Mike Mann: First Look at AR5

September 27, 2013


Mike Mann in LiveScience:

What about the converse claim, promoted by critics, that the IPCC has exaggerated the evidence?

Well, if anything, the opposite appears closer to the truth. In many respects, the IPCC has been overly conservative in its assessment of the science. The new report, for example, slightly reduces the lower end of the estimated uncertainty range for a quantity know as the equilibrium climate sensitivity — the amount of warming scientists expect in response to a doubling of carbon dioxide (CO2) concentrations relative to preindustrial levels (concentrations that will be seen mid-century, given business-as-usual emissions).

The IPCC reports a likely range of 1.5 to 4.5 degrees Celsius (roughly 3 to 8 degrees Fahrenheit) for this quantity, the lower end having been dropped from 2.0 degrees C in the fourth IPCC assessment. The lowering is based on one narrow line of evidence: the slowing of surface warming during the past decade.

Yet there are numerous explanations of the slowing of warming (unaccounted for effects of volcanic eruptions and natural variability in the amount of heat buried in the ocean) that do not imply a lower sensitivity of the climate to greenhouse gases. Moreover, other lines of evidence contradict an equilibrium climate sensitivity lower than 2 degrees C. It is incompatible, for example, with paleoclimate evidence from the past ice age, or the conditions that prevailed during the time of the dinosaurs. (See this piece I co-authored earlier this year for the Australian Broadcasting Corp. for a more detailed discussion of the matter.)

The IPCC’s treatment of global sea-level rise is similarly conservative — arguably, overly so. The report gives an upper limit of roughly 1 meter (3 feet) of sea-level rise by the end of the century under business-as-usual carbon emissions. However, there is credible peer-reviewed scientific work, based on so-called “semi-empirical” approaches that predict nearly twice that amount — i.e., nearly 6 feet (2 m) of global sea-level rise this century. These latter approaches are given short thrift in the new IPCC report; instead, the authors of the relevant chapter favor dynamical modeling approaches that have their own potential shortcomings (underestimating, for example, the potential contribution of ice-sheet melting to sea-level rise this century).

As some readers may know, the conclusion that modern warming is unique in a long-term context came to prominence with the temperature reconstruction that my co-authors and I published in the late 1990s. The resulting “Hockey Stick” curve, which demonstrates that the modern warming spike is without precedent for at least the past 1,000 years, took on iconic significance when it was prominently displayed in the “Summary for Policy Makers” of the 2001 Third IPCC Assessment report. Thus, the “Hockey Stick” curve, as I describe in my recent book, “The Hockey Stick and the Climate Wars,” became a focal point of the attacks by industry-funded climate-change deniers.

So, it might not come as a surprise that one of the most egregious misrepresentations of the IPCC’s latest report involves the Hockey Stick and conclusions about the uniqueness of modern warming. [4 Things to Know About the IPCC’s Climate Change Report]

An urban legend seems to be circulating around the echo chamber of climate-change denial, including contrarian blogs and fringe right-wing news sites. The claim is that the IPCC has “dropped” or “trashed” the Hockey Stick conclusion regarding the unprecedented nature of recent warmth.

A good rule of thumb is that the more insistent climate-change deniers are about any particular talking point, the greater the likelihood is that the opposite of what they are claiming actually holds. The IPCC has, in fact, actually strengthened its conclusions regarding the exceptional nature of modern warmth in the new report. A highlighted box in the “Summary for Policy Makers” states the following (emphasis mine):

In the northern Hemisphere, the period 1983-2012 was likely the warmest 30-year period of the last 1400 years (medium confidence).

The original 1999 Hockey Stick study (and the 2001 Third IPCC Assessment report) concluded that recent Northern Hemisphere average warmth was likely unprecedented for only the past 1,000 years. The 2007 IPCC Fourth Assessment extended that conclusion back further, over the past 1,300 years (and it raised the confidence to “very likely” for the past 400 years). The new, Fifth IPCC Assessment has now extended the conclusion back over the past 1,400 years. By any honest reading, the IPCC has thus now substantially strengthened and extended the original 1999 Hockey Stick conclusions.

