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Winston2014 at 09:58 AM on 5 June 2014Models are unreliable
DSL,
"Models fail. Are they still useful?"
Not for costly policies until the accuracy of their projections is confirmed. From the 12 minute skeptic video, it doesn't appear that they have been confirmed to be accurate where it counts, quite the opposite. To quote David Victor again, "The science is “in” on the first steps in the analysis—historical emissions, concentrations, and brute force radiative balance—but not for the steps that actually matter for policy."
"Models will drive policy"
Until they are proven more accurate than I have seen in my investigations thus far, I don't believe they should.
The following video leads me to believe that even if model projections are correct, it would actually be far cheaper to adapt (according to official figures) to climate change than it would be to attempt to prevent it based upon the "success" thus far of the Australian carbon tax:
The 50 to 1 Project
https://www.youtube.com/watch?v=Zw5Lda06iK0
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Dumb Scientist at 06:53 AM on 5 June 2014Richard Tol accidentally confirms the 97% global warming consensus
It's astonishing that Energy Policy's "review" apparently didn't ask for a single example of the ~300 gremlin-conjured rejection abstracts.
"If I submit a comment that argues that the Cook data are inconsistent and invalid, even though they are not, my reputation is in tatters." [Dr. Richard Tol, 2013-06-11]
Not necessarily. Retracting errors is difficult but ultimately helps one's inner peace and reputation because it shows integrity and healthy confidence. When in a hole, stop digging.
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DSL at 06:33 AM on 5 June 2014Models are unreliable
Winston2014,two things:
1. What does Victor's point allow you to claim? By the way, Victor doesn't address utility in the quote.
2. Oreskes point is a no-brainer, yes? No one in the scientific community disagrees, or if they do, they do it highly selectively (hypocritically). Models fail. Are they still useful? Absolutely: you couldn't drive a car without using an intuitive model, and such models fail regularly. The relationship between climate models and policy is complex. Are models so inaccurate they're not useful? Can we wait till we get a degree of usefulness that's satisfactory to even the most "skeptical"? Suppose, for example, that global mean surface temperature rises at 0.28C per decade for the next decade. This would push the bounds of the AR4/5 CMIP3/5 model run ranges. What should policy response be ("oh crap!")? What if that was followed by a decade of 0.13C per decade warming? What should policy response be then ("it's a hoax")?
Models will drive policy; nature will drive belief.
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Winston2014 at 05:56 AM on 5 June 2014Models are unreliable
Have the points in this video ever been adressed here?
Climate Change in 12 Minutes - The Skeptics Case
https://www.youtube.com/watch?v=vcQTyje_mpU
From my readings thus far, I agree with this evaluation of the accuarcy and utility of current climate models:
Part of a speech delivered by David Victor of the University of California, San Diego, at the Scripps Institution of Oceanography as part of a seminar series titled “Global Warming Denialism: What science has to say” (Special Seminar Series, Winter Quarter, 2014):
"First, we in the scientific community need to acknowledge that the science is softer than we like to portray. The science is not “in” on climate change because we are dealing with a complex system whose full properties are, with current methods, unknowable. The science is “in” on the first steps in the analysis—historical emissions, concentrations, and brute force radiative balance—but not for the steps that actually matter for policy. Those include impacts, ease of adaptation, mitigation of emissions and such—are surrounded by error and uncertainty. I can understand why a politician says the science is settled—as Barack Obama did…in the State of the Union Address, where he said the “debate is over”—because if your mission is to create a political momentum then it helps to brand the other side as a “Flat Earth Society” (as he did last June). But in the scientific community we can’t pretend that things are more certain than they are."
Also, any comments on this paper:
Verification, Validation, and Confirmation of Numerical Models in the Earth Sciences
Naomi Oreskes,* Kristin Shrader-Frechette, Kenneth Belitz
SCIENCE * VOL. 263 * 4 FEBRUARY 1994
Abstract: Verification and validation of numerical models of natural systems is impossible. This is because natural systems are never closed and because model results are always non-unique. Models can be confirmed by the demonstration of agreement between observation and prediction, but confirmation is inherently partial. Complete confirmation is logically precluded by the fallacy of affirming the consequent and by incomplete access to natural phenomena. Models can only be evaluated in relative terms, and their predictive value is always open to question. The primary
value of models is heuristic.http://courses.washington.edu/ess408/OreskesetalModels.pdf
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heb0 at 05:41 AM on 5 June 2014The Skepticism In Skeptical Science
CollinMaessen - Thanks a bunch for the help. I've sent an edited version through the Contact page. Hopefully the raw format isn't too inconvenient.
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Dikran Marsupial at 05:30 AM on 5 June 2014Models are unreliable
Razo wrote "Thats a kind of calibration."
sorry, I have better things to do with my time than to respond to tedious pedantry used to evade discussion of the substantive points. You are just trolling now.
