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Lost in translation: confidence and certainty in climate science

In the lead up to the release next month of the Intergovernmental Panel on Climate Change’s (IPCC’s) Fifth Assessment Report we are exploring concepts of confidence and certainty in climate science. You…

Certainty about humanity’s influence on climate change has been steadily increasing. carnagenyc/Flickr

In the lead up to the release next month of the Intergovernmental Panel on Climate Change’s (IPCC’s) Fifth Assessment Report we are exploring concepts of confidence and certainty in climate science. You can find the other articles here

“Virtually certain”, “extremely likely”, and “high confidence”: these terms get bandied about in climate science, but what do they really mean? And what do they mean for us?

The previous IPCC report (AR4) from 2007 expressed “very high confidence” that global average temperature increases were very likely due to the observed increases in greenhouse gases concentrations.

Various leaked draft reports suggest that in the imminent fifth assessment, our understanding of the human causes of global warming has strengthened. The leaks suggest the upcoming report could raise that level to “extremely likely” or even “virtually certain”.

In this series we have discussed confidence and likelihood. These are used to communicate the degree of scientific certainty in key findings.

In the IPCC reports, confidence is expressed qualitatively and tells us how certain we are that scientific findings are valid. The level of confidence is determined by the type, amount, quality and consistency of evidence. A “very high confidence” means that there is at least a 9 in 10 chance of a finding being correct.

The scales of scientific confidence used by the IPCC http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch1s1-6.html

The certainty of scientific findings is then described using likelihoods. Findings are assessed probabilistically using observations, modelling results or expert judgement. They are assigned a term from a scale ranging from exceptionally unlikely (less that 1% probable) to virtually certain (more than 99% probable).

IPCC measures certainty using the likelihood scale. The highest scientific certainty we can convey is virtually certain (99-100% probability). http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch1s1-6.html

The IPCC uses these scales to convey specific information about our understanding of, and confidence in, scientific findings. Results with low confidence can be framed as such, and are treated as areas that need further investigation. Conversely, scientific findings that are backed up by multiple, consistent and independent lines of high-quality evidence are communicated with high confidence.

It’s understandable that terms like “virtually certain”, “extremely likely” and “very high confidence” create some confusion as to how sure climate scientists are about anthropogenic climate change.

We are “virtually certain”, for example, that there will be an increase in the frequency and severity of extreme high temperatures. At first “virtually certain” might sound unclear. It might sound a little confused, or perhaps that the fundamental science isn’t quite settled yet.

But as we have shown in our previous pieces in this series, the use of the terms “virtually certain” and “extremely likely” illustrates the vast body of consistent scientific evidence around climate change that has been established over the last 150 years.

Often commentators point to remaining uncertainties in our understanding of climate change as a reason to delay on action. But our certainty has been steadily increasing. In 2001, the IPCC concluded that the human influences on the climate were likely (greater than 66% probability) already detectable. This increased to very likely (greater than 90% probability) by the 2007 IPCC report.

This trend is clear. The upcoming report will likely deliver an even stronger statement on the human role in climate change, close to the highest level of certainty we can communicate and reflecting the high level of scientific consensus.

Climate change is clearly a broad, complex problem requiring consideration from scientists, politicians, communities and individuals. But the language employed by the IPCC tells us that human-caused temperature increases is a well-understood theory, comparable to our understanding of gravity.

With this degree of scientific confidence, it’s time to stop suggesting that any remaining scientific uncertainty is what’s holding us back from decisive action on this increasingly urgent matter. With so much at stake, do we really want to bet against these odds?

Join the conversation

104 Comments sorted by

    1. Felix MacNeill

      Environmental Manager

      In reply to Michael Shand

      I second that - simple plain speaking and common sense.

      Seeing the slate is still clean, can I suggest, in advance, a rigorous 'don't feed the trolls' policy?

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  1. George Michaelson

    Person

    If I am told I have a one in ten risk of something, I certainly pause to think about its consequences. If very low confidence equates to a 10% chance something is right, I wouldn't discount it entirely. For anything repeated, 1 in 10 equates (in my mind) to 'amost certainly will be seen, if I do this enough'

    However I notice this is a non linear scale.

    Its noticeable that the 10% figure in likelihood is also a non-linear scale. I cannot impute its value in the 'middle' of this scale as well as I can on the other, where my confidence around 1 in 10 is quite different to 10% likelihood, by the value of the words against 10%.

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  2. Geoffrey Henley

    Research Associate

    "But the language employed by the IPCC tells us that human-caused temperature increases is a well-understood theory, comparable to our understanding of gravity."

    This is nonsense. None of the much vaunted models predicted the observed slow-down in global temperatures. According to argo data, the models are also signifcantly overestimating the rate of ocean heating.

    If the models remain unvalidated, then the only conclusion is that the factors that lead to global climate change are still not well understood.

    Apart from this, the IPCC has been shown to be a compromised organisation. Several influential IPCC scientists have been shown to have strong links to environmental activist organisations such as WWF and Greenpeace so their objectivity must be called into question. The previous IPCC was contributed to by a number of inexperienced scientists promoted to levels way above their competence.

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    1. Mike Swinbourne

      logged in via Facebook

      In reply to Geoffrey Henley

      Nonsense yourself Geoffrey.

      How about you take a good hard look at the Gravity models as well. Notice anything? Oh yeah, they aren't perfect either, and there is a hell of a lot that we don't yet understand about gravity. I don't see you questioning the theory of gravity though. Why is that? Want to question evolution? There's a lot about that we don't understand as well. Quantum physics anyone?

      And the rest of your post about the IPCC etc - that's just more of your usual denier nonsense. Strong links to WWF and Greenpeace huh? And that calls their objectivity into question? I have to ask - I haven't seen you making the same criticism of your denier buddies and their connections and questioning their objectivity because of it.

      But then, consistency, objectivity and rationality are not the hallmarks of your average denier - and Geoffrey is a very average denier.

