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The 97% consensus on global warming

What the science says...

Select a level... Basic Intermediate Advanced

97% of climate experts agree humans are causing global warming.

Climate Myth...

There is no consensus

The Petition Project features over 31,000 scientists signing the petition stating "There is no convincing scientific evidence that human release of carbon dioxide will, in the forseeable future, cause catastrophic heating of the Earth's atmosphere ...". (Petition Project)

Science achieves a consensus when scientists stop arguing.  When a question is first asked – like ‘what would happen if we put a load more CO2 in the atmosphere?’ – there may be many hypotheses about cause and effect. Over a period of time, each idea is tested and retested – the processes of the scientific method – because all scientists know that reputation and kudos go to those who find the right answer (and everyone else becomes an irrelevant footnote in the history of science).  Nearly all hypotheses will fall by the wayside during this testing period, because only one is going to answer the question properly, without leaving all kinds of odd dangling bits that don’t quite add up. Bad theories are usually rather untidy.

But the testing period must come to an end. Gradually, the focus of investigation narrows down to those avenues that continue to make sense, that still add up, and quite often a good theory will reveal additional answers, or make powerful predictions, that add substance to the theory.

So a consensus in science is different from a political one. There is no vote. Scientists just give up arguing because the sheer weight of consistent evidence is too compelling, the tide too strong to swim against any longer. Scientists change their minds on the basis of the evidence, and a consensus emerges over time. Not only do scientists stop arguing, they also start relying on each other's work. All science depends on that which precedes it, and when one scientist builds on the work of another, he acknowledges the work of others through citations. The work that forms the foundation of climate change science is cited with great frequency by many other scientists, demonstrating that the theory is widely accepted - and relied upon.

In the scientific field of climate studies – which is informed by many different disciplines – the consensus is demonstrated by the number of scientists who have stopped arguing about what is causing climate change – and that’s nearly all of them.

Authors of seven climate consensus studies — including Naomi OreskesPeter DoranWilliam AndereggBart VerheggenEd MaibachJ. Stuart Carlton, and John Cook — co-authored a paper that should settle this question once and for all. The two key conclusions from the paper are:

1) Depending on exactly how you measure the expert consensus, it’s somewhere between 90% and 100% that agree humans are responsible for climate change, with most of our studies finding 97% consensus among publishing climate scientists.

2) The greater the climate expertise among those surveyed, the higher the consensus on human-caused global warming.

consensus studies

Expert consensus results on the question of human-caused global warming among the previous studies published by the co-authors of Cook et al. (2016). Illustration: John Cook.  Available on the SkS Graphics page

consensus vs expertise

Scientific consensus on human-caused global warming as compared to the expertise of the surveyed sample. There’s a strong correlation between consensus and climate science expertise. Illustration: John Cook. Available on the SkS Graphics page

Expert consensus is a powerful thing. People know we don’t have the time or capacity to learn about everything, and so we frequently defer to the conclusions of experts. It’s why we visit doctors when we’re ill. The same is true of climate change: most people defer to the expert consensus of climate scientists. Crucially, as we note in our paper:

Public perception of the scientific consensus has been found to be a gateway belief, affecting other climate beliefs and attitudes including policy support.

That’s why those who oppose taking action to curb climate change have engaged in a misinformation campaign to deny the existence of the expert consensus. They’ve been largely successful, as the public badly underestimate the expert consensus, in what we call the “consensus gap.” Only 16% of Americans realize that the consensus is above 90%.

Lead author John Cook explaining the team’s 2016 consensus paper.


Last updated on 8 May 2016 by BaerbelW . View Archives

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Further reading

Further viewing

The "Climate Denial Crock of the Week" video series examines the list of "32,000 leading skeptical scientists."

Naomi Oreskes gives a thorough presentation of the development of our scientific understanding of anthropogenic global warming:

Here is a video summary of the various studies quantifying the scientific consensus on human-caused global warming, as well as the misinformation campaigns casting doubt on the consensus.


Many thanks to Joe Crouch for his efforts in tracking down scientific organizations endorsing the consensus as well as links to their public statements.


On 21 Jan 2012, we revised 'the skeptic argument' with a minor quote formatting correction.


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Comments 601 to 604 out of 604:

  1. bakertrg:

    Your posts give me the impression that you are badly overstepping your subject matter knowledge, your claims to the contrary notwithstanding. They also give me the impression that you aren't sufficiently skeptical regarding the claims advanced by climate science deniers, your claims to the contrary notwithstanding.

    For example:

    There really is very little evidence to support the claim that it's (CO2 emissions) causing global warming on a massive scale when we're simply not experiencing global warming beyond what has repeatedly been experienced in the past.

    Completely incorrect.

    (1) In this recent article, Dana provides a summary of several attribution studies, which quantify the contribution of anthropogenic effects vs. the contribution of natural effects over the past 50-65 years. You will note that most of the anthropogenic contributions either hover around or well overshoot 100% (because natural effects over that time period have been causing cooling).

    (2) How do you know "we're simply not experiencing global warming beyond what has repeatedly been experienced in the past". Sources, please. What is more, past global warming has included both minor and mass extinction events (e.g. PETM, Permian-Triassic extinction) so even if current warming is in line with what's repeatedly been experienced in the past, it doesn't follow that either the process of warming or the end result are desireable from the perspective of maintaining an advanced, affluent, complex human society based on creating reliable surpluses of food for 7.5+ billion people.


    As for this portion of your specific response to me:

    One of the confusing things on this subject is the interchanging of terms "global warming" and "climate change". I'm guilty of this myself, typically global warming or Anthropomorphic Global Warming (AGW) has a negative connotation and puts the cause of change squarely on man and typically makes the supposition that the change is massive and catostrophic.

    As a matter of fact, global warming as a technical term is a subset of (global) climate change. If the global climate is changing, and the change is the result of an increase in the global temperature, global warming is an accurate description. Adding anthropogenic to the term merely (and accurately) indicates the cause of the warming. What is more, the political decision to split hairs over the two terms was launched, not by Al Gore or environmentalists, but by a Republican political strategist to sow confusion about the subject. See here for details.


    The bottom line is that you are coming across as:

    -  being ignorant (as in lacking sufficient knowledge) of the topic,

    -  projecting your lack of knowledge and biases onto others (and especially onto the actual body of evidence), and

    - tiresome to deal with, since many of your claims are trivially easy to recognize as faulty, flawed, or outright false, but require a great deal of hyperlinking and typing to address publicly (hence the Gish Gallop).

  2. bakertrg

    I agree with others that you need to read a lot more with an open, if critical (but not cynical!) mind.

    If you agree global warming is happening across the atmosphere, oceans and cryosphere all together, then you are forced (due to conservation of energy) to presume that the heat balance for the planet is changing. There are only three ways that change can happen: increasing output or radiation from the sun, reduced albedo due to lower atmospheric aerosols, and increasing greenhouse gas concentrations. All other causes of net heating that we know of are trivial.