Just to be clear, calibration or tuning refers to changes made to the model in order for it to improve its behaviour. Baselining is a method used in analysis of the output of the model (but which does not change the model itself in any way).
"I said, narrower is better if you want to predict a number, or justify a trend. "
No, re-read what I wrote. What you are suggesting is lampooned in the famous quote "he uses statistics in the same way a drunk uses a lamp post - more for support than illumination". The variability is what it is, and a good scientist/statistician wants to have as accurate an estimate as possible and then see what conclusions can be drawn from the results.
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Razo at 05:16 AM on 5 June 2014Models are unreliable
Dikran Marsupial wrote "Models are able to predict the response to changes in forcings more accurately than they are able to estimate the absolute temperature of the Earth, hence baselining is essential in model-observation comparisons."
Thats a kind of calibration. I understand the need. People here were trying to tell me that no such thing was happening, and it just pure physics. I didn't know exactly how it was calculated, but I expected it. I know very well that "Models are able to predict the response to changes in forcings more accurately than they are able to estimate the absolute...".
"a constant is subtracted from each model run."
That's offsetting. Please don't disagree. Its practically the OED definition. Even the c in y=mx+c is sometimes called an offset.
"neither broader nor narrower is "better", what you want is for it to be accurate"
I said, narrower is better if you want to predict a number, or justify a trend. I mean this regardless of the issue of the variance in the baseline region.
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dana1981 at 05:13 AM on 5 June 2014Richard Tol accidentally confirms the 97% global warming consensus
He wants to take Cook et al. down, but he failed miserably. His error couldn't be more obvious - he created about 300 rejection abstracts out of thin air from a claimed 6.7% error rate, when in the entire sample we only found 78 rejection papers. This has been explained to Tol several times using several different methods, and he still can't seem to grasp it.
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Doug Bostrom at 04:49 AM on 5 June 2014The Skepticism In Skeptical Science
An excellent article, in my wholly unbiased opinion. :-)
"Unless the doubt is removed by your friend showing you a picture of Morgan Freeman standing on his porch."
And there lies the point where we discover the difference between Collin's "so-called skeptics" and the "pseudo-skeptic."
The so-called skeptic will rejoin with something along the lines of "I'll be; Morgan Freeman on your porch! Who'd a thunk it?"
The pseudo-skeptic will often follow the general path of first accusing you of having altered the photo, and then when you show it to be unaltered output from your digital camera will hypothesize that the digital camera manufacturer is in cahoots with you. More generously, they might offer that Morgan Freeman is an astounding artifact of camera malfunction.
Numerous variations abound on the overall theme of pseudo-skepticism, having in common the feature of starting as a straight line and then if necessary adopting the topography of a Klein bottle if that is what is necessary to avoid acknowledging the simply obvious.
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Composer99 at 04:49 AM on 5 June 2014Richard Tol accidentally confirms the 97% global warming consensus
Basically, it seems to me that Dr Tol doesn't really dispute the existence of the scientific consensus (either in the form of consilience of evidence or the form of consilience of opinion of practicing scientists).
It appears, rather, that he wants to take down Cook et al because... well, because reasons. (At least that is the best I can come up with.)
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CollinMaessen at 03:36 AM on 5 June 2014The Skepticism In Skeptical Science
You can always submit what you have via the contact page:
http://skepticalscience.com/contact.phpIf you submit It there I will eventually receive your feedback. You could also directly contact me via my website and start an email exchange with me about this:
http://www.realsceptic.com/contact/ -
Dikran Marsupial at 03:30 AM on 5 June 2014Climate is chaotic and cannot be predicted
Razo, as I have pointed out, climate (the long term statistical properties of the weather) is not necessarily chaotic, even though the weather is. Climate models do not try and predict the behaviour of a chaotic system, but to simulate it.
"How chaos could impact climate might be more like this, I think. If one could show that global warmimg is effecting the chaotic indicies that cause ElNino to the degree that it becomes a more frequent and long lasting event, ie, the regular weather, that could impact climate."
El-Nino is a mode of internal climate variability, it is one of the things that gives rise to the spread of runs from a particular climate model, but (at least assymptotically) it doesn't affect the forced response of the climate (estimated by the ensemble mean), which is what we really want to know as a guide for policy.
You clearly know something about chaotic systems, however your understaning of climate and what climate models aim to do is fundamentally misguided. Please take some time to find out more about the nature of the problem, as otherwise you are contributing to the noise here, not the signal.
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Dikran Marsupial at 03:21 AM on 5 June 2014Models are unreliable
Razo wrote "But I'm suprised that people use it when comparing models with the actual data."
