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Why we have a scientific consensus on climate change

Posted on 23 March 2011 by Thomas Stemler

A short piece for the general audience of RTR radio, Perth, Australia.
(listen to the original audio podcast)

Recently a research group analysed the current literature on climate science. Their aim was to find out how many of the active researchers in the field agree on man-made climate change. The answer is, 97 out of 100 agree that the climate is changing and that we are causing it.

From my own experience, such a high proportion is quite unusual. As scientists we are trained to be professional sceptics, who doubt everything and who moreover love a good debate. Therefore putting 3 scientists together in a room sometimes results in an argument with 5 different opinions.

While this is the more enjoyable side of science, the more important one is that being sceptic lets us identify errors and improve our understanding of nature.

Climate science is a very special science. It includes experts who study the dynamics and data from the atmosphere, the oceans, glaciers, and so on. Some of us specialise in building models, others use them to make predictions.

So how come that 97 % of the experts agree that the current warming is not natural but a consequence of burning fossil fuels?

First, it is because all our data show that the global mean temperature is increasing, that the glaciers and the arctic ice are melting and therefore sea levels are rising.

Second, we know that burning fossil fuel releases CO2 into the atmosphere. The properties of CO2 were first studied by John Tyndall in the late 1850s. Tyndall was an experimental physicist interested in how different gases absorb heat. John Tyndall's observations were remarkable. His pioneering work eventually inspired physicists to develop the theory of quantum mechanics, but his results about CO2 also led Arrhenius in 1896 to the conclusion that burning fossil fuel will result in global warming. So climate science is a very old science indeed; we have known about CO2 for more than 150 years.

Nowadays we know how much CO2 we put into the atmosphere by using it as our global garbage bin for fossil fuel. All our climate observations show a global increase in temperature. This increase is consistent with the well established properties of CO2.

Taking this into account it is no longer surprising that 97% of the professional sceptics working in the area of climate science agree that we are currently witnessing man-made climate change. The only question remaining is, what do we do? Ignore the facts or generate energy from other sources?

Dr Thomas Stemler is a physicist who is currently an Assistant Professor of Mathematics at the University of Western Australia. He is an expert in forecasting of complex nonlinear dynamical systems.

This podcast is now available on iTunes (or search for "Climate Podcasts from the University of Western Australia" in the iTunes store). Alternatively, you can subscribe to the stream via feedburner.

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Comments 1 to 50 out of 107:

  1. Here is a challenge to the consensus argument. Plenty of graphs and data that show things may not be as certain as the 97% claim.

    Part One.

    Part Two.
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    Moderator Response:

    [DB] To get a proper perspective, you should read this.

  2. I'd like to know the question that was asked of these scientists. I'm a scientist (not involved in climate), and if I'm asked if I believe humans influence the climate, my answer is yes. If I'm asked if the net result is warming or cooling, my answer is "I don't know". If I'm asked if I believe that human activity will cause catastrophic (or even significant)warming in the next 100 years, my answer is that I've seen no real evidence to support this hypothesis. Computer models, yet to be substantiated by real data, are nothing more than interesting.

    My point is that scientists are trained to be very exacting. The question has to be very specific. So show me the actual questions that were asked. I know of many scientists that are yet to be convinced that anthropogenic warming is any more than unsubstantiated theory.
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  3. Norman,

    What is your challenge? The documents you provide are primarily just a litany of the same old, tired and false skeptic arguments, all of which are easily debunked in various parts of this site. There's little point to even looking at them.

    But more importantly, I couldn't find a single reference to refute the 97% consensus argument. What exactly is your point? That you are right, and your documents prove it, therefore 97% of climate scientists couldn't possibly agree with you?

    Personally, I think your post amounts to nothing more than off-topic trolling and should be deleted.
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  4. D'aleo AND icecap. Really. Now, any point on that "challenge" not already debunked here? Why do you go such sources when you can easily see the content is rubbish? A real challenge to consensus science would be in the form of peer-reviewed publication.
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  5. rhymes,
    I've seen no real evidence to support this hypothesis...

    Then you haven't looked. Shame on you. This site is crawling with evidence (unless you simply refuse to see it).
    Computer models, yet to be substantiated by real data, are nothing more than interesting.

    False. 100% false. First, the computer models are more than "interesting" and have real value. But beyond this, evidence from a very wide variety of observations supports both warming and an anthropogenic cause.

    Claiming that you are right because you yourself are ignorant of the facts is hardly an argument.
    I know of many scientists that are yet to be convinced that anthropogenic warming is any more than unsubstantiated theory.

    Yes, but climate scientists? Or just people who are arrogant enough to think they're smart enough to be experts in any field of expertise, when they clearly are not?