    The warming since 1970 has occured despite no net change in solar output, and maybe a slight decline. There was also fairly frequent volcanic production of aerosols that should have cooled the earth. The only major forcing that changed over this period were greenhouse gases (CO2, CH4, N2O). The lack of correlation between warming and the other natural factors that could warm the earth is just as important as the correlation of warming with CO2.

    Scientists aren't satisfied with that though. They also found the effect of CO2 on climate is entirely consistent with physics — in fact this knowledge predates the correlation between CO2 and temp. You simply cannot build a physical climate model that reproduces the current warming from variations in solar radiation and volcanic aerosols alone. People have tried.

    Scientists then found fingerprints in the stratospheric cooling, spectral profiles of IR emission to space and back to earth, and in relative heating of nights and days that are consistent with hypothesis that the change is due to the greenhouse effect. The warming is also consistent with climate sensitivities estimated from warming events in the historical past, and in the paleo record.

    So, to argue against the observed changes being anthropogenic, you are left to somehow argue that CO2 is not human derived. Unfortunately, the human origin of atmospheric CO2 has been proven beyond doubt using multiple lines of evidence well before the IPCC was even formed - in fact that knowledge was one of the reasons the IPCC was formed!

    That is the basis of the scientific consensus. You have to realize that sometimes scientific findings align simply because nature is giving us a clear signal, and this is one of the clearest I've seen in my experience as a scientist.

  3. franklfkin... It would be incorrect to call those negative trends. None of the trends you listed can be determined to be negative since they can't be statistically determined to be different than a zero trend. 

    GISS: 0.022 ±0.157 °C/decade (2σ)

    NOAA: -0.003 ±0.145 °C/decade (2σ)

    HadCRU4: -0.009 ±0.141 °C/decade (2σ)

    HadCRU4hybrid: 0.054 ±0.188 °C/decade (2σ)

    RSS: -0.060 ±0.252 °C/decade (2σ)

    UAH: 0.054 ±0.252 °C/decade (2σ)

    One thing I'm just noticing that is interesting, the RSS and UAH data, which originate from the same satellite data, are almost identical except for the "-" sign.

  4. (snip)  Despite how my posts are being characterized I'm not intent on being a dissenter I am just skeptical of some of what is here and any website pushing that 97% number so hard and calling it the consensus makes me VERY skeptical of both the message and the messenger.

    Sorry if I offended you with my retort Dikran, not my intent but I felt you totally mischaracterized my post drew a conclusion I never made and sent me off to read sources that don't refute my point, aren't relevant to the issue and actually support my position not yours.

    (snip) One of his arguments was that the papers in the 97% number actually don't say man is the main cause of global warming... which is exactly my leaning.  I'm not emotionally vested in this idea, it's just the best answer from the data I have actually researched.  

    dikran 593: 97% of the papers that take a position on the question do take the position that it is mostly anthropogenic.

    next paragraph 

    If you want a study of scientists that are publicly stating that humans are the primary cause of climate change, then you won't find one, because scientists have better things to do

    so 97% of scientists are taking the position that THE cause of global warming is anthropogenic but none of them are publicly stating that humans are the cause of climate change?  Maybe I'm missing something but that seems to contradict itself.

    Despite what it may appear to be my goal is to find answers.  I am skeptical of some of the things that are held to be incontrovertible here. My main question and the reason I'm posting on this thread is because I strongly disagree with the methodology for coming up with the number 97%.  It seems that a lot of scientists think that humans are A cause of global warming and the graphic takes a huge liberty with meaning by saying humans are THE cause.  The meanings are vastly different.  I have tracked down some of the papers I'm going to see how many say THE cause.  

    I'm not a climatologist, I do have a background in physics, computer science and engineering, I have no dog in this fight other than I truly want to know what is happening on our planet if not solely for my edification so that I can at least educate my kids to the best of my ability and speak intelligently on the subject which potentially has massive ramifications going forward.  In any event I am honestly trying to address each counter to my initial post (despite what is pretty close to being dog piled which is my reading comprehension is any good turns out to also be against the comment policy)

    I see the words "easily disproven", but I actually thought it was accepted fact that we have had cooling trends during the modern industrial period despite ever rising CO2 levels. I posted 1900 to 1940 because I believe I read that on this website but in actually going to look I found some different time lines that had downward trends.  1880 to 1915 or 1940 to 1975 would have been a better example for me to use, I stand corrected.

    In any event, the point still remains the same, if the CO2 level is constantly rising and the causation is as great as is being purported shouldn't we see an accelerating temperature change?  According to information IPCC admittedly can not explain temperature has been flat for the last 17 years.  That is very difficult to explain if the problem is accelerating and even suggests that the causation is either much smaller than alarmists suggest (small enough that mother natures natural variance swallowed it whole) or the link to causation is less strong than you're suggesting.

    dr don easterbook gives a fairly informative view both in text and video (though my research shows that he has taken money from the koch brothers) sadly, many players in this discussion have taken funding from one side or another and/or have a book centric profit motive to push their beliefs.  Richard Lindzen also falls in this same space.  Unfortunately it's hard to determine what came first the ideology or the funding, of course the non consensus supporters are going to look for scientists who share their ideology to champion the cause so it's not surprising that the guys who get funded by big business have the anti AGW ideology.   (snip) 

    The video is long but interesting and he does seem to have quite a bit of data.  video  the text can be found here and has a lot of great information.  Dr Lindzen also offers some pretty compelling video's and his credentials are top notch.  That being said his monetary incentive made me watch both videos with a very jaundiced eye.  I found him to be pretty credible but I'm always skeptical of people getting paid for their science by a source that only wants a specific outcome.  

    KR - I briefly looked at Spencer Weart and despite being a believer in global warming comes out against a recent argument for the consensus here.  His post about the flawed assumptions in the paper from PNAS made me think he's at least interested in being objective. A very telling point of his post (made on this very website) here poses a big problem for the 97% number.  He states that while he is convinced by the evidence, he is surprised by the number who are not.  Doesn't appear as if he believes it's only 3% dissenting.  He pointed to several reasons why that number could be skewed and he's a recognized figure on your side of the argument.


    [TD] See "CO2 Is Not the Only Driver of Climate," and if you want to discuss that topic do so there or on other relevant threads, not here.  You are incorrect that there has been no warming in the past 17 years; there are many relevant threads for that topic, but you might start with "What Has Global Warming Done Since 1998?".  Further discussion of those topics on this thread will be deleted without warning.

    [TD] Don Easterbrook is most definitely not "informative."  Just one of many places where his inaccuracies are revealed is here.  Richard Lindzen's errors are numerous; one explanation is here.


    [PW] Your moderation complaints have been snipped, and you've been given Warning #1: You continue to argue in bad faith, you continiue to play word games, you continue to misrepresent other poster's words, and you impute dishonesty from them, too. Cease, or Warning #2 will be your last.