Models are able to predict the response to changes in forcings more accurately than they are able to estimate the absolute temperature of the Earth, hence baselining is essential in model-observation comparisons. There is also the point that the observations are not necessarily observations of exactly the same thing projected by the models (e.g. limitations in coverage etc.) and baselining helps to compensate for that to an extent.
"its quite another to offset model runs or different models to match the mean of the baseline."
This is not what is done, a constant is subtracted from each model run and set ob observations independently such that it has a zero offset during the baseline period. This is a perfectly reasonable thing to do in research on climate change as it is the anomalies from a baseline in which we are primarily interested.
"You seem to be saying a higher variance is better. "
No, I am saying that an accurate estimate of the variance (which is essentially an estimate of the variability due to unforced climate change) is better, and that the baselining process has an unfortunate side effect in artificially reducing the variance, which we ought to be aware of in making model-observation comparisons.
"Having the hiatus within the 95% confidence interval is a good thing, but a narrower interval is better if you want to more accurately predict a number, or justify a trend."
no, you are fundamentally missing the point of the credible interval, which is to give an indication of the true uncertainty in the projection. It is what it is, neither broader nor narrower is "better", what you want is for it to be accurate. Artifically making them narrower as a result of baselining does not make the projection more accurate, it just makes the interval a less accurate representation of the uncertainty.
"Another thing to add, as I understand if the projected values are less than 3 times the variance, one says there is no result."
No, one might say that the observations are consistent with the model (at some level of significance), however this is not a strong comment on the skill of the model."If it is over 3 times one says there is a trend, and not until the ratio is 10, does one quote a value."
No, this would not indicate a "trend" simply because an impulse (e.g. the 1998 El-Nino event) could cause such a result. One would instead say that the observations were inconsistent with the models (at some level of significance). Practice varies about the way in which significance levels are quoted and I am fairly confident that most of them would have attracted the ire of Ronald Aylmer Fisher.
"Can one use thse same rules here?"
In statistics, it is a good idea to clearly state the hypothesis you want to test before conducting the test as the details of the test depend on the nature of the hypothesis. Explain what it is that you want to determine and we can discuss the nature of the statistical test.
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heb0 at 02:35 AM on 5 June 2014The Skepticism In Skeptical Science
This is an excellent article and will be a handy resource to link to every time someone gets pedantic about SkS and the meaning of "skepticism."
This article is concise, engaging and--I think--convincing. However, it has a tremendous number of grammatical errors and awkward wordings. The first part especially could do with more liberal use of commas. It really should be combed over if this article is intended to be a long-term reference. I wouldn't mind doing it myself, but I'm not sure the best way of submitting a proofread version.
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Razo at 02:26 AM on 5 June 2014Models are unreliable
So with regards to baselines.
I can understand the need to do it to compare models, less so with perterbations of the same model. But I'm suprised that people use it when comparing models with the actual data. Its one thing to calculate and present ensemble mean, its quite another to offset model runs or different models to match the mean of the baseline. This becomes an arbitrary adjustment, not based on any physics. Could you explain this to me please?
Also, Dikran you say
"Now the IPCC generally use a baseline period ending close to the present day, one of the problems with that is that it reduces the variance of the ensemble runs during the last 15 years, which makes the models appear less able to explain the hiatus than they actually are."
You seem to be saying a higher variance is better. Having the hiatus within the 95% confidence interval is a good thing, but a narrower interval is better if you want to more accurately predict a number, or justify a trend.
Another thing to add, as I understand if the projected values are less than 3 times the variance, one says there is no result. If it is over 3 times one says there is a trend, and not until the ratio is 10, does one quote a value. looking at the variablity caused by changing the baseline, as well as the height of the red zones in post 723, the variance appears to be about 2.0C, the range of values is about 6.0 (from 1900 to 2100). Can one use thse same rules here?
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Pierre-Emmanuel Neurohr at 01:38 AM on 5 June 2014President Obama gets serious on climate change
"Most importantly, we finally have a president who is a world leader."
We - the non-American part of the world - have a leader. You are very kind to let us know.Some of us could think that even if this plan was actually successful, Americans and their leader would continue to be the most climate-destroying persons on Earth, with something like 15 to 20 t of CO2 per person per year. The US and its leader would continue to set a bad example in all matters related to the climate of the Earth through their ever-increasing obsession for raw materials and energy overconsumption, which cannot but lead to more droughts and more flooding.
It takes quite a bit of extreme nationalism to manage to not see these facts. Orwell would either laugh or cry.
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CBDunkerson at 01:10 AM on 5 June 2014President Obama gets serious on climate change
actually thoughtful wrote: "The President's policies, while an improvement, are in the category of too little to late. And likely a smokescreen for approving Keystone XL - all the while lulling the sheeple into a false sense of complacency."
