Some time ago I was asking the question: ‘How good are these climate models? What sort of predictive value have they shown in modelling future climate? After all, we’ve been doing them for a few decades now.’

A nice person on realclimate.org (there are some, not all of them treat people who disagree with them as the demonised other) directed me to a classic paper by Hansen et al.

"If you want an indication of how well these models do you can go get (J. Geo Res. 93 (1988) 9341) the Hansen GCM paper that people talk about, and compare their results with observed patterns of warming and other things."

Here is the plot from that paper showing the response of overall global temperature (which the authors argue convincingly is a much better parameter than any subset of the data, e.g., whether it snowed at my house or not in a given year) for three different scenarios- A being continued exponential growth, B being a more subdued form of business as usual, and C if drastic cuts are implemented starting a few years ago.

I went and got the Hadcrut3 data set and plotted it on top of this one, as near as I was able, and got this.

There are other data sets out there. I shall plot some of the others and put them up for you.

The Hansen et al. model predicts the greatest degree of warming at high latitudes, fitting observations, but the model also reproduces another feature of observed weather, that those latitudes have the highest natural variability from one year to another.

Update 2012:
Here is another three years of data. I do realise I haven't plotted any of the other data sets. Bad me. The red points are the average of 13 monthly data points averaged on each month, while the blue points are the actual Hadcrut3 monthly global averages you can download yourself.

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…

14% more First Year students agree balancing redox equations is fun!

In a striking improvement over last year's already high student enthusiasm for balancing redox equations, the proportion of students agreeing that balancing redox equations is fun has risen to 83%!

A little note about chain transfer to butyl methacrylate

For good or evil, this paper, which I began writing in 1999 at the request of Professor Bob Gilbert, is finally published. It is a tremendous pleasure to finally be a co-author with David Sangster, the eminence d'or of Australian polymer science. He is the source of the quote which informs my every waking action:

'Just because the model fits the data, it doesn't mean the model is true.'

I have today (10/11/09) found a splendid biography of David Sangster on the website of the University of Sydney.

Royal Society Discussion Paper, Ocean acidification due to increasing atmospheric carbon dioxide. Part Two.

The RSC discussion paper explains the division of ocean waters between an upper zone, where calcium carbonate formation is possible, and a colder lower zone, where it is not possible. The fact that mass transport between these zones is very slow is stressed. The paper does not actually give a pH profile of the ocean, but here is one:

(The little dark dots are the data from today; the big circles are attempts to figure out the situation at various times in the past, which is what the paper I sourced this from is about.)

Note that the vast majority of the volume of the ocean is cold, and relatively acidic. This deep ocean is where an enormous amount of carbon is stored. Transport of carbon dioxide out of or into this layer will not be controlled by thermodynamics (i. e., where carbon dioxide it would most dearly love to be), but by kinetics (i. e., how fast it can get there). Thus, it does not matter to this zone whether or not we are adding carbon dioxide to the atmosphere at a rate unparalleled in Earth’s history or not, because that will not control how fast it gets there. It has to run the gauntlet of the warm water- where it may or may not be converted into calcium carbonate- first.

Remember the figures in the last post on how the carbonic acid equilibria change with temperature. I am now going to make the assertion- which I should now go out and try to verify- that the deep ocean is more acidic *because* it is cold.

To qualify this as-yet-unverified assertion of mine, I should say that I have not yet found any data on the pressure dependence of the pKa values in solutions of reasonable ionic strength, which is also likely to be important.

I suggest that the temperature gradient of the ocean is probably what generates the pH profile, and because transport of carbon dioxide into or out of the ocean is slow compared to how much is already there, it is the temperature dependence of the carbonic acid equilibria which control the speciation observed. Note also that the boundary between the carbonate-forming zone and the non-carbonate forming zone, from our figures below showing what the equilibria do, is going to be dependent both on the pH of the upper layers and their temperature.

Now… if climate change means anything, it means the oceans warming up. Heating the ocean and reducing the pH will pull the carbonate/bicarbonate equilibrium in different directions. I don’t know which is likely to be more significant.

Because the historical record does not show carbon dioxide spouting out of the ocean immediately as temperature increases, but lagging about 1000 years, I am not at all worried about degassing of carbon dioxide starting some feedback loop of badness : until that cold lower ocean where most all of the carbonic acid species are sitting warms up, there is no reason for significant amounts of carbon dioxide to leave the ocean. That is, if degassing of the ocean *is* the reason for the increase in carbon dioxide lagging historical temperature changes. It might not be.

Royal Society Discussion Paper, Ocean acidification due to increasing atmospheric carbon dioxide. Part One.