  5. A cursory glance at Cook et al. 2013 shows that only levels 1-3 are included in the consensus; they explicitly or implicitly agree that most of the warming since 1950 is anthropogenic. A cursory glance at Dr. Spencer's claims places them somewhere in levels 5-7, which aren't part of the consensus.

  6. bakertrg - I expect you will be subject to moderation, due to claims that people are presenting deceptive opinions due to financial renumeration. That said:

    Although Spencer Weart has expressed concerns about a particular study (Anderegg et al 2010), you do not appear to have read his actual comment, which states:

    The statistics are certainly interesting, but must be interpreted as "2-3% of people who have published 20 climate papers are willing to publicly attack the IPCC's conclusions." That is, to me, a surprisingly high fraction...

    If Weart feels that 2-3% rejecting the consensus is a high number, he is hardly disagreeing, now is he? It appears his concerns were with the methods of that particular study, and not the conclusion of an overwhelming consensus. Curiously, you present your information linking a website that appears to be a blog from someone in climate denial, which only reinforces the impression that you, too, are in climate denial. In fact, the more you write, the less interested (IMO) you appear in actual science. It's rather sad that the only lesson you take from Weart is an out of context of a single paper, rather than the copious work on the basics of climate change that I pointed you to. Your reading appears to be rather selective...

    Incidentally, Dr's Spencer and Lindzen are quite familar names, as they have quite a history of climate denial themselves - see here and here.

  7. bakertrg - Also note that Anderegg 2010 (which you seem to be criticizing by proxy in your last post) used completely different methods than Doran 2009, or Cook et al 2013, or Oreskes 2004.

    Yet _all_ of these studies found an overwhelming consensus among scientists, driven by the evidence they they know of, that the dominant cause of recent climate change is anthropogenic. And replication via different methods is one of the foundations of good science. 

    Unless you can present evidence (you know, actual data) that this consensus does not exist, I'm going to have to conclude that (a) you're wrong about the consensus, and (b) you're suffering from confirmation bias and are just not interested in the facts. 

  8. bakertrg...  Please note that moderation complaints get deleted.

    If you challenge a piece of published research, do so by backing your statements with references. If you think Doran was a poor survey, show references that confirm it was poor methodology. Don't just state it with opinion, present why you believe that to be the case. Show research on survey methodology that states why the results are not robust.

  9. I have said this before…the idea that the consensus is evidence of some sort of greed-induced conspiracy among scientists completely baffles me as a scientist. Yes, individuals care about getting grant money to support or students and technicians, but it’s not like we are all friends and family living off a common bank account. We often criticize each other strongly, sometimes with vitriol, about things noone else seems to care about. We compete with each other for limited money and review each others grants, sometimes agressively.

    If I sense someone is falsifying results, I have every incentive in the world to attack them, especially if they are doing different research than I and getting money that I could get. Heck, I even get famous if I overturn their accepted wisdom. And I could make much much more being a shill to vested interests who would prefer we deny climate change. If money were really the main factor here you’d see a lot less of a consensus.

    The fact that I do not know a single scientist who rejects the idea of AGW, despite differences I have with them on a multitude of other issues, is an indication of the power of the scientific arguments supporting it, and the commitments of scientists generally to following the evidence. Nothing in any of the surveys is inconsistent with that impression.

    Contrary to bakertrg’s cynicism, I find it all rather uplifting. If only I could figure out why bakertrg hates me, I’d be a happy camper!

  10. bakertg: 

    Please note that posting comments here at SkS is a privilege, not a right. This privilege can be rescinded if the posting individual treats adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Please take the time to review the policy and ensure future comments are in full compliance with it. Thanks for your understanding and compliance in this matter.

  11. franklefkin @598, thankyou.

    I should have checked more closely before responding to the latest denier cherry pick on temperatures.  As it stands, my claim that bakertrg's claim re 21st century trends being "trivially false" needs to be withdrawn.  It is merely obviously false.

    Obviously false because, firstly, with five established temperature records, claiming a negative trend with two of them show a positive trend is begging the question as to which record is superior.  We can, off course, look for a tie breaker among the records.  Noticing, however, that the only surface record with truly global coverage, and the satelite record with the greatest covered area both show positive trends shows the negative trends of the others to be due to information they exclude rather than a property of global temperatures.  Further, the fact that newer records (HadCRUT4-hybrid, BEST) also show positive trends corroborates GISS and UAH as showing the better record, as do indirect measures of temperature such as Sea Level rise, and receding glaciers.

    Alternatively, we may decide to treat all records alike, and simply take an average - except that the average of the 5 established records gives a positive trend - and including the newer records (HadCRUT4-hybrid; and BEST) makes that postive  rend even stronger.

    Finally, we need only notice that pushing the start date of the trend back one year (two years for RSS), or the end date back to Dec 2010 to make the trends positgive to see that the negative trend even in those records with the trend depends essentially on a chery picked period.

    Regardless of all this, it appears that bakertrg has dropped that claim, so this is now beside the point.

  12. bakertrg wrote "so 97% of scientists are taking the position that THE cause of global warming is anthropogenic but none of them are publicly stating that humans are the cause of climate change? Maybe I'm missing something but that seems to contradict itself."

    do yourself a favour and go and read the paper and the comment thread to see what has been discussed already.  Most papers on climate change are independent of whether the cause of the change is anthropogenic or natural.  To give you an example, I have worked on statistical downscaling, which attempts to estimate the effects of large scale atmospheric circulation (which GCMs model fairly well) on local (e.g. station-level) scale (which GCMs fundamentally can't do beause the grid boxes they use are too large).  A paper on statistical downscaling doesn't need to make any statement at all on what causes climate change because that is not what the paper is about and academic papers tend not to make assertions that are not directly justified by the analysis given in the paper.  There are many other topic in climate change that are not concerned with attribution, which is why relatively few explicitly take a stance.

    Now this will be obvious to anybody that understands the culture of scientific publication.  Scientists do have better things to do with their time than answer questions raised on climate skeptic blogs, and as a result, you will only generally be assured of a climate change paper taking a stance on the cause of the change if the subject of the paper is an attribution study.

    "Despite what it may appear to be my goal is to find answers. "

    Then perhaps next time someone answers your questions, you shouldn't accuse them of being disingenuous and copping out.  This is especially true if you are going to convert

    "97% of the papers that take a position on the question do take the position that it is mostly anthropogenic."


    "If you want a study of scientists that are publicly stating that humans are the primary cause of climate change, then you won't find one, because scientists have better things to do"


    "97% of scientists are taking the position that THE cause of global warming is anthropogenic"

    EMPHASIS yours.

  13. to me it seems this study came about because:

    "the skeptics don't believe that, when surveyed, climate scientists tell the truth about AGW and instead endorse it"

    So, this study studies the papers instead of surveying the scientists, as it can be assumed that they are more likely to state their correct position in their papers.

