In defence of consensus

If I were to hope for psychological subtlety from soap operas, or historical accuracy from Dan Brown, I’d have only myself to blame for my pain. So I realize that I am scarcely doing myself any favours by allowing myself to be distressed by scientifically illiterate junk in the financial pages of the Daily Telegraph. I know that. Yet there is a small part of me, no doubt immature, that exclaims “But this is a national newspaper – how can it be printing sheer nonsense?”

To wit: Ruth Lea, director of the Centre for Policy Research, on the unreliability of consensus views. These are, apparently, “frequently very wrong indeed.” The target of this extraordinarily silly diatribe is the consensus on the human role in climate change. We are reminded by Lea that Galileo opposed the ‘consensus’ view. Let’s just note in passing that the invocation of Galileo is the surefire signature of the crank, and move on instead to the blindingly obvious point that Galileo’s ‘heresy’ represented the voice of scientific reason, and the consensus he opposed was a politico-religious defence of vested interests. Rather precisely, one might think, the opposite of the situation in the climate-change ‘consensus.’ (The truth about Galileo is actually a little more complicated – see Galileo in Rome by William Shea and Mariano Artigas – but this will do for now.)

In any case, the rejoinder is really very simple. Of course scientific consensus can be wrong – that’s the nature of science. But much more often it is ‘right’ (which is to say, it furnishes the best explanation for the observations with the tools to hand).

As further evidence of the untrustworthiness of consensus, however, Lea regales us with tales of how economists (for God’s sake) have in the past got things wrong en masse – apparently she thinks economics has a claim to the analytical and predictive capacity of natural science. Or perhaps she imagines that consensus-making is an arbitrary affair, a thing that just happens when lots of people get together to debate an issue, and not, as in science, a hard-won conclusion wrested from observation and understanding.

Ah, but you see, the science of global warming has been overturned by a paper “of the utmost scientific significance”, published by the venerable Royal Society. The paper’s author, a Danish scientist named Henrik Svensmark, “has been impeded and persecuted by scientific and government establishments” (they do that, you know) because his findings were “politically inconvenient”. What are these findings of the “utmost significance”? He has shown, according to Lea, that there has been a reduction in low-altitude cloudiness in the twentieth century owing to a reduction in the cosmic-ray flux into the atmosphere, because of a weakening of the shielding provided by the Sun’s magnetic field. Clouds have an overall cooling effect, and so this reduction in cloudiness probably lies behind the rise in global mean temperature.

Now, that sounds important, doesn’t it? Except that of course Svensmark has shown nothing of the sort. He has found that cosmic rays may induce the formation of sulphate droplets in a plastic box containing gases simulating the composition of the atmosphere. That’s an interesting result, demonstrating that cosmic rays might indeed affect cloud formation. It’s certainly worth publishing in the Proceedings of the Royal Society. The next step might be to look for ways of investigating whether the process works in the real atmosphere (and not just a rough lab simulacra of it). And then whether it does indeed lead to the creation of cloud condensation nuclei (which these sulphate droplets are not yet), and then to clouds. And then to establish whether there is in fact any record of increased cosmic-ray flux over the twentieth century. (We can answer that already: it’s been measured for the past 50 years, and there is no such trend.) And then whether there is evidence of changes in low-altitude cloudiness of the sort Svensmark’s idea predicts. And if so, whether it leads to the right predictions of temperature trends in climate models. And then to try to understand why the theory predicts a stronger daytime warming trend, whereas observations show that it’s stronger at night.

But that’s all nitpicking, surely, because in Lea’s view this new result “seriously challenges the current pseudo-consensus that global warming is largely caused by manmade carbon emissions.” Like most climate-change sceptics, Lea clearly feels this consensus is pulled out of a hat through vague and handwaving arguments, rather than being supported by painstaking comparisons of modelling and observation, such as the identification of a characteristic anthropogenic spatial fingerprint in the overall warming trend. It is truly pitiful.

“I am no climate scientist”, says Lea. (I take it we could leave out “climate” here.) So why is she commenting on climate science? I am no ballet dancer, which is why, should the opportunity bizarrely present itself for me to unveil my interpretation of Swan Lake before the nation, I will regretfully decline.