My thoughts keep returning to the ‘de-alkalinisation of the oceans’. I started thinking about this the other day, first because I came across that article on coccolithophores in Science, and second because one of my students is writing a review article on the use of polymer additives to stop scale formation in desalination plants. The main scales formed in these plants are calcium sulfate at high temperatures, but at somewhat lower temperatures calcium carbonate or magnesium hydroxide.

The first thing you want to know about, if you want to stop scale forming, is what are the characteristics of the solution it is forming from. So early on in the draft appears this table:

(TDS is ‘total dissolved solids’.)

I went back and had another look at the Royal Society discussion paper that I referenced before. This is the paper referenced everywhere in the web where people are fretting about ocean de-alkalinisation. The range of pH values quoted in this table is greater than the range shown in the pretty map in the Royal Society report. In fact, the range of pH values in this table is greater than the size of the maximum change in surface water pH they predict for Figure 5.

So my first thought was, if changes in surface seawater alkalinity are likely to cause bad effects, we ought to be able to see these effects already in ‘canary in the coalmine’ water bodies- shallow, warm places like the Persian Gulf. The reefs there don’t seem to be in particularly good shape but there doesn’t seem to be any evidence that seawater alkalinisation is contributing to their woes. Anyway, this table got me thinking about the problem again.

In discussing the formation of calcium carbonate scale, my student had to talk about the dependence of the equilibrium constants K₁ and K₂ on temperature and the total ionic strength of the solution, and had referenced this paper by Millero et al., where the following figure appears:

The Millero et al. paper also summarises data from a lot of previous work and gets it all to fall on the same line- see this, for instance:

In case you don’t remember,

pK_a = –log₁₀(K_a),

and in this case, K₁ is the equilibrium constant for the reaction:

H₂CO₃ → HCO₃^– + H⁺

and K₂ is the equilibrium constant for this reaction:

HCO₃^– → CO₃^2– + H⁺

These figures are telling us that in seawater (where I^0.5 ~ 0.83), the equilibrium position of both these reactions is further over to the right hand side than if they were happening in common or garden distilled water. And they also tell us that the warmer the water, the further the equilibrium will be over to the right hand side as well.

I plotted up a graph showing how the speciation of pH should change in seawater using the values in this paper and got this figure:

The Royal Society Figure 2 is pretty much the same as mine. It shows carbonate kicking in at a slightly lower pH, but there are different K₂ values floating around in the literature and I'm not sure what value they used.

Zooming in on the pH range important for discussing what is going on in the oceans:

Getting rid of the log scale, and looking at the carbonate/bicarbonate equilibrium only:

More to follow.

C'est la vie

A while ago the prolific Anonymous asked me:

What do you think about the de-alkalinisation of the oceans. Anything ruinously doom and gloom possible there? Is adaptation of water species quick enough by your reckoning?

I have recently been thinking about this a lot, due to work I am doing on calcium carbonate formation in desalination plants, and will offer a substantial critique of this particular bugbear soon.

But in the meantime, I came across this nifty figure in Science the other day and thought I would share it with you. If someone had asked me, 'how will marine organisms respond to changes in total carbonic acid species concentration?', I like to think I would have been prescient enough to draw a figure like this one. Find a niche and fill it: such is the way of living things!

Dialogo

Simplicio: Have you heard? The Powers wish to reduce the amount we teach, so that we will have more time for research, and thus will produce more and better research.

Sagredo: I think the second part of your syllogism does not follow from the first.

Simplicio: Why, how is that?

Sagredo: One of us cannot have more than twenty-four hours in a day. But if one has a single intelligent and dedicated postgraduate student, then one has forty-eight. If one has two, one has seventy-two, and so forth. It is the many hours that come from having many students that enable us to produce more and better research.

Simplicio: True, but I cannot see how having a few more hours for research can hurt us.

Sagredo: Where do you suppose postgraduate students come from?

Simplicio: Most of them are from places like Tartary and Hind, are they not?

Sagredo: Yes, many of them are. They are attracted from diverse foreign lands by the splendour of the learning in our land. But many other places of learning seek also to attract them, and day by day the scholars of their own lands grow wealthier and more astute, so that one day no more will come to us.

Simplicio: That would be a calamity! So where else do they come from?

Sagredo: We raise them here, by teaching undergraduates.

Simplicio: Aha! There is no problem, then. Under the new system we will surely continue to teach undergraduates.

Sagredo: Simplicio, do you suppose all undergraduates are suitable to become postgraduates?

Simplicio: I guess not. Some are damnably simple.

Sagredo: Yes, it is only the few who hunger and thirst for knowledge that are suitable to become postgraduates. If we give our undergraduates half as much as we did before, and other places of learning continue to offer a full cup of learning, where will undergraduates like that go?

Simplicio: You think they will not come here?

Sagredo: Many of them will not.

Simplicio: But surely there are many who would not leave our lovely place of learning for the City of Dreadful Night or other distant places?