Actually, given how long he has 'delayed deciding' on Keystone XL it seems very likely to me that Obama will wait until after the congressional elections this November and then kill the proposal. If he were going to approve it he should have done so by now. Delaying allows Democrats in fossil fuel states to boost their chances of election by campaigning in favor of it. Then, once the midterms are over, Obama can kill it without impacting the balance of congressional power for the remainder of his presidency.
As to, "too little to late"... I'd say rather that Obama is enacting regulations which would force a rapid phase out of coal... if that weren't already happening without them. Natural gas, wind, and solar have been shredding the coal power industry in the Unitied States. That said, these new regulations should speed up the process. Thus far, coal plants have mostly been running to 'end of life' and then shutting down in favor of other sorts of power generation. These new regulations will force many existing coal plants to shut down before reaching their end of life.
The regulations don't go far enough to completely resolve U.S. emissions problems, but again... I don't think they need to. 'Market forces' are already taking care of that. The initial fall of coal was due to natural gas, but in the past few years natural gas power development has dwindled and solar has soared... last quarter new electricity generation in the U.S. was 74% solar, 20% wind, 4% natural gas, 1% geothermal, and 1% everything else. That's 95% renewable. Obviously it will take time to replace all the existing fossil fuel based power generation, but when nearly all new electricity production developed is renewable the changeover is inevitable.
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Razo at 00:46 AM on 5 June 2014Climate is chaotic and cannot be predicted
correction:
The key phrase is *'for certain values of the parameters'*, not 'oscillating unpredictably'.
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Razo at 00:44 AM on 5 June 2014Climate is chaotic and cannot be predicted
I seem to be being critisized for not making any assertion by the moderator and making false assertions by others. So I will try to make an assertion here, to at least be worthy of the criticism. ;-)
Firstly, my previous post was adding to the definition of chaos. Although I do not know why it would be rebuted, a rebuttal would be on my definition of chaos. I didn't touch the rest of the argument.
But now I will. It's seems to me that people are confusing randomness and mathematical chaos a little.
"For certain values of the parameters, the overall movement of the atmospheric air was oscillating unpredictably"
The key phrase is 'for certain parameters', not 'oscillating unpredictably'.
"Actually proving that these indices are chaotic is exceedingly difficult, but Tziperman et al. (1994) showed in a simple model how El Niño is likely a seasonally induced chaotic resonance between the ocean and the atmosphere."
The key phrases here are 'induced chaotic resonance', which I called 'alternative equilibrium configurations', and 'proving that these indices are chaotic is exceedingly difficult'. But then, I'm not sure if the next sentance is correct:
"Chaotic influences from oceans and volcanoes etc. makes both weather more unpredictable and creates the unpredictable part of the 'wiggles' around the average trend in climate"
That is, although volcanic eruptions are chaotic in the regular sense or the word and can impact the climate greatly, do they involve indicies that are chaotic at certain values? Also, I don't think the formation of high pressure air masses come about after thier chaotic parameters reach a critical value.
How chaos could impact climate might be more like this, I think. If one could show that global warmimg is effecting the chaotic indicies that cause ElNino to the degree that it becomes a more frequent and long lasting event, ie, the regular weather, that could impact climate. Or maybe if one could show that the pacific trade winds, that are presently causing a slow down of average global surface temperatures, are an induced chaotic resonance caused by global warming itself.(These are just absolute hypothetical ideas by me, I am not saying this is happening. the point is indicies reaching critical values)
Regarding Lorenz's chaotic systems of rising warm air, well its on the scale of local weather thats going on all the time. I would guess it is accounted for emperically in the models as required (depending on the purpose of the model: forcasting, climate change, or downscaling etc)
Moderator Response:[JH] This post, sans the first paragraph, is the type of post we are accustomed to seeing on the SkS comment threads. It has a beginning, a middle, and an end.
FYI, Moderation complaints are also prohibited by the SkS Comments Policy.
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dhogaza at 00:12 AM on 5 June 2014President Obama gets serious on climate change
"Why didn't he do this the day he entered office in 2008?"
Because the Supreme Court ruling affirming the right of the EPA to regulate cross-state emissions was announced on April 29, 2014, perhaps? Remember that an appeals court had struck down that right a couple of years earlier.
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dhogaza at 00:10 AM on 5 June 2014President Obama gets serious on climate change
"Howabout "FUSION" our own earth bound sun feeding electricity into a revamped National Grid by 2030...there's a goal!!"
If past history is any indication, in 2030 fusion will still be 50 years in the future, just as it is today.
Money is being spent on fusion research. Progress is still unimpressive. Perhaps the nut will crack someday, perhaps it will always be a dream.
But criticizing Obama for not banking on fusion is rather silly.
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geoffrey brooks at 22:34 PM on 4 June 2014President Obama gets serious on climate change
I can see from the howls of protest from the coal industry and coal states that:
1) Coal becoming only 30% (down from 40%) of the USA electrical power by 2030 - is too little too late. A target the USA is unlikely to meet with the measly greedy politicians we have in charge.