Only in the “up is down, black is white” bizarro world of climate-change denial could one pretend that the IPCC has failed to confirm the original Hockey Stick conclusions, let alone contradict them. [How Words Affect Climate Change Perception]

The stronger conclusions in the new IPCC report result from the fact that there is now a veritable hockey league of reconstructions that not only confirm, but extend, the original Hockey Stick conclusions. This recent RealClimate piece summarizes some of the relevant recent work in this area, including a study published by the international PAGES 2k team in the journal Nature Geoscience just months ago. This team of 78 regional experts from more than 60 institutions representing 24 countries, working with the most extensive paleoclimate data set yet, produced the most comprehensive Northern Hemisphere temperature reconstruction to date. One would be hard-pressed, however, to distinguish their new series from the decade-and-a-half-old Hockey Stick reconstruction of Mann, Bradley and Hughes.

Conclusions about unprecedented recent warmth apply to the average temperature over the Northern Hemisphere. Individual regions typically depart substantially from the average. Thus, while most regions were cooler than present during the medieval era, some were as warm, or potentially even warmer, than the late-20th-century average. These regional anomalies result from changes in atmospheric wind patterns associated with phenomena such as El Niño and the so-called North Atlantic Oscillation. [U.S. Will Warm Dramatically By 2084, NASA Model Shows (Video)]

Colleagues and I, quoting from the abstract of our own article in the journal Science a few years ago (emphasis mine), stated:

Global temperatures are known to have varied over the past 1,500 years, but the spatial patterns have remained poorly defined. We used a global climate proxy network to reconstruct surface-temperature patterns over this interval. The medieval period [A.D. 950-1250] isfound to display warmth that matches or exceeds that of the past decade in some regions, but which falls well below recent levels globally.

These conclusions from our own recent work are accurately represented by the associated discussion in the “Summary for Policy Makers” of the new IPCC report (emphasis mine):

Continental-scale surface-temperature reconstructions show, with high confidence, multidecadal periods during the Medieval Climate Anomaly (year 950-1250) that were, in some regions, as warm as inthe late 20th centuryThese regional warm periods did not occur as coherently across regions as the warming in the late 20th century(high confidence).

However, never underestimate the inventiveness of climate-change deniers. Where there’s a will, there is, indeed, a way: A meme now circulating throughout the denialosphere is that the IPCC’s conclusions about regional warmth contradict our findings, despite the fact that those conclusions are substantially based on our findings.

One could be excused for wondering if climate-change deniers have lost all sense of irony.


41 Responses to “Mike Mann: First Look at AR5”

  1. omnologos Says:

    Sad evolution of an embittered man, wheeled out not for science expertise but to write the usual trite backfooted invective.

    Every time Mann speaks a tiny bit of evidence dies.

    • All the deniers are going to come out the woodwork now and you know what, you’re not even particularly interesting.
      What exactly do you care about “evidence”? Ad hominem, means that you attack the person instead of the subject… and you do it because the science is in and the “evidence” makes you look just like a flat-earther.
      Go on tell us how good smoking is for the whole planet’s health!

      • omnologos Says:

        Mann speaks about “deniers” and pretty much nothing else. Science it ain’t .

        • jeff cowdrey Says:


          You are being very selective in your reading, emphasizing one aspect above all others. It is almost like you have a cherry-picking obsession. Why is that, do you think?

          • omnologos Says:

            In a comment to a post about Mann communicating to the masses I comment about how badly Mann is communicating to the masses – are you complaining because I’m not OT? 🙂

        • The sheer sweet irony of an obsessed ‘denier’ troll such as yourself suggesting that Mann does nothing else but speak about ‘deniers’, is certainly not lost on me.

