Category Archives: agw

The sound of an idol toppling

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Like most of the world around it, the Church of England is so caught up in busyness and anxious make-work that it has ceased to attend to what is truly happening in the world around it; and as attention is simply another word for prayer this is a grievous fault.

If the Church were to pay attention, I believe that it would perceive one immensely important fact in particular: the great idol of our time is toppling. The idol is science, or, more particularly, the idol is a particular form of scientific and technical expertise that has been shepherded by a priestly class of laboratory-coat wearing men (well – in the story that is told, mostly men) who have journeyed into the greater mysteries and emerged bearing gifts and blessings for the people.

This idolatry, this white coated religion, has its foundation myths (Galileo!) and rituals (the scientific method!), its seminaries and its churches just like any other faith. Walter Brueggemann, in writing about the prophetic imagination, notes that when Moses, the archetypal prophet, seeks to inspire the people of Israel with a belief that things do not have to be the way that they are, that it is not an eternal truth that the Israelites must be enslaved by the Egyptians, a crucial step comes when the technocrats of the Pharaoh contend with the technocrat of YHWH – and they come up short (see Exodus chapters 7-9). Each time Moses and Aaron take a step to demonstrate the power of YHWH the magicians of Egypt are able to match the demonstrations using their own powers – until they cannot. There comes a point when the powers of the establishment are no longer sufficient to provide for the people, when they are shown as no longer omnipotent and omniscient, all wise, all benevolent.

There comes a point when the god bleeds.

Which is where we are now in the West. We have experienced an immense crisis, whose ramifications are still rippling through our lives. Rippling? Maybe a rip-tide. Covid 19 – from whence did it come? Almost certainly from gain of function research in a scientific laboratory in Wuhan. From the place of expected blessing has come a curse. The cure for the curse? A white coated woman in a laboratory achieved something amazing (Sarah Gilbert) yet the issues with the mRNA style vaccines (Pfizer, Moderna) seem to only grow with time. We have embarked upon an immense social experiment, whereby fear of a contagious virus has been deliberately stoked in order to justify unprecedented levels of social control. People in England, from where I write, have for the most part gone along with this. It’s what we tend to do, this is the land of the obedient queue. Yet there comes a point when that obedience comes to an end and the Anglo-Saxon plants their feet in the ground and says ‘No’. Then the authorities have to navigate around a new reality.

(It’s what happened with Brexit.)

So the apparatus of science and the religion of technological expertise is wobbling, it is uncertain – but why am I so sure that this wobbling is in fact an incipient toppling? Because of climate change. Not so much climate change itself but the scientific and technical apparatus that surrounds it, that has been so on display in Glasgow in the COP negotiations when we do not simply see the expected hypocrisies from the great and good who jet in from overseas in order to lecture the peons on the virtue of doing without, but also in those one might reasonably expect to know better – such as the Green politician from Brighton who flew to Glasgow rather than taking the train. The gap between the ritual intonations of ‘climate change’ and the people who are being lined up to change their patterns of life is becoming increasingly large. The people are noticing more and more, and are paying more and more attention, and some time soon the tipping point will be reached and the underlying science behind the rhetoric will be brought out blinking into the light.

At which point there will be much anger. The poor are being asked to pay for the choices of the rich; I am thinking parochially – the poor in post-industrial England are being asked to change their patterns of life (gas boilers, cars), all the things on which they rely, in order to… what exactly? The claims will be of seas rising, and nations vanishing, and mass migrations and so on and so forth – yet because the cost of the changes being demanded of the poor will be so great upon the poor, the poor will rightly say ‘prove it’, and the naked panjandrums will stand blinking and mumbling and Greta will denounce the blah blah blah and the Anglo-Saxon will say ‘No’.

For the IPCC itself no longer foresees disaster under the heading of climate change. The ‘consensus’ of 97% of scientists – which is itself a falling away from the true faith, for true science has no place for ‘consensus’ – will be shown as not very interesting. The climate is warming – yes – but how dangerous is the warming, what is the best way to respond to the warming, adaptation or mitigation and most of all, with Brueggemann in mind but as Rowan Williams once phrased the single most important question in Christian political thought: “Who pays the price?”