    The world is crawling with retired physicists and engineers who will dispute global warming. I don't know why, but it's endemic. Every grumpy old man with a college degree and a career in the sciences (but not climate science) seems to want to angrily deny global warming.

    The fact that they do is hardly a weighty argument.

    Let me see, who should I trust? Thousands of climate scientists, actively working in the field, or a bunch of retired physicists and engineers who think they know better than everyone else, have little care for the future, and yet have repeatedly, over the course of the past decade, failed to substantively counter the data and logic which demonstrate the truth behind global warming?
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  6. I believe the study Dr. Stemler is citing is Expert Credibility in Climate Change by William R. L. Anderegg et al. published in the Proceedings of the National Academy of Science found here:

    http://www.pnas.org/content/early/2010/06/22/1003187107.abstract

    The scientists discussed in the study all self-identified in one way or other as accepting or rejecting the scientific consensus, for instance by signing petitions and so on.
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    Moderator Response: [DB] Hot-linked URL.
  7. Sphaerica - I've been looking at climate change literature for the past 10 years. Where possible I get as close to original data as possible. I follow sea level, CO2 etc trends around the world. I don't take anything at face value, and I'm prepared to ask the hard questions. I've read much of the literature on this site.

    So, I don't just take the claims of this article at face value. I want to know the questions asked, the answers given, and who these scientists are. I've investigated this sort of detail before in surveys, with very disturbing findings.

    You mentioned retired engineers and physicists. Perhaps they are the ones who have time to go into detail, and make informed judgments, rather than follow the popular trend.

    My question remains - what were the exact questions asked of these scientists, and who were they?
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  8. Further to Sphaerica's post, I'm an engineer (not yet retired, and hopefully not grumpy!). A mechanical engineer at that, so I have a fair bit of eduction in and understanding of heat transfer.

    I've been reading a *lot* of scientific papers & articles on climate change over the past five years or so.

    One thing I've noticed (which most of us on this site have noticed) is that the "it's not happening" arguments are remarkable, in the sense that there is no substantial, scientifically verifiable evidence for them. None at all.

    Contrast that with the view that it is happening, where you have literally gigabytes (probably terabytes, actually) of supporting data, and thousands of pages of scientific analysis that either directly confirms the human-caused global warming hypothesis, or does not contradict it in any way.

    That's not to say that we know everything about global warming - it's a rich field of research, with scientists learning something new every day. There are many areas of dispute as to exactly how the extra heat trapped by greenhouse gases affects the planetary climate, and the nature & extent of the various feedback mechanisms. But the fundamental question as to whether CO2-driven global warming exists has long since been answered in the affirmative.

    Unfortunately for us, the more scientists learn, the worse it looks. :-(

    One last point: I have to say, I'm continually puzzled how anyone with university-level education in heat transfer can deny the existence of the greenhouse effect. But then I remind myself that some of my fellow students really struggled through, barely passing subjects on the back of rote learning with little real comprehension. That might explain some of it, perhaps.
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  9. rhjames @ 7: have a read of the article linked by the moderator in post #1. It answers your questions as to what was asked & by whom.
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  10. I note in the link provided by Norman that D'Aleo or whomever else concocts a graph of winter temps in some region over 9 years and makes it a "trend."
    In another one they look at temp at the 100 to 300 mb level and label that as "mid troposphere." That's really kinda funny considering that the 100 mb level is around 53 000 ft. Some mid level that is.

    I spent about 30 seconds on the site to pick up these 2 screamers.

    Sorry Norman, I'm not a scientist but I know when someone is trying to fool me. The red flags at D'Aleo's are all over the place, so many of them that one can hardly see any data.
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  11. Norman - That's quite a Gish Gallup; a collection of half-truths, falsehoods, and misrepresentations. Here's a repeat of what I posted on a 'skeptic' site in this regard:

    1) Warming is said to be unprecedented and accelerating. It is neither.

    See It's not happening, Pre-1940 Warming Causes and Logic - We're warming pretty fast, driven by CO2, the changing levels of which are unprecedented. We're heading for a very high interglacial temperature the likes of which we haven't seen since the peak of the Holocene, if not higher. And warming is definitely accelerating.

    2) Global warming is not GLOBAL.

    Uh, what!? Every record shows global warming. See It's not happening. This is utter bull - warming is faster in the Northern hemisphere, but it's global and it's happening.

    3) Winters would grow increasingly warm.
    4) The entire Northern Hemisphere would experience less snow and snowcover

    Globally, yes. Locally, in some regions, the relatively warmer Arctic is pushing the jet stream south, and some regions are seeing more peak snowfall. But winters are shorter, spring arrives earlier, fall stays later, and crops and flowers bloom earlier. Definitely happening.

    5) Increasingly positive AO

    I'll let others speak to this - I hadn't heard that this was a consensus opinion.

