Monday, November 3, 2008

In which I place myself beyond the pale of civilised discourse

Firstly, an observation on scientific models, coagulated in the enthralling world of emulsion polymerisation:

Whenever you are trying to model some complex phenomenon, the fit of the model to the data can be improved by adding more adjustable parameters. A complex phenomenon will usually be dependent on a large number of factors, but the fact that the model fits the data better when you incorporate an additional factor may or may not mean that new factor is important: it might just mean that the additional parameter(s) you have incorporated are improving your fit. This is another thing the David Sangster told me: ‘With enough adjustable parameters, you can fit a camel.’

So there is a tension between the complete model, which contains all the factors that ought to be physically important – but might be meaningless because of all the guesstimated parameters you have put in to quantify these factors- and the simple model, which ignores things that might be physically important, but also avoids adjustable parameters. If you go too far in one direction, you get a model that can fit any possible data; too far the other, you get the well-known ‘assume a spherical horse’ punchline.

This also means that when you are modelling a complex phenomenon, you will tend to base your model on the processes that are best known, where you don’t have to pick numbers out of the air for your adjustable parameters, and you will ignore if you possibly can the role played by processes that are less understood, which would force you to bring in rubbery parameters.

Now to place myself beyond the pale. Some time ago I made the assertion:

‘Anthropogenic global warming is a fact, but we shouldn’t do anything about it.’

The second part of this statement is a considered opinion, based on facts and reasoned deductions from them. The first part of this statement, I have realised over the last few months, is based on an irrational mood.

That is: in the laboratory, and considering the atmospheres of the planets in toto, there is a perfectly splendid mechanism by which increasing the concentration of atmospheric carbon dioxide should increase temperatures. It is a really good mechanism, based on rock-solid physics. But is there any evidence that this mechanism is responsible for observed temperature change globally? Evidence, in the scientific sense, is where a model has predictive value: it does not just fit the data we have, but tells us what future data is going to look like. I did not examine this question before I made the statement above. Instead, I relied on the irrational mood that it seemed like wishful thinking that there was some sort of feedback mechanism providentially cancelling out this Greenhouse warming effect.

Let us consider these two famous graphs:

What do they tell us? They show us a correlation between carbon dioxide concentration and average global temperature. They also tells us, very clearly, that there are factors other than carbon dioxide which contribute to the world’s temperature.

We could also draw graphs that show some sort of a correlation between sunspot activity and global temperature, and earthshine and global temperature, and the number of pirates and global temperature. The last of these three graphs would be a joke circulated by the Church of the Flying Spaghetti Monster. The other two are graphs where it is easy to construct a testable mechanism for how the correlation might work. These mechanisms are not as solid or as well understood as the Greenhouse mechanism. They rely on more rubbery adjustable parameters. If we ignore them, do we have a spherical horse? If we include them, do we have a camel?

What is signal, and what is noise, in the Hadcrut3 temperature curve?

An idea that was in fashion when I was an undergraduate was the Gaia hypothesis of James Lovelock. You don’t hear much about it nowadays. You might remember that it was all about negative feedbacks keeping the global ecosystem in balance, life keeping things tickety-boo for life. I bring it up here as a hand-waving justification for a recent shift in my irrational mood: given that there is a grain of truth in Lovelock’s ideas, it now seems to me reasonably likely that there would be a negative feedback mechanism tending to minimise the effects of any carbon dioxide we add to the air.

I must now revise my assertion:

‘Anthropogenic global warming is a conjecture with limited predictive value, and we shouldn’t do anything about it.’

And I have to apologise for some of the slighting references to global warming denialists I have made previously.

And unfortunately I have nerfed one of the major motivations for establishing this blog, which was to use any perceived authority associated with my real name to push the line that we shouldn’t take any action to stop anthropogenic global warming. By denying AGW to be a fact, I have placed myself outside the pale of civilised discourse and disqualified myself from making any statements on the issue that will be taken seriously.

Son cosas de la vida…


winstoninabox said...

knowing your disdain for all things wikipedia...

Dr. Clam said...

You have me wrong, winstoninabox, I am a big fan of wikipedia! The radical democratisation of knowledge is overwhelmingly a good thing.

Marco said...

Hah. You just want to be different from me now. To me the real enemy is still the linear views and the correlation of various views with ones peers. If the enemy is the line, your original view better attacks it, as the view that "Anthropogenic global warming is a conjecture with limited predictive value, but we should still act as if it was true and dangerous, as a large scale social experiment to see if we could have actually saved the earth if it depended on reductions of 50% by 2050"

Jenny said...

Theres an article on this in the latest RACI mag. I haven't read it yet, but it looks a bit Oh woe, hand wringy.

Dr. Clam said...

Must be your turn to write them a letter, Jenny! :)

Mackay_male said...

Chris, thanks for blogging your thoughts. I find them helpful reflections. Having dismissed AGW, I wonder if you could turn your thoughts to ocean acidification due to the same A. C02.