The rich will ask the poor to change their ways but the poor will once again vote for their own betterment, and the climate will shift, in earth as in politics, and as above so below the idols will topple. The rich will use the inherited rhetoric of the scientific and technological hegemonies and they will be rejected, and the idol of science will topple with them. No longer will science be seen as the repository of blessings and wisdom; instead the intertwining of science and technology and capitalism will be rejected as a whole, from pharmaceutical exploitations to farming interventions the fundamental wrongness of the apathistic stance will be perceived and rejected – for it will be asking people to be cold in the winter, and it will have lost its power of persuasion.

I hope that we don’t face a Butlerian Jihad, for those in white coats have indeed given many blessings to the people, but for so many reasons the thought patterns of scientific and technological rationality need to be, have to be, incorporated into a larger, wiser, deeper understanding. Theology must become the Queen of the Sciences once again. In one of those little ironies of history, if in the long run we are to ensure a safe place for the Richard Dawkins of this world, it will likely only be if a recognisably Christian culture is re-established.

Else there shall be war and famine and pestilence and death – and Hell shall follow.

The idol hasn’t toppled yet, but it is moving, and wobbling, and in another year or ten or twenty it will fall, and great will be the falling of it. Then, once again, the communities of the faithful will start to pick up the pieces and seek to preserve as much as possible of the good, whilst seeking to ensure the practice of virtues that might inhibit a return to the bad. The world will continue to turn, the tides will rise and fall, and human follies shall remain inescapable.

Kyrie Eleison.

The great green herring of the IPCC

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So those who know me know that I’m a dissident, old-fashioned and curmudgeonly sort, “afflicted with the malady of thought” – and that applies especially to Green things, where I find myself repeatedly annoyed by what I think of as ‘the great green herring’ of climate change.

I see the IPCC process as simply yet another form of the technological imperialism, the death-complex, that drives out our common humanity in favour of unacknowledged puritanical theologies and self-hatreds (I don’t doubt warming, nor human contributions to that, but all the coverage is about the most unlikely outcome). Fear is the mind-killer.

I like Schumacher’s idea of appropriate level technology, and the importance of the human scale, emphasising our biological and social nature and the importance of what we have in common. That is where we need to concentrate our attention – not with pandering to the fear-factories of modern media because we think that being seen is sufficient.

To put that in concrete terms – our future is not going to be electric cars, nor will it be people riding around on horseback, it will be everyone using a bicycle, and our communities will be geared around that, not the interests of the motorists.

The truth is that no matter what measures are taken to respond to climate change we are not going to be able to carry on in the way that we have been. We are still tracking the ‘world model’ outlined in the Limits to Growth, which means that in ten to fifteen years – AT BEST – we are going to go through a breakdown and collapse.

Personally I think it has already started – and it will solve the climate change problem fully no matter what we do. I first started studying climate change in 1989 – I still have my Greenpeace report on Global Warming on my bookshelf! – but what made me start questioning the orthodoxy was discovering LTG. You can’t be worried about both LTG and climate change – the one cancels the other.

Human life will carry on. Human civilisations will carry on. I think that the UK is well placed (in many senses) for a good future. The only question is how much damage the death-complex will make as it struggles with its own demise. When something is unsustainable that means that it will not be sustained, it will come to an end. Our machine civilisation, this asophic industrial fascism, will come to an end.

I am interested in what comes afterwards. What comes afterwards will be determined by the stories that we tell each other (which is why the Dark Mountain group is so important). I think a healthy story has to be rooted in the greatest story ever told – the only story that leads to long-term, healthy and sustainable communities. It’s also why we need a much better national narrative – more on that another time.

For a sense – a much more effectively-written sense – of what I am on about, have a read of this by Wendell Berry. Our human future begins with a hug.

Click to access Berry-Health-is-Membership.pdf

I don’t want to sound like a crazy person

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I don’t want to sound like a crazy person – which is an acknowledgement that I know I sometimes do.