    6) Global warming may lead to a permanent or semi-permanent El Nino

    Again, I don't believe this was a consensus opinion. If not, both this and #5 are strawman arguments. I will note that some circulatory patterns, such as the Indian Ocean Dipole (IOD), do appear to be settling into one state as a result of climate change.

    7) Atmosphere will warm faster than surface (because that is where the heat trapping gases are).

    This appears to be a variant of the "Hot spot" argument. See There's no tropospheric hot spot. Observations match models and physical predictions, although old data (poorly calibrated) may have indicated otherwise before corrections.

    8) Record highs and heat waves are increasing

    Record high temperatures versus record lows

    9) Sea levels are rising at an increasing rate

    See: Sea level rise is exaggerated, Sea level rise predictions are exaggerated. The ARGO floats versus older XBT data are still rather contentious, as calibration of the XBT's is, well, poor. There is ongoing work here, but so far, the data doesn't contradict predictions or theory.

    10) Droughts and floods will worsen in places like Australia

    So far, the data appears to support this. More is needed, and in the next 10-15 years I expect that the data will reach statistical significance. It may have already; I'll leave it to others in that regard.

    ---

    So, Norman, this link of yours is not supportable as criticism of AGW. You have obviously not used the 'Search' link on this site, or you would have seen multiple replies in that regard. Why did you post this link?
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  12. If rhjhames was following climate science literature closely at all, he'd already know about Anderegg et al., it made quite a splash last year. I'm a scientist (biologist) who follows climate matters and I read about it, and even downloaded and read it. If he wanted to get close to the original data he'd have done that too.

    So I question how closely he's actually following the literature, and I wonder what kind of scientist he is.
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  13. To say Tyndale's "pioneering work eventually inspired physicists to develop the theory of quantum mechanics" sounds like quite the overstatement. His name is not even mentioned in any of the short works I have read on the history of QM.

    Other than that, this podcast looks quite good.
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  14. KR at 15:33 PM,re "I will note that some circulatory patterns, such as the Indian Ocean Dipole (IOD), do appear to be settling into one state as a result of climate change."

    What causes you to arrive at that conclusion, particularly with regards to the IOD, but also generally for those other systems that apparently appear to be settling into one state?
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  15. This is a call for more rigour in "case making":

    1. The term "consensus science" is an oxymoron - at least if you do your science a la Popper. If you DON'T do your science a la Popper then by all means feel free to add whatever terms you wish to what you call "Science". "Real" Science ONLY deals with trying to know more by attempting to disprove what we think we already know. Holy huddles don't count. New advances in any discipline almost invariably come from outside the self congratulatory back slapping in-crowd.

    2. It may well be that Dr Stemler does a good job in his broadcast of addressing the issues raised. I hope to listen but time does not yet allow. BUT the short piece above does a very poor job of making a good case, which is a shame - all material on such an important matter that is intended to sway the less or un convinced should be carefully thought out. Otherwise you are just preaching to the choir, or taunting the lions (as I am probably doing here :-).)

    1. The paragraph above starting "First ..." is neutral with respect to the point being argued, and so essentially pointless.

    2. The paragraph starting "nowadays" is questioned by vanishingly few of any persuasion and is not germane to making the desired point.

    3. The paragraph starting "Second ..." is close to information free as the issue for a very large majority of all persuasions is not the well understood basic thermal behaviour of gases but the magnitude of the multiplying factors caused by feedbacks - "forcing" in the jargon of the day. There are other secondary factors which merit discussion, but if the pertinence of an argument to the above points is not made clear in a summary, then others than the choir may wonder if it's going to be worth listening to he podcast.

    Russell McMahon
    apptechnz@gmail.com
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  16. Normal # 1

    The main claim your link makes is that theres been no warming over the last 15 years. The data you provide is for 9 years, is selective and deceptive, and shows a slight warming trend anyway. Some of it also looks fraudulent to me but Ill give you the benefit of the doubt there, but appreciate Im very, very sharp. Since you seem determined to quote nonsense, I wont bother furthur.
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  17. rhjames at 5:18 reckons
    --------
    You mentioned retired engineers and physicists. Perhaps they are the ones who have time to go into detail, and make informed judgments, rather than follow the popular trend.
    --------
    The overall position of this demographic is not known.

    However the noisy ones commenting in climate skeptic blogs follow a pattern:
    1. Claims that "I am smart and climate scientists are stupid"
    2. Followed by some comment proving they are incompetent in their own technical field.
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  18. so :
    " 97 out of 100 agree that the climate is changing and that we are causing it."