    The study came up with 32% Endorse AGW.

    How do we get to 97%?

    "oh...we surveyed them"



    [JH] You are skating on the thin ice of sloganeering whcih is prhobited by the SkS Comments Polcy. 

    Please note that posting comments here at SkS is a privilege, not a right.  This privilege can be rescinded if the posting individual treats adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Please take the time to review the policy and ensure future comments are in full compliance with it.  Thanks for your understanding and compliance in this matter.

  14. Mytheroo...  I would highly suggest you take the time to read the research paper you're commenting on. The answer to the question, "How to we get to 97%?" is there.

    Of papers that take a position, 97% of the published research supports the idea that humans are the primary cause of warming.

    If you like, you can use the 32% figure too, but you have to compare that, then, to the rejection rate which goes down below 1%.

    No matter how you prefer to slice it, the overwhelmingly dominant position in the published literature is that human emissions of CO2 are the primary cause of warming.

  15. Is it too much to ask that people read just the infographic?

  16. 97% ? Pfff... Until 1887, 100% of scientists agreed on the existence of aether...

  17. Murmur, it is absolutely given that a consensus does not make a theory correct. However, this is article is putting to bed the myth that there is no scientific consensus. For policy makers, going with the consensus is the only rational choice. If you were ill, would you be like this guy? It's not like there is any other credible theory of climate.

  18. Has skeptical science done an article responding to the American Physical Society Framing document on climate science which raised substantial questions on the state of climate science:

  19. PhysicsProf, the document you link is worded and presented in a rather peculiar fashion. What is its exact origin?

    When I go to the APS website and follow the links, I find this page:

    It is much more consistent with the normal tone of APS statements, which usually do not contain an abundance of graphs and data, or text highlighted in red. I looked at a variety of other statements and none of them has a format similar to the one you linked. I had too much difficulty to keep the document running on my computer to study it in enough detail, it kept on triggering error messages when trying to scroll. However, I did see a reference to the CimateAudit blog, which I find highly suspicious. APS does not normally refer to blogs of any kind.

    Do you know where exactly that document came from? As I see it, it appears more fraudulent than anything else. Did you talk to anyone at APS about it?

  20. I sent an e-mail with the url to APS, hopefully they'll respond in a few days and tell us something on the nature of this statement.

  21. PhysicsProf @618 & PhilippeChantreau @619/620.

    The APS is reviewing its statement on Climate Change and the document link given @618 is to a document that was an early part of that process. It is a pukka APS document produced by the sub-committee appointed to look into the review. (It is the "Framing Document for Workshop" mentioned on the page linked above.) It was a sort-of agenda document for a workshop held in January this year. What was curious was the list of experts invited to that workshop. These included obvious suspects (Bill Collins, Isacc Held, Ben Santer) and controversially arch-denialists Lindzen, Curry & Christy. I know of no offical reason for their invite but there was comment I read that this would disarm L,C&C who often claim nobody listens to them. The workshop transcript is available on-line and stretches to 573 pages (of big print).

    The next step in the process, a decisionof  whether to stick with the old statement from 2007 (which itself got some skeptics grinding teeth) or whether to start a process to develop a fresh statement - that decision has yet to be made. However the whole thing got a lot of airing in March when a professional twit of the British press called Delingpole kicked off a story that L,C&C had been appointed to the committee considering the APS statement review. Although utter bunk, the skeptical twitosphere feasted heavily on this "news" for some days.

    So we await the outcome of the sub-committee's deliberations.

  22. "L,C&C who often claim nobody listens to them"

    Someone at APS listened enough to bother with yet another ClimateAudit insinuation of impropriety, which I find a little disappointing. Of course, if "skeptics" were part of that commitee then all bets are off...

    L,C & C were listened to when they first spoke. As they kept on repeating themselves, the amount of listening they garnered decreased, which is entirely normal and even desirable. Sometimes I wish that the the mass media out there would have the same sloganeering policy that SkS has.

    L, C&C receive exactly the attention they deserve from the scientific community and way more than that in the public media, they have no reason to complain.

  23. So I gather the answer to my question is no, there hasn't been an article addressing the concerns raised by the American Physical Society. While Linzen, Curry and Christy were part of the actual workshop, my understanding was the framing document was from the APS without the input of the three. I did read the whole 573 pages of the workshop which was pretty fascinating but most of the questions in the framing document weren't directly addressed. What interests me is the current discussion feels like politicians slamming each other rather than scientists analyzing a problem ("this is all a hoax"--because scientists love secret meetings to fool the public; or "you're a denialist"--because Holocaust imagery is always in good taste). What I liked about the APS document was it asked serious questions a scientist rather than a politician would ask seeking to understand the basic science involved.

  24. PhysicsProf - If and when the APS releases an updated statement, it might be worth commenting upon it to the APS. Right now, it's silly to claim that a draft in progress, particularly with biased committee membership, is the opinion of the society as a whole. 

    Why would you treat an unapproved draft as the opinion of the APS?

  25. KR @624:

    "Why would you treat an unapproved draft as the opinion of the APS?"

    Particularly as it is not a draft, but a "framing document" that may have deliberately set out to encapsulate "skeptical" arguments without either endorsing those arguments or even agreeing that they are sensible, but merely in order garner responces to what are considered to be contrary opinion.

  26. Of course the framing document is not a position paper expressing skepticism on climate change. But they are serious questions that good scientists are asking. The IPCC report makes strong statements and the APS committee is inquiring into the basis of those statements. The 2007 APS statement on climate change is one of the pillars of the scientific consensus on climate change. That position is being reviewed by this committee. I think they are asking good questions. I would assume there are good answers and that is why I asked if they had been addressed. But so far I only hear defensive responses that don't address substance. If all you have is condescension, I am clearly in the wrong place for information.

  27. Well I havent read every line the workshop transcript but it certainly looked to me like the questions likely of interest to L,C&C were being addressed. Got an example of a particularly interesting question that you feel was not addressed?

  28. "How are IPCC confidence levels determined?"

    "What caused the 5% increase in confidence from 2007 to 2013?"

    How is the persistent factor of 3 uncertainty in climate sensitivity consistent with the IPCC confidence levels?

    How long must stasis exist before a firm declaration of a problem with the models?

    There also was a discussion (p 11) of the uncertainty of ocean heat flux data being 10-20% (or 20 W/m2) versus the change in global heat flux due to AGW since 1900 being less that 2 W/m2 (a factor of 10 less).

    I guess these would be a starting point....

  29. PhysicsProf @628:


    "How are IPCC confidence levels determined?"

    As with many of the questions in the framing document, this question merely demonstrates the authors of the questions simply could not be bothered doing their homework:


    "What caused the 5% increase in confidence from 2007 to 2013?" 

