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« Lessons from the shop floor | Main | The debate at the FST »
Thursday
Jul032014

Where there is harmony, let us create discord

My recent posts touching on statistical significance in the surface temperature records have prompted some interesting responses from upholders of the climate consensus, with the general theme being that Doug Keenan and I don't know what we are talking about.

This is odd, because as far as I can tell, everyone is in complete agreement.

To recap, Doug has put forward the position that claims that surface temperatures are doing something out of the ordinary are not supportable because the temperature records are too short to define what "the ordinary" is. In more technical language, he suggests that a statistically significant rise in temperatures cannot be demonstrated because we can't define a suitable statistical model at the present time. He points out that the statistical model that is sometimes used to make such claims (let's call it the standard model) is not supportable, showing that an alternative model can provide a much, much better approximation of the real world data. This is not to say that he thinks that his alternative model is the right one - merely that because it is so much better than the standard one, it is safe to conclude that the latter is failing to capture a great deal of the variation in the data. He thinks that defining a suitable model is tough, if not impossible, and the only alternative is therefore to use a physical model.

As I have also pointed out, the Met Office does not dispute any of this.

So, what has the reaction been? Well, avid twitterer "There's Physics", who I believe is called Anders and is associated with Skeptical Science, tweeted this:

Can clarify their position wrt statistical models - in a way that might understand?

A response from John Kennedy appeared shortly afterwards, which pointed to this statement, which addresses Doug Keenan's claims, noting that there are other models that give better results and suggesting that the analysis is therefore inconclusive. Kennedy drew particular attention to the following paragraph:

These results have no bearing on our understanding of the climate system or of its response to human influences such as greenhouse gas emissions and so the Met Office does not base its assessment of climate change over the instrumental record on the use of these statistical models.

I think I'm right in saying that Doug Keenan would agree with all of this.

Anders has followed this up with a blog post, in which he says I don't understand the Met Office's position. It's a somewhat snide piece, but I think it does illuminate some of the issues. Take this for example:

Essentially – as I understand it – the Met Office’s statistical models is indeed, in some sense, inadequate.

Right. So we agree on that.

This, however, does not mean that there is a statistical model that is adequate.

We seem to agree on that too.

It means that there are no statistical models that are adequate.

Possibly. Certainly I think it's true to say that we haven't got one at the moment, which amounts to the same thing.

Then there's this:

[Statistical models] cannot – by themselves – tell you why a dataset has [certain] properties. For that you need to use the appropriate physics or chemistry. So, for the surface temperature dataset, we can ask the question are the temperatures higher today then they were in 1880? The answer, using a statistical model, is yes. However, if we want an answer to the question why are the temperatures higher today than they were in 1880, then there is no statistical model that – alone – can answer this question. You need to consider the physical processes that could drive this warming. The answer is that a dominant factor is anthropogenic forcings that are due to increased atmospheric greenhouse gas concentrations; a direct consequence of our own emissions.

Again, there is much to agree with here. If you want to understand why temperature has changed, you will indeed need a physical model, although whether current GCMs are up to the job is a moot point to say the least. (I'm not sure about Anders' idea of needing a statistical model to tell whether temperatures are higher today than in 1880 - as Matt Briggs is fond of pointing out, the way forward here is to subtract the measurement for 1880 from that for today - but that's beside the point).

All this harmony aside, I hope you will be able to see what is at the root of Anders's seeming need to disagree: he is asking different questions to the one posed at the top of this post. He wants to know why temperatures are changing, while I want to know if they are doing something out of the ordinary. I would posit that defining "the ordinary" for temperature records is not something that can be done using a GCM.

I think Anders' mistake is to assume that Doug is going down a "global warming isn't happening" path. In fact the thrust of his work has been to determine what the empirical evidence for global warming is - when people like Mark Walport say that it is clear that climate change is happening and that its impacts are evident, what scientific evidence is backing those statements up? I would suggest that anyone hearing Walport's words would assume that we had detected something out of "the ordinary" going on. But as we have seen, this is a question that we cannot answer at the present time. And if such statements are supported only by comparisons of observations to GCMs then I think words like "clear" and "evident" should not be used.

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  • Response
    Response: Comment
    This is an attempt at a response to Andrew’s post Andrew, you say, I think Anders’ mistake is to assume that Doug is going down a “global warming isn’t happening” path. In fact the thrust of his work has been to determine what the empirical evidence for global warming is Well, ...

Reader Comments (307)

Mailman, Harry Passfield

Please be polite to other commenters.

Jul 3, 2014 at 9:26 PM | Registered CommenterBishop Hill

As with soooo many others this guy just doesn't grok the main situation on our watery planet ... El Nino is a feedback, an OHC/solar response to lowered atmospheric temperatures. Sensitivity due to 'our' 'added' co2 will pan out at less than or equal to 0.0K - a la Ferenc Miskolczi. Prepare for chills not fever.

Jul 3, 2014 at 9:32 PM | Unregistered CommenterHenry Galt

Bish: OK. Point taken. But do you think that if I told 'em what the NH was I'd be telling 'em anything they didn't already know?