    May I offer an explanation of this "quite unusual " proportion? that the question is so vague that it is difficult to say "no". What is "changing" ? climate ? well I do not know anybody who lived 30 years ago in tropical, temperate, or Arctic zones and who has changed the name of its climatic zone ! The north of France is always rather cool and rainy and Mediterranée is always a marvelous see. So "climate" in the original meaning hasn't changed for anybody - scientists may have thought that "average surface temperature " has changed - but that cannot be contested. It has changed, that is only intrumental measurements. And that we "are causing" it ? well may be - there must be some anthropic changes. Even big dams change climatic conditions (although not enough to change the overall qualification , as I said). Deforestation, change of land use, urbanization all change the local precipitations and temperature. And of course CO2 is contributing. So it is almost impossible to answer "no, we aren't changing anything".

    But the given explanations are somewhat strange :

    "From my own experience, such a high proportion is quite unusual. ...
    So how come that 97 % of the experts agree that the current warming is not natural but a consequence of burning fossil fuels?

    First, it is because all our data show that the global mean temperature is increasing, that the glaciers and the arctic ice are melting and therefore sea levels are rising."

    So the question is about the cause of the change, and the justification is "because it is observed"? I don't really understand the relevance of the explanation.

    "Second, we know that burning fossil fuel releases CO2 into the atmosphere.
    Nowadays we know how much CO2 we put into the atmosphere by using it as our global garbage bin for fossil fuel. All our climate observations show a global increase in temperature. This increase is consistent with the well established properties of CO2."

    another strange formulation : we explain that 97 % (an "unusual proportion" ) of scientists do agree by the fact that the increase is "consistent" with ? (notwithstanding the fact that the main issue is that of retroaction, not the primary IR absorption?) Well it is not "unusual" that a very large majority of scientists accept theories : special or even general relativity, quantum mechanics, and biological evolution is probably accepted by a still larger proportion of scientists. So why does the post qualify this proportion as "unusual"? probably because the given reason ("consistent with") is usually considered as "weak evidence" and not "definitive proof". The "unusual" thing is that so many scientist agree on so weak evidence (not simply that "so many scientists agree").if they were definitive proof of the purely anthropogenic evidence, this would not be unusual : this would be normal. But the post does not really offer an explanation of why. May I offer an explanation : that other things than scientific considerations interfere with the answer.
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  19. Gilles complains of a question too vague and ends his post with an accusation that is even more so, although what he hints at is the usual stuff. Yes, Gilles, you may offer an explanation. None of the word salad above qualifies as such.
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  20. rhjames: check the link you were first given! The 97% was originally from a small sub-section of those polled by Doran & Zimmerman for a 2009 paper.

    Anderegg, 2011 found about the same figure using different methodology, as explained in the post.
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  21. 19 Philippe : maybe you can give a constructive opinion of why a 97 % agreement is considered as "unusual" , for a proven theory ?
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    Moderator Response: [Dikran Marsupial] You can't prove a theory regarding the real world, only disprove (Popper), so your question is based on a fundamental misunderstanding. Taking that into account, the question becomes "why is a 97% agreement considered as "unusual" for a generally accepted theory?" then the question is merely a tautology posed as a question. As the article suggests, scientists pick holes in theories for a living, so 97% consensus would be unusual if the generally accepted view didn't have good support from the theory, experiment and observation. Thus the 97% consensus would be unusual only if the skeptic objections were as solid as presented on e.g. skeptic blogs. In my view, it isn't unsual.
  22. It's a standard climate skeptic debating point to express contempt for a "consensus of climate scientists".

    My standard answer to this is that it is not just a consensus of points of view.
    It is much stronger than that.
    It is really a "consensus of evidence".
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  23. so what do you understand from : "From my own experience, such a high proportion is quite unusual."

    which "experience" is he talking about ? a tautology is not "unusual" , usually ...
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    Moderator Response: [Dikran Marsupial] As I said, it would only be unusual if the claims against the consensus view were credible. If such claims were credible it would be unusual as the divisive nature of scientists would prevent such a large consensus if there actually were grounds for division. However, the substantive point is that there is a general (if not complete) consensus, so please move on to a discussion on the substantive issue, rather than quibbling irrelevant details.
  24. @22 LazyTeen (is there another kind?):