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    2. Dennis Singer

      Student

      In reply to Geoffrey Henley

      The IPCC don't do science. They manage the creation of summary reports of the state of knowledge of climate science.

      "None of the vaunted models...etc" your time interval is too short to separate natural variability from a predicted trend of ~0.15 deg C per decade. You need about 30 years of data before you can make the sorts of pronouncements you're making.

      According to argo data, there is a massive accumulation of thermal energy in the oceans - therefore, global warming's occuring.

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    3. Christopher Nheu

      logged in via Facebook

      In reply to Geoffrey Henley

      Excellent Geoffrey. Your source... I mean. No "frakking" consensus? Like as though there wasn't conflicts of interest there.

      Besides, I'd much rather heed the words of an environmentalist with a "conflict of interest" than that of an oil baron. I don't think it's so bad that he/she would have a vested interest in saving our environment, I'd like to think most of us do!

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    4. Mike Swinbourne

      logged in via Facebook

      In reply to Geoffrey Henley

      Goodonya Geoffrey. Providing a link to a denier blog as support for your position.

      I haven't laughed so hard for years.

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    5. Geoffrey Harold Sherrington

      Boss

      In reply to Mike Swinbourne

      Mike,
      What an ignorant comeback.
      I guess you have read the material presented and can affirm that it is nonsense.
      You guys have to realise that it's not the cover of the book that you look at, it's the contents.
      Sorry, the childs' game of "go to the naughty corner for reading that" is over. It's not unusual these days to get a better analysis on blogs that you sneer at, than it is on mainstream blogs like RealClimate. Remember it?
      I'm looking forward to your learned, scientific destruction of the material I presented. If you can't add insight to the comments, don't press the Go button.

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    6. Mike Swinbourne

      logged in via Facebook

      In reply to Geoffrey Harold Sherrington

      Look forward all you like Geoffrey, but your comments will not goad me to read something from a denier blog. Unlike you, I respect my brain cells to much to subject them to that sort of nonsense,

      Try linking to a science paper written by a scientist and published in a respected peer reviewed journal that has also stood up to scrutiny by other scientists. You know - something with credibility.

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    7. Geoffrey Harold Sherrington

      Boss

      In reply to Mike Swinbourne

      Not much logic there, Mike. You introduced the bigoted term about denialist blog. My more experienced & open mind accepts good data from wherever it can be found. For example, how do you handle a new paper in a pre-publication release? Do you ignore it until it is peer reviewed, a process that can take a year with easy recalcitrance?
      How do you handle information that is not the basis for a paper, like a weekly udate of polar ice extent?
      C'mon, now, you know you are arguing from a diminishing viewpoint as the modern blog is replacing the much abused old peer review system. Do keep up with the times.

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    8. Mike Swinbourne

      logged in via Facebook

      In reply to Geoffrey Harold Sherrington

      "......My more experienced & open mind accepts good data from wherever it can be found....."

      Like I said Geoffrey, you are a funny man. When you make such obviously incorrect statements I cannot stop myself from laughing long and hard. You accept data all right - but you have a very effective filter which only allows that information that you want to hear, while rejecting anything which questions your preconceived notions. All you do is trawl around the deniersphere looking for things that you think validate what you have already decided to be true. That much is obvious, because all you ever do is link to opinion pieces from denier blogs, and never provide anything like real science. And then you make foolish claims like blogs being better than peer review.

      Your mind isn't more experienced Geoffrey - it is well past it's "best by date".

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    9. Brandon Young

      Retired

      In reply to Geoffrey Harold Sherrington

      "the modern blog is replacing the ... old peer review system"

      You have to be able to switch off most of your intellect to propose this nonsense. Subjective argument replacing accountable argument.

      Is it still possible to honestly get the logic so upside down?

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    10. Geoffrey Harold Sherrington

      Boss

      In reply to Brandon Young

      But Brandon,
      It's happening. In real life.
      It is becoming increasingly common for the authors of papers to show a pre-release version on a blog before the final polish and submission. They can get early feedback that way and increase their chances of acceptance.
      As for peer review, I do that also, but I have read of people whose submitted papers took a year to review, partly because (in 2 notable cases), the papers were rebuttals of another paper. The process was slow because the Journal selected an author being rebutted, as a reviewer. That smells of a system in its failing years and getting somewhat desperate.
      But that's climate work. Forever dragging others down. Ref Climategate and the evil connivings therein.

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    11. Brandon Young

      Retired

      In reply to Geoffrey Harold Sherrington

      It is a failure of intellect to not be able to distinguish between rational and irrational argument. Mentioning "Climategate" suggests you are either unable or unwilling to do so.

      At the moment I think it is more a case of "unable" for you, which would mean no amount of reasoning could lead you to a rational conclusion.

      On the other hand, if you can see the difference but are just feigning ignorance for the fun of being provocative or persuasive, there might be a chance you get bored with that and start to participate in serious argument.

      Cheers, either way

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    12. Mike Swinbourne

      logged in via Facebook

      In reply to Brandon Young

      Brandon

      This is how Geoffrey works.

      He has a preconceived notion of whether or not climate change is real; based entirely on ideology rather than any evidence based science.

      He cannot maintain that view if he read science, because the science and the evidence is quite emphatic - he is wrong. That would shatter his fragile ego, so he must adopt an extreme position based on cognitive dissonance. The science says he is wrong, so he therefore rejects the science. Given that science is based…

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    13. Brandon Young

      Retired

      In reply to Mike Swinbourne

      @Mike Swinbourne

      Absolutely. Very well said. I appreciate and agree with all of that.

      While it is fun to deconstruct his irrationality, I think it is valuable to not simply dismiss him as a skeptic, but to also value him as a skeptic that is willing to put his irrationality to public scrutiny, not aware or not caring that all of us to his Left can see through him and his arguments.

      This may offer us some insight into how the irrational mind works. In turn it may allow us to better understand how to bring the irrational minds along with us to see, firstly, how much danger humanity faces from climate change, and secondly, the best way to counter that threat.

      So rather than scare him off, I welcome more of his garbage arguments.

