Bishop Hill Where there is harmony, let us create discord
Jul 3, 2014 Climate: Statistics Climate: Surface 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 @MetOffice clarify their position wrt statistical models - in a way that @aDissentient 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.
Bishop Hill
In my post above I said:
If you want to understand why temperature has changed, you will indeed need a physical model.
As I put it in a tweet to Anders, he and I are in glorious harmony.
He has just replied:
No, I really don't think we are. If you want to understand GW you need a physical model.
I laughed so much I got cramp in an intercostal.
Reader Comments (307)
"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".
bit of a jump there.
Evidence for the forcings is due to human activities
Dare I suggest that the main factor in Anders disagreement with you and Dougalugs is your ideology. As yours is the wrong kind Anders will disagree with you even though you are all saying the same thing.
Mailman
[BH: See the update to the post!]
Very nicely done.
A survey of scientists was conducted as to what they believed was the direction of “Up”. One scientist pointing vertically, at right angles to the horizontal; all the others pointed at different angles, to about 45° below the horizontal.
Conclusion: with such a divergence of opinions, it has to be concluded that no one scientist can claim to be correct; the actual direction of “Up”, therefore, has to be the mean of all the directions indicated by the whole of those present. The consensus, thus derived, is that “Up” is anywhere at an angle of 30.325° above the nominal horizontal.
Further work is being undertaken to determine what “Horizontal” is.
Too many nots here?
The need to disagree when one really doesn't is what we should perhaps call 'denier' syndrome.
"Dare I suggest that the main factor in Anders disagreement with you and Dougalugs is your ideology. As yours is the wrong kind Anders will disagree with you even though you are all saying the same thing."
Asking for and evaluating evidence is now an ideological position? I suppose if Western Rationalism is defined as an 'ideology' then I suppose it would be.
For the fun of the argument, lets not quibble about the quality of any 1880 temperature measurement, lets assume its a perfectly adequate construct; and lets accept that present temperatures are higher now than in 1880. By way of explaining that, Anders says: 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." Well yes, one does need to consider the physical processes that COULD drive this warming. One COULD also consider that natural processes dwarf man's activity. Warmists need to argue their case, not just proceed by assertion.
The reason they fight this point so vehemently is because they want to go beyond the chemistry and physics into unproven feedbacks. The feedbacks require there to be something alarming and clearly unnatural, not just a modest warming from CO2. I sometimes wonder if current conditions persist, the warmists will have to claim that natural forces have driven us into a little ice age, that we can't see because of rapid AGW.
Plus I've just had a look over at that blog and it's not surprising who is posting over there, BBD, Eli, Wots et al. The usual catastrophiliacs.
Also it's amazing to see the kinds of mental gymnastics going on over there where Anders completely ignores the question being asked and instead answers his own imaginary one.
In the Real World (tm), Anders must be a "Team" climate scientist?
Regards
Mailman
Ps. Doug, I think it's pointless trying to engage them as you are on a hiding to nothing. They will just ignore your posts and answer questions you never asked (ala your comment about the pr item not being the MO's actual response).
Without the physical understanding of long term variability, less than 1 out of 30 climate science journal articles are worthwhile.
(Before this thread was opened, I posted the following on a previous thread.)
I posted the following at And now there is physics. ("Your comment is awaiting moderation")
____________________________________________________________________________
I think there may be some misunderstanding of a key point here. If you have a statistical model for the process that generates a random signal, you can use this to decide whether what you are observing is:
- simply the signal fluctuating as normal
- the signal is no longer fluctuating as normal because something has changed significantly and what you are now seeing is unlikely to have been generated by a process described by your model.
This is standard stuff in (for example) detecting the seismic signature of a nuclear detonation against background seismic activity. Or the noise of a nuclea submarine against the background of normal undersea noise. When your tests show that something that no longer has the normal statistical characteristics, you can infer that something has changed.
My understanding of Andrew Montford's point is that, in the absence of a statistical model for climate variations in the absence of anthropological effects, you can't say whether the recently observed changes are out of the normal range of statistical variability. I think you agree with him on the nonexistence of adequate statistical models.