    Yes. Consensus is a consequence of solid evidence and hypothesis/theory, not a proof of it. To the standard "skeptic" strawman "Consensus is not proof," part of my resposne is often something along the lines of "No, consensus isn't proof, and no one says otherwise, but it is evidence of evidence."
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  25. moderator : I know that this will be soon censored, but this is kind of a private conversation : how can you honestly defend the opinion that the science is proved, if even their best defenders implicitly say the opposite ? and how can you claim that you defend honestly science , if you're not even able to let this question appear and answer it easily ?
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    Moderator Response: [Dikran Marsupial] Nowhere have I sais the science is proved, in fact I explicitly said that such proof is fundamentally impossible "You can't prove a theory regarding the real world, only disprove (Popper)". Perhaps you need to read what is written in replies to your posts more carefully (on that topic, your recent comment implies that the 97% consensus is unusual, when if you read the article, it explicitly states that it is not unusual - read the last paragraph). BTW if you want to have a private discussion, email would be a better option, my email address is dikranmarsupial@gmail.com .
  26. a remark on this :" If such claims were credible it would be unusual as the divisive nature of scientists would prevent such a large consensus if there actually were grounds for division. However, the substantive point is that there is a general (if not complete) consensus"
    In my opinion, you defend a very delicate position where the "consensus " must be just large enough to provide evidence that things are "true", but not large enough to justify that you need to argue against "contrarians". The same is true for the whole research in climate science. You need to argue that things are really so well understood that it is unacceptable to contest them, but that we still need to pay for researchers and support climate scientists. That is the really unusual thing - usually we do research when the situation is not yet clearly understood
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  27. So in my opinion, it would be highly desirable to precise what is not enough understood to justify keeping on doing research
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    Moderator Response: [Dikran Marsupial]Try reading the IPCC WG1 scientific basis report, it is full of discussion of what is uncertain and in need of further research. The job has already been done, perhaps you ought to read more and post less, at least until you have researched possible answers to your questions (the WG1 report is an excellent place to look for answers).
  28. The article of Doran and Zimmerman (2009), mentioned by MarkR above (#20 presently), should be taken as the source of the claim "97 out of 100 [active researchers in the field] agree that the climate is changing and that we are causing it". Anderegg et al. cited it. Anderegg et al. derived a similar number by some different statistics as well, but that might not be a fair sample of active climate scientists. Doran's article was also dicussed by Jeff Masters at Weather Underground blog.
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  29. SME @15: Well done for bringing up Popper. Have you read Kuhn and Feyerabend? They may give you a slightly different perspective.

    But actually, I think there is considerable space for the idea of consensus science even in Popper work (especially if we introduce Bayes as well).

    The naive understanding of Popper is that hypotheses fall into two classes: falsified and not-yet-falsified. Unfortunately that model is so simple as to leave science as almost useless.

    In practice, scientists constantly assess how much confidence they have in different hypotheses. Popper describes this by asking how many 'severe tests' (tests which could falsify the hypothesis) a hypothesis has survived. The term 'consensus science' may be understood in exactly these terms - when a hypothesis has survived many severe tests, and many alternative hypotheses have failed those tests, then the result among scientists in the field approaches consensus.

    (All this can be said more precisely in Bayesian probability terms, but I think in practice the social nature of scientific consensus is probably more important most of the time. Hence we are talking about a study on the views of scientists.)
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    Moderator Response: Well said, thanks.
  30. Ho Chi Minh used to get about 97% vote every time he stood for election. So too did many other leaders of Peoples Democratic Republics.

    I would much preferred 51% of those democratic peoples to have voted for their leaders, and 51% of scientists to agree on all the main facts of AGW.

    ( -Snip- )
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    Moderator Response: [DB] Off-topic portion deleted.
  31. "I would much preferred 51% of those democratic peoples to have voted for their leaders, and 51% of scientists to agree on all the main facts of AGW."

    Comparing scientific consensus to a brutal dictatorship is less than convincing, to say the least. You may "prefer" to have only 51% of climate scientists agree on the main points of AGW, but wishing it doesn't make it so. And imagining that their acceptance of AGW is done at the point of a metaphorical gun is also wishful thinking, because you have nothing to back your wish up with. Reality is not very yielding to our personal preferences.
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  32. "Try reading the IPCC WG1 scientific basis report, it is full of discussion of what is uncertain and in need of further research"

    My personal experience is that when I'm read the IPCC WGI report, I don't find any certitude concerning the exact role of CO2 in the XXth warming. Although I would also admit that "average temperature" (not really "climate" ) is changing, and that mankind probably contribute to this change. But I'm not going much beyond- and certainly not up to the conclusions that GW is the worst problem in the world. I have no idea of how many scientists would say the same - but actually I don't really care about that.
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    Moderator Response:

    [DB] You keep insisting on a simple answer to a complex question and then reject the answers given you without an obvious demonstration that you've objectively tried to understand them.

    If your aim is not to understand the science of climate change but to simply offer up non-science-based rhetoric with no sourced links to substantiate your contrarian positions, then other websites exist to serve that purpose.