Jul 3, 2014 at 9:41 PM | Registered CommenterHarry Passfield

This is not a question of statistics, nor a question of physics and/or chemsitry. It is simpler than that. It is a question of fact.

It is a fact that we do not know what the temperature was in 1880. It is a fact, somewhat more surprising, that we do not know, within a reasonable margin of error, what the temperature is today. Based on these facts, we do not know whether it is warmer today than it was in the 1880s, period.

What we can say is that it appears that it was 'warm' in the 1880s and the 1930s, and that the temperature today is not, bearing in mind measurement errors applcable to ascertaining and calculating past and present temperaures, substantially different.

Maybe it is warmer today, I would not be surprised if it was, but we simply do not know. It is merely guesses and inferences based upon imperfect data sets, and systems of measurement which are being over extrapolated.

Jul 3, 2014 at 9:53 PM | Unregistered Commenterrichard verney

The atmosphere centred model (don't tell me it's a fully ocean atmosphere coupled model or I'll point and laugh) currently used in GCM's can't hindcast more than 50 years, and only then if you fudge the aerosol parameters.

Our solar based model successfully hindcasts 1000 years of C14 and Be10 records.

As a physical model it has some issues (don't they all?), but the R^2=0.9 match to 400 years of solar observational data (Sunspot numbers) is pretty good. Certainly knocks the socks off the trace gas aficionados efforts.

Pity the IPCC's leading author James Annan got Copernicus' Martin Rasmussen to axe the journal because it contradicts their model output. We'd appreciate some properly presented criticism rather than blatant censorship.

Jul 3, 2014 at 9:59 PM | Unregistered CommenterRog Tallbloke

ATTP

Again, I do wonder why the blog owner doesn't pop in and clarify these misconceptions

1. Why on earth would you think he should do so? 2. What makes you think we’d take a blind bit of notice if he did? Maybe it’s because we’re not a bunch of kids that need to be “corrected” and told what to think. In the same way that he obviously doesn’t feel the need to micromanage his blog in case it drifts off message, or to hand out bans to anyone who disagrees with him whilst citing non-existent rudeness to justify it.

Jul 3, 2014 at 10:03 PM | Registered CommenterLaurie Childs

Laurie,


What makes you think we’d take a blind bit of notice if he did?

Good point. I stand corrected.

Harry,


But do you think that if I told 'em what the NH was I'd be telling 'em anything they didn't already know?

Well, I'll never know unless you try.

Anyway, what I will say is that this has been interesting, but I suspect that the discussion has rather run its course. Maybe we can continue this another time. Then again, maybe not ;-)

Jul 3, 2014 at 10:11 PM | Unregistered CommenterAnd Then There's Physics

ATTP: NH? GIYF. DIY. But you know that as well. I guess that as you can't falsify the NH you try to deny it. Hmmmm, where have I heard that before?? See ya.

Jul 3, 2014 at 10:34 PM | Registered CommenterHarry Passfield

Entropic man/ATTP
Are you sure, has everything been budgeted for, no unknown unknowns? I wouldn't want to bet on that. For instance more CO2 than expected has been removed from the atmosphere, an unknown percentage is fixed by photosynthesis. According to what I've read between 8 & 12 photons are required to fix each CO2 molecule. If you are unsure of how much of man made CO2 is fixed by photosynthesis or even which type of photosynthesis, as a different number of photons are required in each case your energy balance is more like a number plucked from the air.

Also temperatures have been higher in the past, something else we can agree on? Therefore this is just another natural variation within normal limits.

Jul 3, 2014 at 10:55 PM | Unregistered CommentersandyS

Can I get this right please?

From 1980 ish, the surface temperature record showed a warming trend - nothing in itself unusual in that, however research showed that the rate of increase recorded was unprecedented, and at a time when CO2 emissions were climbing - therefore a correlation was drawn between the two, and in lieu of any other viable explanation, this was put forward as proof of causation, lots of research went in to researching the science behind this to support the causation theory.

From about 1998, surface temperatures stopped climbing at this previously unprecedented rate - although CO2 has continued to rise at a fairly constant rate.

Whilst there are alternative theories about where the 'energy' has gone to that would otherwise cause this surface temperature rise, (ie. into the sea) As I understand it there is as yet no coherent explanation WHY the warming flipped from surface temperatures to the oceans.

Right so far?

That last element, an explanation for the change, seems to be pretty vital to the cause, I wonder why its not been addressed yet?

Jul 3, 2014 at 11:00 PM | Unregistered Commenterlord voldemort

This stuck me in the "Lectures on Physics" posted by Martin A:

There is no known exception to this law - it is exact so far as we know. The law is called the conservation of energy."

Feynman et al were cautious even with conservation of energy, contrast that to the stance "it must be CO2".