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    14. Mike Swinbourne

      logged in via Facebook

      In reply to Brandon Young

      I wish I could agree with your views about potentially bringing the pseudo-sceptic along with us Brandon, but alas I cannot.

      People like Geoffrey are the climate science version of creationists. And like creationists, it is impossible to shake them from their ideology, because they just keep reading the writings of similarly deluded individuals and having their ideology reinforced.

      Unfortunately, unlike creationists who are just harmless fools who cannot influence anything of importance other than the education of their own children, climate deniers can affect everyone. The best approach is to concentrate on educating young people in the sciences so they don't end up like Geoffrey.

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    15. Brandon Young

      Retired

      In reply to Mike Swinbourne

      Yes, but being on the Right, Geoffrey does not even realise that everyone to his Left is less deluded than him, and that ultimately there is objective truth and enlightenment at all. We are not aiming for him, but just enough of those in the middle to constitute a critical mass of political will for a rational response to climate change. The swinging thinkers, if you will.

      And yes, better education would certainly help, but we do not have the time for political will to build over a generation, and education can not sufficiently overcome the negative effect our media has on the psychology of people in the middle.

      To me, the only hope left is an evolving online media that will incorporate fact checking technology in all content, including our posts, and hold all arguments up to rational scrutiny.

      Unfortunately, the battle to repress that evolution has been underway for some time, mostly outside the public domain, and those that are winning are not on our side.

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  3. David Arthur

    resistance gnome

    While we can split probabilistic hairs about the attribution of observed climate change, we can also be absolutely certain of the underlying mechanism (molecular physics and thermal energy transfer).

    Rather than posing the question as "can we discern and attribute climate change from our observations?", perhaps it is better posed as "given molecular physics and thermal energy properties, can we devise a non-anthropogenic cause for the observed climate change?"

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    1. Sophie Lewis

      Postdoctoral Research Fellow at University of Melbourne

      In reply to David Arthur

      Hi David, here is an interesting article that delves into these types of questions in relation to extreme events (http://link.springer.com/article/10.1007%2Fs10584-012-0441-5) - "The answer to the oft-asked question of whether an event is caused by climate change is that it is the wrong question. All weather events are affected by climate change because the environment in which they occur is warmer and moister than it used to be."

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    2. Felix MacNeill

      Environmental Manager

      In reply to David Arthur

      Yes - the complex/probabilistic bit is how/when/where - that it WILL happen in one way or another is the bit that is beyond argument.

      Interestingly it seems to be the very thing that AR5 is saying; there's no meaningful doubt about the basic mechanisms and processes, but it is turning out to be surprisingly hard to precisely predict local details, particularly over the shorter term.

      It seems that what this really means is that, while mitigation is a no-brainer, adaptation is looking distinctly trickier than many peole had hoped.

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    3. Geoffrey Harold Sherrington

      Boss

      In reply to David Arthur

      David, In that case, you should have the ability to produce an equation that quantitatively and correctly links global temperature with the concentration of GHG gases in the atmosphere.

      Sorry, there is none.

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    4. David Arthur

      resistance gnome

      In reply to Geoffrey Harold Sherrington

      Mr Sherrington, you've got a lot to learn: the reasons there is no simple one-on-one correlation between atmospheric greenhouse gas concentrations and global average surface temperature is that there are numerous other processes involved, all with their own time characteristics.

      For starters, here are a few such processes: net ocean heat absorbtion, net cryosphere (ice) heat absorbtion, reflectivity of atmosphere and surface (albedo), variations in heat dissipation rates due to extreme weather and volcanic events extending past the tropopause. After Prigogine, we should even look at weather variation itself as a dissipative system, and include that in our energy balance.

      There are, of course, many more factors to be considered.

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    5. Geoffrey Harold Sherrington

      Boss

      In reply to David Arthur

      David,
      Do you think I have not known this and worked with it for years? I'm not naïve, you know.
      So here's a question back. In the face of such uncertain effects, as to timing, let alone magnitude in what might be a chaotic system, why are we discussing probability?
      If you can't put an equation to it, how do you quantify uncertainty, except by guessing?

      BTW, I regard the current fad of changing the theme to "increased incidence of extreme events" as unproven. Every case I've looked at in depth…

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    6. Geoffrey Harold Sherrington

      Boss

      In reply to David Arthur

      David,
      I started an audit of the fundamentals that you say are "absolutely certain ... (molecular physics and thermal energy transfer). On the first day of looking, it became apparent that
      (a) a review of fundamental equations, their coefficients and exponents, was needed to see if modern computers able to carry more bits had been used to update these. It might have been done. I'm still looking.
      (b) it is far from clear that the relations between energy generated by GHG absorption of IR and frequency…

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    7. David Arthur

      resistance gnome

      In reply to Geoffrey Harold Sherrington

      Thanks Mr Sherrington, I'm relieved that you're not naiive. but your suggestion that I should have the"ability to produce an equation that quantitatively and correctly links global temperature with the concentration of GHG gases in the atmosphere" suggests, if not naivety, then at least a little facetiousness.

      Regarding use of probability to describe chaotic phenomena, probabilistic result are the results of applying statistical methods to problems where detailed mechanistic equations are not…

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    8. David Arthur

      resistance gnome

      In reply to Geoffrey Harold Sherrington

      If you can find a rebuttal to John Tyndall's results, go for it.

      Meanwhile, the correlation between atmospheric greenhouse gas content and climate as discerned from paleoclimatological studies is overwhelming. That you can pick holes in theorists' attempts to reproduce the results mathematically is irrelevant to the veracity of the observation.

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    9. Geoffrey Harold Sherrington

      Boss

      In reply to David Arthur

      David,
      Most palaeo reconstructions are calibrated againt an exiting temperature/time series. These series are deficient because of the widespread, subjective adjustment of what the thermometers showed.
      If you had studied this topic in the detail that I have, you also would be calling for an independent audit.
      If we are talking uncertainty on this thread, why not start from way back near the beginning, with the real uncertainty about temperature.