Bill
That phrase "proceed by assertion" sums it up perfectly.
tell you why a dataset has [certain] properties. For that you need to use the appropriate physics or chemistry
No that is not true at all. Multivariate regression is routinely used to tell you which inputs (regressors) have a statistically significant impact upon the phenomenon you're looking at and their coefficients allude to how much of an impact they're having. Now that comes with important assumptions but the idea that you cannot ascertain why a certain dataset has certain properties from a statistical model is nonsense. It is a linchpin of econometric and indeed a similar approach using PCs (and a poor implementation too) was used to produce the infamous hockey stick based on the very principle that one could discern controls for psychical processes from statistical models.
Of course the statistical models don't tell you why some phenomenon are important and why; but then that's a different question.
I have been lurking for some time now. I do have some questions about this exchange, though.
On the other blog (and elsewhere) the primary piece of evidence cited in favour of the "consensus" is (aiui) is that, because of increased CO2, the climate is gaining energy and that this must, therefore result in higher temperatures, whether we can see them or not.
My questions are:
(A) is it right to talk about "gaining" energy when what we are actually talking about is retaining more energy (all energy coming from the sun)?
(B) if temperatures have been increasing since the little ice age, what processes caused the climate to gain (or retain) the energy needed to do this prior to industrialisation?
(C) what account (if any) is taken of the release of the stored energy contained in fossil fuels? Does that add energy to the climate over and above any Co2 emissions?
(If my questions are foolish, be nice:-)
One of the biggest breakthroughs in industrial statistics occurred in the 1920s when Dr Shewhart of the Bell Laboratories came up with a way to decide when it was likely that a cause of some of the observed variability in a system could be identified. He discovered that engineers and quality control managers, as well as machine operators, who ignored this method were liable to mount wasteful investigations into what they thought were odd or unacceptable data values, and almost inevitably make changes to the production process from which the data came. Such interventions generally made the process worse, i.e. with more variability that it had before. There was a great effort in those days to reduce the noise in telephone connections, and part of this was aimed at reducing the variation from one telephone handset to the next. They dreamed of replacing the old phrase 'as alike as two peas in a pod', with 'as alike as two telephones'. But many well-intentioned efforts were making things worse.
The underlying notion is that in complex systems, such as manufacturing processes, there are a great many causes of variation – generally people involved can come up dozens at the drop of a hat. In a well-controlled system, this results in predictable outputs within ranges or limits. The inevitable zigs and zags observed when data is plotted and found to lie within these limits are believed to be causal – they just look like random variation because so many factors are influencing the process in lots of little ways – but it would in general be very hard indeed to take a particular excursion, say the highest value observed last week, and find the reason or reasons why it happened. Such investigations are not only likely to unproductive, they are liable to be harmful since people charged with 'doing something' about a problem (that 'highest value' might be highly undesirable for example), will generally find 'something to do' about it. Shewhart showed how that could often make matters worse if the process had not actually changed in any way to produce an unusual-seeming value. By changing the process in situations in which the process had not actually changed when it produced last week's highest value (e.g. of a measured length of a manufactured part), the change may just add a new source of variation that might make the process worse than before.
The great practical value of his insights came in part from knowing when to leave a process alone, and in part from knowing when to mount an investigation to track down causes of change. In essence, his method was a signal detection system usable on the shopfloor, and it has been credited with a tremendous contribution to quality and productivity in the decades since.
Now industrial processes can be complex enough, but they are not as complex as the climate system which has influential factors acting on a mind-boggling range of space and timescales. Furthermore, industrial process monitoring data can be of far higher quality than that which has been accumulated about climate. We also know that important factors such as orbital parameters do change, and that the system has had major transitions in the past between, most notably, periods with and without major long-lasting icesheets. A simple monitoring system of the Shewhart kind would indeed allow the weather gods to note using remote sensing that something out of the ordinary had happened during such transitions. We could well do with some such system on the far shorter timescales of greatest interest to us – which are say the order of a few decades. We are hampered by data quality and data sparseness problems, but a goal of producing a statistical model that would be widely accepted over such short timescales would be a highly desirable one.