    [Dikran Marsupial] You said it would be desirable to "precise what is not enough understood to justify keeping on doing research". The statements of uncertainty in the IPCC WG1 provide you with exactly the precis you want, it is a bit daft to then complain that the IPCC report doesn't provide "certitude". Science isn't about "certitude" it is about assessing the plausibility of the competing hypotheses that remain after you ignore the ones that are inconsistent with the observations. I have pointed out to you repeatedly that there is no proof of any theory regarding causality in the real world, it is fundamentally impossible. If you want certitude, stick to mathematics, or politics (where words like "proof" and "certainty" have weaker connotations).
  33. DB : I am not rejecting the answers. I am rejecting the claim that we have definitive answers, and that no doubt is now allowed. That's not a "rhetoric" point of view. That's a point of view, and for me it is scientifically based, because science is exactly that : examining pieces of evidence and keep researching as long as they aren't clear.
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    Moderator Response:

    [DB] Then it is clear you simply do not understand how science works nor the meaning of scientific consensus. This would be a step towards greater understanding in both matters. I suggest reading it.

  34. DB : I'm sorry, but I have no reason to believe you're more qualified than me to judge what a real scientific attitude is.

    Example drawn from your link :

    "Teacher : 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."

    "Settled facts" and "very likely" is obviously contradictory : "settled facts" means absolute certainty - there is absolutely no doubt that the origin of solar energy is thermonuclear fusion, for instance, for we don't have any plausible other explanation.

    on the other hand , "much of this warming is very likely due to human activities." is not a "settled fact" - actually it is not even a "fact" ! which "warming" are we talking about ? if we consider the 10000 last years, it is certain that much of the warming is not due to human activities.
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    Moderator Response: [Dikran Marsupial] I have already pointed out to you today that you are not reading the replies to your posts very well. I have also pointed out that there can be no absolute certainty regarding causal relationships in the real world. The fact that you have just ignored the second point reinforces the truth of the first. It is ridiculous pedantry to assume that "the science is settled" means there is absolute certainty; most are able to use their common sense to reconcile the two statements as meaning something along the lines of "the evidence is very strongly in favour of the generally accepted theory". The "regarded as" implies that the theory is only treated as if it were an established fact, not that it actually is one, i.e. a very safe assumption. As I said, please read comment more carefully and try and find the truth in them rather than (what you incorrectly consider to be) the inconsistencies.
  35. Good grief ... don't people get tired in going round in circles?
    We did "settled science" here
    Settled facts, in real world science, are always established against a background of uncertainties... anyone who has ever done science knows that.

    And, 34 Gilles "I'm sorry, but I have no reason to believe you're more qualified than me to judge what a real scientific attitude is."
    Given the support of your hypothesis here, you can't really claiming to have shown any real scientific prowess now, could you.
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  36. Worth seeing what he writes about Wikipedia:
    “A 2010 paper in the Proceedings of the National Academy of Sciences analysed "1,372 climate researchers and their publication and citation data to show that (i) 97–98% of the climate researchers most actively publishing in the field support the tenets of ACC outlined by the Intergovernmental Panel on Climate Change, and (ii) the relative climate expertise and scientific prominence of the researchers unconvinced of ACC are substantially below that of the convinced researchers". Judith Curry has said "This is a completely unconvincing analysis," whereas Naomi Oreskes said that the paper shows that "the vast majority of working [climate] research scientists are in agreement [on climate change]... Those who don't agree, are, unfortunately—and this is hard to say without sounding elitist—mostly either not actually climate researchers or not very productive researchers." Jim Prall, one of the coauthors of the study, acknowledged "it would be helpful to have lukewarm [as] a third category."

    In addition, you can visit this site to see here all magnitude the controversy about AGW.

    Historian and theorist of the scientific process and professor Weiner described as "the sequence of events" the creation and "life" of a scientific theory: a hypothesis - the research process = theory - the process of falsification = consensus - the process of falsification = 9?% - the negation of the theory - its "death"; only a few (?) percent = constants doctrine scientific.

    Skeptics are therefore needed, even in the case of consensus. A list of (achievements, name) - is still imposing.

    To this list I would add the Polish climate scientists - professors - about the great experience of science. The authors more famous research in my country, I mention: Marsz, Trepińska, Boryczka, Ustrnul ...
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  37. The first paragraph indicates to me that the 97% figure was reached by analyzing "current literature" in the climate sciences, not by means of a cleverly crafted survey as claimed by rhjames.
    I have not had time to listen to the complete audio so I do not know if the source is made more clear there.
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  38. DB, les : sorry but your comments do not content any scientific evidence that you're right- actually you're just claiming that you're right, or referring to other threads where you're claiming that you're right.
    I agree that absolute certainty does not exist, strictly speaking - however it exists "For all practical purposes". As an example, I am ready to accept ANY bet (even at 1 to 1000000) that the sun will rise tomorrow. So we could define a certainty "FAPP" by accepting any bet at any odd- after all, one dollar is one dollar.
    Personally, I am ready to bet at any odd on the validity of the gravitation law up to some (computable) accuracy, that no biological species will suddenly appear from nothing, or that nothing will disprove the fact that the Universe is more than 10 billion years old.