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    10. David Arthur

      resistance gnome

      In reply to Geoffrey Harold Sherrington

      Thanks for that response, Mr Sherrington.

      Here are a few palaeoclimatological studies you might want to investigate:
      1) Lithium isotope evidence for enhanced weathering during Oceanic Anoxic Event 2. Nature Geoscience, 2013; DOI: 10.1038/ngeo1875
      2) Cretaceous oceanic anoxic event 2 triggered by a massive magmatic episode. Nature 454, 323-326 (17 July 2008) | doi:10.1038/nature07076
      3) Slow release of fossil carbon during the Palaeocene–Eocene Thermal Maximum. Nature Geoscience, 2011…

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  4. Marc Hendrickx

    Geologist: The Con is a bad Monty Python sketch, for climate sense see: http://www.thegwpf.org/

    Of interest this Radio interview with Judy Curry on the topic at hand....

    'Uncertain' Science: Judith Curry's Take On Climate Change

    http://www.capradio.org/news/npr/story?storyid=213894792

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    1. Gerard Dean

      Managing Director

      In reply to Marc Hendrickx

      Heeeesssssssssss back!!!!!

      Gerard Dean

      Note to Moderator: I accept that my above comment has nothing whatsoever to do with the article above, however I am 'virtually certain' that many fellow commentators will be overjoyed to see the return of Mr Hendrix. Note that the use of 'virtually certain' is my pathetic attempt to link my comment to the article.

      Have a good week end moderator.

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    2. Marc Hendrickx

      Geologist: The Con is a bad Monty Python sketch, for climate sense see: http://www.thegwpf.org/

      In reply to Gerard Dean

      Gerard good to see that the entrenched opinions have not changed one iota since I was last here. And the range of authors is still very very narrow.

      It's a little like a gold fish bowl, which reminds me it's time to feed the fish.

      cheers
      M

      PS back ....but virtually certain it won't be for long

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    3. Gerard Dean

      Managing Director

      In reply to Marc Hendrickx

      Mr Hendrix,

      One way of keeping onside of the dreaded 'Moderator' is to stick to the point of the article. As far as I can ascertain the authors of the above article have attempted to make the point that the IPCC is 'virtually certain' of the facts of climate change.

      The authors might remember that the IPCC's earlier prediction that the earth was'virtually certain' to warm has been stymied by the earth's refusal to do so, despite increasing CO2 emissions.

      Frankly, if the authors want to improve confidence in climate science reporting, I am 'virtually certain' they should present the facts instead of playing word games.

      See, now the moderator is very happy because I have ruthlessly stuck to the point of the article.

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    4. Marc Hendrickx

      Geologist: The Con is a bad Monty Python sketch, for climate sense see: http://www.thegwpf.org/

      In reply to Gerard Dean

      Virtually: Adverb
      Nearly; almost.
      By means of virtual reality techniques.

      Virtual certainty an interesting concept, especially if achieved through "virtual reality techniques". Given the performance of climate models the later definition is most certainly apt.

      IPCC: Certainty by means of virtual reality techniques?

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    5. Geoffrey Harold Sherrington

      Boss

      In reply to Marc Hendrickx

      Judith Curry is a senior and respected climate change authority, a prominent contributor to past IPCC reports. In her interview (which I have read), she mainly deals with uncertainty. That was not her choice, it was the choice of the broadcaster after taking 2 days of interviews.
      Anybody here willing to challenge the credentials of Judith Curry?
      Anybody here disagree with her summary of uncertainty?
      She's rather more senior than the writers of the opinion piece above.

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    6. Marc Hendrickx

      Geologist: The Con is a bad Monty Python sketch, for climate sense see: http://www.thegwpf.org/

      In reply to Geoffrey Harold Sherrington

      Yes, sad that her contributions have been looked over by The Con's curators. Perhaps if she did a rap version she might get more attention like one of the authors above.

      A link to that video (your taxes at work) available via this post by prof. Bunyip.

      http://bunyipitude.blogspot.com.au/2012/10/karolygate-i.html

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    7. Gary Murphy

      Independent Thinker

      In reply to Marc Hendrickx

      We are certain that global warming is happening.
      We are certain that it is a result of greenhouse gas emissions.
      We are certain that the more we emit the worse it will be.

      Are you insinuating that because we are not very good at predicting the effects in the short-term we shouldn't worry about it?

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    8. Geoffrey Harold Sherrington

      Boss

      In reply to Gary Murphy

      Gary,
      We are certain that some global warming has happened.
      We are certain that for the past decade or more, the rate of warming has stagnated.
      We are certain that some of the change is due to greenhouse gas emissions, but we have been unable to quantify how much is.
      We are NOT certain that the more we emit the worse it will be (what is 'it'? I'm taking it as global warming.) There have been past periods of decades when the GHG were rising while the temperature fell. Maybe, if it happened before, it will happen again.

      That's about as much as science can say about the present levels of comprehension.

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    9. Gary Murphy

      Independent Thinker

      In reply to Geoffrey Harold Sherrington

      Wrong. The rate of warming has increased over the past decade. Oceanic heat content and ice sheet melting has increased. Because surface temperatures haven't consistently exceeded the el nino spike of 1998 yet does not mean the earth has stopped warming. But you have been around here long enough to know this by now. So you are being deliberately deceitful.

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    10. Geoffrey Harold Sherrington

      Boss

      In reply to Gary Murphy

      An increase in the rate would be an acceleration. I hope that you are not suggesting this, against the evidence
      There is inadeqate sampling in both time and space of ocean temperatures. One cannot conclude an increase. If there is an increase in the deep oceans, it is hard to describe a mechanism.
      I'm not being misleading. My working career was very much concerned with validation of measurements and as a team, we were highly successful. We did this in a dogma-free environment. I have no dog in the global warming fight. I just deplore poor science.

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    11. Dennis Singer

      Student

      In reply to Geoffrey Harold Sherrington

      "We are certain that for the past decade or more, the rate of warming has stagnated."