Simon Jenkins has recently argued in the Guardian that science should not be compulsory beyond primary-school level. I don’t think we need be too reactionary about his comments, though I disagree with much of them. But when a director of a ‘policy research centre’ shows such astonishing ignorance of scientific thinking, and perhaps worse still, no one on a national newspaper’s editorial or production team can see that this is so (would the equivalent historical ignorance be tolerated, say?), one has to wonder whether increasing scientific illiteracy still further is the right way to go. In fact, the scientific ignorance on display here is only the tip of the iceberg. The real fault is a complete lack of critical thinking. There are few things more dangerous in public life than people educated just far enough to be able to mask that lack with superficially confident and polished words.

But it’s perhaps most surprising of all to see someone in ‘policy research’ fail to understand how a government should use expert opinion. If there is a scientific consensus on this question, what does she want them to do? The opposite? Nothing? A responsible government acts according to the best advice available. If that advice turns out to be wrong (and science, unlike politics, must always admit to that possibility), the government nevertheless did the right thing. If this Policy Research Centre actually has any influence on policy-making, God help us.

Decoding Da Vinci, decoded

I’m hoping that anyone who feels moved to challenge my dismissal of Fibonacci sequences and the Golden Mean in nature, in the Channel 4 TV series Decoding da Vinci will think first about how much ends up on the cutting-room floor in television studios. I stand by what I said in the programme, but I didn’t suggest to the presenter Dan Rivers that Fibonacci and phi are totally irrelevant in the natural world. Sure, overblown claims are made for them – just about all of what is said in this regard about human proportion is mere numerology (of which my favourite is the claim that the vital statistics of Veronica Lake were Fibonacci numbers). And the role of these numbers in phyllotaxis has been convincingly challenged recently by Todd Cooke, in a paper in the Botanical Journal of the Linnean Society. But even Cooke acknowledges that the spiral patterns of pine cones, sunflower florets and pineapples do seem to have Fibonacci parastichies (that is, counter-rotating spirals come in groups of (3,5), (5,8), (8,13) and so on). That has yet to be fully explained, although it doesn’t seem to be a huge mystery: the explanation surely has something to do with packing effects at the tip of the stem, where new buds form. It’s a little known fact that Alan Turing was developing his reaction-diffusion theory of pattern formation to explain this aspect of phyllotaxis just before he committed suicide. Jonathan Swinton has unearthed some fascinating material on this.

So the real story of Fibonacci numbers and phi in phyllotaxis is complicated, and certainly not something that could be squeezed into five minutes of TV. I shall discuss it in depth in my forthcoming, thorough revision of my book The Self-Made Tapestry, which Oxford University Press will publish as a three volume-set (under a title yet to be determined), beginning some time in late 2007.

Paint it black

I don’t generally tend to post my article for Nature’s nanozone here, as they are a bit too techie. But this was just such a cute story…

Nanotechnology is older than we thought. The Egyptians were using it four millennia ago to darken their graying locks.

Artisans were making semiconductor quantum dots more than four thousand years ago, a team in France has claimed. Needless to say, the motivation was far removed from that today, when these nanoparticles are of interest for making light-emitting devices and as components of photonic circuits and memories. It seems that the ancient Egyptians and Greeks were instead making nanocrystals to dye their hair black.

Philippe Walter of the Centre for Research and Restoration of the Museums of France in Paris and his colleagues have investigated an ancient recipe for blackening hair using lead compounds. They find that the procedure described in historical sources produces nanoparticles of black lead sulphide (PbS), which are formed deep within the protein-rich matrix of hair [1].

That the chemical technologies of long ago sometimes involved surprisingly sophisticated processes and products is well known [2]. The synthesis of nanoparticles has, for example, been identified in metallic, lustrous glazes used by potters in the Middle Ages [3]. Such practices are remarkable given that ancient craftspeople generally had no real knowledge of chemical principles and had only crude means of transforming natural materials, such as heating, at their disposal.

The nanocrystal hair dye is particularly striking. Walter and colleagues say that these particles, with a size of about 5 nm, are “quite similar to PbS quantum dots synthesized by recent materials science techniques.” Moreover, the method alters the appearance of hair permanently, because of the deep penetration of the nanoparticles, yet without affecting its mechanical properties.

That makes the process an attractive dyeing procedure even today, despite the potential toxicity of lead-based compounds. Walter and colleagues point out that some modern hair darkeners indeed contain lead acetate, which forms lead sulphide in situ on hair fibres. In any event, safety concerns do not seem to have troubled people in ancient times, perhaps because of their short life expectancy – as well as using lead to dye hair, the Egyptians used lead carbonate as a skin whitener, and toxic antimony sulphide for eye shadow (kohl).