2) If US clean coal technology truly exists - it should be given to China and other coal burners - and we should help implement it. A $5 tax on oil to invest in this and other clean energy - such as fusion.
3) We should keep the Carbon in the ground - coal is the dirtiest and most expensive to clean up. The 2030 goal should be less than 5% electricity from coal
4) We already subsidizes the farming industry not to grow crops...
why not the coal industry not to mine it???
A tax on Natural Gas (much cleaner) used to generate electricity could be levied and given to the coal industry to keep their coal in the ground. The monies for not mining should be spent on re-educating the work-force, maintaining their pensions, providing transitional payments, and ensuring that they get excellent health benefits - not to enrich the greedy. If the miners are not mining, the coal will stay where it belongs in the ground - NOT in the air.
5) President Obama - you need imagination, planning and foresight to help save the planet. Lets see some. Howabout "FUSION" our own earth bound sun feeding electricity into a revamped National Grid by 2030...there's a goal!!
Geoffrey Brooks
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Dikran Marsupial at 18:56 PM on 4 June 2014Climate is chaotic and cannot be predicted
Razo, I should point out that just because weather is chaotic that does not imply that climate (the long term statistical properties of the weather) is similarly chaotic. It is not difficult to think of other phsyical systems where this is the case, for example a double pendulum in the presence of an electromagnet.
Sadly expertise in one field is often a recipe for the Dunning-Kruger effect when moving into a different field as it can blind you to the important differences between fields and give undue confidence in ones ability that makes you unable to see your mistakes. The climate modellers are experts in their field, best to understand first and make assertions afterwards.
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calyptorhynchus at 15:05 PM on 4 June 2014President Obama gets serious on climate change
oops 2009
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calyptorhynchus at 13:12 PM on 4 June 2014President Obama gets serious on climate change
Why didn't he do this the day he entered office in 2008?
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Tom Curtis at 09:59 AM on 4 June 2014Climate is chaotic and cannot be predicted
Razo @71, I am going to disagree with TD. You have not shown the relevance of your claims. You are not a researcher into climate models drawing inspiration from another field. Nor do you show how that inspiration from another field should effect our thinking about climate models. At best you have pointed out that in another field there are certain problems and that it is possible that the same problems exist for climate models. As a response to that, pointing out that it is also possible that they do not exist for climate models is an adequate rebutal.
In this case, however, we can make a stronger rebutal because we know future climate states are constrained by the requirements of conservation of energy, and hence constrained by the forcing history. As such, it is analogous to a hollow ball containing a 3D triple pendulum running down a u shaped track. The detailed motion of such a ball will be chaotic, but the mean path and velocity of the ball will be well constrained, and departures from those means will be short term variations only.
Moderator Response:[TD] Tom, I didn't write that Razo showed the relevance of his/her claims, only that he/she at least tried this time. Better than before. Nonetheless, Razo's followup post was mere continuation of his/her sermonizing without addressing the specific features of climate models that have been explained to him/her; so I deleted it.
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Razo at 08:33 AM on 4 June 2014Climate is chaotic and cannot be predicted
i will respond still to this question as it is directed to me. You may delete them if you wish.
TC, its still relevant because the mathematics of physical phenomena can be very similar between many fields in the physical sciences: electromagnetics, fluid dynamics, thermodynamics...(it's been many years ago now since university). climate models integrate partial differential equations. One can get inspiration from other fields, and many breakthroughs are done this way.
I don't want to take more room on this post for this, but it's a fundemental point.
Moderator Response:[TD] Good, at least you explained what you claim is relevant. However, you continued to fail to address how the specifics of climate models that have been explained to you are trumped by the "lessons" of models of entirely different domains.
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Mal Adapted at 08:28 AM on 4 June 2014President Obama gets serious on climate change
"We finally have a president that understands science."
Well, yes. My votes for Obama have been decisions on the margin, like all my votes have become over the years. He's done some things I really don't like, but since the only 2012 GOP presidential primary candidate to explicitly support both the teach of Evolution in public schools and the scientific consensus on AGW dropped out of the race early, and several of the rest actually renounced their previous support for the consensus, my choice for Obama was clear.
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Tom Curtis at 08:18 AM on 4 June 2014Climate is chaotic and cannot be predicted
Razo @69, so? Did the person in question have experience of climate models, and tell you that the same considerations applied to climate models? Did they explain how the climate was supposed to evade the limits placed by conservation of energy on variability in climate? If not, your analogy has no relevance to the discussion, and your implied argument from authority is irrelevant.