      Presumably you're referring to global average surface air temp. If so, you speak too soon - a decade "or so" is not a sufficiently long period of time to make a conclusion to a 95% likelihood that the warming rate is ~0.15 deg C. You need about three decades. There's too much natural variability and not enough linear rise in a 10 year period. Definitely no certainty in what you're saying. Certainty is a terrible word anyway.

      The radiative imbalance caused by a "pulse" of CO2 takes a long time to correct (hundreds of years), but the warming trend per decade can seem rather slight (fractions of a degree).

      Climate scientists have a good enough understanding of the climate system to show that there is >95% likelihood that the warming trend over the last few decades is not caused by a natural forcing.

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  5. Gerard Dean

    Managing Director

    I am trying to get a handle on a scientist's concept of 'virtually certain'.

    What better scientist to consult than our Chief Climate Commissioner, Professor Flannery. In 2007 he was 'virtually certain' that our falling rainfall volume wouldn't fill our dams, and even if it did rain, the earth would be so warm it would prevent runoff into those empty dams.

    Now that we have had record rains and our dams are near full, does that mean the 'virtually certain' was not so certain after all.

    Gerard Dean

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    1. Mike Swinbourne

      logged in via Facebook

      In reply to Gerard Dean

      I'll explain it to you Gerard.

      I am 'virtually certain' that you are a troll, and that you will mindlessly parrot the phrase "Jet A1" nearly every time you post.

      It doesn't happen all the time, but my model is not perfect and I am unable to predict the fine details such as exact content of every post. But the model is good enough to show that it is your favourite trolling phrase, and over the long term you will use it more often than not.

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    2. Gerard Dean

      Managing Director

      In reply to Mike Swinbourne

      Did someone say JetA1.

      They did, but alas again, there is no ethical justification for climate change aficionado's CHOOSING to burn the stuff for their own pleasure trips to Europe while simultaneously telling the farmers and machinists and cleaners and building workers and teachers to STOP burning fossil fuel.

      This is not a matter of trolling, it is a matter of ethical human behaviour.

      Of that, I am 'Virtually Certain'

      Gerard Dean

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    3. Dennis Singer

      Student

      In reply to Gerard Dean

      Commenters online always say the things that you claim Tim Flannery said. It sounds like you're saying those things just cause everyone else is.

      But I can't find any evidence that Tim Flannery said those things.

      Could you help me and point me to a reference?

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    4. Ken Fabian

      Mr

      In reply to Dennis Singer

      Dennis, it was said on abc Landline -

      PROFESSOR TIM FLANNERY: We're already seeing the initial impacts and they include a decline in the winter rainfall zone across southern Australia, which is clearly an impact of climate change, but also a decrease in run-off. Although we're getting say a 20 per cent decrease in rainfall in some areas of Australia, that's translating to a 60 per cent decrease in the run-off into the dams and rivers. That's because the soil is warmer because of global warming…

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    5. Michael Sheehan

      Geographer at Analyst

      In reply to Gerard Dean

      I wonder how wise the IPCC is in using the word "confidence" at all. The reason being that when we hear "95% confidence", we immediately presume they are using the standard definition, which is an range/interval constructed from actual data, either directly observed, or from simulations.
      While the IPCC's 'consensus' methodology is a perfectly valid methodology, they would be wiser to restrict discussion of results from that methodology to "agreement", leaving the use of "confidence" to describe the data, independent of the more subjective 'polls' taken from groups of scientists.
      This confusion is exacerbated by the number 95%, which also just happens to be the very two standard deviations from the mean, we are used to dealing with when discussing confidence intervals.

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  6. Gerard Dean

    Managing Director

    There is one thing that is 'absolutely certain' and that is that all the climate change activists and scientists responsible for the IPCC report will lecture the rest of us to stop burning fossil fuels, and then will choose to burn JetA1 for their own pleasure.

    Furthermore, I have 'very low confidence' any of them will offer us an ethical justification for their duplicitous behaviour.

    'More likely than not'

    Gerard Dean

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    1. John Schomberg

      logged in via email @gmail.com

      In reply to Gerard Dean

      Straw man argument. Whether or not they avail themselves of air transport irrelevant to the point.

      Even if the entire IPCC representatives swore of petroleum based transport, donned saffron robes and became vegan I suspect you would still manufacture a reason to ignore their advice.

      My friend Bob has been sitting on rock meditating on world peace and sustainability for 10 years. He's the real deal, Gerard. Why aren't you changing for him?

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    2. Gerard Dean

      Managing Director

      In reply to John Schomberg

      Mr Schomberg

      As a teacher, I am sure you understand the importance of credibility.

      My point with JetA1 fuel is that most of it is burnt not for mundane day to day energy that we need to drive to work, or take the train or power our milling machines or lights in the classroom - rather it is purely burnt for pleasure, to fly to Europe for an academic conference or holiday.

      Where credibility comes in is that if you really believe that burning fossil fuels must cease to stop dangerous climate change, how can you continue to burn fossil fuel for your own pleasure.

      It is a simple, ethical question that nobody on The Conversation has yet addressed, Of that, I am 'virtually certain', no absolutely certain.

      Gerard Dean

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    3. Geoffrey Harold Sherrington

      Boss

      In reply to Dennis Singer

      No, one can not. If you pay a penance for your carbon footprint, you have little certainty that your money will be spent as you might desire it to be. You can only be 'carbon neutral' if you know that remediation offsets of the correct magnitude have been applied - and probably that the offsets are capable of affecting the global temperature, which is very hard to prove.

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    4. Philip Dowling

      IT teacher

      In reply to John Schomberg

      It is a pity that teachers no longer can differentiate between of and off.

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  7. Sean Lamb

    Science Denier

    "We are “virtually certain”, for example, that there will be an increase in the frequency and severity of extreme high temperatures"

    I am virtually certain you actually don't have a clue. While CO2 probably represents a modest warming effect, it is neither the only or the most significant input.
    If solar activity declines to little ice age levels then temperatures will reduce, possibly increased CO2 levels will buffer this slightly.

