything. I just say I don’t know.

    (I can’t know the educational background of other commenters, but I have suspicions many of the most vocal advocates of CAGW have no technical education. Econ 101 was the flunkout course for business majors. Engineers all made A’s without cracking a book. I can still remember snickering at the gasps of horror when the professor drew a graph on the board.)

    As far as predicting the unknowable future, it seems to me more than harsh to berate me for a lack of omniscience. I have only enough understanding of the planets history and how the biosphere works to say that I have insufficient knowledge to predict the future.

    All that aside, let’s stipulate for a moment that we are looking down the barrel of CAGW for an absolute fact. Now what do we do? The people screaming the loudest don’t seem to have an actual plan. I can only assume they hope someone else will fix it for them if they scream loudly enough. The screaming just exhales more carbon dioxide.

    When I express doubt that anything meaningful will be done to stabilize CO2 levels, it’s because I have a glimmer of what that will require in time and money. For billions of people effective fixes to the problem in the next 100 years have the potential to be just as catastrophic.

    I invite people to take concrete steps to be part of a solution and spend less time speculating about the relative intelligence of those they perceive as opponents. I don’t care if they respond to this comment or not.

    We can hope that as yet undiscovered technology will change the calculus.

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  44. 44. Benfun 1:06 pm 05/10/2013

    ST – Post 8 boils down to “the climate is always changing and how can we know the future” Both classic TP. A simple go to reference is which keeps a record of all the standard denier talking points and provides detailed, well documented rebuttal.

    Syz – Great! Please succeed.


    Your originating post posed the question of who is a skeptic or a denier. These aren’t really useful terms.

    You are either up to date on cosmology or you are not. Maybe you are well versed enough to know the interesting edge case issues like the constraining characteristics of dark matter. Being a dark matter denier isn’t a rational option. You can have an alternate theory to explain the gravitational effects observed in galaxies, i.e. there is no “denier” role. And if you chose an alternative theory you couch your support for it knowing all the recent evidence that makes your case challenging (eg. measured lensing effects of dark matter).

    Being an AGW denier means you are not up to date on climate science, you don’t have an alternative explanation for the hundreds of measured phenomena associated with a warming climate driven primarily by human actions and you do resist accepting AGW by repeating talking points developed by a well funded, well orchestrated campaign of tobacco, oil and gas PR firms. A denier’s only role is to retard any dialog or consideration of action.

    If a 10 mile asteroid was detected on a 30 year collision course with earth. First we’d debate the accuracy of the physics and measurements, once that was resolved we’d develop best-worst case scenarios, we’d plan to mitigate it and we’d plan for the possible failure to mitigate. We wouldn’t just say it’s up to private companies and individuals, government is useless for this. We wouldn’t tolerate a corporate funded campaign to discredit the scientists and the science and we’d take the threat seriously. The key difference here is that the asteroid doesn’t invalidate any current ideology or belief system. AGW does.

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  45. 45. rkipling 2:12 pm 05/10/2013


    Great! I just said let’s stipulate you are correct. Why continue to argue the point? Now give us a plan with an estimate of how much it will cost.

    Your asteroid problem example has a much more straight forward set of solutions and would be orders of magnitude less costly.

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  46. 46. rkipling 4:33 pm 05/10/2013

    crickets chirping

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  47. 47. Benfun 5:22 pm 05/10/2013

    So many solutions available.

    1. Stop subsidies to carbon emitting energy.
    2. Spend half that savings to advance R&D in clean tech, use the other half to cut buy down the deficit
    2. Implement a carbon tax
    3. Set the tax up so that it directly pays consumers.

    A $115-per-ton carbon fee would add a dollar to the per-gallon price of gasoline but would raise enough revenues to pay every adult American as much as $3,000 per year.

    Policy: Stop making it worse. Invest in new R&D to make it better. Make pollution directly cost the polluter and empower consumers to make a choice with their money and offset their pain if they choose to continue to pollute.

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  48. 48. rkipling 5:38 pm 05/10/2013

    Well okay, that’s a start. Write letters to politicians. Form a political action committee. But CO2 will still increase at about the same rate.

    Run the numbers. It’s a much larger problem than that. I’m not hostile to reducing dependence on fossil fuels. Everyone just needs to understand the fundamental and massive changes to the economy required to do it. I encourage you to continue thinking and advocating for specific changes.

    Try to quantify what effect the specific proposals will likely have. Don’t do it for me. Do it for yourself and your own understanding.

    Arguing with commenters here will not help much beyond its entertainment value.

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  49. 49. rkipling 5:42 pm 05/10/2013


    I’m not suggesting you go away from comments. But take some action. Who knows? Your efforts might make a significant difference.