Jul 3, 2014 at 11:23 PM | Unregistered Commenterclimatebeagle

Bish: Please be careful claiming that there is a statistical model that "can provide a much, much better approximation of the real world data" - if that statistical model behaves like random walk. The earth's climate cannot behave like a random walk, which is characterized by data that drifts indefinitely far from the starting position given enough time. For the simplest random walk, drift would increase with the square root of time. If the drift in temperature observed in the last 100 years (about 1 degC) were due to a process similar to a random walk, one would expect about 10-fold more drift (10 degC) in the last 10,000 years (still in the Holocene) and 100-fold more drift (100 degC) in the last million years, and 1000-fold more drift (1000 degC) in the last 100,000,000 years. This is obviously absurd. A model that behaves like a random walk is a statistical possibility, but appears to be absurd from the perspective of radiation physics (Planck feedback) and climate history (limited to swings of less than about 25 degC?).

It would be better to stick to the agreed upon position - an adequate statistical model for detecting "significant" warming exists.

As you noted, it was warmer last year (2013) than it was in 1880 (even given the uncertainty in calculating mean global temperature for both these years. It was warmer in the decade of the 2000s than in the 1880s (difference of two means). Or the 30 years - the minimum period usually considered to define a climate - from 1980-2010 vs. 188o-1910

Jul 3, 2014 at 11:32 PM | Unregistered CommenterFrank

> Please be careful claiming that there is a statistical model that "can provide a much, much better approximation of the real world data" - if that statistical model behaves like random walk. The earth's climate cannot behave like a random walk, which is characterized by data that drifts indefinitely far from the starting position given enough time.

Come on, Frank. Don't be such a party pooper. It's way more fun to ask for random walk models with brand new predictive powers!

Jul 3, 2014 at 11:41 PM | Unregistered Commenterwillard

so glad that Willard returns to the fray...but saddened that he does not seem to know what the fray is about...maybe wilk arm-waving objections by Neven will help to orient the Willard

Jul 3, 2014 at 11:52 PM | Unregistered Commenterdiogenes

on the other hand...maybe Willard might say (note the subjunctive) just what makes a prat like him stay in this debate, since he has nothing to add?

Jul 3, 2014 at 11:57 PM | Unregistered Commenterdiogenes

Voldemort: I don't think that is quite correct.


From 1980 ish, the surface temperature record showed a warming trend - nothing in itself unusual in that, however research showed that the rate of increase recorded was unprecedented, and at a time when CO2 emissions were climbing - therefore a correlation was drawn between the two, and in lieu of any other viable explanation, this was put forward as proof of causation, lots of research went in to researching the science behind this to support the causation theory.

I dispute that "research showed that the rate of warming was unprecedented". It was indeed claimed to be unprecedented by a few overexcited individuals, but not on the basis of research. They clearly didn't look hard for possible precedent because if they had they would have found many examples of similar periods of warming in the past. Similarly the wording "in lieu of any other viable explanation" suggests somebody actually looked for other viable explanations and didn't find any, which isn't really a good description of what happened.

Jul 4, 2014 at 12:08 AM | Unregistered CommenterIan H

> what the fray is about

Perhaps are you referring to this, Diogenes:

Doug Keenan argues that significance means that the temperature rise could not be reasonably attributed to natural random variation. He then seems to argue that significance can only be determined using a statistical model. Furthermore, he suggests that there is a statistical model (driftless ARIMA(3,1,0)) that would allow us to conclude that the surface temperature could indeed be simply some random natural variation. Furthermore, he suggests that the Met Office have admitted that their statistical model is inadequate.

http://andthentheresphysics.wordpress.com/2014/07/02/come-one-andrew-you-can-get-this

Do you dispute this?

If you don't, you might need to retract your insults regarding my capacity to orient myself in the fray.

***

Now, notice how the famous "agreement" applies to a more select group in Douglas' response:

[Y]ou will find that there is broad agreement among those (few) who have both integrity and knowledge. There are three main points.

1. There is no observational evidence for significant global warming, due to any cause—natural or anthropogenic. (Claims to the contrary are based on insupportable statistical analyses.)"

[...]

Notice how "the MET Office" becomes "those (few) who have both integrity and knowledge". Since this "agreement" rests on the notion of "insupportable statistical analyses," I'd rather think that Douglas is begging the very question he's rhetorically asking. And that's notwithstanding the very wording used (e.g. "observational," a new lukewarm ringtone that introduced Nic Lewis), and his last jab about "alarmism" whence nothing in his editorial supports that idea, which will have to wait for now.

***

In a nutshell, here's Douglas' pickle. Considering that there are no models that satisfies Douglas except perhaps (and only perhaps) random walks, please explain why he insists on an agreement about a platitude that may look a lot like the platitude "all models are wrong."

In other words, Douglas might need to release some more emails.

***

Let me know when the MET Office will accepts that climate can be modelled as a random walk. Until then, it might be nice if Douglas will finally acknowledge that he released his correspondence with Richard Muller without permission. If he could also respond to Richard's accusation of statistical pedantry, that would be nice too.

However lukewarm you may feel about short selling "yes, but random walk," dear Diogenes, it may be getting a bit late.

Jul 4, 2014 at 12:27 AM | Unregistered Commenterwillard

Surely the 'null hypothesis' is that any temperature changes since 1880 - or any other year - are the result of natural variations?