Chris Fellows said...

Good sir, if you scroll down through the previous posts, you should find three or four addressing the alkalinisation of the oceans. I should appreciate any feedback you may have!

Klaus Rohde said...

Sounds interesting (this and the following ones), but I must think it over carefully before I can respond intelligently (if at all). At first glance it seems to me that one can argue in this fashion about everything and conclude: ???? (this is what I meant when I said: I have to think it over carefully first).

Chris Fellows said...

It is good to hear from you again, Klaus!

At first glance it seems to me that one can argue in this fashion about everything and conclude: ????

Well no, not everything, in most things there are models with much better predictive value- we do not have to conclude ???? when we are discussing when the next eclipse of the sun will be visible from Tristan da Cunha, or how to make a glow-in-the-dark rabbit using jellyfish protein, or what will happen to the share price of Consolidated Widgets if we suddenly go out and by four million of them... there are good quantitative models for very many things.

I wanted to include an illustration of exactly what I meant by the AGW model lacking predictive value, but was not able to due to my scanner misbehaving... or more exactly, by my lack of technological nous stopping me from getting my scanner to do what I want. I shall have another go later today.

Anonymous said...

There is a light screwed into the ceiling of the veranda outside my home, a phony moon drawing insects out of the dark. They cover the ceiling like pepper; flying ants, moths, frantic black things almost too small to see. The human looks up with contempt, if it responds at all. How mindless these vermin are, what a blind thing instinct is. What a nuisance, these insects!

There are false moons that draw human beings just as surely, that can draw whole peoples and whole worlds. There are ideas that have been placed in the sphere of mind for humans to follow by things that are not human, who care for us not at all, who feel the same insectoid contempt towards us. Beware, you humans in the midst of a vast crowd, blinded by the radiance of one overwhelming idea!

If you are steering by a true guide, you will almost always be alone...

The spiderwebs grow thick around the light outside my home; around the light feed geckoes with skin like babies. The insects die; the human who uses the light does not care. He has turned it on; he will turn it off when he needs it no longer.

You are insects who have been drawn to a false idea; you are blinded by it and do not see the spiderwebs strung in your path, the tongues waiting to devour you. I am the gnat who warns you, I am the gnat who knows; I call out; close your eyes to this idea you follow; seal your heart, and wander into the cool night. Open your eyes when you can no longer hear the beating of ten thousand wings around you; when you are no longer conscious of a single mind that thinks as yours! Then you will be free, free to be guided by the earth's one moon!

journeymanj said...

What a delight to have someone in flight . Maybe you' like to talk sometime why our young people are not tending to study chemistry- what a disaster for competent ecological discusssions

Chris Fellows said...

I am the wrong person to ask why young people are not studying chemistry - since I have always found chemistry to be exciting and interesting and can't understand anyone not liking it! It is like asking Wally Lewis why young people are not playing rugby league. However, I think:

1)Parental attitudes are the single largest determinant of what students study, and the 'Silent Spring' generation of parents with very negative views of chemistry is still influential. Our enrolments in chemistry are well up the past two years so I think this demographic bolus may be passing. *knocks wood*

2)In the 'Asian Century' there are plenty of bright students in India and China - and elsewhere, I am blown away by the energy of chemistry postgrads in Thailand, for instance - studying chemistry, so globally the outlook is not so dire.

HelmutSchiretz said...

If one wishes to sway public opinion one doesn't draw graphs for the inquisitive mind as 99.9% or thereabouts of humanity don't have inquisitive minds - a point often missed or overlooked by academics.

Hence the simplification of graphs of the proposition of anthropogenic amplification of CO2 production due to fossil fuel combustion over the past 50 years or at least since the advent of the industrial revolution (steam locomotives and the like) ...

We can of course view these interpretations as some kind of organised scientifically based propaganda - or not - designed to affect administrative policy decisions ( ala Al Gore et al or even Garnaut and Flannery) ...

At the end of the day why this scientific community seeks to influence society (for whatever reason - be it funding or real science) and through them policy makers is irrelevant. The probability that one theory is more likely to be true than another should be the guiding principle.

We revert to the Heisenberg uncertainty principle as an example of that argument. namely the Argy Bargy between Heisenberg and his contemporaries in quantum physics versus the matrix mechanistic position (or the physics of such questions of the validity of wave theory in explaining propagation of energy within the electromagnetic spectrum.

Given time, the theories melded to some extent and continue to do so as cosmologists explore the universe extracting data for them to analyse and draw "some" conclusions.

Much of science is about searching for an answer to a question or dare I say a theory or hypothesis and then finding by answering (if that is indeed possible) that question another question arises - there's no LOOP to this - expect the unexpected !!!!

HelmutSchiretz said...

how come your email blocks me ???

HelmutSchiretz said...

Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the server for the recipient domain by [].

The error that the other server returned was:
554 Service unavailable; Client host [] blocked using Barracuda Reputation;