However, I also know that sometimes the crazy person is right, and not just in a ‘stopped clock is right twice a day’ sense. Sometimes the crazy person is right simply because they are outside the social consensus, in the way of children and naked emperors; sometimes also the desire to be a child, and mock the nakedness of emperors, is a temptation for those who are more cynical than innocent.

So I accept the hazards involved in speaking from an unusual perspective. I accept most of all that ‘of course I could be wrong’ and perhaps what I most want from speaking about what I see is a refreshed dialogue, new perspectives that can show me where I am wrong. I am thirsty for the truth.

I have my own biases, most of which flow from a profound commitment to the Christian tradition, which has given me a respectful scepticism towards “the science” and a realistic appraisal of the nature of human evil.

All of which is a bit of throat clearing. This last year – these last few years – have been difficult ones. I have often proclaimed that I wanted to write more, and then not done so. So I’m not going to proclaim anything about how often I shall write. All I want to say is: I’m going to write some things that will make me sound like a crazy person. This is me trying to find the truth, and providing updates along the way – I am a work in progress.

It’s all about the symbolism

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josh cagw ice
I have long thought that the green movement made a huge strategic mistake by going ‘all in’ on global warming as the goad to try to change human behaviour. Sadly, after several rounds of ‘double or quits’, even the smallest events get used against the narrative. It’s time for those who are persuaded of the reality of the Limits to Growth to accept that the political argument about global warming has been lost, for at least another generation, and try and find a more productive way to communicate important truths. Hint: it won’t involve Chris Huhne.

Those odd and pesky little facts

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So: this is the global temperature trend of the last fifteen years. It is downwards. (Found here)

Now, in and of itself, that doesn’t mean very much – it could all be part of the natural fluctuation within an overall increasing trend, etc etc blah blah blah. (Although, obviously, the longer it continues, the more difficult the ‘mainstream consensus’ will find it to brush things away).

However, what I want to compare and contrast this graph with, is this one, showing use of fuels through the twentieth century (from Gail Tverberg).

Notice how the use of fossil fuels (=oil) really kicked off after the Second World War and that we are now using some four times as much per year as then. Now it occurs to me that if the relationship between the use of fossil fuels and the temperature of the earth was in any way a direct one, then we would be observing a similar acceleration in the year on year increase of temperature as can be seen in the use of fossil fuels. What we observe instead is a contra-indication. Not only is there no acceleration of the increase, there isn’t even an increase!

Clearly, carbon dioxide is only one factor in a chaotic system, and there simply isn’t a direct and linear relationship between the increase of CO2 in the atmosphere and global temperature change. That’s just a pesky little fact.

The interesting question, to my mind, is about how far the increase in temperature in the second half of the twentieth century is anomalous when compared to other periods of history – eg, when compared to the trend since 1700, or the trend since about 1800, or the trend since about 3000 BC. This, however, leads us into Hockey Stick territory – and it explains why that remains such a totem. If the Hockey Stick is correct, then the acceleration can be (just about) found. Yet if the Hockey Stick is fraudulent – which I believe it to be – then this is some strong empirical evidence running against the CAGW hypothesis. I shall maintain my watching brief.

Time for a Reformation of science

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I first published this May 12, 2010. It seems even more appropriate in the light of what Gleick has done.In a comment on my Montford review, Byron said this:

“while it is possible that sometimes an emperor needs to hear that he has no clothes from a child, in general, credentials matter. I would not presume to be able to judge between competing scientific professionals working on climate change. Instead, I will have a strong bias towards those who are actively publishing in recognised peer-review journals and whose work is accepted by reputable national and international scientific bodies.”

As a general point, I think this has some force as an argument. Philosophically speaking it is an appeal to authority, and whilst, as such, it has no logical force (literally none!) and is irrelevant to an argument, in human terms I see it as significant, and reasonable to take into account. The question is: is the child seeing something that everyone else can see when it is pointed out? Or is the child not seeing something because it requires education or maturity in order to see it?