Jul 4, 2014 at 1:02 AM | Unregistered CommenterWFC

conservation of energy is not valid as there is always the fungability with "e=mc**2 "

Jul 4, 2014 at 1:39 AM | Unregistered CommenterJoeBidensBrainSurgeon

Jul 4, 2014 at 1:39 AM | Unregistered CommenterJoeBidensBrainSurgeon

conservation of energy is not valid as there is always the fungability with "e=mc**2 "

Er, fungibility?

Too bad Feynman is no longer with us. You could have pointed out his misconception to him.

Jul 4, 2014 at 7:56 AM | Registered CommenterMartin A

Completely off topic but over at Paul Hudsons he has a note from the MO saying 1998 has been revised down to third warmest. Anyone know what this is about?

Mailman

Jul 4, 2014 at 8:21 AM | Unregistered CommenterMailman

Mailman,

According to the HadCrut4 temperature record 1998 is the third warmest year on record, after 2005 and 2010. I think that it is still the warmest year according to HadCrut3, so maybe that is what he is referring to.

Jul 4, 2014 at 9:10 AM | Unregistered Commenterandrew adams

It is interesting observing the spread of comments here, loosely based around a central theme, sometimes touching very close to base point, sometimes drifting off into orbit, but always circling around the common thread. In fact I'm sure there is a statistical model which could approximate very closely the divergence and convergence of comments on such a blog, programmed with a common starting point (not absolutely agreed by all or even perceived by all as being the same), then forced by a number of varying, sometimes competing narratives. The essence of the real conversation, though in here, tends to get obscured by overlapping themes. If one reads the blog post very carefully, then wades through every comment, it should be possible to distil it from the accumulation of 'detritus' (in the politest possible sense - my own included) held in place by the gravitational pull of the main argument, but it's a bit of a task. I guess such is the nature of investigating climate change in general, though the competing and overlapping 'narratives' provided by Nature and humans' faltering attempts to explain what is happening in Nature, is vastly more complex.
In order to get to the quintessence of the debate on climate change then, perhaps we do need a whole series of new narratives separated out from the main mass, so that each can be judged in artificial isolation and then hopefully put back together coherently at the end. But as far as I'm concerned, the science should be the starting point and the end point of such a process because, in the final analysis, we either are, or we are not having a significant impact on the climate of our planet and that will only be determined according to physical processes, however complex and convoluted they may be. All else is an unwelcome distraction.

Jul 4, 2014 at 9:28 AM | Unregistered CommenterJaime Jessop

On thing that's missing from this discussion - or at least, has not been stated as clearly as needed - is that it's not sufficient to sue physical models, they have to be validated physical models. You have to first *demonstrate* that the physical model can reliably predict outcomes over the range of inputs of interest to within the stated accuracies; that the inaccuracies and uncertainties are small enough for the purpose to which they are being put.

But as the climate scientists say of this model-based approach: "The approaches used in detection and attribution research described above cannot fully account for all uncertainties, and thus ultimately expert judgement is required to give a calibrated assessment of whether a specific cause is responsible for a given climate change." That is to say, a scientific demonstration built on quantified empirical evidence and validated physical models is not yet possible, but they nevertheless have formed an opinion.

Regarding "random walks", they're exactly as valid/invalid as "linear trends".

Regarding energy conservation, the rule is that the change in the total energy in any volume of space is equal to the net energy crossing its borders. This implies that if no energy crosses the borders (the system is isolated) then the energy content must be constant. Conservation of energy has no problem with open systems. Similarly, the argument about evolution is based on a misunderstanding, too - and it was about the 2nd law of thermodynamics rather than the first, and the idea of evolution increasing order - but I'll not get into that as it's off topic. E = mc^2 doesn't invalidate conservation of energy. Energy and mass are the same thing - there's no conversion from one to the other. If you give something more energy (kinetic/potential/whatever) it has slightly more mass as a result. Part of the rest mass of atoms is the binding energy (potential energy) of the protons in the nucleus. When these bonds are broken, the total rest mass of the resulting fragment atoms is lighter, the remainder of the mass is in the form of the mass resulting from their kinetic energy. (In fact, "mass" is equivalent to the energy-momentum-stress tensor, because in four dimensions they're all the same thing. But that's a teeny bit complicated and getting waaaaaay off topic...)

Jul 4, 2014 at 9:42 AM | Unregistered CommenterNullius in Verba

Yeah, what NiV said. :)

Jul 4, 2014 at 10:08 AM | Registered CommenterRichard Drake

While it was a plausible hypothesis that CO2 may have caused that 'missing' warming because the solar correlation to sunspots etc had stopped at around 1960. Of course there is more to solar influence than sunspots and Solanki, Lockwood and even Michael Mann agree that the real solar correlation (which stretches back a helluva long way as tallbloke reminded us) stopped formally at 1980 to 1985. Since the CO2 hypothesis had been unable to replicate the 1945-1975 cooling period (ignoring aerosol handwaves) and since the hypothesis also breaks down post-1998 then that just leaves a short period from 1980/1985 to 1998 that might be deemed unnatural; ie a mere 13 to 18 years. Not only is that period far smaller than the 30 years the pause deniers now demand in order to formally acknowledge the current blindingly obvious temperature plateau, it also coincides exactly with the well-observed pdo climatic shift.....