Sagredo: Yes, we must pin our hopes on such as those. But consider: if we teach them half as much, what will we need to do when they commence as postgraduate students?

Simplicio: I am not sure. I recall there are forms to fill out?

Sagredo: Besides that. We must perforce teach them the other half, if they are to work as well as postgraduates in the City of Dreadful Night work. And when we have done that, what must we do?

Simplicio: I suppose we must fill in some more forms.

Sagredo: Yes, for by then the first year of their candidature will be over.

Simplicio: It would seem, then, that you think this change will diminish our chances of doing more and better research, rather than increase them?

Sagredo: Most certainly. Why would a student who would make a good postgraduate in Physics or Chemistry do an undergraduate degree at a place of learning that does not take that discipline seriously?

Simplicio: Then I suppose the Powers wish to reduce our teaching hours for some other reason?

Sagredo; That is what I had thought.

Simplicio: Perhaps it is that they must be reduced because of this thing that has come from Bologna?

Sagredo; Ah, but the places of learning that have already gone down that path teach many more hours than we do.

Simplicio: Hmm. Perhaps it is, Sagredo, that those studies they wish to cut are only those where the numbers of undergraduates have been falling, so that we may conserve our resources, as our wealth wanes?

Sagredo: That would be a sensible course of action- but you see, Simplicio, it is the studies where numbers of undergraduates are holding steady that the Powers wish to cut back.

Simplicio: Ah.I see. Perhaps- no, that makes no sense. (sighs)
I wish Salviati was here to explain what was going on.

Sagredo: So do I, Simplicio.

Simplicio: It is a pity the Powers never replaced him, when he took his renowned research group to Brescia...

Two Cultures are Better than One

I have been asked to read this document in preparation for a meeting of the School Research Committee. It would be cruel to ask you to do so as well, but if you want to, please go ahead. It is basically a proposal for muddling the 'Two Cultures' back together in a porridge by structuring humanities studies around 'evolutionary theory' and stressing that 'evolutionary theory' is a 'form of narrative that functions within its social and historical context'.

I assert that:

Inappropriately mixing poorly-thought-out ideas from biology with the humanities gave us the First World War, the Second World War, and the Holocaust.

Inappropriately mixing poorly-thought-out ideas from the humanities with biology gave us the only comparable man-made catastrophe of the second half of the 20th century, the famine associated with Mao's 'Great Leap Forward'.


Let's not go there.

Things I don’t understand: The ‘Collapse’ of the Wavefunction

(NB: Let it not be supposed that the long delay since I last wrote something headed ‘Things I don’t understand’ means that there are not many, many, many, many other things that I don’t understand.)

In chemistry, the results of quantum mechanics that we are interested in are spectra. Whether these are lines in the ultraviolet/visible region corresponding to transitions between electronic states, or lines in the infrared region corresponding to transitions between vibrational states, or lines in the microwave region corresponding to transitions between rotational states, they are all transitions between energy states which are quite nicely defined.

We cannot ‘observe’ a chemical system in a particular state. We do not make a ‘measurement’ to see what state it is in. What we observe, what we measure, is its transition from one state to another. It seems entirely useless, as well as nonsensical, to say that a particular molecule was not in its first excited vibrational state until we hit it with a photon to give an anti-Stokes Raman peak.

In fact I am really quite vague about what sort of experiment you would do, in the traditional orthodox quantum mechanical sense, to measure the state of a system in such a way that its wavefunction ‘collapses’.

I don’t like the ugly discontinuity that the ‘collapse’ of a wavefunction introduces to quantum theory.

I don’t like the appearance of a privileged status for an ‘observer’ it introduces.

I especially don’t like the whole elaborate mass of New Age piffle that has been erected on this privileged status, a mass which has infected and compromised the otherwise splendid ouevre of Greg Egan, for instance.

A while ago I first came across de Broglie’s pilot-wave theory, and was impressed in my naive chemist’s way by the straightforward way it cut through the paradoxicality of the two-slit experiment. I wanted to know how this model had been developed since de Broglie cast it aside, and how the ‘collapse of the wavefunction’ looked in the pilot wave model. I couldn’t find anything then, because I didn’t know enough to look for the ‘de Broglie-Bohm’ model.

Apparently the collapse of the wavefunction is not a problem in the de Broglie-Bohm model. So it is non-local. Big deal. Every 1s hydrogen orbital wavefunction we tell our first year students about has a non-zero value at every point in the universe (though Excel, bless its heart, says with 15 digit precision that it is zero more than about a nanometre away from the nucleus). Better non-locality than mystical Copenhagen interpretation waffle about an ‘observer’, or worse yet, the deeply dippy ‘Many Worlds’ interpretation.

But why the de Broglie-Bohm model doesn’t get into trouble with the wavefunction collapsing- that’s something I don’t yet understand.