The recipe for making the lead-based hair dye is simple. Lead oxide is mixed with slaked lime (calcium hydroxide, which is strongly alkaline) and water to make a paste, which is then rubbed into the hair. A reaction between the leads ions and sulphur from hair keratins (proteins) produces lead sulphide. These proteins have a high sulphur content: they are strongly crosslinked by disulphide bonds formed from cysteine amino acids, which gives hair its resilience and springiness (such bonds are broken in hair-straightening treatments). The researchers found that the alkali seems to be essential for releasing sulphur from cysteine to form PbS.

The French team dyed blond human hairs black by applying this treatment for three days. They then looked at the distribution of lead within cross-sections of the hairs using X-ray fluorescence spectroscopy, and saw that it was present throughout. X-ray diffraction from treated hairs showed evidence of lead sulphide crystals, which electron microscopy revealed as nanoparticles about 4.8 nm across.

The nanoparticles decorate fibrillar aggregates of proteins within the cortex of hair strands – the inner region, beneath the cuticle of the hair surface. High-resolution microscopy revealed that these particles are highly organized: they seem to be attached to individual microfibrils, which are about 7 nm in diameter and are formed from alpha-helical proteins. Thus the distribution of particles echoes the supramolecular arrangement of the microfibrils, being placed in rows about 8-10 nm apart and aligned with the long axis of the hair strands. So the ancient recipe provides a means not only of making nanocrystals but of organizing them in a roughly regular fashion at the nanoscale – one of the major objectives of modern synthetic methods.

The discovery throws a slightly ironic light on the debate today about the use of nanoparticles in cosmetics [4]. Quite properly, critics point out that the toxicological behaviour of such particles is not yet well understood. It now seems this is a much older issue than anyone suspected.

References
1. Walter, P. et al. Early use of PbS nanotechnology for an ancient hair dyeing formula. Nano Lett. 6, 2215-2219 (2006) [article here]
2. Ball, P. Where is there wisdom to be found in ancient materials technologies? MRS Bull. March 2005, 149-151.
3. Pérez-Arantegui et al. Luster pottery from the thirteenth century to the sixteenth century: a nanostructured thin metallic film. J. Am. Ceram. Soc. 84, 442 (2001) [article here]
4. ‘Nanoscience and nanotechnologies: opportunities and uncertainties.’ Report by the Royal Society/Royal Academy of Engineering (2004). [Available here]

A sign of the times?

The ETC Group, erstwhile campaigners against nanotechnology, have launched a competition for the design of a ‘nano-hazard’ symbol analogous to those used already to denote toxicity, biohazards or radioactive materials. My commentary for Nature’s muse@nature.com on this unhelpful initiative is here.

I worry slightly that the ETC Group is a soft target, in that their pronouncements on nanotechnology rarely make much sense and show a deep lack of understanding of the field (and I say this as a supporter of many environmental causes and a strong believer in the ethical responsibilities of scientists). But I admit that the announcement left me a little riled, filled as it was with a fair degree of silliness and misinformation. For example:

“Nanoparticles are able to move around the body and the environment more readily than larger particles of pollution.” First, we don’t know much about how nanoparticles move around the body or the environment (and yes, that’s a problem in itself). Second, this sentence implies that nanoparticles (here meaning human-made nanoparticles, though that’s not specified) are ‘pollution’ by default, which one simply cannot claim with such generality. Some may be entirely harmless.

“Some designer nanomaterials may come to replace natural products such as cotton, rubber and metals – displacing the livelihoods of some of the poorest and most vulnerable people in the world.” I don’t want to see the livelihoods of poor, vulnerable people threatened. Yet not only is this claim completely contentious, but it offers us the prospect of a group that originated from concerns about soil erosion and land use now suggesting that metals are ‘natural products’ – as though mining has not, since ancient times, been one of the biggest polluters on the planet.

“Nano-enabled technologies also aim to ‘enhance’ human beings and ‘fix’ the disabled, a goal that raises troubling ethical issues and the specter of a new divide between the technologically “improved” and “unimproved.”” Many of these ‘human enhancements’ are silly dreams of Californian fantasists. There’s nothing specific to nanotech in such goals anyway. What nanotech does show some promise of doing is enabling important advances in biomedicine. If that is a ‘fix’, I suspect it is one many people would welcome.