Of course it is difficult to convince anyone to admit they may have wasted 30 years teaching the wrong thing and since entire University departments, foundations, think-tanks and numerous other organisations now expressly depend on the warming scare then it will likely take another natural cooling period to finally reject the hypothesis just as it ended the previous episodes of warmist hysteria in 1900 and 1945 that were, of-course, interspersed with cooling scares.

Jul 4, 2014 at 10:10 AM | Unregistered CommenterJamesG

Several commenters need to look up the standard definition of random walk (Brownian motion, Wiener process). Its mean deviation from its starting point is 0. It does not 'drift indefinitely far from the starting position given enough time'. It must return to its starting position infinitely many times. It goes on long runs upwards and downwards. Beenstock et al(2012) show temperatures since 1880 are not incompatible with random walk.

That said, an ARIMA model for temperatures only seems useful as a yardstick against which better specified models might be compared (statistically).

Jul 4, 2014 at 10:42 AM | Unregistered Commenterbasicstats

basicstats "Its mean deviation from its starting point is 0"

I'm not sure exactly what you mean by that, but check this post from a little while ago:

http://motls.blogspot.co.uk/2010/03/tamino-vs-random-walk.html

or the wiki entry:

http://en.wikipedia.org/wiki/Random_walk

both of which assert that after a long duration a random walk's deviation from it's starting point is proportional to the square root of the duration.

Jul 4, 2014 at 11:13 AM | Unregistered Commenternot banned yet

Nullius in Verba - see my comment bottom of p1 of this thread...

IMO Anders doesn't know anything about hypothesis formulation and testing. He is simply doing the same old, same old extrapolation of "radiative physics".

Jul 4, 2014 at 11:22 AM | Unregistered Commenternot banned yet

Well it seems to me that the question Bish is asking is "what is normal" which somehow gets misinterpreted by Anders (deliberately?) instead in to an answer along the lines of "it has warned a fraction of a degree since 1645 THEREFORE Mann Made Global Warming (tm) is true".

Mailman

Jul 4, 2014 at 11:31 AM | Unregistered CommenterMailman

"Several commenters need to look up the standard definition of random walk"

There are several. You're talking about the rooted random walk, which is defined to be zero at time zero, and then has a binomial distribution for all other times with mean zero and linearly increasing variance. It's true that it almost certainly returns to zero infinitely often, but the probability of it doing so also decays towards zero with time. The bell-shaped distribution spreads out and flattens over time, so the peak of the distribution at zero gets smaller, proportional to 1/Sqrt(t). Because the probability is shrinking more slowly than the number of opportunities for it to happen is increasing, in an infinite amount of time it will happen infinitely often, but it is also getting infinitely rare, and the more typical value will be far from zero.

Strictly speaking, the ARIMA process Doug was using was not a random walk, which is the name given only to one particular stochastic process with some of the same properties. What they were actually talking about was whether the time series was 'stationary', which is not quite the same thing.

However, everyone agrees that a non-stationary stochastic process is not physically possible for temperature, in exactly the same way as they agree that a non-zero linear trend isn't physically possible. If you extend a non-zero trend forwards or backwards in time far enough, you'll eventually wind up with temperatures below absolute zero in one direction, and temperatures hotter than the sun's core in the other. For the *actual* underlying process to be a linear trend is physically and logically impossible.

However, nobody objects on this basis because everybody knows it is only being used as an approximation that is only considered valid over a short time interval. We know there are higher-order terms that when added will cancel this divergence out, but the observed interval is too short for us to tell what they are, so we omit them. In the interval under study, they're too small to have a significant effect, and we know not to use the linear trend to try to predict outside the interval.

In exactly the same way, a non-stationary ARIMA process is being used as an approximation to a stationary one, and is only considered valid over a short time interval. It arises for exactly the same reason - the observed time interval is too short to resolve the higher-order terms that would cancel the divergence out, so we're neglecting them. But we're not asserting that they're *actually* zero, only that they're too small to be measured with the data we've got.

Objections on the grounds that ARIMA processes are not physically realistic are junk, since it is only being claimed that they're a better fit than a non-zero linear trend, and in that sense they're rather better behaved than it too. After all, the typical magnitude of a non-stationary ARIMA process only goes up with the square root of time, while that of a linear trend goes up linearly with time.

Statisticians use non-stationary ARIMA routinely for variables that are known to be bounded, for very good reason. They're not stupid. It's just an approximation.

Jul 4, 2014 at 11:47 AM | Unregistered CommenterNullius in Verba

not banned yet,


both of which assert that after a long duration a random walk's deviation from it's starting point is proportional to the square root of the duration.

That's not quite right, I think. What I think you've quoted is the rms (root mean square) distance. If you were to repeat a random walk process a large number of times, and plotted the position after n steps for each random walk, the distribution would be symmetrical about the starting position. The rms position would, however, be Sqrt(n).