          • omnologos Says:

            Your puerile attempt at rhetoric doesn’t change the fact that here we are with a prominent climate scientist with opportunity to reach out at people interested in science and all he does is reply to unnamed “deniers” as he’s been forever doing.

            He’s an expert alright, at cheap political scoring.

    • Omno, Michael Mann has authored 140+ more peer reviewed research papers than we have, and evidently 140+ more than you’ve noticed.

      • omnologos Says:

        Charles -your comment is meaningless. I did call him a prominent climate scientist.

        I repeat: now is when most with scarce interest are exposed to climate stuff -and Mann dedicates himself to denigrate others’ opinions, thereby exposing them. It’s self-debasing.It’s the whining face of the climate wars.

    • You got to be kidding me. Have you been sleeping through all the media around Mann that the deniers started? After all they attacked him and even brought him to court. Ofc he is pissed, I would too with the kind of ridiculous witch hunting that has been going on. If anyone doesn’t speak about science its the Koch funded think tanks and all the deniers who seriously need to pull their head out of their ass.

      You come across as yet another shill with ad homin attacks against Mann, and hence is just another denier defending fossil fuel interests.

      • omnologos Says:

        JCL – just to clarify, Mann is free to talk about anything he likes, and he is also free to feel embittered and surrounded by people that hate him to their guts. I am sure he has very good reasons for that. That is not my point.

        My point is that Mann has got himself so entangled into that “war”, we only hear from him (=websites like Live Science reach out to him asking for copy) uniquely for low-level polemics.

        Sounds like if the journos need an attack dog, they call for Mann. Is that a good way to make one progress his scientific career? I think not.

        • Why do you think we only hear from him about these matters which you feel does him no credit? Perhaps it has something to do with the fact that media in general don’t like to report on boring complex and detailed science but needs headlines? In that sense Mann is just what they need, and I feel he is very capable of getting across the message with credibility considering his track record of science.

          You have a personal attention span problem if you are unable to get the message because you can only see the man (Mann). He is still talking about the settled science, no matter how you feel he is basking in glory or whatever makes you feel his message isn’t important. THAT is not Mann’s problem, that’s yours.

          • omnologos Says:

            JCL – the LS article came out because of the AR5 date.

            Can you imagine doctors having the chance of being in the spotlight because a new vaccine has come out, spending all their time to whine about anti-vaxxers? Me neither.

          • But you cant compare those, doctors are often believed when they say a vaccine is good for the people. We still have a problem getting politicians to actually act on climate change and part of the blame is that anti-science still has too much political power. I perfectly understand him talking about deniers running their campaign, especially since he is personally attacked by them as if doing science was suddenly a crime.

          • omnologos Says:

            JCL – I don’t think the meaning of my doctor/vaccine example got through.

            Anyway, if anybody is worried about the planet’s climate, the last thing to do is waste time explaining to people the ideas of people who are not worried about the planet’s climate, and especially in very unflattering terms.

            CC has disappeared from many people’s radar, so this chance by Mann should be considered forever lost.

    • Glenn Martin Says:

      Don’t you ever get tired of being wrong?

  2. andrewfez Says:

    …but one Mann stands in their way…

  3. Having met Michael Mann, I can say that he is anything but embittered. He speaks to packed houses, signs lots of books, and basically has a great time interacting with the public.

    And when he wins big judgements against the CEI and NRO, I’m sure that he’ll have a great time auctioning off all their stuff on eBay.

    • omnologos Says:

      caerbannog – perhaps he’s got to improve his writing style. Everyone with a little media savvy knows that if all you do is talk about your opponents’ remarks, all the reader will get is…a list of your opponents’ remarks. Because if you spend time to rebuke them and nothing else, it means those remarks are _very_ important.

      Imagine if the HST guys wrote about their astronomy by always making a list of how wrong the astrologers are…as I said, it would not be science, just empty polemics.

      • anotheralionel Says:

        Omno’, it would seem Michael Mann really gets your goat.

        Your argument from assertion that Mann is an embittered soul is beyond parody given the themes on your own web site.