    I am not ready to bet at any odd on predictions based on the fact that the global warming since 1900 is mainly anthropogenic. Are you ? if yes, I'm interested in a bet with you at a very interesting rate ... for me :).
    0 0
    Moderator Response:

    [DB] The linked post I gave you contained a parable; one based on a National Academy of Science statement (a reference which should have answered much of your questions about scientific consensus and warming attribution). Ironic, you being a teacher failed to note that. As a teacher then, you were given homework to do (you blew off the reading assignment). Your grade is based on you doing the work assigned to you; that is incumbent on the student, is it not?

    "Feed a man a fish and he'll be fed...for a day

    Teach a man to fish and he'll never be hungry again."

    So either contribute to your own edification on this by doing the homework given you or cease wasting the valuable time of those well-meaning people who are trying to help you.

    Your choice.

  39. grrr .. do not contain
    0 0
  40. #30: "I would much preferred ... 51% of scientists to agree on all the main facts of AGW."

    Why do I suspect that if you got your preference, you'd be declaring AGW null and void because 'only' 51% agree?
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  41. So far as I know, even the few 'skeptic scientists' (e.g. Lindzen, Spencer, et cetera) "agree on all the main facts of AGW". At this point the only thing remotely cluefull people question is how much AGW there will be... and even there 'less than 2C for a doubling of CO2' is the belief of a vanishingly small minority.
    0 0
  42. 38 Gilles - my links refer to past pists I never claimed my links provide scientific evidence of any thing if you think they should have, that kind of ironed my point about your [lack of] grasp if what science is.
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  43. Well the problem here is that the data is in question. And I know people are going to argue about this but Richard Lindzen himself has said the surface station records are questionable. Furthermore, the IPCC has changed the radiative forcing value of co2, 3 times, with all adjustments being lowered.
    0 0
    Moderator Response: See the Argument "Temp record is unreliable," and put further comments about surface station records' quality there, not here.
  44. Jay... Lindzen's record so far is not so stellar. Skeptics hold him up as an example but his arguments are not so strong as they like to believe. He's focusing on the right area, uncertainties in climate sensitivity mostly related to cloud effects, but he's not been able to establish the numbers he's presented in a substantive and meaningful way.

    Lindzen says surface station records are unreliable but we now have satellite data that almost perfectly corroborates the surface station data.

    And as for the IPCC changing radiative forcing down three times... I'm not finding that to be accurate.

    Here is a the diagram from the TAR.

    And here is the same diagram from the AR4.

    You will note that actually the radiative forcing of CO2 went up in AR4.

    You should also note that this is an area of research that has a "high" level of understanding.
    0 0
  45. It'd be nice if there were a 'persistent thread' or somesuch where people could ask questions/make claims. As it is they get scattered all over and the moderators are always playing 'whack-a-mole' trying to get things onto the proper thread.

    Jay Cadbury, the radiative forcing value of atmospheric CO2 will change as the concentration does. Since the concentration is increasing I don't see how the IPCC estimates can be decreasing... unless you are looking at forcings against different baseline values or somesuch. That said, I recall that Michael Crichton used to make a similar claim about the estimated temperature change from a doubling of CO2 decreasing... but he did so by falsely citing the highest value in the range of estimates as the only estimate. If you instead took the lowest value then the IPCC estimate increased each time... basically, the uncertainty range got smaller with each report as additional studies were performed. The most likely value has remained about 3C for a doubling of CO2 in all of the IPCC reports.
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  46. "The answer is, 97 out of 100 agree that the climate is changing and that we are causing it.

    From my own experience, such a high proportion is quite unusual. As scientists we are trained to be professional sceptics, who doubt everything and who moreover love a good debate. Therefore putting 3 scientists together in a room sometimes results in an argument with 5 different opinions."

    Actually, the reason I think it's unusual is that it's an issue that has political/economic implications, and such issues tend to bring out a lot of industry shills, ideologues, and contrarians seeking fame.
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  47. Well DB

    actually you seem to have charged yourself with a burden : convince skeptical people that you're right. For if your only goal is to convince those who are already convinced, all the work you're doing is not very worthwhile. So you seem to have chosen some way of convincing people : sticking on scientific facts and argue scientifically.

    I'm curious to know if you have good arguments to be convincing. So far, what I've seen is only reassessed things that everybody who is interested in this issues has already seen thousands of time. I try to present the issues I see with your arguments. Now if your answer is "you're not a good guy, you haven't made your homework", well, technically, you have missed your goal. For if you think that the goal is to convince a vast majority of people of giving up all FF, to avoid a catastrophe for the whole mankind, (obviously not an easy one), it's not a good idea to insult these people who make some efforts to come here - but try to present their own argument and explain why they don't believe a priori in everything you're saying. That's not "my" choice, that's "your" burden.