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Razo at 07:55 AM on 4 June 2014Climate is chaotic and cannot be predicted
I would point out the person that told me this was a person that could read Bell laboratory research on superconductors and say that the same math can apply to solid mechanics and bifurcation, ST Ariaratnam.
Moderator Response:[JH] So what! Name dropping is no substitute for well-reasoned comments that are relevant to the OP, or in response to someone else's on-topic comment
Per the SkS Comments polciy (which you should read in its entirety):
The purpose of the discussion threads is to allow notification and correction of errors in the article, and to permit clarification of related points.
Very few of your posts have met this standard.
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Razo at 07:53 AM on 4 June 2014Climate is chaotic and cannot be predicted
Okay then.
i offered the phrase 'alternative equilibrium configuration' as a concept to help people understand chaotic systems changimg states. Before I used to have a kind of mythical understanding of bifurcation problems. When it was told to me, it was a real help in understanding.
Second I continue the very simple analogy of modelling columns to suggest requirements for a model: the alternative configuration has to be programmed into the model, the numerical algorithm has to be very robust.
these may seem trivial to some, but I don't think they are. I am not making any statement on the worthiness of existing GCM.
Moderator Response:[TD] This site is not an appropriate place for you to ruminate on topics marginally or totally irrelevant to climate change. You have responded to moderator requests to specify the relevant point you are trying to make by posting more ruminations and your own admission that you are not addressing the "worthiness of existing GCM." We will begin to simply delete your posts that are irrelevant to the topic.
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John Hartz at 07:14 AM on 4 June 2014Climate is chaotic and cannot be predicted
All: Please do not Post any responses to Razo until he makes a specific point about the OP. .
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Tom Curtis at 07:12 AM on 4 June 2014Climate is chaotic and cannot be predicted
Razo @64, when it comes to chaos, many people who are slightly informed probably have the lorenz attractor in mind as archetypical of strange attractors:
With the lorenz attractor, after a given number of steps (successive evaluatons of the formula), it is not even possible to predict which lobe you will be in so that you truly have a bifurcation. The bifurcation is reversible, however, which makes it quite unlike column buckling. More importantly, the lonrenz attractor is not the only strange attractor, and not all strange attractors have a multilobe shape. The rossler attractor, for example, has a single lobe:
With the rossler attractor, it is not possible to tell well in advance on which side of the "orbit" you will be, but you will generated values will always orbit the same point. The analogy to bifurcation fails.
The climate system is even more precictable than a rossler attractor (in one sense). Specifically, thermodynamics requires the climate system to have a net zero energy exchange between the planet and space over a very short term. Consequently while it is not possible to predict far in advance exactly how far the planet will diverge from that equilibrium point within limits, it is possible to predict that it will track the equilibrium point very closely (within plus or minus 0.3 C from observations over the holocene).
There is a possibility, however, of genuine bifurcations. Melting of ice sheets, release of methane, large scale vegetative die back and other possible consequences of global warming could suddenly shift the equilibrium point. Such sudden shifts, however, are almost certainly towards a warmer climate. That is, to the extent that models fail to capture such bifurcations, they underestimate the potential risk from global warming. It is strange that when pseudo-skeptics plead the chaos of the climate system, they always assume that that chaos is predictable, and will counter the effects of global warming. We know enough, however, to know the genuine bifurcations are unpredictable, and will make things worse.
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Razo at 06:13 AM on 4 June 2014Climate is chaotic and cannot be predicted
I could add to my last post ^^^, about modeling column buckling. Its a rather simple problem but is analogous to bigger chaos problems, I think.
In order to model column buckling you need to do equilibrium in the deformed configuration. That is, the other possible degrees of freedom and their physcal behaviour have to be introduced in to the model. For numerical models, the increment steps and constiuative relations algorithms must be able to handle large changes.
Moderator Response:[JH] What is the point you are attempting to make?
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Razo at 05:56 AM on 4 June 2014Climate is chaotic and cannot be predicted
Strangely, there are not a lot of comments on this topic. LOL
The little I know on chaos I would like to share. As it was explained to me by ST Ariaratnum, an apparent god in random vibrations. Chaotic systems are analogous to bifurcation problems, like column buckling. As a forcing reaches a critical value, large changes in the system can occur.
A column buckles when it reaches its critical load. Ariaratnum however prefered to call it the 'alternate equilibrium configuration'. So the column buckles when it reaches a state where it can resist the load by deforming in a different way. At this forcing, this altrenate configuration stores less potential energy (this last sentance I don't remember well).
Moderator Response:[JH] What is the point you are attempting to make?
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actually thoughtful at 05:11 AM on 4 June 2014President Obama gets serious on climate change
The President's policies, while an improvement, are in the category of too little to late. And likely a smokescreen for approving Keystone XL - all the while lulling the sheeple into a false sense of complacency.
I realize that appears a tad cynical. I submit it is also accurate.