    There is a whole chapter of the latest IPCC report on this topic, which apparently the framers of the question could not bother to read.  Here is the summary:

    "Combination of Evidence
    Human influence has been detected in the major assessed components of the climate system. Taken together, the combined evidence increases the level of confidence in the attribution of observed climate change, and reduces the uncertainties associated with assessment based on a single climate variable. From this combined evidence it is virtually certain that human influence has warmed the global climate system. Anthropogenic influence has been identified in changes in temperature near the surface of the Earth, in the atmosphere and in the oceans, as well as changes in the cryosphere, the water cycle and some extremes. There is strong evidence that excludes solar forcing, volcanoes and internal variability as the strongest drivers of warming since 1950. {10.9.2, Table 10.1}"

    If that is not clear enough, let me spell it out.  The attribution is for anthropogenic warming since 1950, ie, 60 odd years ago.  The most commonly cited frequency for major oceanic fluctations is 60 years.  A 60 year cycle will not raise temperatures over a full cycle.  Therefore oceanic fluctuations are eliminated as a significant factor.  Net volcanic foring and solar forcing since 1950 have been negative, or nearly so.  Therefore they are not the cause of recent trends.  That leaves anthropogenic factors as the dominant (>50%) cause of the warming.  That conclusion is further supported by fingerprint arguments, and more detailed attribution in a host of areas.  The increase in confidence comes because, firstly, at time extends to 60 years the potential role of oceanic cycles minimizes; and as we continue through the very low activity of the current solar cycle, the potential that it was the Sun further minimizes.


    "There also was a discussion (p 11) of the uncertainty of ocean heat flux data being 10-20% (or 20 W/m2) versus the change in global heat flux due to AGW since 1900 being less that 2 W/m2 (a factor of 10 less)."

    From the relevant chapter of the IPCC:

    " Net Heat Flux and Ocean Heat Storage Constraints 

    The most reliable source of information for changes in the global mean net air–sea heat flux comes from the constraints provided by analyses of changes in ocean heat storage. The estimate of increase in global ocean heat content for 1971–2010 quantified in Box 3.1 corresponds to an increase in mean net heat flux from the atmosphere to the ocean of 0.55 W m–2. In contrast, closure of the global ocean mean net surface heat flux budget to within 20 W m–2 from observation based surface
    flux data sets has still not been reliably achieved (e.g., Trenberth et al., 2009). The increase in mean net air–sea heat flux is thus small compared to the uncertainties of the global mean. Large and Yeager (2012) examined global ocean average net heat flux variability using the CORE data set over 1984–2006 and concluded that natural variability, rather than long-term climate change, dominates heat flux changes
    over this relatively short, recent period. Since AR4, some studies have shown consistency in regional net heat flux variability at sub-basin scale since the 1980s, notably in the Tropical Indian Ocean (Yu et al., 2007) and North Pacific (Kawai et al., 2008). However, detection of a change in air–sea fluxes responsible for the long-term ocean warming remains beyond the ability of currently available surface flux data sets."

    First note that the increase in ocean heat content is tightly constrained.  As it happens the total Earth surface change in heat content from 1971-2010 was to 274 [196-374] zetajoules.  That equates to a forcing of 0.42 [0.3-0.54] W/m^2 averaged over that period.  93% of that warming was in the ocean.  Over that period, solar forcing was net negative, volcanic forcing was net negative, and oceanic fluctuations cannot give the ocean heat, merely shift it around.  That leads to the IPCC conclusion that it is "very likely" that anthropogenic factors have "made a substantial contribution to upper ocean warming" using a method independent of observation estimates of the value of individual fluxes.

    However, the IPCC quote properly refuses to specify the contribution form the magnitude of any individual flux, or combination thereof because the evidence on individual fluxes is not exact enough.  This, quite frankly is kindergarden stuff.  If we have a pool being filled from three different sources, each of which varies substantially from minute to minute in its outflow, but the volume of water in the pool increases steadilly, we know the net flow into the pool is positive and the average flow per minute even though we may be completely in the dark as to which source provides the greatest contribution in any given minute.

    4)  As shown above, the questions raised by you echoing the framing document have been more than adequately answered by the IPCC already.  It is sufficient response to all of them (and all the questions in the framing document I have read) to simply reply, read the IPCC report.  Of course, the original framers of the questions obviously have read sufficient of the report to present facts out of context, and frame questions in such a way as to create maximum confusion, even though a simple reading of the report already answers all the questions.

    I emphasise "original" because it is quite possible, indeed probable if they are competent, that the APS committee has just presented a document of denier talking points so that said deniers cannot reasonably complain their points have not been addressed. 


    PS: @623 you wrote ' "you're a denialist"--because Holocaust imagery is always in good taste" '.  Everybody else will have noted that you are the only person invoking the Holocaust here.  The will probably recognize that if you call Paul tall, that does not prevent you calling Mary tall as well, and that in no way implies they have the same gender.  Likewise, if some people have called people who doubt the history of the Holocaust on unreasonable grounds "Holocaust deniers", that I call people who doubt AGW on unreasonable grounds "AGW deniers" in no way implies that the latter have offensive views on the Holocaust - only that they deny AGW on unreasonable grounds.  My language is not limited by your determination to use the taking of  offense as a rhetorical tactic.

    PPS:  This is all well of topic on this thread, and I expect any reply on any of these issues (or other questions) to be in an appropriat thread.  Not doing so is a vioation of the comments policy and should result in your comment being summarilly deleted.

  30. I guess one could stretch the argument that, if APS revises isstatement, the consensus amongst scientists (not clkimate scientists) could be weakened and perhaps that's why PhysicsProf brought it up here. I am still unimpressed by the contents of that "framing document." I disagree that it resembles scientists asking questions in a sincere effort to understand. The arguments in it are well examined in the IPCC report. All of them are the object of current research and an abundance of litterature exists on them. Quite frankly, it reads more like a gish gallop and does not carry the to me the impression of sincerity that PhysicsProf advertises. I do not find that expressing this constitutes condescension.

  31. From what I gathered from people who were at that workshop, the APS board had a clear understanding of the situation ahead of time. It sounded like this was more about giving certain "skeptics" a chance to vent ahead of updating the APS position statement. 

    I would guess the framing document was a way of pulling up questions that "skeptics" put forth, though knowing those questions have been already answered to full satisfaction by the IPCC.

    I agree with Philippe. This doesn't strike me as a reasonable list of questions, except to those who don't have a full grasp of the scientific evidence on climate change. It's a list of talking points that have been addressed, repeatedly, in full.

  32. Well the questions Physicsprof thought interesting would mostly be case of RTFM, so no surprize that not much discussion of them. LC&C are very familiar with the content of the IPCC WG1. What is more surprizing is why these questions were there at all. It does not seem reasonable to me that anyone in APS who is questioning the consensus on climate change would not have read the document.