Those in the CO2 Control Knob camp need no such model. Observations which conflict with a cherished theory are a distraction. Theirs is a revealed truth which they are driven to share, and to 'get some something done about'. They have, to pursue the industrial analogy a little further, won the attention of the management, and so all manner of memos and changes and 'improvements' are being instigated. We are to walk or cycle more. We are to switch off lights or use (toxic) lightbulbs that give off poor light but use less electricity, we are to build windmills in the factory grounds, put solar panels on the roof, and install diesel generators to cover the frequent occasions when neither provide adequate supplies. Meanwhile, important processes and urgent problems inside the factory are being neglected, and it looks like we might go out of business altogether.
Those who favour a calmer, and more scientific approach, cannot but fail to notice that the CO2 Big Driver theory has not led to any improvement in predictive skill, and that there are many 'observational metrics' that contradict the simple-minded excursions of second-sight that the theory encourages in its followers. Such as snow being a thing of the past in the UK. Such as hurricanes getting 'worse', or tornadoes and other extreme weather events becoming more frequent in the States. Or sea levels rising in dramatically different ways from the past. Or polar ice sheets disappearing. Or Himalayan glaciers ceasing to be, and so on and on. Past and present data though can be brushed aside by the acolytes. The future data will be on their side. So they say.
So, merely observing that there is no convincing statistical evidence of anything extraordinary going on in key 'observational metrics' such as temperatures is to tread on the toes of the faithful. They are liable to get upset by any reduction of attention from the future which they are so wedded-to. It is a threat, presumably, to their credibility amongst the wider public – so many of whom have yet to be converted to 'the cause'.
What did I tell you Bish? Anders disagreement with you is solely driven by your ideology. He hates you because you are of the wrong "faith".
Regards
Mailman
Many are hopelessly confused about the issue of whether warming has taken place at all, and the issue of whether it is anything outside of a range that could be described 'normal' or expected. Hence the routine use of the D-word. And that is before the topic of attribution is even broached.
Yet almost wilful obscurity, not clarity, characterises the arguments about statistical significance that are routinely fed to, and propagated by, the wider MSM such as the BBC. The BBC don't know any better, but that is not a credible excuse for many proponents of AGW.
Thanks for the Update where Andrew writes:
and Anders says back to him:
Andrew and Anders. You say potato and I say potahto. Let's call the whole thing off.
Earlier I said this should be called
by which I mean the syndrome you start to exhibit after you and your allies have called other people deniers for no good reason for so long. You have to deny agreement (inevitable verb) even when it's crystal clear it's there. As our host casts it it's the Prayer of St Francis in reverse. Should we ask the current Pope to lend a hand?
I sometimes wonder if current conditions persist, the warmists will have to claim that natural forces have driven us into a little ice age, that we can't see because of rapid AGW.
Jul 3, 2014 at 11:22 AM | TinyCO2
=========================================================
It's already happened
http://www.bbc.co.uk/news/science-environment-16439807
BBC News - Carbon emissions 'will defer Ice Age'
http://www.carbonbrief.org/blog/2012/01/lethal-ice-age-prevented-by-climate-change/
http://wattsupwiththat.com/2013/04/27/good-news-elevated-co2-may-extend-interglacial-prevent-next-ice-age/
http://www.ibtimes.com/next-ice-age-1500-years-prevented-carbon-dioxide-emissions-393160
Every possible eventuality is now covered by and caused by AGW.
interesting comment, John Shade. Thanks.
The "precautionary principle" tells us to stop subsidizing making babies
Which would immediately hem in turd world immigratin by 90%, their main bx case destroyed.
How can all these women so heartless and pursue the destruction of Gaiia for their own proudness feelings??
This should be made public and they should be sentenced to long prison sentences.
As a corrollary, many a champagne socialist head would explode contributing to some more carbon saved (less conference seats in fancy places to jet to),
Anders' (ANDthenthEReSphysics?) objection to questioning whether the post industrial rise in temperatures, in particular the late 20th century rise, can be deemed to be "statistically significant" is rooted in his belief that the rise in temperatures is predominantly due to man. Therefore, by definition, in the longer record (much of which cannot be sufficiently accurately discerned) of natural temperature variation, the last 150 years increase would indeed be statistically significant. Problems: we can't prove for sure that the 19th and 20th century rises in temperature are 'extraordinary' in terms of past natural variation and we do NOT (contrary to warmist protestations) have a viable physical model which would demonstrate that recent changes in temperature COULD be due to anthropogenic climate forcings. Bummer. Hence the pressing need for a 'new narrative' and new, improved 'post normal' climate science.
jferguson: Seconded - and I raise your 'interesting' to 'seminal'.