IMO Anders doesn't know anything about hypothesis formulation and testing.

Quite possibly, but I'm not sure why that's all that relevant.


He is simply doing the same old, same old extrapolation of "radiative physics".

What else should I do. Make up some new physics?

basicstats,


Beenstock et al(2012) show temperatures since 1880 are not incompatible with random walk.

I haven't looked closely at Beenstock et al. (2012), but have no reason to think that this isn't what they've found. My question would be, though, so what? There is no known process that can simply randomly perturb our surface temperatures in a way that would produce what we have observed. Therefore, IMO, showing that temperatures since 1880 are not incompatible with a random walk tells us nothing (or very little) about the actual processes involved. To understand why our surface temperatures have behaved as they have you have to do more than simply run some kind of statistical model. You need to introduce the relevant physics and chemistry.

Jul 4, 2014 at 11:47 AM | Unregistered CommenterAnd Then There's Physics

"There is no known process that can simply randomly perturb our surface temperatures in a way that would produce what we have observed."

On the contrary - there are several. Longer-term random variations in cloudiness as suggest by Roy Spencer are one possibility. Another example was given by Lorenz, the guy who invented Chaos.

However, the issue is not whether we know of any physical mechanisms that could cause such changes, the issue is whether we understand the physics well enough to be able to eliminate the possibility of any that we *don't* know about.

The point is, you can't do detection/attribution by testing for linear trends against an AR(1) model of natural variation, which is what the Met Office initially said they were doing before wiser heads there got them to back off. That doesn't mean there aren't any. It only means we don't have the evidence.

Jul 4, 2014 at 12:02 PM | Unregistered CommenterNullius in Verba

Nullius,


Longer-term random variations in cloudiness as suggest by Roy Spencer are one possibility

Spencer asserted, without evidence, that clouds could play this role. I don't think that's a particularly scientific way to develop a physically motivated model.


the issue is whether we understand the physics well enough to be able to eliminate the possibility of any that we *don't* know about.

I think that it is rare (impossible) for physics to definitively tell us that there are no alternative explanations that we don't yet know about. However, physics can tell us if something is plausible or not. I fail to see how suggesting that it could be something we haven't yet discovered/determined is particularly scientific. It doesn't invalidate our current understanding.


The point is, you can't do detection/attribution by testing for linear trends against an AR(1) model of natural variation

No, the point is that you can't do attribution studies without including a physical model. AR(1) is not a model of natural variation. It is simply a model of variation.

Anyway, I have to try not to spend today simply commenting on blogs, as I have some of my own research to do. Nice chatting :-)

Jul 4, 2014 at 12:27 PM | Unregistered CommenterAnd Then There's Physics

Jul 4, 2014 at 10:42 AM | Unregistered Commenter basicstats

Beenstock et al(2012) show temperatures since 1880 are not incompatible with random walk.

That said, an ARIMA model for temperatures only seems useful as a yardstick against which better specified models might be compared (statistically).

What is so special about 1880? Holocene temperatures from GISP2 ice core data. (source data: ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/summit/gisp2/isotopes/gisp2_temp_accum_alley2000.txt )


Ian H (Jul 4, 2014 at 12:08 AM) I agree with you that the late 20th century temperature rise is certainly not unprecedented. I don't think it is even significant.

I also have to sympathise with Joanna on this. 180-odd posts and no-one has mentioned the elephant in the room. A small (3 or 4%) reduction in tropical and mid-latitude cloud clover, and a corresponding increase in insolation, easily explains the increase in average global surface temperatures in the late 20th century (along with a little UHI, dodgy station selection, homogenisation, and spurious 'value-added' adjustments of course). And if the temperature rise is not a result of the extra insolation, where did all this extra energy from the Sun go to?

So I am with Bish and Keenan on their statistical model argument; trying to claim the late 20th Century warming is statistically significant, with only 150 years worth of data is clearly tenuous at best, especially when looked at in the context of the GISP2 and Vostok proxies. But I still fear it is a cul-de-sac digression which takes the focus off the VERY LARGE ELEPHANT in the room.

Jul 4, 2014 at 12:47 PM | Registered Commenterlapogus

"Spencer asserted, without evidence, that clouds could play this role. I don't think that's a particularly scientific way to develop a physically motivated model."

What makes you think he did so without evidence?

"I think that it is rare (impossible) for physics to definitively tell us that there are no alternative explanations that we don't yet know about. However, physics can tell us if something is plausible or not. I fail to see how suggesting that it could be something we haven't yet discovered/determined is particularly scientific. It doesn't invalidate our current understanding."

Somebody once described science as like stumbling around blind in a darkened room. To start with, you're trying to identify everything by feel. Gradually, you build up a mental map of where everything is, until you've got things figured out well enough to find the light switch. Then everything is clear and there are no shadows left in which unknowns can hide. (At which point of course you move on to the next darkened room.) The point is that in a field with detailed well-validated models, where you can reliably predict pretty precisely what is going to happen in any given circumstance (and have demonstrated it), there's little room for major unknowns. As the models get better verified, it becomes harder and harder to explain why the models worked so well, and how you never noticed such a major omission before. If we had models that could accurately predict the climate in any small region of the Earth (bar maybe a few exceptions), and explain all the major features of the weather and climate globally, it would be hard to explain where unknown mechanisms could be hiding. You never know for certain, but it gives some confidence. But when you've got a big mysterious mess very little of which you understand, and all your models disagree in detail with observations, it's like there is a huge dark space you can't see into. It's far more likely then that you're missing something. In fact, it's virtually certain.