  33. Given an organism in an environment one can state that the most adaptive will, by definition, be the most likely to survive. In order to adapt to an environment, an organism must understand it. One could say that the ability to understand ones environment is perhaps the best measure of intelligence that exists. As far as evolution is concerned it is the only measure that counts. Being able to do math and calculate a trajectory does not count, but being able to dodge a predator definitely does count. If two organisms share about the same abilities to react to a given situation then the organism that can read the situation the most accurately is the one most likely to survive.

    Now consider Global warming. A search of the internet will quickly demonstrate that the vast majority of species on the planet are moving to the poles, or are moving, if they can, to higher elevations. In addition to that, the timing of migration patterns are changing. If this data is not accurate then not only are all climate scientists part of this climate gate conspiracy, but so are all botanists, ethologists, marine biologists, and microbiologists, entomologists and probably some others. So there is the first bit of information: If you do not believe that the climate is warming on a global scale then in terms of evolution you are less knowledgeable about your environment (less intelligent) then the great majority of animals, plants, insects, and even ocean dwelling single celled organisms like plankton. Yep, you are dumber than a plant or an insect.

    The pattern of GW denial sort of follows that of, and is similar to the arguments used to deny the correlation between smoking and cancer and a host of other diseases. You had actual scientists looking at the best available evidence on one side, and then you had paid charlatans with degrees in science working for corporations whose interests were threatened on the other. That was not 100% mind you, but it was pretty much how the advocates of the two positions lined up. A prime example is Dr. Frederick Seitz who sold out to become a spokesman for big tobacco and tried to convince people that tobacco was harmless. Later, after, at least according to many who were close to him, he became senile, he sold out to climate deniers.

    Now in this case on one side we have not only actual scientists doing their best to explain available information in light of best understood implications of thermodynamics, quantum mechanics, black body radiation etc. but you have almost all other life forms on the planet. By other forms of life, I mean almost every entity on the planet living in all but the most except extreme areas.

    Now if we accept GW, the next question is: what causes it? Trust me, it is not the sun which for the past 50 years has remained fairly constant or produced less radiation over that time while temperatures have risen. It has not changed much in the past 2000 years. Neither has known cosmic ray counts. This leaves galactic unicorn farts and CO2. We know about CO2, and how it would work, and the most likely results. We have no evidence of unicorn farts, but we do know about bloviation sources from hot air producers.

    Another red herring from AGW people are the failure of computer models and the testability of theories. If the prediction of a theory fails then the theory is false. Well folks, then I guess that the germ theory of disease is false. Clearly, many people exposed to "so called germs" never get sick. On the other hand people get sick who have never been exposed to these "so called germs" But wait, they are not really germs, they are viruses. See -— those scientists keep changing their story. Because they are in the pay of big pharma who just want to sell us drugs to make us sick so that they can make us more sick. And space that is another hoax. You know that the sun goes around the earth, just go outside and look for yourself. What? You believe the so called scientists?

    And speaking of hot air producers. This is a standard equation in statistics, the Gaussian integral. If you can not follow the proof, then you do not have a basic understanding of one of the most basic equations in statistics, which means that you do not understand statistics, which means that you are as competent to argue a point of view on AGW as you are to advocate competing forms of cancer treatment without ever having had a course in biology.

    But since AGW deniers acutely suffer from Dunning-Kruger effect:, they will continue to bloviate.

  34. Link is broken:

    13 countries have signed a joint statement endorsing the consensus position: 

  35. If we acknowledge that 97% of climatologists agree with the concept of anthropogenic global warming can we a) agree that 97% is less than 100%, and b) that scientists have, throughout history, repeatedly come to majority conclusions that were wrong, and therefore c) admit that consensus on issues of scientific inquiry conveys no moral or intellectual prerogative?

  36. Andy Robinson - We can certainly agree on that, as well as noting that

    • d) Usually the majority of experts are indeed correct, and
    • e) Holding minority positions (far less than 1% per hypothesis, as there are multiple and contradictory proposed 'climate skeptic' mechanisms) means holding to a position that most people familiar with the subject(s) feel is in no way credible. 
    • f) For people not deeply versed in a complex subject, expert opinion makes for the most reasonable heuristic in deciding policy - to do otherwise is a very bad, and in fact irrational, bet.

    To act as if the minority opinions are in fact correct is to fall prey to the Galileo fallacy - if people perceive you to be wrong, you usually are wrong. There are far far more loons doing living room 'science' than actual geniuses out there. 

  37. KR @636

    We can also note that even when scientists are wrong, they are often right enough (e.g. Newton's laws of motion)

  38. If the question in the concensus sudy had been "Is recent climate warming solely due to human influences" then it would be interesting to know what the answers would have been.

    Of course concensus doesn't mean right which is the implication of the video. Concensus is always being proved wrong and science doesn't work and never has worked on the basis of concensus as I hope all the participants on this site well know.

    Thirty years ago there was an unshakeable concensus in medical science that the main group of stomach ulcers were caused by excess acid secretion. It took a new scientific discovery to prove that the concensus was wrong. The cause of an unpleasant condition that had affected more than 1 billion people and that affects around half the US population over 60 years old is a bacteria Heliobacter Pylori. New drugs were invented that treated it and the previous treatment was dropped.

    Of course it is worth knowing that 97% of research papers and / or their authors attribute global warming to humans but as the video says, it's the science behind it that counts, and just because the papers are peer reviewed in itself proves nothing about whether the scientific proposal / theory is necessarily right. Some ability to falsify the theory must exist (as happened in the case of H.pylori) otherwise it's just the latest best estimate - no matter how great the concensus.

    The fact that only half the public believes that it is proven that AGW is the sole or main cause of global warming says something to the idea that the proof is not necessarily there and publicising it (there has been a ton of that) can't alter the impression that there is a long way to go before we are remotely close to knowing for certain. 

    One reason for being confident about there being much more uncertaintly than the 97% concensus suggests is that there is nothing like a concensus, let alone proof, of what caused (and causes) the extreme natural variations in climate throughout geological time.This variation is well documented and almost certainly has a variety of underlying causes which are likely to be very different from C02 or other MM emissions even if higher greenhouse gases levels have often been present. For example we do know that glaciers existed at the poles when C02 levels were a hundred times the current concentrations. 

  39. Peter Lloyd @638...

    My first question for you would be: Have you read the Cook et al paper yet? I ask this because you seem to be operating under a number of assumptions that in error.

    Firstly, the basis of the study was to evaluate whether research papers endorsed or rejected the IPCC position that human's are primarily responsible for warming of the past 50 years. The IPCC statement on this matter suggest that there is a >95% confidence level that human's are responsible for more than half of the warming. Part of the position the IPCC states is tha the most likely figure is that human's are responsible for 110% with a high end likelihood of 160%.

    Even at >100% contribution no one is going to claim that human's are "solely" responsible for warming. There are always natural warming and cooling factors at work. Thus, your statement would be one that 100% of scientific researchers, and scientific research would reject.