Simple-minded excursions of second-sight. I've not seen a better description of a phenomenon we've observed so many times, not just from Dr Viner. Thanks once again John Shade.
There is no hamrony here as claimed.
The two contrasting positions are:
There is no statistical model, so your claims are unproven until you can show otherwise.
VS.
There is no statistical model, so my assertions are descriptive of a real threat until you can show otherwise.
Quite a distinction.
Mailman:
Totally disagree. The world doesn't just consist of people like Doug and those like Anders. There are multitudes who are not yet clear in their minds what they think about these issues and these are open dialogues - by which I mean not that nothing is censored but that even after unjustified snips there is more than one point of view on display to consider and digest. An immensely worthwhile exercise.
@WFC
It is right to say that increased CO2 will by itself cause the climate system to gain energy. AFAIK, most people here will also accept that.
(A) Does the atmosphere gain energy when its average temperature rises? Yes.
(B) This is the right question. No one has an answer good enough to fully explain geological observations.
(C) Too small to make a difference.
Someone else may answer differently.
rhoda:
Well, there's a lot of hamming going on from one side, on that I'll agree.
I think you put the difference fairly but it's not one put clearly by Anders and his ilk, because it shows which side is right and which is wrong. They have to make a difference out of
where there is no difference. Because, for those who don't care to come over here to check, it makes out that Anders' opponents are completely dumb or malign, in line with the label 'denier'. That one term drives so much for me by now. It's my CO2, my trace gas, my control knob!
Yes so once again it comes back to the models where the conclusion is obtained directly from the input assumptions. If you assume nature is dominant - as it now appears to be, after 17 years of no reaction to a manmade warming amplifier, then there is no need for any manmade component in the model, and hence no alarm.
At which point they'll go back to the statistics argument again, or a paleo argument, or indeed anything, however unphysical or contradictory to keep the gravy train on the tracks in full knowledge that journalists and politicians are too thick to notice.
It seems to me that the contrasting positions are more fundamental than rhoda's.
ATTP: the climate has gained energy as the result of ACO2 emissions, therefore it must have warmed as the result (whether we can measure it or not) and that that warming must be considered to be "unnatural".
BH: we have no way of properly testing whether recorded temperature increases are out of the ordinary.
They are therefore coming at this issue from opposite ends. ATTP is assuming that unnatural warming has occurred and that the inability to isolate it from the "norm" is a failure of statistics. BH otoh, is coming from the Lets see what is actually happening, end.
JamesG:
But nobody has that level of knowledge of the future. Five years ago I'd never heard of David Rose. Too many counsels of despair. The truth is mighty and will prevail. Monckton's not wrong about that.
Anders,..not very bright. Gets upset easily. If the inspiration for your blog name comes from BBD....
WFC:
And that once again makes clear which position is scientific and which isn't. So the difference must be purported to be about something else. Misdirection all.
very tall guy at Theres'Physics blog gets it:
Except I don't seen Montford or Keenan making points (2) or (3). In fact, I see climate activists making point (2) *all the time*.
What this means is when proponents of global warming theory encounter (1) and understand it, they don't like it. Which is why they attach their representations of your un-mentioned thoughts and try to shoot it down.
To modify verytallguy's formulation, (2) should be thrown away and (3) should simply and properly be modified:
Therefore (drum roll…) ‘ of course manmade climate change is not “clear” from the instrumental record.
That should be enough.
Anders thinks that If you want to understand GW you need a physical model. But the Bishop thinks If you want to understand GW you need a physical model.
A dilemma !!!
I will follow Pirsigs advice and go between the horns of this dilemma, my position is that If you want to understand GW you need a physical model.
EOptimist: Thesis-Antithesis-Synthesis at its most powerful. Even Hegel would be impressed.
(A) is it right to talk about "gaining" energy when what we are actually talking about is retaining more energy (all energy coming from the sun)?