"No, the point is that you can't do attribution studies without including a physical model. AR(1) is not a model of natural variation. It is simply a model of variation."

So is a linear trend. And if we agree that you can't do attribution studies without a validated physical model, then what are we arguing for? If you think so, then surely you should be joining us in asking for global warming believers to stop doing it?

Jul 4, 2014 at 12:54 PM | Unregistered CommenterNullius in Verba

Good comments from NiV (as always).

Anders is in a room where the light only shines on radiative physics.

Jul 4, 2014 at 1:29 PM | Unregistered CommenterH2O: the miracle molecule

Nullius,


And if we agree that you can't do attribution studies without a validated physical model, then what are we arguing for?

We are having this discussion because there appear to be people who think that they can draw stronger conclusions from statistical models than is justified. If statistical models - alone - cannot determine attribution, using this to argue that we, therefore, don't know what's happening is logically inconsistent.

Jul 4, 2014 at 1:30 PM | Unregistered CommenterAnd Then There's Physics


Anders is in a room where the light only shines on radiative physics.

No, I'm in a room where the light only shines BECAUSE OF radiative physics :-)

Jul 4, 2014 at 1:32 PM | Unregistered CommenterAnd Then There's Physics

> [T]he issue is whether we understand the physics well enough to be able to eliminate the possibility of any that we *don't* know about.

Interestingly, "the issue" is not quite explicit in what says Douglas or our beloved Bishop. Some, but not me, might even say that's because they need to agree or, as Douglas suggested at AT's, it's "a rhetorical technique, to misdirect people from that issue". Nullius used the same trick with his "neither models are valid" a bit earlier.

The issue is that what is conveyed by Douglas and our beloved Bishop with their “the statistical models are inadequate” is quite incompatible with what AT and the MET Office convey. To claim that both “stances” are compatible is the main misdirection of that ClimateBall ™ episode. The trick here is to focus on “claims” and forget about what they are meant to imply.

So we thank Nullius for having voiced the appeal to ignorance implicitly implied by Douglas' rhetorical technique.

If Douglas would clarify if he asked Richard Muller before releasing his correspondence with him, that would be nice too.

***

Oh, and if anyone wants to research the “yes, but random walk,” this has been debated to death on an old Amazon thread a while back:

You continue to claim that you are optimizing a model even after Vaughan and I have repeatedly explained that you have no model. A model has parameters with physical meaning. You have one parameter – a seed for the mathematical generation of pseudo-random numbers. You are playing with numbers – no reality involved. You have not performed model identification. There is no model. DO YOU UNDERSTAND?

http://www.amazon.com/tag/science/forum/ref=cm_cd_pg_pg$1?_encoding=UTF8&cdPage=$1&cdSort=oldest&cdThread=Tx3TXP04WUSD4R1

The Vaughan in question is Vaughan Pratt.

Jul 4, 2014 at 1:51 PM | Unregistered Commenterwillard

Martin A

Seismic identification of nuclear explosions vs earthquakes is based on geometry and first arrivals, and they in turn are based on a geophysical Earth model. Detection requires a global array of detection stations, and individual stations also use arrays of detectors.

The global seismic monitoring network exists precisely because the US/Nato wished to monitor USSR nuclear weapon testing.

You can run whatever statistics you want, but that has nothing to do with discriminating between tectonics and nuclear testing.

Jul 4, 2014 at 1:54 PM | Registered CommenterHector Pascal

So after all this, what sense shall we make of the surface temperatures? Let us count the ways:

1.Linear trend
2.Driftless ARIMA
3.Step changes
4.Random walk.
5.Linear plus 60-yr cycles(Akasofu)
6. Solar-Astromonical Model (Scafetta)

Ladies and gentlemen, step right up and place your bets.

Which one will predict the future and be verified?

Jul 4, 2014 at 1:58 PM | Unregistered CommenterRon C.


Which one will predict the future and be verified?

Well, given that the first 4 have no physical motivation and the latter two have virtually no physical motivation (curve fitting exercises) I wouldn't bet on any. And, if any of them do happen to match what happens in the future it will be more by luck than design. I don't think that one can call a model that has no underlying physical mechanism verified, even if it does happen to match what happens in the future.

Jul 4, 2014 at 2:08 PM | Unregistered CommenterAnd Then There's Physics

"We are having this discussion because there appear to be people who think that they can draw stronger conclusions from statistical models than is justified. If statistical models - alone - cannot determine attribution, using this to argue that we, therefore, don't know what's happening is logically inconsistent."

I agree. But if statistical models and unvalidated models are all that's been put forward as evidence, then we can't say with any confidence we know what's happening. Your refutation needs to reference evidence from a validated physical model.