    So let's make some comments on the "logics" presented in your thread

    "1. Increasing the level of a greenhouse gas in a planet’s atmosphere, all else being equal, will raise that planet’s surface temperature."
    True
    "
    2. CO2 is a greenhouse gas."
    True

    "3. CO2 is rising."
    True

    "
    4. Therefore (given 1-3 above) the Earth should be warming."

    Wrong - you forgot "all else being equal". It just disappeared. Nothing insures that "all else " stay equal

    "
    5. From multiple converging lines of evidence, we know the Earth is warming."

    time scale missing, but ok, let's assume it's at decadal time scale

    "6. The warming is moving in close correlation with the carbon dioxide."

    wrong. It has some correlation, but not very close - CO2 is exponentially rising whereas temperature has a much funnier behaviour.

    "
    7. The new CO2 (as shown by its isotopic signature) is mainly from burning fossil fuels."
    Probably true.
    "
    8. Therefore the global warming currently occurring is anthropogenic (caused by mankind)."

    Obviously simplistic - which part ? how much? who said that "everything else was equal"?

    so rather poor logics -not a very good teacher in my sense.
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    Moderator Response:

    [Dikran Marsupial] Stating that all things not being equal does not make it true. If you want to show that point was wrong, you need to specify what conditions are not equal and why they invalidate the hypothesis. Also while CO2 is rising exponentially, the forcing is logarithmic in CO2, and hence the expected warming trend is linear (once internal climate variability is considered). That is the expected correllation and it is pretty much what is observed, so that point is at best pedantry over the exact meaning of "correlation". Lastly, of course it is simplistic, this is a blog for discussion of the science for the general public, of course it is going to be simplistic. Also being simplistic doesn't make it wrong. For a less simplistic explanation, quantification, see the IPCC WG1 scientific basis report. DBs logic is fine.

    [DB] In case anyone's curious about the correlation of warming and carbon dioxide, r = 0.874 for ln CO2 and dT 1880-2008.

  48. @Rob

    I asked Dr. Happer about the surface station versus satellite record and will post the response once I have it.
    0 0
    Moderator Response: Not on this thread, because I will promptly delete your comment. Post it on the correct thread I pointed you to.
  49. @Rob

    Do you much about the Bern model? Is it important to the IPCC assessment?
    0 0
  50. In the meantime, I asked him about co2 saturation and here is what he had to say.

    As for CO2 saturation, yes, it is saturated in the sense the warming due to more CO2 is proportional to the logarithm of the CO2 concentration, not to the concentration itself. I am attaching some graphics to illustrate this "saturation." You will have to know a fair amout of physics to follow the remaining discussion. The first slide shows the "logarithmic" response of temperature to increasing CO2 levels. As you know, log (0) = - infinity, so what is meant by logarithmic is that the response function fits a logarithm pretty well for CO2 concentrations above 100 ppm or so. The reason for the "logarithmic" response is shown in the subsequent slides, the first of which has some blackbody curves superimposed on the MODTRAN model spectrum. For CO2 concentrations above a few 100 ppm the CO2 absorption band at 666 cm^{-1} (about 16 microns) is nearly "saturated," and the earth emits at about the ~ 220 K temperature of the tropopause over most of the band. More or less CO2 makes almost no difference in the central part of the band, as you can see from the figures. The exceptions are: 1) the sides of the band, where the CO2 emission is from altitudes below the tropopause, where the atmosphere is warmer and therefore a better emitter of radiation; 2) from the extremely narrow spike in the center of the band. This is the intense "Q branch" (as opposed to the much broader "P and R branches" that make up most of the band. The very strong Q branch is radiating from altitudes in the stratosphere, where it is warmer than the tropopause. The radiation efficiency from the sides of the bands does diminish as you add more CO2. Almost all of the direct greenhouse warming due to increasing CO2 comes from line broadening. You can see from the figures that it is not a very big effect. Qualitatively, satellite measurements of the earth's spectra look almost exactly like the MODTRAN model calculations attached here. The details are different for different locations, for example, the Sahara desert, or the tropical Pacific Ocean. And the calculations are for clear air. The picture changes dramatically when there are clouds -- which is another story.

    The bottom line is that the logarithmic response (other things being equal) is very solid physics if you ignore any changes in cloud cover or water vapor. From what data I have seen, it seems that clouds and water vapor do not cause much amplification and may in fact attenuate the direct warming from added CO2.
    0 0
    Moderator Response: [muoncounter] See the existing thread on CO2 saturation. Try to put comments on the appropriate thread; use Search. [not muon] Or peruse the List of Skeptic Arguments

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