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shoyemore at 04:57 AM on 4 June 2014President Obama gets serious on climate change
This is surely not a complete coincidence? Obama and Xi must have been having some contacts on the matter.
Absolute cap to come into effect, climate adviser says on the day after US announces ambitious carbon plan
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KR at 04:44 AM on 4 June 2014Models are unreliable
nickels - If you feel that the climate averages cannot be predicted due to Lorenzian chaos, I suggest you discuss this on the appropriate thread. Short answer: chaotic details (weather) cannot be predicted far at all due to nonlinear chaos due to slightly varying and uncertain detailed starting conditions. But the averages are boundary problems, not initial value problems, are strongly constrained by energy balances, and far more amenable to projection.
Steve Easterbrook has an excellent side-by-side video comparison showing global satellite imagery versus the global atmospheric component of CESM over the course of a year. Try identifying which is which, and if there are significant differences between them, without looking at the captions! Details (weather) are different, but as this model demonstrates the patterns of observations are reproduced extremely well - and that based upon large-scale integration of Navier-Stokes equations. The GCMs perform just as well regarding regional temperatures over the last century:
[Source]
Note the average temperature (your issue) reconstructions, over a 100+ year period, and how observations fall almost entirely within the model ranges.
Q.E.D., GCMs present usefully accurate representations of the climate, including regional patterns - as generated by the boundary constraints of climate energies.
---
Perhaps SkS could republish Easterbrooks post? It's an excellent visual demonstration that hand-waving claims about chaos and model inaccuracy are nonsense.
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Anthony10658 at 04:15 AM on 4 June 2014Republican witness admits the expert consensus on human-caused global warming is real
Another misdirection. Let's forget 97% and just say "Most" or "almost all" research point to human industrial and agricultural byproducts as being the cause of rising global temperatures. Then the debate moves to -1) is this bad and 2) if yes what can and should we do about it.
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Dikran Marsupial at 03:32 AM on 4 June 2014Models are unreliable
"The future is uncertain nonetheless."
A statement of the exceedingly obvious. However you have not written anything that would support the contention that the future is any more uncertain than the model projections state, or that the models are not useful or basically correct.
"If we had observations of the future, we obviously would trust them more than models, but unfortunately …… observations of the future are not available at this time. (Knutson & Tuleya – 2005)."
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nickels at 03:16 AM on 4 June 2014Models are unreliable
Oh, and this inability to integrate the model forward with accuracy doesn't even touch on the fact that the model itself is an extreme approximation of the true physics. Climates models are jam-packed with adhoc parameterizations of physical process. Now the argument (assuming the model was perfect) is that averages are computable even if the exact state of the climate in the future is not. Its a decent arguement, and in general this is an arguable stance. However, there is absolutely no mathematical proof that the average temperature as a quantity of interest is predictable via the equations of the climate system. And there likely never will be. But, again, all of this is not a criticism of climate modelling. They do the best they can. The future is uncertain nonetheless.
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Composer99 at 03:11 AM on 4 June 2014Antarctica is gaining ice
edaaaa - Please re-post your comment to a thread where it is on topic.
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nickels at 03:07 AM on 4 June 2014Models are unreliable
@scaddenp, in fact the navier stokes are absolutely non-predictable. This is what the whole deal with Lorenz is all about. In fact, we cant event integrate a simple 3 variable differential equation with any accuracy for anything but a small amount of time. Reference:http://www.worldscientific.com/doi/abs/10.1142/S0218202598000597
Now, if we assume that climate scientists are unbiased (I've been in the business, this would be a somewhat ridiculous assumption), the models would provide our BEST GUESS. But they are of absolutely NO predictive value, as anyone who has integrated PDE's where the results matter (i.e. Engineering) knows.
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KR at 02:36 AM on 4 June 2014There's no empirical evidence
Note: I am not stating that Von Storch is a pseudo-skeptic, just that the selection of 1998 is statistically ill-considered, and that claims of trends from that time point are not supported by the data.
Further discussion on this topic (i.e. no warming since...) should probably move to this thread, as it is somewhat off-topic here.
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Dikran Marsupial at 02:34 AM on 4 June 2014There's no empirical evidence
Just to add to KR's comment, if you look at a comparison of the AR4 SRESA1B model ensemble with the observations (courtesy of RealCLimate):
you can see that the observations were further into the upper tail of the envelope of model runs than they are into the lower tail of the distribution in recent years.
Now, ask yourself why the skeptics were not interested in pointing out the model observation "inconsistency" in 1998. Cherry picking indeed, the 1998 one clearly wasn't ripe. ;o) -
KR at 02:19 AM on 4 June 2014There's no empirical evidence
Razo - WRT Von Storch and the avoidance of ENSO effects on trends, it is notable that: if you select as an endpoint an extrema value from a time series, the statistical significance of anything terminating there is much much lower.