Down to four out of six

This letter, to The Australian's Higher Education Supplement, didn't get published either. So here it is:

I was saddened to read Barry Brook's endorsement of the cry 'Don't feed the troll!' If you are in the business of science education, you should treat every comment on your blog as a legitimate inquiry from a seeker-after-truth and respond politely. If your science is good, it will be obvious to your other readers if their response is to "sidestep valid critiques and ignore counter-evidence". If your science is good, it also doesn't matter how many times you repeat yourself. You will be improving the delivery of your message all the time.

It doesn't do any good to call people who disagree with you names ("sceptics, denialists, contrarians, delayers or delusionists" ... "cut of the same anti-intellectual cloth") or accuse them of being on the take ("Groups with vested interests in business as usual..."). If you are trying to communicate with those who are not already in your camp, such ad hominem attacks are worse than useless.

I thought it was unfortunate that an article entitled 'Science must prevail' contained no actual science. A calm 622 words outlining the physical mechanism of the Greenhouse Effect and the observational evidence for anthropogenic global warming would have been a much better use of space.

Best regards,

Chris Fellows

TANSTAAFL

I heard this on the radio this morning.

I direct your attention to this fragment in particular:

...you can creep along just using the electric motor which is great, you have zero emissions...

Well, no, if you creep along just using the electric motor, eventually you will run out and stop moving. From my vague understanding of how these things work, you need to run the gasoline engine to charge up the batteries.

I worry how much these sort of fuel-efficient vehicles are affected by what we might call the 'low-calorie pretzel' effect. The diet snack food has fewer calories, so you eat more of it. You are already 'doing the right thing' by driving your gee-whiz environment-friendly car, so you take it on trips where a person with a vehicle which is more expensive to run might walk, bike, or use public transport to save money...

We are our most valuable resource

The monthly publication of the Royal Australian Chemical Institute, Chemistry in Australia, has just printed my reply to an article they reprinted from Chemical and Engineering News a few months ago. It is not on the Web, and I don't have the scanner attached at the moment, but this is what I said:

Just felt compelled to write in response to the reprinted article by Rudy Baum, ‘Too many people?’, in ‘Your say’.

I grew up in the desert of Arizona, and I too have been saddened to see that landscape submerged under urban sprawl. I have no doubt that rising global temperatures will shift Earth’s arid bands further from the equator, making Victorian rangelands and many other environments more marginal for agriculture. I mourn every species lost as we humans have spread across the arid landscapes of America and Australia with our livestock and feral animals.

However, I think there is no evidence whatsoever that we need a ‘new economic paradigm’. In my lifetime, I have seen our current economic paradigm deliver incredible benefits to the peoples of Asia, and more and more countries reach a standard of living where responsible environmental management can become a duty, rather than an unaffordable luxury. As standards of living rise, population growth rates fall. In Europe today I understand only Albania and Iceland have birth rates above replacement level. Even countries like Iran are rapidly nearing zero population growth. At some point in the next fifty years, on current trends, world population growth is going to stop. This will be long before we reach the limits of the carrying capacity of the Earth. Long before we even come close.

The suburbs of Phoenix may be ugly, but the density of population in the Arizona deserts is less than historical population densities in many Asian deserts. Furthermore, population density need not correlate directly with environmental degradation. Those suburbanites are not grazing goats in the desert. They are not collecting firewood there. I confidently venture that they are using much less water per capita than Australian suburbanites are. You would need thousands of them to make the same impact as one irrigated cotton farm- cotton farms like the ones that used to line the highway between Tucson and Phoenix, and which were all gone the last time I was there.

Not long ago I visited another desert landscape rapidly being covered by urban sprawl, in Dubai. I didn’t find it depressing. I found it exhilarating, and was filled with wonder at the capacity of human beings to create, to build, to adapt. As we humans change the world, we adapt to the changes we make. The richer we are, and the better-educated we are, the better we adapt.

There is no need to run around calling for a new economic paradigm. Why should anyone listen to us, anyway? We have no special expertise in social engineering. If we want to change the world, let us do it in the time-honoured way that scientists have been changing the world for centuries: by figuring out interesting things about the universe that can be used to solve technical problems. There are cost-neutral or cost-saving actions that we can take to reduce the waste associated with our economic system by orders of magnitude. All that is required is that we continue to think imaginatively, and in an evidence-based way.

I guess what I am trying to say can be summed up in the words: ‘half full, not half empty’. Even the shift in the arid bands further from the equator is very far from being an unmitigated catastrophe - when was the last time you heard about drought in the Sahel?

(Why was there a reprinted editorial from Chemical & Engineering News in ‘Your say’, anyway? Don’t we have any opinions of our own, making it necessary for us to import American ones? I at least have been a naturalised Australian since 1996.)

Best regards,

Chris Fellows MRACI