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    1. David Arthur

      resistance gnome

      In reply to Sean Lamb

      If solar activity "declines" as you describe, you'll also need the other contributing factors, notably large-scale reafforestation (generally associated with depopulation), to get any much effect.

      On the other hand, if solar activity doesn't decrease as you describe, we'll cook, so you may get the depopulation.

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    2. Sean Lamb

      Science Denier

      In reply to David Arthur

      Or a simpler explanation - and simpler explanations are preferable - you are mistaking your group-think slogans for reality.

      I love the denial that puts decline in quotes - I mean obviously solar activity must be an absolute flat line, otherwise the whole scare campaign collapses.

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    3. Dennis Singer

      Student

      In reply to Sean Lamb

      "I am virtually certain that..." how did you arrive at that level of likelihood? Gut instinct?

      So your gut instinct trumps the likelihoods calculated with numerous GCMs?

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    4. Christopher Nheu

      logged in via Facebook

      In reply to Sean Lamb

      A troll if ever I saw one. Science denier?
      Please go live on your flat world at the centre of the universe.

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    5. Geoffrey Harold Sherrington

      Boss

      In reply to Dennis Singer

      Oh Dennis,
      Have you ever studied a CMIP?
      There is essentially no agreement between models and actuality. See my post above.
      Even the methodology of arriving at a comparison of climate models, then taking the mean of an ensemble, is statistically indefensible.

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    6. David Arthur

      resistance gnome

      In reply to Sean Lamb

      Thanks for those remarks Mr Lamb.

      My use of inverted comments is intended to indicate that I am less certain than you seem that the Little Ice Age was purely and solely attributable to declined solar output; observations at the time didn't look at total solar irradiance, the amount of energy the sun was putting out, but only at sunspot occurrence - an approximate indication only (http://en.wikipedia.org/wiki/Solar_variation#Sunspots).

      There's a nice helpful blog piece, with lots of informative…

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    7. Dennis Singer

      Student

      In reply to Geoffrey Harold Sherrington

      "There is no agreement"...depends on what "agreement" means to you. What exactly do you mean? At some level no model, of any sort, agrees completely with observations.

      If multiple climate models built and validated independently make similar predictions, that is certainly significant.

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  8. Geoffrey Harold Sherrington

    Boss

    Climate science is not lost in translation. It's lost before translation.
    The following link shows a comparison of numerous climate models, predicting or hindcasting the climate of near-surface temperatures, compared with actual, observed temperatures.
    http://www.geoffstuff.com/ChristyCMIP5.JPG

    Put simply, you are on risky ground talking about confidence when the main projections for the future lie outside the range of actual. You are, in effect, talking of a "Hypothetical" confidence because it does not match with reality. Under these circumstances, it is just silly to talk about "(5% confidence" and so on.
    First, you have to get your data right.

    Ref: http://www.drroyspencer.com/2013/06/epic-fail-73-climate-models-vs-observations-for-tropical-tropospheric-temperature/

    Dated June 4, 2013. Data are linearised to make comprehension more easy.

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    1. Marc Hendrickx

      Geologist: The Con is a bad Monty Python sketch, for climate sense see: http://www.thegwpf.org/

      In reply to Geoffrey Harold Sherrington

      Thanks Geoff,
      Why hasn't The Con posted Spencer's comparison? The disparity between models and observations a sure indication that said models are falsified. As Feynman say....if it disagrees with experiment, it's wrong.

      www.youtube.com/watch?v=viaDa43WiLc

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    2. Account Deleted

      logged in via email @drdrb.net

      In reply to Marc Hendrickx

      Because even John Christy disagrees with Roy that this well-known divergence in the tropical troposphere (not anywhere else in the atmosphere) is significant. Because there are other measurements which do show agreement, but Roy doesn't show them on his graphs. Because Roy has a long history of making strong assertions on weak evidence which turned out to be bogus. etc.

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    3. Account Deleted

      logged in via email @drdrb.net

      In reply to Marc Hendrickx

      I think these are referring to different things - that looks like a graph of surface temperature anomaly, not tropical tropo/stratosphere anomaly.
      If that grey envelope is a 2 sigma distribution then current temps are still within it - below the trend by about the same amount that 1998 was above the trend. Not very surprising considering El Nino 1998) tends to transfer heat out of the oceans, and La Nina (2008, 2010 in particular) to transfer it back again.

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    4. Marc Hendrickx

      Geologist: The Con is a bad Monty Python sketch, for climate sense see: http://www.thegwpf.org/

      In reply to Account Deleted

      hanging more epicycles off a failed model!

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    5. Account Deleted

      logged in via email @drdrb.net

      In reply to Marc Hendrickx

      So as well as climate change, you don't believe in the existence of ENSO?
      Anything else I should be ruling out of reality? The moon landings, perhaps? After all, James Hansen works for NASA, who can tell how far back in time the rot goes?

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    6. Marc Hendrickx

      Geologist: The Con is a bad Monty Python sketch, for climate sense see: http://www.thegwpf.org/

      In reply to Account Deleted

      I really am sick and tired of being told I don't believe in climate change by ignorant commentators on this site who have nothing more to do than make things up.

      I see that James you describe your self as a "Social Policy Researcher" so I guess you are used to making things up. How does it feel to be aboard the B-Ark?

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    7. Account Deleted

      logged in via email @drdrb.net

      In reply to Marc Hendrickx

      Perhaps you should consider why you give everyone on this site the impression that you don't believe in climate change, if this is not the case.

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    8. Marc Hendrickx

      Geologist: The Con is a bad Monty Python sketch, for climate sense see: http://www.thegwpf.org/

      In reply to Account Deleted

      Can't help your inability to read and comprehend.

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    9. Account Deleted

      logged in via email @drdrb.net

      In reply to Marc Hendrickx

      Perhaps you could point to some comment you've made on this site where you've indicated that you believe in what the scientific consensus on anthropogenic global warming is telling us. All you have to do is supply a link, and I will dutifully struggle to read and comprehend it.