There's a good discussion of this over on Tamino, under Cherry-p. Von Storch followed in the trail of many a pseudo-skeptic, and selected the 1998 El Nino (3-sigma in scale) as one of his trend endpoints. Without noting the fact that it was indeed a time series variation extrema.
In the presence of such selection of an extrema, the required p-value for statistical signifcance can be 10x normal!! That's because in any system with noise you can find short trends up and down, meaning once you start selecting extrema endpoints, you need far more supporting data to make your claim(s). Supporting data that simply doesn't exist in the temperature record.
1998 trend claims are the essence of cherry-picking, of selecting a subset of data that appears to support a claim while ignoring the remainder of the data that contradicts that claim. It's a "fallacy of selective attention, the most common example of which is the confirmation bias", and such claims are logical fallacies.
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edaaaa at 01:28 AM on 4 June 2014Antarctica is gaining ice
I simply ask a factual question as to the basis of the study pointing to 97.1% peer reviwed abstracts. The opening excerpt quantifies the study in the following "...peer-reviewed scientific literature, examining 11 944 climate abstracts from 1991–2011 matching the topics 'global climate change' or 'global warming'. We find that 66.4% of abstracts expressed no position on AGW, 32.6% endorsed AGW, 0.7% rejected AGW and 0.3% were uncertain about the cause of global warming. Among abstracts expressing a position on AGW, 97.1% endorsed the consensus position that humans are causing global warming..." - After doing the math - Including the small percent of those that do not support AGW) doesnt this mean that 97.1% of 4014 (or so) abstracts and not 97.1% of the science "community" or scientists agree ?? And if so, in the interest of truth and fact, dont you seek to clarify this within the media so they can more intelligently inform the public ?? - http://iopscience.iop.org/1748-9326/8/2/024024/pdf/1748-9326_8_2_024024.pdf
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heb0 at 00:17 AM on 4 June 2014Republican witness admits the expert consensus on human-caused global warming is real
"The science isn't settled" in much the same way that "the models are wrong." Just as models are by definition not completely accurate, scientific understanding of the climate is incomplete. But both of those statements, on their own, are useless, and both of them could be said about any field of scientific research, no matter how universally accepted. They require quantification to be anything meaningful. Yet, those who trumpet them don't seem interested in quantification, only in spreading that message.
I don't know much about Richard Tol, but lately he strikes me much like Roger Pielke: stubbornly contrarian yet slipperily vague. If memory serves me correctly, both have a strange habit of pedantically seizing on miniscule points of contention and then trying to use that to justify rejecting much larger parts of the science. When you call them on it, it's almost impossible to get them to admit which part of the conensus they disagree with, yet they will, if unchecked, make pretty denial-ish claims. It's fitting that they were both invited as witnesses.
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Alexandre at 22:45 PM on 3 June 2014Republican witness admits the expert consensus on human-caused global warming is real
I don't expect "skeptics" to build on previous conclusions or aknowledged evidence. It wouldn't surprise me if Tol claimed that "the science isn't settled" next month. Climate inactivity does not rely on coherence - quite the opposite.
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Tom Curtis at 20:01 PM on 3 June 2014Human CO2 is a tiny % of CO2 emissions
scaddenp @257, based on ice core data, there is approximately a 90 ppmv rise in CO2 concentration between glacial and interglacial. That yields a CO2 increase per degree C between 11.25 and 30 ppmv per degree C with the former for an 8 C increase in temperature, and the later for an assume 3 C increase. A reasonable central estimate is 18 ppmv per degree C (5 degree increase). For the 0.8 C increase in temperature experienced since the industrial revolution, that yields and expected increase of 14.4 ppmv or 12% of the CO2 increase todate. As you say, it is unlikely that all of that increase would have happened over so short a time.
As an alternative emperical measure, taking the global temperatur anomaly from 1010 AD to 1800 AD (Mann 2008) and ice core CO2 records, the regression shows an 8.1 +/- 2.9 ppmv increase in CO2 per degree C. Based on that regression the expected increase for the global temperature increase since the pre-industrial of 0.8 C is 6.5 +/- 2.3 ppmv of CO2, or 3.5 - 7.3%. The time resolution of the CO2 record is 75 years, and I used a 75 year average of the temperature record to maintain equivalent resolution. That regression, therefore, yields a reasonable but not precise estimate of the increase that would have occurred from temperature increase alone.
As far as showing the absurdity of the pseudo-skeptic claims that the increase in atmospheric CO2 was caused by the temperature increase goes, the difference between 3% and 10% is not relevant. Therefore I indulged my habit of using conservative (for my position) estimates for rough figures where it makes little difference. The long and short, then, is that, yes I agree with you. But I don't think the difference is enough to warrant keeping track of for rough estimates.
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