    Secondly, you appear to be under the incorrect assumption that Cook et al was attempting to infer whether the science was "correct." That is not the case. If you read the paper, the whole point is that most non-scientists do not understand what the actual level of scientific consensus is. The paper is quantifying the consensus and presenting that in juxaposition to what the general population thinks the consensus is.

  40. "Concensus is always being proved wrong and science doesn't work and never has worked on the basis of concensus as I hope all the participants on this site well know."

    This argument makes no sense.  There is now a consensus that H. pylori is important in most ulcer cases. Your argument suggests should we ignore that consensus because it could be wrong.  But that is the case with any proposition open to scientific questioning.  

    You are getting "faith" mixed up with "consensus."  Consensus is about the current state of understanding given the information in front of us.  It is critical to progress in science since it provides the methods, assumptions and questions needed to direct futher study.  Without consensus, science would slow to a stand still because there would be no agreement about assumed knowledge to direct future research.  In the case of H pylori, the question now becomes why 2/3s of people are infected, but relative few show any syptoms.

    What consensus is not is unshakeable belief in a proposition. Consensus can be overturned because it is based on evidence.  If evidence suggests the consensus should be overturned, a new consensus usually forms around a new proposition that is better supported by the evidence.  Such paradigm shifts are extremely important in science, and come in all shapes and sizes.  Much research can be seen as interesting because it challenges assumptions.  But large scale revolutions, where a well established point of consensus that is central to many lines of research is overturned in favor of a new idea, is not the rule.  That is why Kuhn referred to normal science in opposition to revolutionary science.

    Climate science has settled on a consensus about current warming because the evidence points in a particular direction.  At present there is no alternative hypothesis that fits the observations in front of us.  Could there be an H. pylori we haven't seen in the climate that causes recent warming?  Given that climate is governed by well established (by consensus) laws on transfer and conservation of energy, and we can measure most of the key flows and modifying factors, it seems unlikely. You would have to challenge the consensus on thermodynamics, or radiative transfer, or physical chemistry, because those agreed principles underlie this more specific consensus.

  41. The consensus on stomach ulsers story you present is one that has little basis in fact. Here is what Dr Marshall said of their work:

    Even after your self-experiment, the medical community remained sceptical that H. pylori was connected to stomach ulcers. How did you finally convince them?

    We were keen to present our data and announce that we had discovered the cause of ulcers, so we submitted our paper to the Australian Gastroenterology meeting in 1983. It was rejected. Fortunately, my boss at the time had some experience with Campylobacter, which was becoming a popular explanation for infectious colitis, or inflammation of the colon. Helicobacter looked similar, so I spoke to a Campylobacter expert in Britain and we sent him some cultures. He grew them and became excited about it, too. Then, in 1984, we went to a meeting of microbiologists, who are always interested in any new microbe, and things really took off after that. It took a few more years to gain support from gastroenterologists.

    [added emphasis]

    As you can see, this was an idea that did not take long for the scientific community to accept.

  42. In short, the consensus is not about blind acceptance.  The consensus has power precisely because scientists are challenging or have continually challenged it in various ways, and yet it has stood. The idea that there is a dichotomy between consensus and skeptical inquiry fails to appreciate how the process works..

  43. Thank you gents

    I haven't had a chance to read the paper and accept the point about endorsement of the IPCC position

    Thank you for agreeing that there are other factors at work in global warming and bearing in mind the strength of those as demonstrated by climate history then any claim that man - made factors are anywhere near as large as 100% or greater are going to have to demonstrate the current and past natural changes and how they interact. No one knows this yet.

    I would point out that the huge red circle at the top of this thread with the 97% figure in it says "Global warming is happening and we are the cause" without the caveat that it is not the only cause.

    As a result, however interesting it may be that half the population doesn't share the 97% figure, the concensus view remains guesswork and miles away from the experimentally demonstrated effect of H. pylori that I used as a contrast.

    You don't show in what way my H. plyori story has "little basis in fact" or isn't relevant. It is true that H.pylori is the primary cause of many stomach ulcers. There undoubtedly will be many elements of how and why that remain unknown as yet. The point is not to make too much of the fact that there was a strong concensus about the previous view. In general medical science is quite good about not creating an idea of certainty unless the experimental evidence is very strong indeed.

    My problem with the waving around of the 97% figure is it gives a false impression of the certainty if you don't temper it in the same pronouncement. 

  44. Peter Lloyd:

    You are essentially admitting to arguing from ignorance. Please desist (arguing from ignorance, that is).

    Maybe you don't know much about paleoclimate, but that doesn't mean nobody knows. (See chapter 5 of the IPCC AR5 WG1, or any paleoclimate articles at this website.)

    Maybe you don't know much about the sum of radiative forcings, or findings from paleoclimate, that allow climatologists to calculate that human emissions of greenhouse gases are responsible for 100+% of recent warming, but that doesn't mean nobody does.

    Regarding paleoclimate findings supporting "global warming is happening and we are the cause", see Tom Curtis' comment here regarding Marcott et al 2013; in which Tom notes that Marcott et al found:

    Global temperature, therefore, has risen from near the coldest to the warmest levels of the Holocene within the past century, reversing the long-term cooling trend that began ~5000 yr B.P.

    In other words, little temperature wiggles up-and-down notwithstanding, human emissions are the only cause of the current sustained warming trend.

    Maybe you don't know about the enormous evidence base that undergirds the consensus position, but that doesn't mean nobody does - in fact, the consensus position exists as a result of the evidence base (Like in any other field of science with a strong consensus position (*)).

    As just a tiny example, consider this Skeptical Science post discussing the basics of the greenhouse effect. Note the final image presented in the article, taken from Conrath et al 1970 in which they ran an experiment, comparing theoretically calculated vs. empirically measured infrared radiance.

    Kindly also provide actual documentation that the mainstream position among doctors and medical researchers regarding stomach ulcers was an "unshakeable consensus" as you assert.

    (*) Unless you care to suggest that, say, plate tectonics, quantum electrodynamics, gravity-as-distortion-of-spacetime, and evolution of biological organisms are also "guesswork".

  45. Peter Lloyd...  "You don't show in what way my H. plyori story has "little basis in fact" or isn't relevant."

    You stated that there was an unshakable consensus. I quoted for you the words of one of the researchers who discovered the H. plyori saying it only took a few years for his work to become accepted. That means, in actuality, that previous consensus was very quickly overturned by presenting the research.

  46. 645. I think we are at cross purposes here. Neither of us doubt that there was a, let's call it strong, or established if you like, consensus prior to the discovery of the effect of H. pylori. Neither of us disagrees that new evidence did change the consensus although I would argue that the fact that it took as long as it did illustrates that medics were very keen to hold on to their previous consensus view.

    Where we would probably disagree is on whether there is sufficient scientific proof underlying the consensus on the degree of man-made global warming and the degree to which that consensus is reflected correctly in the statements made at the top of this thread.