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  50. 50. Benfun 6:06 pm 05/10/2013

    Appreciate the encouragement. What you are suggesting is being done and being done with a concerted effort on building the case and educating the corporate and policy decision makers.

    A glimpse of that here for instance.

    There’s many good groups working diligently on this.

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  51. 51. CarefulReview 6:16 pm 05/10/2013


    You claim that the observation “the climate is always changing” identifies rkipling as a denialist.

    But that is true, isn’t it? The important thing is to determine why, correct? So what was thoughtless, untrue or inaccurate about post #8 (1:06 am 05/9/2013)? You do remember your post #10, don’t you, “a lot of ideologically aligned people regurgitate the same inaccurate and fabricated talking points as evidenced by some of the comments already added to this article.”?

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  52. 52. CarefulReview 6:27 pm 05/10/2013


    From your link, in re those $1.9 trillion a year subsidies: paragraph 3, sentence 3.

    “Contrary to popular opinion, the developed world does very little of this kind of thing. Direct fossil fuel subsidies (“pre-tax” subsidies) are overwhelmingly concentrated in the developing world”

    So the question remains, what will you DO about fossil fuel consumption?

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  53. 53. SilverTusk 6:33 pm 05/10/2013


    As you posted in an earlier thread, “There is nothing at all that you can present to denialists that will change their opinions.”

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  54. 54. mtobis 1:13 am 05/11/2013

    Some common misconceptions in this thread that are causing familiar threads of confusion. I’d like to address two of them.

    1) Current temperatures are unprecedented in human history. This is absolutely false and is not part of the scientific consensus. Current temperatures, while very high for the recent two million year period, are quite comparable to those of 7000 years ago and a couple of previous occasions. Nor is the rate of increase, while very rapid, unprecedented; comparable warming rates occurred at the deglaciation around 12000 years ago. What is unprecedented, observationally, is the rate of increase of CO2. It is **expected** that the temperature and the rate of increase of temperature will soon enter unprecedented territory. It would be surprising if we continue business as usual for a few decades. It may be locked in already. A vast preponderance of evidence agrees with this prognosis. But we are still on the edge; it has not happened yet.

    2) The debate often centers around what fraction of the observed warming is anthropogenic. The presumption is that the fraction lies between 0 and 100%, and that surely it is not all the way to an extreme. This sounds reasonable but it is wrong. In fact the preindustrial trend up to about 1700 AD was a gradual cooling. The anthropogenic signal is superimposed on that. So the most likely outcome is that the anthropogenic component is slightly more that 100% of the observed trend, while the natural component is toward cooling.

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  55. 55. CurrentOutlook 5:44 am 05/11/2013


    “In fact the preindustrial trend up to about 1700 AD was a gradual cooling.”

    Except for the preindustrial periods when the climate was warming

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  56. 56. whburgess 9:59 pm 05/11/2013

    It seems a lot of factors are being left out of the discussion as to why AGW deniers exist.

    1. They are not first hand experts in the science and data needed to evaluate the issue.

    But neither are the vast majority of people who accept AGW.

    2. They haven’t personally talked with and are not acquainted with a significant number of first hand experts/scientists on the issue. So they have no first hand way of knowing whether there really is a consensus among experts and exactly as to what that consensus consists of regarding the 3 layers of facts laid out in this blog post.

    Then again, neither are the vast majority of people who accept AGW.

    3. All ‘deniers’ know is that the ‘mainstream media’ blames every change in the weather on AGW while claiming that there is scientific consensus on the subject and that the ‘science is settled’. Calling deniers ‘crazy’ for not believing that journalists can be trusted is nothing more then political posturing which in itself undermines the message of crises; surely if the crises is as bad as alarmists claim, why would intelligent pundits set their cause back by making it a political issue and occasion for partisan vitriol and ridicule, going on extensively about how Republicans are ‘anti-science’, etc? Why is Al Gore, a presidential nominee for one political party, the face of the AGW alarmists? Isn’t that quite the genius PR move for folks trying to get a political consensus on the idea that the world as we know it could end? Those goofy lefty partisans on the Nobel prize committee did their part as well in making it a political issue.

    There will not be clarity on this subject until it is admitted that the denialism is not about denying science or scientists but about the perceived political motivations and bias of the main stream media; a perception which is only reinforced by complete lack of seriousness involved in the continued use of the issue by folks on the left to score political points.

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  57. 57. Chryses 6:39 am 05/12/2013

    The politicization of this subject is one of the larger, if not the largest, obstacle in the way of selecting useful responses.