When Luther nailed his theses to the church door, he was protesting against corruption in the church. The reason that his protest triggered the Reformation (rather than it happening at a different time, eg a hundred years earlier) was because of two principal things (IMHO!): a widespread understanding that the church was rotten, which undermined the support for the church from within, and the political situation in Germany which allowed Luther to gain practical support and shelter. I’ve always found it intriguing that the countries which ended up Roman Catholic were the countries where there was an existing realpolitik settlement with the Vatican in 1517.

The question at issue with regard to the Hockey Stick raises similar issues. When McIntyre started up his Climate Audit blog, it was the equivalent of the 95 theses. In just the same way as Luther believed himself to remain a faithful Christian, and not be inventing a new religion, (and, in fact, had the church responded with integrity, he would have remained a Catholic) so too do McIntyre’s criticisms not raise any questions about the theory of scientific investigation. Instead, the questions raised are about the current practice of that scientific investigation, most especially with regard to paleo-climatology and the weight given to certain alleged results in that field. More broadly – and Montford is good at bringing out these details – the questions raised by McIntyre cut very deeply into the rhetoric of science as it is presently employed. The issue is whether the current practice of peer-review is sufficient for establishing truth, or whether, in this particular case as an exemplar, the process of peer-review has been corrupted, allowing vested interests to control the flow of funding and research. In other words, in just the same way as the medieval church preserved the rhetoric of Christianity whilst collapsing into corruption and turning salvation into a cash-cow, is the scientific establishment now colluding in the covering up of malpractice in order to keep the lines of funding open?

Let’s return to the question of authority. In the medieval era the priests were the embodiment of authority, with the ability to excommunicate all rebels. In the contemporary era excommunication takes the form of withholding or withdrawing funding. Just as priests had the capacity to bully, eg through the confessional, so too do present scientific authorities have the capacity to distort processes in their own interests, eg through blackballing particular researchers or boycotting or belittling particular publications that do not toe the line. This was what “climategate” was about. As repeated by most of the participants, the actual truth of the Hockey Stick graph is in itself pretty marginal to the question of AGW. What it is not marginal to is the question of the legitimacy of the scientific establishment. A light has been shone into the inner workings, and just as the church tried to obscure the reasons for Luther’s protests (called the Catholic or Counter-Reformation) so too do the propagandists for the establishment say, either, ‘move along now, nothing to see, everything is fine’, or else, ‘just a few bad apples, the rest of science is healthy and fine’.

The truth of this depends on the truth about the Hockey Stick itself, which is why it has acquired totemic significance. Which brings me back to the question of the Emperor’s New Clothes and how we are to argue about the science. Byron’s comment at the top of this post is not, as such, an unreasonable position to hold. It does, however, assume good faith on the part of the scientific community. If that good faith is held in question then there is nothing else to be done except to begin to investigate the points at issue. To say that this can only be done by scientists is to accept the closed circle of authority – it is the equivalent of the church saying ‘trust us’ to Luther. That does not mean that everyone has equivalent authority (the Protestant error) – what it means is that the only way to establish truth is for all the arguments and assumptions to be brought out into the open.

It is this which has most persuaded me that McIntyre is on to something. The response of the establishment to McIntyre’s questioning has been to close ranks and stonewall. What an outsider can do most effectively is raise up settled assumptions to the light. A genuinely scientific community will be able to defend those assumptions, or, if they are indefensible, be able to creatively renew itself by revising those assumptions. Although I am not a trained scientist, I am a trained philosopher, and what that training has given me is the ability to judge a good argument. In other words, it is beyond my capacity to assess, eg, the impact of cloud cover in climate models (IMHO the modellers are still awaiting a Copernicus – the models seem like Ptolemaic systems about to collapse under the weight of their own complexity). It is not beyond my capacity to assess whether, eg, the RealClimate community is engaging with the arguments that McIntyre is raising. When I see evasion, equivocation, deception and the refusal to release information – in short, when I see science not treated as a holy endeavour – then red flags go up and I start to suspect that indulgences are being flogged to build a new St Peter’s.