Jul 4, 2014 at 2:19 PM | Unregistered CommenterNullius in Verba

ATTP - more on the elephant:

Palle & Laken 2013, Global cloud anomaly (%), 1983-2012) graph

analysis of Australian-Temperature after adjustment for cloud cover

IPCC ignores and buries cloud cover.

What evidence do you have that increased insolation from reduced tropical cloud cover did not result in the increased average surface temperature in the in the late 20th Century? Or where did all this energy go?

What explains the similar rates of warming in 1860-80 and 1910-40 when anthropogenic CO2 emissions were much less than today?

I contend that the satellite cloud cover data, and the GISP and Vosktok ice core data shows that CO2 has feck all to do with it. The only logical conclusion is that the AGW thesis is mostly bollocks, and at atmospheric CO2 is a very minor player in the climate system. The question now is how long will it take the wider scientific community to come to terms with the fact that they backed the wrong horse (or chose to stay silent) and come clean to the politicians and the media that they fucked up big time. The team and most other climate scientists with vested interests and funding are going to obsfucate and deny this for as long as they can. But as someone said yesterday, the truth will out in the end.

NIV - when I wrote "180-odd posts and no-one has mentioned the elephant in the room" I obviously hadn't seen your post at 12:02pm!

Jul 4, 2014 at 2:21 PM | Unregistered Commenterlapogus

Nullius,


Your refutation needs to reference evidence from a validated physical model.

I don't think I'm doing the refuting here.

Iapogus,


What evidence do you have that increased insolation from reduced tropical cloud cover did not result in the increased average surface temperature in the in the late 20th Century?

Well, you can look at Soden & Held (2006) and the recent IPCC document (which I'm not going to search for you) which conclude that clouds have produced a small positive feedback.

Jul 4, 2014 at 2:36 PM | Unregistered CommenterAnd Then There's Physics

I'm betting on this one.

A number of published papers and openly available data on sea level changes, glacier retreat, freezing/break-up dates of rivers, sea ice retreat, tree-ring observations, ice cores and changes of the cosmic-ray intensity, from the year 1000 to the present, are studied to examine how the Earth has recovered from the Little Ice Age (LIA).

We learn that the recovery from the LIA has proceeded continuously, roughly in a linear manner, from 1800-1850 to the present. The rate of the recovery in terms of temperature is about 0.5°C/100 years and thus it has important implications for understanding the present global warming.

It is suggested on the basis of a much longer period covering that the Earth is still in the process of recovery from the LIA; there is no sign to indicate the end of the recovery before 1900. Cosmic-ray intensity data show that solar activity was related to both the LIA and its recovery.

The multi-decadal oscillation of a period of 50 to 60 years was superposed on the linear change; it peaked in 1940 and 2000, causing the halting of warming temporarily after 2000. These changes are natural changes, and in order to determine the contribution of the manmade greenhouse effect, there is an urgent need to identify them correctly and accurately and remove them from the present global warming/cooling trend.

Akasofu 2010

Jul 4, 2014 at 3:19 PM | Unregistered CommenterRon C.

Mr Physics, your responses are little tidbits that would not have survived the scalpel at your own blog. Not useful. There are numerous examples of systems driven by 'physics' (well, how else can it be) that produce unpredictable outputs from our deterministic representation of their physics.

Jul 4, 2014 at 3:22 PM | Registered Commentershub

Shub,


your responses are little tidbits that would not have survived the scalpel at your own blog.

I'm assuming that you're implying that some (yourself for example) have made much more insightful, scientifically credible, and throughtful comments on my blog (that I then deleted) than I've made here. I'm not a particular fan - or really capable - of judging myself, but if that were true, I'd be bitterly disappointed.

Jul 4, 2014 at 3:28 PM | Unregistered CommenterAnd Then There's Physics

Scafetta is also looking good, updated to May 2014.
http://people.duke.edu/~ns2002/#astronomical_model_1

"Also an anthropogenic global climate change effect - greenhouse gas emission (GHG) plus urban heat island (UHI) plus land use change (LUC) - is likely present, but its overall contribution to climate change, also during the last decades, appears secondary to that associated to natural cycles.

It is possible that the global temperature will remain approximately steady or perhaps it will slightly cool for the next 2-3 decades, up to the 2030s, because the quasi 60-year cycle entered in its cooling phase around 2002 and the 115-year solar cycle will approach its minimum in 2030s yielding to a new grand solar minimum, which will have its own characteristics and will likely differ from the Maunder and Dalton solar grand minima.

The harmonically modeled natural cooling should be strong enough to compensate the projected anthropogenic warming, which cannot be more than a third of what calculated by the current climate models adopted by the IPCC because of geometrical constrains due to the presence of natural cycles. This conclusion also derives from the fact that solar variability at multiple time scales can be approximately reconstructed and, apparently, predicted with planetary tidal cycles plus a solar dynamo cycle."

Maybe I will put some money on Scafetta as well.

Jul 4, 2014 at 4:10 PM | Unregistered CommenterRon C.

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