        Also it appears that you are not slow in casting aspersions and with far less provocation.

        Don’t forget that Mann has, after years of painstaking work, not least in working towards an understanding of science and the scientific method but in his dendroclimatology work that has yielded a valuable insight into temperature development over the last millennium and now further back.

        To be sure there was a very small error in one part of the resulting hockey stick chart that was picked up on by a mining engineer with a smattering of statistical knowledge who then proceeded to blow the whole thing out of proportion and cry foul. The only foul was in that mining engineers subsequent behaviour making a thorough nuisance of himself FOIAing for data in a method tantamount to a DOS attack on the unwary recipients.

        The fact that science does not work that way and that the mining engineer flew in the face of reasonable behaviour, considering he already had said data, should make one wary of believing his side of the story.

        Mann suffered greatly as a result, a whole publishing industry and bloggers making capital out of this manufactured controversy resulting, why would you expect Mann not to counter the outrageous lies promoted by his protagonists. They chose to be protagonists when Mann would really rather have simply got on with more science. But of course this was part of the devilish plan, throw impediment in the way of science to slow down the messengers.

        And then of course here are all the other hockey-stick type graphs developed using other methods and proxies that more or less agree with Mann’s work.

        Would you keep quiet and take it, particularly when an entity tries to take legal action.

        Sorry, but Mann’s protagonists deserve all the criticism they get.

        Some insight into omno’s cognitive framework, and dissonance:


        Did you really write this:

        And so for example, AGW is logically fallacious as it has providential undertones. In other words, for (catastrophic) AGW to be upon us right now, something akin to a God or gods (or god-like creatures) has/have to be taking care of us. Because for (catastrophic) AGW to be happening, several amazing coincidences must have recently happened:…

        Oh! I see that you did:


        My! My! What a long list of straw-men and argument from absurdity.

        Now that I have entered the arguments I suppose that I can expect an inquisition. This seems to be your style as even David Attenborough falls foul of your ire.

        Tree of life, maybe you would prefer the way that Richard Dawkins approached this in ‘The Ancestor’s Tale: A Pilgrimage to the Dawn of Life’.

        • omnologos Says:

          anotheralionel – it seems you want to put me writing in my own blog (average reading is around 500/day) and in my own time on par to Michael Mann writing in Live Science to a much wider public for a very special occasion.

          What can I say, thank you very much.

          As for the “logical impossibility” page, I know that many people don’t get it, and I know that the people that don’t get it won’t understand it even if I explained it with pictures. So I shall leave you content in your ignorance and satisfied in your rhetorical failure (see above). Another miracle soon to be added: AR5 WG1 will be found in total, absolute, perfect, complete agreement with years and years of SkS writing.

    • greenman3610 Says:

      that will be a sweet day

  4. ‘conservative’ IPCC estimates…

    • Excellent talk by Mann. He really has a perfect point about risk management, that we buy insurance for our houses even though its exceptionally small chances for it burning down. We really need to take the risks of climate change in the same view, only its really the whole ecosystem and civilization that is at stake here. I mean if there was even a tiny 1% chance of a meteor hitting earth we’d be manning all stations to get that thing blasted or moved to another course. But now there really is a 95% chance of climate change affecting our lives in major ways.

    • astrostevo Says:

      Great interview and clip there. Thanks earlbramleyhoward. Bookmarked. 🙂

  5. neilrieck Says:

    Micheal Mann man is a hero scientist and anyone who disagrees obviously views science trough the prism of politics. I read his book “the hockey stick wars” last year and found it clear, concise, and well referenced.

    As for the so-called “warming hiatus”, let me put it in terms that scientifically illiterate people might be able understand: your wife wants to cook a Thanksgiving turkey so she preheats the oven to 375 degrees then pops in the bird. The oven thermostat cycles on-off-on to maintain the desired temperature. When the thermostat is in a cycled off phase, you could say this is a “warming hiatus” and yet it is possible to burn the bird because it is still hot. In fact, insulation around the oven’s interior means the bird could dry out, or burn, in the event of a power failure.