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    10. Marc Hendrickx

      Geologist: The Con is a bad Monty Python sketch, for climate sense see: http://www.thegwpf.org/

      In reply to Account Deleted

      What is it telling you James?

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    11. Account Deleted

      logged in via email @drdrb.net

      In reply to Marc Hendrickx

      What is what telling me?

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    12. Dennis Singer

      Student

      In reply to Geoffrey Harold Sherrington

      Interesting graphs, I'm wondering why the observational data has such a smooth trend-line given that there is so much noise in the troposphere eg due to El Nino cycle. My understanding is that it has been very difficult to come to a conclusion about actual warming trends in the tropical troposphere for this reason.

      Also, I'm wondering what the uncertainty is supposed to be with each graph, and what scenarios/conditions are being modelled?

      I think that a more informative set of graphs would be simply the modelled vs actual total accumulation of thermal energy in the ocean-land-atmosphere system. After all, uncertainties in modelling do increase if the region of observation is smaller, eg if we're looking at a specific section of atmosphere in a narrow band around the earth.

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  9. Marc Hendrickx

    Geologist: The Con is a bad Monty Python sketch, for climate sense see: http://www.thegwpf.org/

    The listed likelihood terminology is really quite strange and demonstrates a strong bias towards alarm. The notion that an event is " exceptionally unlikely" and yet it has a probability in the order of 1 in 100 is a contradiction. It indicates the scale of probabilities has been poorly thought out and not properly calibrated to the real world.

    In landslide risk assessment the similar term "rare" has an annual probability of 1 in 100000. The term "barely credible" has a probability of 1 in a million.

    The later term is a good descriptor of the likelihood terminology used above.

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  10. Marc Hendrickx

    Geologist: The Con is a bad Monty Python sketch, for climate sense see: http://www.thegwpf.org/

    Based of the advocacy statement that concludes this article two thing are clear. First the authors would benefit from reading a recent comment piece by Tamsin Edwards. In The Guardian. This includes the following paragraph...

    http://www.theguardian.com/science/political-science/2013/jul/31/climate-scientists-policies

    I became a climate scientist because I've always cared about the environment, since a vivid school talk about the ozone layer (here, page 4) and the influence of my brother, who was green long before it was cool. But I care more about restoring trust in science than about calling people to action; more about improving public understanding of science so society can make better-informed decisions, than about making people's decisions for them. Science doesn't tell us the answer to our problems. Neither should scientists.

    The second is that neither appears to be familiar with the ALARP principal when it comes to risk management.

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    1. Gary Murphy

      Independent Thinker

      In reply to Marc Hendrickx

      When you are dealing with a very complex system which has positive feedbacks it is very risky to change it.

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    2. Geoffrey Harold Sherrington

      Boss

      In reply to Gary Murphy

      Gary,
      Can you name me a positive feedback that has been studied and reported well enough to be sure it exists and is large enough to be a significant factor in change?
      Do you know that estimates of climate sensitivity have been steadily falling since they were first discussed?
      Do you know that this might mean that positive feedbacks, if they exist significantly, might be offset by negative feedbacks? The surface sea temperature of the tropics seems to be influenced by a negative feedback, for example, that causes it to top out.

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    3. Marc Hendrickx

      Geologist: The Con is a bad Monty Python sketch, for climate sense see: http://www.thegwpf.org/

      In reply to Gary Murphy

      Gary FYI...via wiki

      "ALARP stands for "as low as reasonably practicable", and is a term often used in the milieu of safety-critical and safety-involved systems. The ALARP principle is that the residual risk shall be as low as reasonably practicable. It has particular connotations as a route to reduce risks SFAIRP (so far as is reasonably practicable) in UK Health and Safety law.
      For a risk to be ALARP it must be possible to demonstrate that the cost involved in reducing the risk further would…

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    4. Gary Murphy

      Independent Thinker

      In reply to Geoffrey Harold Sherrington

      Positive feedbacks in the climate system:
      Increased water vapour (greenhouse gas) in the atmosphere as a result of increased temperature.
      Ice sheets reflect more incoming energy than open water.
      Melting permafrost release very large amounts of methane (a very powerful greenhouse gas).

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    5. Gary Murphy

      Independent Thinker

      In reply to Marc Hendrickx

      That link is just an idealogical, denialist rant that flies in the face of the scientific evidence.

      Where do the authors say they want zero risk?

      Reducing emissions reduces the risk.

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    6. Marc Hendrickx

      Geologist: The Con is a bad Monty Python sketch, for climate sense see: http://www.thegwpf.org/

      In reply to Gary Murphy

      Stop the presses The Guardian and Tamsin Edwards now "Deniers"- Gary Murphy says so!

      From that "Denialist "rant from the "Denier" Paper The Guardian:

      "Even scientists who are experts – such as those studying the interactions between climate, economy and politics, with "integrated assessment models" – cannot speak for us because political decisions necessarily depend on values. There are many ways to try to minimise climate change (with mitigation or geoengineering) or its impacts (adaptation…

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    7. Gary Murphy

      Independent Thinker

      In reply to Marc Hendrickx

      So you don't like scientists who advocate policy?

      So why do you then link to a 'plan' written by a scientist who is clearly advocating policy?

      Is it different when you agree with the policy being advocated?

      Who do you work for Mark? A geologist from Newcastle - I wonder.

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    8. Mike Swinbourne

      logged in via Facebook

      In reply to Gary Murphy

      Gary

      To be fair on Marc, he is not an ardent denier like some. Marc actually accepts that the climate is changing and that humans are (at least partially) responsible. You just would not understand that based on the way he often cheers on the more irrational deniers and never takes them to task, in the same manner that he likes to take the CAGW crowd to task. If Marc was a little less hypocritical and a little more consistent in his criticisms, his position would become plainer.