If agw was a purely abstract argument then the scientific community could be left to get on with it, and the paradigm shifts can be allowed to happen on generational time-scales, which is normal. The difference is that the agw thesis is highly politicised, not just in the vast funding being put towards it, but in prospect. In the end, the best arguments will win – and the best arguments are those that expose themselves completely to the judgement of the community. They are the ones that allow little children to ask obvious questions, and run the risk of being found naked. They are not the ones that employ a vast retinue of retainers to suppress all dissent, and ostracise such small children from the conversation.

This is something that the better scientists have recognised, and are taking steps to address (I’m thinking here of someone like Judith Curry, who seems to me to be asking all the right questions). More broadly, I’m coming to see that the process of peer-review, which has not historically been a necessary part of science, could best be replaced by transparency. Information wants to be free. What the vernacular Bible was to Protestantism, the blogosphere will be to this new science – a sociological revolution triggered by a technological shift. Of course, I could be completely wrong, but in my view, just as Luther triggered the Reformation, and in due course the Protestant church, I suspect that what McIntyre has done is trigger a new and Reformed style of science – one in which openness and transparency are the hallmarks, and which is faster, more dynamic, more creative – and more accurate – than the existing magisterium.

Three factors

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A bit of a riff on my ‘hate it here’ post (NB newish readers should probably see this post for a bit more on the ‘hate’ part).

I’m not very good at discerning the timing of events – that is, I underestimate the amount of inertia in the system, and things happen much more slowly than might be expected on abstract logical grounds. That said, these are things that I see being important over the next fifteen years or so:

– first, the whole question of Islam/terrorism, and the likely political and strategic conflicts and realignments that might come about in the Middle East;
– second, the ongoing financial crisis and deflation, leading to (probably) a shift in economic power to the East;
– thirdly, crashing into resource limits, especially the peaking of the oil supply.

Now all of these three are going to interact in multiple and unpredictable ways. What I’m pretty sure about, however, is that coming out on the other side, we will be in a very different place. Which is why a lot of the prognostications that depend upon more or less ‘business as usual’ seem rather unreal to me.

I hate it here (updated)

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Thought I’d revisit this post from December 2006 (which I was reminded of by a conversation with Byron)

I wanted to use a blog post to write down how I see things panning out. I’ll probably re-appraise this on a regular basis, to see how my expectations are matching up with reality. I am conscious of an element of wishful thinking in the analysis – the simple truth is that I hate the way that the world is presently arranged, and I long for it to end. Maranatha!
One background assumption – I believe that humankind will not change its behaviour until it has exhausted all the alternatives. So this is pessimistic.
Point 2: the impact of a decline will spark a number of positive feedback systems, exacerbating the crisis. The positive side is that there will be some warning of what is coming, for those who can read the signs of the times. However, people will still not believe the scale of what is coming until it is too late. There will be a severe shortage of fuel throughout the West. Governments will ration it; at the bottom of the rationing heap will be the private user. Given the scale of the problem private commuting based upon fossil-fuels will cease, never to return. (This is a good thing. Kill the car! Let us be human!)
Point 3: one key positive feedback system will involve wider armed conflict throughout the world, especially in the Middle East. The key question there is whether the outcome will be an expansionist Islamist caliphate or an eventually nuclear Islamic civil war. I believe that the US/UK leadership is now actively fostering the latter. More widely, the West will outcompete the 3rd World for scarce petroleum and this will provoke die-off, especially in Africa. There are likely to be huge population flows towards the West in the coming two decades. Watch Mexico/US relations on this question, especially in the coming 18 months. Christians should also be aware of the push towards scapegoating of minorities, and be prepared to resist this.
Point 4: The solutions to global warming and peak oil are one and the same: powerdown and renewables. The most important long term question is whether and how far to continue using fossil fuels to preserve people in life, or whether we are able, in this generation, to make an effective change to a lower-energy and renewable civilisation. I do not believe that there are any cost-free options. There are many possibilities for a more peaceful transition; these are what Christians must spend their time working towards, so far as they are able and the divine grace precedes them. The princes of this world will deny them, and the world of the flesh will ignore them. The key issue is how far the angel of death is allowed to come.
BTW “I hate it here” is the title of Spider Jerusalem’s column. Spider Jerusalem is my hero.