    In this metaphor, we are the cooking turkeys and CO2 is the oven insulation.

  6. […] CMCC; Skeptical Science; Climalteranti; Real Climate; Michael Mann; Greg Laden (grafici); da Climate Crock il solito Per fortuna che Silvio c’è, tanto sto all’estero trasuda odio verso Michel […]

  7. mbrysonb Says:

    I’m really quite interested in the form of cognitive disorder being displayed by Omnologos here. The word itself (Omni = all + logos = word) suggests something I’m sure is unintended (all words?!).

    Dr. Mann has both a brilliant record as a publishing scientist, and the energy and commitment to engage simultaneously in a critical public discussion, despite the calumnies and distortions and sheer abuse that’s been heaped on his head. He had a choice, when the IPCC drew so clearly and effectively on his (and his colleagues’) work to conclude that recent global surface temperatures are exceptional over a very long period of time. Statistical nit-picking aside, multiple reviews of that work and new analyses drawing on further data continue to confirm and extend his results.

    He could have withdrawn from the fray and focused only on his own work as a scientist (he could have been what Omnologos apparently would regard as a ‘good boy’ and just kept on writing up good scientific work). But instead he has stepped into the public debate (where absence is equated with concession and retreat) and pushed back against the lies and distortions that continue to delay the policy response this issue so desperately demands.

    But Omnologos seems to think that criticizing your opponents and replying to your critics is simply beneath any true, pure ‘scientist’. A better recipe for complete ineffectiveness I can hardly imagine. For the rest of the schoolyard barbs and whining, all I can say is, if it pisses people like the self-styled ‘Omnologos’ off, he must be doing something right.

    • omnologos Says:

      mbrysonb – opining about my internet monicker is usually accompanied by a general lack of interest in actually reading what I write. But I am feeling a good boy myself this morning so I will explain in points even Broncos haters would understand.

      1. AGW has been going way down in the public’s interest, judging from what shows up in the newsmedia

      2. However, the IPCC publication deadline is still capable to generate headlines

      3. IOW since the IPCC has fixed dates for when to get its reports out, the newsmedia will talk about that as a matter of course, thereby recapturing the public’s interest for AGW, at least temporarily

      4. LiveScience decided to piggyback on the IPCC news by offering a free space to Mann to say anything he wanted, in full knowledge more people would read it than, say, if published six months ago or hence

      5. IOW Mann was given the occasion to get some AGW message across to many more than usual

      6. Unfortunately, the only message that comes across is that some people have been making Mann feel very crossed, and they have made a series of statements that Mann himself has the courtesy to explain to the public for them.

      7. The average reader with little AGW interest has likely reacted like for most negative campaigning, and is convinced now that AGW is a nasty area where people insult each other and that it’s better to stay away from it.

      8. Mann’s LS piece’s contribution to avoid catastrophic AGW is extremely likely going to be exactly zero.

      9. In the meanwhile, the public’s attention will move on to something else.

      It’s like catching the ball alone a few yards from the touchline and then proceeding to do some celebratory dance routine in order to mock the other team because of some past bad blood with them INSTEAD OF scoring.

      • redskylite Says:

        omnologus – The IPCC AR5 report was designed to educate, advise, help world governments and leaders about the state of the climate and man’s contribution to it (in the view of 600+ specialists from many different geological areas), not to grab headlines and public attention. There is a strong chance that mankind is on the path to causing extinction of many species of co-inhabitants and possibly our own by continuing to exploit fossil fuels and by producing GHG’s (this maybe a long time in the future and not seem urgent to you). What do you believe in ? (do you want to continue with coal and oil ? are you against wind, geothermal and solar) I just see you criticise and put down everything and everybody. Do you just enjoy argument like the Monti-python parrot sketch participants ? Do you deny the experiments done nearly 200 years ago that confirm GHG’s effects ? Sorry but I don’t get you at all. Please try saying something positive for once. Thank you positivity will be appreciated by me as I am very tired of listening to negativity.