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  58. 58. Chryses 12:47 pm 05/12/2013

    The posts from mtobis (#54) and CurrentOutlook (#55) are excellent examples of why I’m unable to shake off my doubts about AGW. I think that at least some portion of the current warming is due to human activities, but how much? mtobis presents a persuasive argument that most if not all of it is AGW. Immediately following mtobis’ post is CurrentOutlook’s that references studies backed by data showing that there are at least two exceptions to mtobis’ line of reasoning.

    If it is true that these exceptions are real, then why should I assume that the current warming is anything other than just another exception?

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  59. 59. Ian St. John 11:55 am 05/13/2013

    The distinction is easy. Science gathers evidence until it can state a theory with confidence that almost all who know the subject will be convinced by the evidence (and what else is ‘proof’).

    That said, science is always ready to take a new position if evidence is presented that shows the theory wrong or incomplete.

    This is the basis of skepticism. To keep an open mind for conflicting evidence.

    So ‘skeptics’ are those who have a competing theory or evidence that overturns a theory.

    Denialists, on the other hand, don’t need any evidence. They ‘believe’ based on their own ignorance, politics, or motives for rejection such as owning stock in fossil fuel companies.

    Belief fuels denialists. Science fuels skeptics.

    NOW comes the fuzzy logic. What if someone is convinced by the ‘evidence’ but the evidence is bogus, incomplete, misstated, etc. The fossil fuel industries ‘war on science’ is fuel for some to say that they are skeptics when they point to this junk science.

    Are you a skeptic when you are ‘convinced’ by the blogs on WhatsUpWithThat? A denialist? Or just a ‘useful idiot’?

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  60. 60. Ian St. John 11:59 am 05/13/2013

    “I am still undecided on someone like Bjorn Lomborg who seems to have started out as a firm denier but gradually gravitated toward the skeptic camp.”

    I suspect that he is of the ‘opportunist’ class. He goes with whatever he thinks will gain him employment or fame. You can tell by the ‘flip flop’. He doesn’t care what the facts are, just whether he can personally profit from it.

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  61. 61. Dr. Strangelove 11:48 pm 05/13/2013


    It’s not only deniers and skeptics. There are two other types: believers and fanatics. I define them as:

    Deniers – unreasonable and unscientific; more interested in propaganda than science.

    Skeptics – reasonable and scientific; genuinely interested in science and knowing the truth; unconvinced of AGW and/or GW disaster.

    Believers – same as skeptics but pro-AGW

    Fanatics – same as deniers but pro-AGW

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  62. 62. lucia 11:24 am 05/19/2013

    Ashutosh Jogalekar,
    Terminology has sprung up at climate blogs precisely because it is difficult to communicate a range of differences in beliefs and attitudes and because advocates of various stripes like to use words as labels– often using them differently. Beyond that, the belief system is often treated as a scalar variable (i.e. denier to alarmist range), but it’s more of a tensor.

    So, for example, other labels include “Sky Dragon”, which corresponds to people who absolutely deny radiative physics, Lukewarmers who mostly fall into debating “How much will it exactly warm? Will it warm equally everywhere?”. These labels operate on the “What does radiative physics say? How responsive is the earth’s temperature to CO2? axis. So, that’s one of the dimensions.

    Your post does touch on another dimension which is: What’s would the impact of 1C warming (or however much one suggest)? Some people do put forward arguments that it would be good, others that it would be bad. Some, that the benefit is not monotonic. So for example 0.5C in 1 century might be good, but agree that both -20C and +20C would be bad. So this is a 2nd dimension. ( In case you are wondering, yes, there are some people who at least seem to argue that even +10C would be ok because it’s happened before during some period. cenozoic? I can never remember the period bandied around.) Occasionally these arguments touch on the rate of warming. So for example +2C might be ok if it happened at 0.2C/century, but might not be so great if it happens at 2C/century.

    There is also a dimension that relates to the level of trust one can put in information presented to the public. That is: Does one believe science communication is totally unspun? A little spun? Heavily spun? Affected by a degree of noble cause corruption? Much of the “climategate” type discussion, discussions of gatekeeping motivated reasoning on the part of a fraction of scientists and so on fall here . So this is at least a 3rd dimension.

    Of course we get a lot of interaction with these. So, for example, those who deny radiative physics also tend to believe in lots of gatekeeping at journals and heavily emphasize climategate. That said: quite a few people who believe radiative physics works (just as it does in blast furnaces), that CO2 has risen, it’s been put there as a result of burning fossil fuels etc, might still disapprove of activities at CRU revealed in the “climategate emails” and believe there is some gatekeeping at journals.

    If one tries to collapse these three dimensions into a 1 dimensional scalar, they will have a hard time where on the “denier”- “skeptic”- “CAGW promoter” scale a person falls on. While I’m sure one can take a dot product and create a “length” metric, I don’t think it means much!

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