And so on. I was one of those who wrote to the Royal Society, when they were preparing their report on nanotech, urging that they take seriously the social and ethical implications, even if these lay outside the usual remit of what scientists consider in terms of ethics. I feel that is an important obligation, and I was glad to see that the Royal Society/RAE report acknowledges it as such. But sticking ‘Danger: Nano’ stickers on sun creams isn’t the answer.

When it’s time to speak out

[The following is the unedited form of my latest article on muse@nature.com. The newsblog on this story is worth checking out too.]

By confronting ExxonMobil, the Royal Society is not being a censor of science but an advocate for it.

When Bob Ward, former manager of policy communication at the Royal Society in London, wrote a letter to the oil company ExxonMobil taking it to task for funding groups that deny the human role in global warning, it isn’t clear he knew quite what he was letting himself in for. But with hindsight the result was predictable: once the letter was obtained and published by the British Guardian newspaper, the Royal Society (RS) was denounced from all quarters as having overstepped its role as impartial custodians of science.

Inevitably, Ward’s letter fuels the claims of ‘climate sceptics’ that the scientific community is seeking to impose a consensus and to suppress dissent. But the RS has been denounced by less partisan voices too. David Whitehouse, formerly a science reporter for the BBC, argues that “you tackle bad science with good science”, rather than trying to turn off the money to your opponents. “Is it appropriate”, says Whitehouse, “that [the RS] should be using its authority to judge and censor in this way?”

And Roger Pielke Jr, director of the University of Colorado’s Center for Science and Technology Policy Research, who is a controversialist but far from a climate sceptic, says that “the actions by the Royal Society are inconsistent with the open and free exchange of ideas, as well as the democratic notion of free speech.”

Yes, there is nothing like the scent of scientific censorship to make scientists of all persuasions come over all sanctimonious about free speech.

The problem is that these critics do not seem to understand what the RS (or rather, Bob Ward) actually said, nor the context in which he said it, nor what the RS now stands for.

Ward wrote his letter to Nick Thomas, Director of Corporate Affairs at ExxonMobil’s UK branch Esso. He expressed surprise and disappointment at the way that ExxonMobil’s 2005 Corporate Citizenship Report claimed that the conclusions of the Intergovernmental Panel on Climate Change that recent global warming has a human cause “rely on expert judgement rather than objective, reproducible statistical methods”. Ward’s suggestion that this claim is “inaccurate” is in fact far too polite.

Model uncertainties and natural variability, the report goes on to claim, “make it very difficult to determine objectively the extent to which recent climate changes might be the result of human actions.” But anyone who has followed the course of the scientific debate over the past two decades will know how determinedly the scientists have refrained from pointing the finger at human activities until the evidence allows no reasonable alternative.

Most serious scientists will agree on this much, at least. The crux of the argument, however, is Ward’s alleged insistence that ExxonMobil stop funding climate-change deniers. (He estimates that ExxonMobil provided $2.9 million last year to US organizations “which misinformed the public about climate change.”) Actually, Ward makes no such demand. He points out that he expressed concerns about the company’s support for such lobby groups in a previous meeting with Thomas, who told him that the company intended to stop it. Ward asked in his letter when ExxonMobil plans to make that change.

So there is no demand here, merely a request for information about an action ExxonMobil had said it planned to undertake. Whitehouse and Pielke are simply wrong in what they allege. But was the RS wrong to intervene at all?

First, anyone who is surprised simply hasn’t being paying attention. Under outspoken presidents such as Robert May and Martin Rees, the Royal Society is no longer the remote, patrician and blandly noncommittal body of yore. It means business. In his 2005 Anniversary Address, May criticized “the campaigns waged by those whose belief systems or commercial interests impel them to deny, or even misrepresent, the scientific facts”.

“We must of course recognise there is always a case for hearing alternative, even maverick, views”, he added. “But we need to give sensible calibration to them. The intention of ‘balance’ is admittedly admirable, but this problem of wildly disparate ‘sides’ being presented as if they were two evenly balanced sporting teams is endemic to radio, TV, print media, and even occasional Parliamentary Select Committees.”

In response to his critics, Ward has said that “the Society has spoken out frequently, on many issues and throughout its history, when the scientific evidence is being ignored or misrepresented”. If anything, it hasn’t done that often enough.

Second, Ward rightly ridicules the notion of ExxonMobil as the frail David to the Royal Society’s Goliath. The accusations of “bullying” here are just risible. The RS is no imperious monarch, but a cash-strapped aristocrat who lives in the crumbling family pile and contrives elegantly to hide his impecuniosity. In contrast, the climate sceptics count among their number the most powerful man in the world, who has succeeded in emasculating the only international emissions treaty we have.