        • omnologos Says:

          redskylite – I have mixed feelings on these topics. I can understand the enthusiasm for protecting the environment, yet my vision of it has been jaded by too many scams and even outright ruining of the environment resulting from various pushing towards being green.

          I am therefore particularly sensitized to the occasions when “green champions” shoot themselves in the foot.

          Forget about my motivations though, and see how by amazing chance or synchronicity, Salon is saying the same things I stated above, in a more wider context:


          So the message to advocates is clear: Avoid rhetoric or actions that reinforce the stereotype of the angry activist. Realize that if people find you off-putting, they’re not going to listen to your message. As Bashir and her colleagues note, potential converts to your cause “may be more receptive to advocates who defy stereotypes by coming across as pleasant and approachable.”

          One might even conceive a scenario where Mann has been trapped in his “anti-deniers bitterness” by very clever and very manipulative people who simply understood how to make him shoot himself in the foot.

          • You didn’t really reply to the question, but rather just told us again how the “greens” are shooting themselves in the foot and generally being a nuisance. That isn’t constructive criticism, that’s just another ad hom at a group of people.

            So perhaps we should reformulate the question:

            Do you believe that CO2 is causing global warming, or is it a natural process?

            Do you believe that global warming will affect you personally or your children (if you have any)?

            Do you believe humanity should take action on this problem? (if you believe it to be a problem at all).

          • omnologos Says:

            Jcl – those questions are OT -and if I answered them a nice soul here will claim I’m trying to focus attention on myself

          • omnologos Says:

            Eheheheh…three negatives for quoting Salon – I shall try Mother Jones 😉

          • I don’t see why they are OT with regards to why you want to spend time attacking “greens” and Mann over coming with constructive ideas about the problem of global warming. You seem to be an intelligent person with words so perhaps you can enlighten us on how you got convinced that AGW is “noise” in your life and not something we should strive towards solving? Clearly you don’t respect the scientists – and that is ok, some people we like – some we don’t – but there is a real problem if you don’t respect the science either. Perhaps you had an unfortunate episode in your years in school? I’d really love to know how a person can be so convinced that this particular branch of science isn’t right while another one explaining e.g. electrons in a way that we can use its science to make iPads do.

            I am sure you will keep posting on these articles so instead of just coming across as the “person in opposition” all the time, perhaps you can enlighten us with your story so we can understand this?

          • omnologos Says:

            You’re making lots of assumptions and statements – how about this …in the unlikely circumstance greenman dedicates a post to me (can’t imagine why though -my main contribution is finding long lost documents by chance and obstinacy) I’ll reply to your satisfaction. Hope that doesn’t happen 8)

  8. redskylite Says:

    Good Job Mike Mann. I was fairly neutral on AGW/Climate Change until I had time to study the field, which I have been doing since leaving work in 2008. I now have firmly taken sides and realise the size of the problem, which despite of all the complexities is quite simple in my view. I have seen many comments from readers in reply to unbiased media IPCC AR5 reports disputing it (I imagine they are not climate scientists). Quite a few talk of scientists saying we were heading for a little ice age a few years ago (why should we believe them now ?). My own late sister also believed this (and many followers of Madam Curry also argue this too). I now see the LIA report was mainly spread by the “Climate Depot”, which is sponsored by a US conservative group in Washington (who are in turn sponsored by Exxon/Mobil amongst others, it was based on the theory of one Danish scientist (not a climate scientist), and yet it stuck in the minds of so many. How low can these selfish interest groups get ? – I think a lot of the public are past convincing (although we should never give up) and look to schools and teachers to get the honest science across to our future generations. This is the most important thing in my opinion.

  9. anotheralionel Says:

    My vote is to ignore omno in future he is only here to argue with whoever about whatever and there is no future in that.

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