    I think that looking at the science and its credibility is important and that the use of "consensus" is being corrupted to give a false impression of certainty

    644. No. I am arguing that there is ignorance and you seem to be in denial of it! It is freely admitted by paleo-climatologists that they know a lot about many of the factors involved but not enough to know the exact reasons behind paleo-climatic changes. 

    Taking your Tom Curtis conclusion from Marcot et al:

    "Global temperature, therefore, has risen from near the coldest to the warmest levels of the Holocene within the past century, reversing the long-term cooling trend that began ~5000 yr B.P.

    and your conclusion from it:

    "In other words, little temperature wiggles up-and-down notwithstanding, human emissions are the only cause of the current sustained warming trend."

    The conclusion you draw cannot logically be made from that Marcot statement. There maybe many reasons for the cooling and for the most recent warming of which human emissions are likely to be a contributory factor. 

    The enormous evidence base that you cite does not preclude other factors causing the most recent warming and whilst you are right that there is a lot of knowledge about paleo climate I have yet to see anything that comes close to proof that C02 changes are the main factor in those. As I said before icecaps existed at both poles when C02 concentrations were 100 times the current levels.  

    ...."Unless you care to suggest that, say, plate tectonics, quantum electrodynamics, gravity-as-distortion-of-spacetime, and evolution of biological organisms are also "guesswork"."....

    I don't care to say it because they are all demonstrably true and repeatedly proven by observation and / or experiment. The theories and mechanics behind them have been, and are, still subject to many different "consensuses". But none of those causal theories are held as unshakeable truth in the way, say for example, that the movement of crustal plates is, via something described as plate tectonics. This will not be falsified.

    The same cannot be said for the claim that man-made emmissions of C02 are causing 100% (ish) of temperature increases on earth.


    [JH] You are now skating on the thin ice of excessive repetition which is banned by the SkS Comments Policy.

    Please note that posting comments here at SkS is a privilege, not a right.  This privilege can be rescinded if the posting individual treats adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Please take the time to review the policy and ensure future comments are in full compliance with it.  Thanks for your understanding and compliance in this matter.

  47. Peter... The point isn't that it took so long. Once actual evidence was presented scientists changed their position based on the evidence. The previous position was one where there was little active research that made up the basis of the consensus position. 

    AGW is not a case where little research is being done and scientists are just accepting what has been assumed.

    This is an issue that has been actively researched for 100 years. There are thousands of papers coming out every year on various aspects of man-made climate change. It's a field of intensive research.

    In the past 100 years there have been various challenges to the core idea that increasing greenhouse gas concentrations will warm the planet. Each of those challenges have been shown to be wrong. And in the meatime, more and more research is being published confirming the consensus position.

    The comparison to H. pylori is just not a valid.

  48. Peter Lloyd - The consensus on AGW, although very consistently measured in the high 90%'s, is not immutable

    In the early 20th century the consensus on climate was that natural causes predominated. There were early researchers like Tyndall Fourier, and Arhennius who made some quite prescient predictions, but until the mid-20th century there was no general opinion that anthropogenic factors were important. But then things changed due to new evidence. Callendar in the 1930's (AGW a factor in early 20th warming), Plass (radiation balance) and Revelle (oceans won't absorb all anthropogenic CO2) in the 1950's, Keeling measuring CO2 in the 1960's, Manabe and others in the 1970's modelling GHG effects, etc - all contributed to the body of evidence. 

    And over the 1960's-1980's, the scientific consensus on climate changed, to the currently held view that AGW is the dominant factor in recent warming, accounting for ~100% of it (with natural factors such as insolation providing negative contributions)

    The consensus changed due to evidence and how it is viewed by those who have studied these topics. It could certainly change again - but that would require a considerable amount of new (and contrary) evidence to that effect. There's no sign of such whatsoever - just inconsistent, contradictory and unsupported claims (it's the sun, it's a cycle, cosmic rays, it's not happening at all, there's a grand conspiracy toward a 'World Order', etc), claims that appear, quite frankly, loony. 

    Now, as to the meaning of such a strong scientific consensus - that's important because laypeople (quite wisely) will take expert opinions into consideration when deciding public policy. 

    You've claimed uncertainty where it doesn't exist. And your comments simply don't hold up in the face of the evidence. 

  49. "The enormous evidence base that you cite does not preclude other factors causing the most recent warming."

    Actually, it does preclude them as that list is really rather small.  It would have to be something that affected the net heat balance of the earth by affecting incoming radiation (solar inputs, aerosols, clouds), the reflectivity of the earth (ice caps, land use changes) or the ability of the surface to cool (greenhouse gases).  The only thing that has been changing in a way that should increase global heat balance over the last 40 years are greenhouse gases.  

    Your equivalent of H pylori would be to discover a new way for heat to be produced, absorbed or lost by the atmosphere in a large enough quantity to challenge the importance of those other factors.  I'd argue the likelihood that such a missing component of the heat budget exists and has not been seen is virtually nil, because we can close the heat budget now.

    "and whilst you are right that there is a lot of knowledge about paleo climate I have yet to see anything that comes close to proof that C02 changes are the main factor in those. "

    First, what explains variations in paleo climate does not have to be the same thing that explains current climate change.  I.e., The glaciations were not initiated by CO2, but they were exacerbated by feedbacks that increased CO2.  Current warming is only really related to changes in greenhouse gases though.

    Second, we will always know less about what drives paleo climate because we know less about the key factors that drive global heat balance in the distant past than we know about the present, for which we have precise measurements.   The lack of certainty about past climate variations does not undercut what we have learned by studying current conditions.  Still, there have been puzzles raised by past climate conditions that have seemed to challange the consensus, which has generated futher research to understand the factors underlying the energy budget better for those periods.  I can't think of a current case in paleoclimate, however,  that hasn't been reconciled with the accepted role of CO2 in climate once more was understood about conditions affecting the earth's energy balance.

    "As I said before icecaps existed at both poles when C02 concentrations were 100 times the current levels."

    A case in point.  Actually, the high CO2 concentrations during large glaciations in the paleozoic were discovered by scientists trying to understand how the earth became deglaciated after essentially freezing over.  Glaciation of the earth should have been hard to overcome because a white earth reflects a lot of sunlight, and therefore greatly reduced incoming energy. That lead many to doubt evidence that the earth was actually glaciated — because it still would be.  

    But, the glaciations alsostopped processes that typically removed CO2 from the atmosphere, allowing it to build up, which heated the earth and allowed the glaciers to melt.  So paradoxically, the phenomenon you hold up as challenging a role for CO2 in climate, is actually understood by scientists to reinforce the idea that CO2 is important in climate.  


    [PS] See here and here and here for the science on climate and past high CO2 levels. One of the most popular myths.

  50. This story


    came up yesterday, about the consensus; I wonder if it deserves a response?


    [RH] Hotlinked url.

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