(B) if temperatures have been increasing since the little ice age, what processes caused the climate to gain (or retain) the energy needed to do this prior to industrialisation?
(C) what account (if any) is taken of the release of the stored energy contained in fossil fuels? Does that add energy to the climate over and above any Co2 emissions?
(If my questions are foolish, be nice:-)
Jul 3, 2014 at 12:00 PM | Unregistered CommenterWFC
WFC:
(A) I think the question is simply a question of terminology - what you call a thing does not change what is (or is not) happening.
(B) Good question. So far as I know the little ice age (nor the medieval warm period) and what caused them to end has never been explained. Which for me confirms my belief that 'climate science' does not know its arse from its elbow.
(C) The energy released by burning of fossil fuels for a year (and nuclear reactor output if you want to add that in) is miniscule compared with the energy from the Sun that the Earth intercepts during that period.
According to Wikipedia, the energy from the Sun reach the Earth in one year is 10^24 joules
=1 000 000 000 000 000 000 000 000 joules. (A 100 watt light bulb consumes 100 joules of energy in one second.)
According to the same source, total world annual energy consumption in 2010 (presumably fossil + nuclear + everything else) was 10^20 joules ie one ten thousandth of the energy reaching Earth from the Sun in that period. Since the majority is from fossil fuel, it should serve as an estimate of energy from fossil fuel.
So it's miniscule - but larger than I would have guessed. Any effect on climate would be completely unmeasurable.
http://en.wikipedia.org/wiki/Orders_of_magnitude_%28energy%29
Richard D
We had the acid rain scare and before the science was properly 'in' we had already developed policy to retrofit SO2 scrubbers at great cost or close plant down. The science came in and said it was a miniscule to negligible problem. Nobody noticed because journalists ignored this unsexy, non-story and it apparently faded out of sight as an issue for the public and the greens alike. Except that the policy was still in place: Didcot A and Cockenzie were closed down not because of CO2 emissions but due to SO2 emissions to inhibit that non-existant acid rain problem. If the management of our main power station, Drax, hadn't switched to the crazy idea of burning trees then they'd have fallen foul of the same directive. Despite the truth, this is the level of stupidity we are dealing with!
Martin A
I have no knowledge of the statistics used in the analysis of seismic signatures of nuclear explosions, but their identification depends on maths, not statistics. When an earthquake occurs, strain is released, and crustal motion is in opposite directions on either side ot the fault. In some locations the P wave first arrivals will be oriented towards the source, in others the first arrivals will be opposite to the source. A focal plane solution will give the location, the orientation of the fault in 3D, and a description of the fault type.
With a nuclear explosion (expansion in all directions) all first arrivals will be moving away from the source. The signature is quite distinct, and no statistics needed here.
Anders can't agree with a 'denier' even when he's saying exactly the same thing because it's against the Climate Scietivists Code (Mann would spank him for it). He would be giving credibility to 'deniers' and that's not permitted under any circumstances. Everything 'deniers' say has to be 100% wrong, the complete opposite of the 'truth' otherwise it would be, at least partially, right - which is impossible - right?
It is a useful test though - anyone who behaves like Anders isn't a scientist - he's just a corrupt activist liar - and a fool.
Richard,
I doubt those who are yet to make their mind up read Anders blog.
Mailman
JamesG, I agree about the facts of acid rain, insofar as I have studied them. But not all the journalists who were taken in at the time have remained silent. One has written:
That was Matt Ridley of course, in December 2010. Ridley's influence is far greater today than it was in the 1980s, I would judge, and his policy scepticism in the climate area is informed by this earlier experience. Such voices make a tremendous difference. We cannot be sure of the future but my own view is that the collapse of CAGW (with emphasis on the C) will be a moment for reevaluation much more widely. I accept though that some nutty subsidies may last longer than they should, despite such an intellectual sea-change.
Mailman: It's almost certainly true that more open-minded people will find this blog more congenial and the situation is all the better for that. But without the non-sequiturs in that one this side wouldn't be so much fun today and so convincing today. Thanks to Doug as well as Andrew for that.