Ten indicators on global warming

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I thought this was rather good (= clear, coherent and substantiated). Links at the original article.

1. Humans are currently emitting around 30 billion tonnes of CO2 into the atmosphere (CDIAC). Of course, it could be coincidence that CO2 levels are rising so sharply at the same time so let’s look at more evidence that we’re responsible for the rise in CO2 levels.
2. When we measure the type of carbon accumulating in the atmosphere, we observe more of the type of carbon that comes from fossil fuels (Manning 2006).
3. This is corroborated by measurements of oxygen in the atmosphere. Oxygen levels are falling in line with the amount of carbon dioxide rising, just as you’d expect from fossil fuel burning which takes oxygen out of the air to create carbon dioxide (Manning 2006).
4. Further independent evidence that humans are raising CO2 levels comes from measurements of carbon found in coral records going back several centuries. These find a recent sharp rise in the type of carbon that comes from fossil fuels (Pelejero 2005).
5. So we know humans are raising CO2 levels. What’s the effect? Satellites measure less heat escaping out to space, at the particular wavelengths that CO2 absorbs heat, thus finding “direct experimental evidence for a significant increase in the Earth’s greenhouse effect”. (Harries 2001, Griggs 2004, Chen 2007).
6. If less heat is escaping to space, where is it going? Back to the Earth’s surface. Surface measurements confirm this, observing more downward infrared radiation (Philipona 2004, Wang 2009). A closer look at the downward radiation finds more heat returning at CO2 wavelengths, leading to the conclusion that “this experimental data should effectively end the argument by skeptics that no experimental evidence exists for the connection between greenhouse gas increases in the atmosphere and global warming.” (Evans 2006).
7. If an increased greenhouse effect is causing global warming, we should see certain patterns in the warming. For example, the planet should warm faster at night than during the day. This is indeed being observed (Braganza 2004, Alexander 2006).
8. Another distinctive pattern of greenhouse warming is cooling in the upper atmosphere, otherwise known as the stratosphere. This is exactly what’s happening (Jones 2003).
9. With the lower atmosphere (the troposphere) warming and the upper atmosphere (the stratophere) cooling, another consequence is the boundary between the troposphere and stratophere, otherwise known as the tropopause, should rise as a consequence of greenhouse warming. This has been observed (Santer 2003).
10. An even higher layer of the atmosphere, the ionosphere, is expected to cool and contract in response to greenhouse warming. This has been observed by satellites (Laštovi?ka 2006).

(My position is still basically as set out here though.)

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The Hockey Stick Illusion – a brief criticism of a criticism

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Real Climate has published something of a review of Montford’s book. When I read it (yes, I do read Real Climate, as much as I can – that is, I tend to have enough time, I just find it difficult to digest nonsense 😉 it occurred to me that it was a perfect example of bad criticism, and thus – as I’ve mentioned before – something which I do think falls into an area where I have a little expertise.

I’m only going to explore one item in Tamino’s review; for more substantial responses go here and here; in brief, Tamino doesn’t engage with the substantive argument. No change there then.

First, it will be worth summarising one of the arguments that Montford makes. Rather helpfully for the statistically challenged, like myself, Montford takes time to explain what Principal Components analysis (PC analysis) actually does: it sifts raw statistical data in order to extract significant information (notable patterns). Crucially, each ‘sifting’ extracts less useful information than the last, so PC1 is very useful but each successive PC is less so. Montford: “while the PC1 might explain 60% of the total variance, by the time you get to PC4, you might be talking about only 6 or 7%. In other words, the PC4 is not telling you much of any significance at all”. Montford uses this very helpful analogy:

“The PCs are often described as being like the shadow cast by a three-dimensional object. Imagine you are holding an object, say a comb, up to the sunlight, and it is casting a shadow on the table in front of you. There are lots of ways you could hold the comb, each of which would cast a different shadow onto the table, but the one which tells you the most about the object is when you expose the face of the comb to the light. When you do this, the sun passes between the teeth and you can see all the individual points. You can tell from the shadow that what is being held up is a comb. This shadow is analagous to the first PC. Now rotate the comb through a right angle, so that you are pointing the long edge of the comb to the sun. If you do this, the shadow cast is just a long thin line. You can see from the sahdow that you are holidng a long thin object, but it could be just about anything. This would be the second PC. It tells us something about the object, but not as much as the first PC. You can rotate through a right angle again and let the sunlight fall on the short edge of the comb. Here the shadow is almost meaningless. You can tell that something is being held up, but it’s impossible to draw any meaningful conclusions from it. This then, is the third PC.”

This is how Tamino ‘responds’:

Principal Components

For instance: one of the proxy series used as far back as the year 1400 was NOAMERPC1, the 1st “principal component” (PC1) used to represent patterns in a series of 70 tree-ring data sets from North America; this proxy series strongly resembles a hockey stick. McIntyre & McKitrick (hereafter called “MM”) claimed that the PCA used by MBH98 wasn’t valid because they had used a different “centering” convention than is customary. It’s customary to subtract the average value from each data series as the first step of computing PCA, but MBH98 had subtracted the average value during the 20th century. When MM applied PCA to the North American tree-ring series but centered the data in the usual way, then retained 2 PC series just as MBH98 had, lo and behold — the hockey-stick-shaped PC wasn’t among them! One hockey stick gone.

Or so they claimed. In fact the hockey-stick shaped PC was still there, but it was no longer the strongest PC (PC1), it was now only 4th-strongest (PC4). This raises the question, how many PCs should be included from such an analysis? MBH98 had originally included two PC series from this analysis because that’s the number indicated by a standard “selection rule” for PC analysis (read about it here).

MM used the standard centering convention, but applied no selection rule — they just imitated MBH98 by including 2 PC series, and since the hockey stick wasn’t one of those 2, that was good enough for them. But applying the standard selection rules to the PCA analysis of MM indicates that you should include five PC series, and the hockey-stick shaped PC is among them (at #4). Whether you use the MBH98 non-standard centering, or standard centering, the hockey-stick shaped PC must still be included in the analysis.

[…snip…]

The truth is that whichever version of PCA you use, the hockey-stick shaped PC is one of the statistically significant patterns. There’s a reason for that: the hockey-stick shaped pattern is in the data, and it’s not just noise it’s signal. Montford’s book makes it obvious that MM actually do have a selection rule of their own devising: if it looks like a hockey stick, get rid of it.

So – Tamino’s argument is that because the hockey-stick shape emerges with the fourth ‘cut’ it still counts as statistically significant. Although he accepts that the standard convention is to use just two passes (= PC1 and PC2) he goes on to say “applying the standard selection rules to the PCA analysis of MM indicates that you should include five PC series, and the hockey-stick shaped PC is among them (at #4)”. (Please shout if I’ve misunderstood the substantive point that Tamino is making here.)

Can people see why I find this an inadequate response to Montford? Montford explains PC analysis at length, and a significant element of the argument is that the #4 cut doesn’t give useful data. Tamino at first accepts this (with a link expanding the acceptance) but then seems to go back on himself by simply asserting that five series should be included, and that the hockey-stick shape (#4) is significant. Why? Where is the argument for this?

There are ways in which Montford could be shot down here – and I would imagine that a competent statistician, familiar with these issues, could do it quite swiftly _if_ Montford is wrong. My point is a broader one – purely as a matter of rhetoric, Montford has the more compelling argument. He makes a point and explains it in detail – I understand the argument that Montford is making and it seems coherent. Tamino’s response is very different, in effect it is merely an assertion, which we are to take ‘on authority’. As the authority of the realclimate site is – for me – completely shot, the argument falls.

If there is another place where realclimate defends the statistical usefulness of a PC4 analysis, I’d be interested to read it.