And it’s not just the oil industry (and its political allies) that the RS faces. The media are dominated by scientific illiterates like Neil Collins, who writes in the Telegraph newspaper à propos this little spat of his “instinctive leaning towards individuals on the fringe”, that being the habitual raffish pose of the literati. (My instinctive leaning, in contrast, is towards individuals who I think are right.) “Sea level does not appear to be rising”, says Collins (wrong), while “the livelihoods of thousands of scientists depend on our being sufficiently spooked to keep funding the research” (don’t even get me started on this recurrent idiocy). I fear the scientific community does not appreciate the real dangers posed by this kind of expensively educated posturing from high places.

If not, it ought to. In the early 1990s, the then editor of the Sunday Times Andrew Neil supported a campaign by his reporter Neville Hodgkinson suggesting that HIV does not cause AIDS.

Like most climate sceptics, Neil and the HIV-deniers did not truly care about having a scientific debate – their agenda was different. To them, the awful thing about the HIV theory was that it placed every sexual libertine at risk. How dare science threaten to spoil our fun? Far better to confine the danger to homosexuals: Hodgkinson implied that AIDS might somehow be the result of gay sex. For a time, the Sunday Times campaign did real damage to AIDS prevention in Africa. But now it is forgotten and the sceptics discredited, while Neil has gone from strength to strength as a media star.

On that occasion, Nature invited accusations of scientific censorship by standing up to the Sunday Times’s programme of misinformation – making me proud to be working for the journal. As I recall, the RS remained aloof from that matter (though May mentions it in his 2005 speech). We should be glad that it is now apparently ready to enter the fray. Challenging powerful groups that distort science for personal, political or commercial reasons is not censorship, it is being an advocate for science in the real world.

Physics gets dirty

[This is my Materials Witness column for the November issue of Nature Materials.]

My copy of The New Physics, published in 1989 by Cambridge University Press, is much thumbed. Now regarded as something of a classic, it provides a peerless overview of key areas of modern physics, written by leading experts who achieve the rare combination of depth and clarity.

It’s reasonable, then, to regard the revised edition, just published as The New Physics for the 21st Century, as something of an authoritative statement on what’s in and what’s out in physics. And so it is striking to see materials, more or less entirely absent from the 1989 book, prominent on the new agenda.

Most noticeably, Robert Cahn of Cambridge University has contributed a chapter called ‘Physics and materials’, which covers topics ranging from dopant distributions in semiconductors to liquid crystal displays, photovoltaics and magnetic storage. In addition, Yoseph Imry of the Weizmann Institute in Israel contributes a chapter on ‘Small-scale structure and nanoscience’, a snapshot of one of the hottest areas of materials science.

All very well, but it begs the question of why materials science was, according to this measure, more or less absent from twentieth-century physics but central to that of the twenty-first. Indeed, one might have thought that the traditional image of materials science as an empirical engineering discipline with a theoretical framework based in classical mechanics looks far from cutting-edge, and would hardly rival the appeal of quantum field theory or cosmology.

Of course, topics such as inflationary theory and quantum gravity are still very much on the menu. But the new book drops topics that might be deemed the epitome of physicists’ reputed delight in abstraction: gone are the chapters on grand unified theories, gauge theories, and the conceptual foundations of quantum theory. Even Stephen Hawking’s contribution on ‘The edge of spacetime’ has been axed (a brave move by the publishers) in favour of down-to-earth biophysics and medical physics.

So what took physics so long to realize that it must acknowledge its material aspects? “Straight physicists alternate between the deep conviction that they could do materials science much better than trained materials scientists (they are apt to regards the latter as fictional) and a somewhat stand-offish refusal to take an interest”, claims Cahn.

One could also say that physics has sometimes tried to transcend material particularities. “There has been the thought that condensed matter and material physics is second-rate dirty, applied stuff”, Imry says. Even though condensed matter is fairly well served in the first edition, it tended to be rather dematerialized, couched in terms of critical points, dimensionality, theories of quantum phase transitions. But it is now clear that universality has its limits – high-temperature superconductors need their own theory, graphene is not like a copper monolayer nor poly(phenylene vinylene) like silicon.

“Nanoscience has both universal aspects, which has been much of the focus of modern physics, and variety due to the wealth of real materials”, says Imry. “That’s a part of the beauty of this field!”