Why so many people falling for 'The climate has increased energy due to CO2'. That is definitely NOT a given. You'd have to prove it, and 'CO2 traps heat' will not do. You need a physical model. Much warming theory relies on energetic balance, sunshine in equals radiation out. No trapped heat.
Nothing much is happening. If it does, we can adapt to actual conditions, not those predicted on the basis of unproven models which have so far provided no verifiable predictions.
Rhoda: 100% with you on that.
@WFC
I think you've nailed it. When Anders adds "GW" into the statement, he reveals an assumption that a warming trend exists and must be explained by physical factors (eg. "forcings"). Anders' position also includes the assumption that a linear trend imposed upon the data is a satisfactory statistical model to explain what is happening.
As William Briggs points out in the link above, the linear trends implies that the forcing is constant. This can only be proven if that same trend skillfully predicts the future. As we know, those predictions of CO2 forcing have not been successful since 1998.
I think when Confused says the paragraph "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." is "a bit of a jump", that to me is a huge understatement. It is an impossible jump to make.
The statement is supposed to be the *result* of scientific research, but in our post-modern-science world is used as an input. The IPCC states this then looks for supporting evidence to confirm it, on the same level as the IPCC model outputs being used as 'data' inputs to other models as if they were real. It is preposterous and unjustified. Every record shows that CO2 follows temperature, not lead it, and it is simply mind bogglingly brazen to think that man can overturn such a basic cause-effect relationship with ~0.0012% of the atmosphere that is man's CO2.
@ Martin A @ Richard Blake
Thank you for those replies.
One more - arising from the discussion in the other blog:
Doesn't the law of conservation of energy require a closed thermodynamic system to apply? Is the Earth a closed thermodynamic system?
And, if it is held to be so, how do the evolutionists feel about that?
(Note - I do not subscribe to creationism in any way. It just appears to me to be ironic that the one theory (AGW) appears to require a closed system, whilst the other (evolution) requires an open one.)
I tried to link to a comment on my blog, but that failed, so I'll try repeating it below.
Okay, we agree that we need a physical model to understand what drives changes in our surface temperature (at least I think we do). We also agree, I think, that a statistical model - alone - cannot explain what these physical processes are. So, maybe you can explain what you mean by this
In fact the thrust of his work has been to determine what the empirical evidence for global warming is
The empirical evidence is that surface temperatures are higher today than they were 100 years ago. I think we agree that this is a true statement. You can also throw in OHC and reductions in ice mass if you want to consider empirical evidence for overall warming. On the other hand, if you mean empirical evidence for anthropogenic global warming then we seem to be back where we started. We can't determine that with a statistical model alone. Therefore suggesting that we don't have empirical evidence for something based on models that are unable to establish this, seems to be a rather circular argument.
So, we seem to agree on the limitations of statistical models. We seem to agree on the need for physical models if we wish to understand the processes involved. However, you still seem to be arguing that deficiencies in statistical models mean that we can't be certain that global warming is happening. That doesn't appear logically consistent.
Of course, whilst we are quibbling over whether the instrumental record can be demonstrated to unequivocally show the fingerprint of anthropogenic global warming, warmists continue the search for alternative metrics, even to the point of proclaiming that 'surface temperature is a lousy metric of global warming'. No doubt, this is largely prompted by an inconvenient 17 and a half year 'pause' - which is not a pause really, so they would have the public believe. It's still getting hotter. 2010 is the new hottest year on the Met Office's Hadcrut 4 dataset, which replaced Hadcrut 3 where 1998 was the hottest. The satellite data though, still have 1998 as the warmest since 1979, so this will require to be 'fixed' or pointedly ignored. The warming 'trend' though, despite their best efforts to demonstrate otherwise, is still subbornly neutral and increasingly divergent from the AGW climate models. Hence the Met Office are spending millions more of taxpayers' money on more sophisticated computer models which dispense with the need to 'prove' global warming via the temperature record and instead will be able to detect the 'fingerprint' of AGW in patterns of extreme weather. And who are we to disagree?
An oldie for Anders - words from someone he might respect but not apparently agree with:
http://www.youtube.com/watch?v=viaDa43WiLc
Anders: "No, I really don't think we are. If you want to understand GW you need a physical model....."
Perhaps, but
"...with verifiable predictive power"
seems to be missing.