      No, Marc…

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  11. Philip Dowling

    IT teacher

    it is clear that the authors have are much more up-to-date than me.
    The notions of repeatable identical stochastic experiments are no longer a requirement for determining probability. They obviously use the method preferred used by sports writers talking about the favourites on Saturday.
    Similarly the notions of logic once beloved by pure mathematicians that stated that no conclusion could be stronger than any preceding statement has been superseded by ideologically driven "scientists" whose main skill seems to be based on a more advanced form of joining the dots that most five year olds find entertaining for a few years before moving onto more advanced skills.

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    1. Geoffrey Harold Sherrington

      Boss

      In reply to Philip Dowling

      Philip,
      Well put. The authoritative guess is,in this branch of poor science, an entity able to produce statistical significance. Not.
      I'm pleased that there are still some people who see through the post-normal science junk.

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    2. Dennis Singer

      Student

      In reply to Philip Dowling

      Can you suggest a way to do "repeatable stochastic experiments"?

      And what has pure math got to do with science anyway. One creates models based on observations, the other is a study of invented abstract structures.

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  12. Peter Reefman

    Project Manager

    Thanks for an excellent article. As I read I reflected on times I've been asked my "views", and I've tried to make the people in the conversation aware of how to interpret the numbers. I think I'll now use an analogy like: Imagine you live on a REALLY busy road like Parramatta Rd or St Kilda Rd, and your driveway happens to be across from a small street. Studies have found that during peak hour your likelihood of having an accident while trying to scoot across St Kilda Rd etc into that street is "Extremely likely". None the less, you are determined to show that there is still uncertainty and the case is not "proven", and the studies had vested interests! So you'll do it with your eyes closed to prove that the studies are flaky. Oh, and put your children and grandchildren in the car with you. They probably won't need seat belts! Here's the keys to your car!

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    1. Marc Hendrickx

      Geologist: The Con is a bad Monty Python sketch, for climate sense see: http://www.thegwpf.org/

      In reply to Sophie Lewis

      The only problem of course is that in reality the likelihood in the example provided is NOT "Extremely likely" >95%. For all road crashes the fatality rate is on the decline. For 2011 in NSW it was 5 deaths per 100,000 population. By contrast cardiovascular disease for 2007 claimed 240 per 100000.

      The less than credible terminology above does not even cover the actual risk (0.005%). So it is an exceptionally poor analogy.

      The problem lies in the perception of risk. It seems Sophie and Ailee and Peter are biased heavily towards the henny penny end of the scale. It is a wonder how you are able to get out of bed in the morning, perhaps the tin foil hats help?

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  13. Mark McGuire

    climate consensus rebel

    It might be easier to explain the "certainty" if you deal directly with the public.

    Volunteers from Getup! could don sandwich boards with the slogan, "The end of the world is 95% nigh" and hand out pamphlets with those tables above.

    Maybe the UN-IPCC could include Lotto results for 2100 as well.
    That will make people look.

    Meanwhile, the rest of us will continue pointing & laughing at your gullibility.

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  14. Catherine Ayres

    Doctoral Candidate in Sociology at Australian National University

    It's a shame that many comments on articles like this so often descend into tired and pointless quibbling. I'm sure there are many readers like myself who appreciate the article but don't want to get dragged into relentless battles in the comments section, or are wary of feeding the ever-gluttonous trolls.

    Having said that, my thanks to the authors for this excellent series. Clear synthesis of some of the issues around scientific theories and terminologies from those working in the field are much appreciated by those of us interested, but not trained in such things. Great job.

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    1. Marc Hendrickx

      Geologist: The Con is a bad Monty Python sketch, for climate sense see: http://www.thegwpf.org/

      In reply to Catherine Ayres

      Catherine,
      Here's a challenge. Perhaps you (or the authors) can provide a succinct paragraph about how one rationally and logically differentiates between 99%, 95% and 90% certainty. It is missing in the article above. To many here it seems that this is a post modernist construct that has no basis in evidence based science. It's use in climate science highly unusual and it appears something designed to cover its many deficiencies.

      So please tell me, how is the difference between 99% and 95% certainty…

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    2. Brandon Young

      Retired

      In reply to Marc Hendrickx

      Hey Marc. I will give your challenge a crack, but I will rephrase the question as "Why can't you see any value in the decision to use a
      classification system for probabilities?" It is not quite a succinct paragraph, but it is all straight forward logic. Here goes:

      1) There are two types of thinking available to our minds: Rational and Irrational thinking.

      2) Rational thinking can deal with uncertainty. (It can take ideas, strip them of any value judgment, juggle them around, run what-if…

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  15. Davd Mitchell

    Hydrologist

    Thanks for the great article, to me this idea of scientific certainty/uncertainty and confidence is a major barrier to effective communication of climate change.

    A recent article in American Meteorological Society’s Bulletin of the American Meteorological Society.
    http://www.ametsoc.org/2012stateoftheclimate.pdf

    presents the current measured climate data and discusses the concept of Essential Climate Variables (ECV)
    To quote
    "44 ECVs covered the atmospheric, oceanic, and terrestrial…

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    1. Sophie Lewis

      Postdoctoral Research Fellow at University of Melbourne

      In reply to Davd Mitchell

      Thanks for the link David! This is the last in this series, but you're right, we just touched on these concepts and there is plenty more that could be discussed in terms of certainty and confidence.

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    2. Marc Hendrickx

      Geologist: The Con is a bad Monty Python sketch, for climate sense see: http://www.thegwpf.org/

      In reply to Sophie Lewis

      Yes that article by Judy Curry would help clear things up a lot. Perhaps The Con's curators would look into it. In the interests of free debate I'm sure Sophie and Ailie would support its publication here.

      here's that link again...

      http://journals.ametsoc.org/doi/pdf/10.1175/2011BAMS3139.1

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  16. MItchell Lennard

    Researcher - Distributed Energy Systems

    Firstly thanks to Sophie and Allie for a great series of articles.

    The debate so well summarised by these last two articles, and treated in far more detail by the Curry paper(s), is of course only a debate about one half of an equation. It is important to remember why the IPCC even bothered to try and estimate probability in the fist place. It was not because they wanted to build confidence in the results they where reporting but rather they know that policy makers ( us as it turns out) are looking…

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