December 2013

Sceptics and supporters

From Jack Barrett

Since I was singled out as a ‘prominent sceptic’ in Philip Ball’s article I thought it would be a useful to outline my main views.

The basic physics is settled and has been for many years. There are two ways of approaching it. One is the preferred ‘top-down’ method in which, for every frequency in the terrestrial spectrum, the altitude is determined at which the optical density (absorbance) of the atmosphere above it is such that the probability of an upwardly emitted photon reaching space is 0.51. This altitude is regarded as the emission level at the particular frequency. Any increase in the concentration of a greenhouse gas (GHG) will increase the emission levels of all its constituent frequencies. If an emission level is in the stratosphere, where temperature increases with altitude, emission intensity is increased and this causes cooling of the region. If the level is in the troposphere, where temperature decreases with increasing altitude, emission intensity is reduced and this forces the surface–troposphere system to warm up. Taken together, the two aspects of emission occur to ensure radiative balance with the incoming solar radiation. Both stratospheric cooling and surface–tropospheric warming are being observed.

The alternative approach is the ‘bottom-up’ method, which gives the same results, but can be misinterpreted, as I did in my early paper. It is easy, but wrong, to conclude that, because the majority of radiation emitted by the Earth’s surface is absorbed by the first 100m of the atmosphere, no increase in the concentrations of GHGs will have any further effect. John Houghton corrected my error, which was to ignore that the passage to space through the atmosphere is at every level restricted by GHGs and that further restrictions occur with higher concentrations. It is possible that chemists’ unfamiliarity with thermal emission radiation is the basis of some scepticism.

The top-down approach is fully developed in my e-book Global warming: the human contribution, which also contains discussions of the global temperature sensitivity of the atmosphere to a doubling of the concentration of CO₂. This is where genuine scepticism is valid. The 70 or so models reported by the International Panel on Climate Change (IPCC) still produce a range of possibilities for this sensitivity value from 1.5K to 4.5K, but seem to be homing in on one or other of two ‘most probable’ values of 1.8K and 2.5K. My own empirical approach gives a value of 1.84K.

There are extreme sceptics who are deniers of the basic physics and who also do not believe that human activity is responsible for the increased concentration of atmospheric CO₂ observed since 1850. I’m particularly disappointed by these views when they are expressed by people with science degrees. The correlation between atmospheric CO₂ concentration and cumulative carbon emissions since 1850 is almost perfect and there is convincing additional evidence from studies of ¹³C/¹²C ratios that the extra CO₂ originates in fossil fuels.

I’m concerned about the IPCC’s view that we must not allow the human effects on the atmosphere to produce warming greater than 2°C above the pre-industrial value. So far the warming has been about 0.9°C, so there is 1.1°C to go. There has been very little discussion of the observed difference in warming of the northern and southern hemispheres. Over the 34 years that there have been satellite records of global temperatures, it is clear that the north is warming at a rate about 2.4 times that of the south. For a global mean temperature increase of 2°C, this means an increase of about 2.8°C for the northern hemisphere and that, if it occurs, is a matter of serious concern. A +4°C heat wave in France practically destroyed their agriculture for the season and the IPCC report that food plants, even by means of genetic modification, cannot be adapted to do well if that temperature increase were to become the norm.

REFERENCE

J Barrett, Spectrochimica Acta, 1995, 51A, 415 

J Barrett CChem MRSC 

Arundel, UK

From Walter Mason

It might have been more logical if Philip Ball had asked why people other than chemists have more enthusiasm for global warming. After all, climate behaviour is very much a chemistry-related study. So if chemists are more sceptical of global warming, it is perhaps because they are more knowledgeable about the subject, more aware of the complexity of climate behaviour, more able to see the pros and cons, or less ready to jump to swift conclusions. 

Research chemists know that novel and apparently straightforward chemical experiments can be fickle, and must be peer reviewed for reliability. 

Industrial chemists know that the rather more complex industrial processes often require constant fine tuning, as the basic ingredients, with a mineral or organic origin, can be anything but constant. 

Yet these experiments and processes are simple indeed, compared with the complications of the many known, and probably some as yet unknown, aspects of Earth’s climate – with no chance of fine tuning, or peer review. Small wonder if chemists want to question and keep an open mind – or just watch and wait till the outcome becomes clear. 

And, sadly, while the attention of enthusiasts and sceptics alike is focused on global warming, the far greater danger to the world of over-population continues uninterrupted.

E W Mason CChem MRSC 

Stockport, UK

From John Allen

Philip Ball’s article is excellent and likely to stir up plenty of discussion. 

The tragedy about global warming is that while the greenhouse effect is long established and real in respect of rising CO₂ in the atmosphere, recognition is increasingly blurred by arguments over the perceived measured effects because of the large number of other climatic sub-plots and non-linear observations. These run over much longer time scales and our priority must remain to do all that we can. The subject is so huge that we should expect ‘chemists’, who are by nature inquisitive, to hold many views.

January 2014 is the 150th anniversary of the appointment of Angus Smith as inspector of alkali works, setting up a regime for the control of industrial emissions to air from the most difficult industrial processes. Smith was a legend in environmental matters and while his Victorian values have been scorned, now might be a good time to revisit them. 

I have written an article detailing Smith’s achievements, charting a brief history of air pollution control and adding my own recent experiences in environmental issues. These relate to ‘carbon’ and its equilibrium between soils, forestry, peat bogs, grasslands and the atmosphere. I believe our knowledge here is well short of the scientific standards required in such an important debate. 

The radical economist Ernst Friedrich Schumacher said that the world would be a better place if we rejected an ‘idolatory of gigantism’ that dominates western thinking. I agree with this, believing that there are many opportunities allowing huge numbers of people and organisations to take responsible action. At the individual level this may require commitment to use less energy, either by using it more efficiently or change in lifestyle. Prospects of abundant renewable electricity at 2–3 times the current price are beginning to look attractive as technologies mature. We should remain optimistic.

J Allen CChem FRSC

Preston, UK

Sky-high successes

From Cath Brown

I was saddened to read Melvyn French’s letter suggesting that only directly applicable research should be carried out.

Firstly, I would dispute his suggestion that research in the past focused solely on ‘finding solutions to day to day problems’ - surely many of the greats in the field were motivated principally by scientific curiosity, judging from their work?

Secondly, while no one would dispute the importance of developing new medical treatments and new technologies to ameliorate environmental problems, we are not in the situation that all other available monies are devoted to these worthy causes, with only a few recalcitrant researchers holding out with their ‘useless’ studies. There are many other areas that could be cut first, if throwing money and time at these problems is indeed the answer.

Let us also remember that blue sky research has often been found to have applications at a later date. However, even if it does not, intellectual curiosity and a desire to know and understand the world and the universe better are part of what make us human. Few seem to begrudge the physicists’ expensive quest for evidence to support electroweak unification - why object to rather less costly academic endeavours in chemistry?

C Brown 

Birmingham, UK

From Mark Foreman

Melvyn French expressed the view that speculative (blue skies) research on dinosaurs and new super heavy elements is of little use and that research that is relevant to the treatment of human diseases should be encouraged. I think this combination of views is interesting but incompatible. 

I would like to point out that one possible means of curing cancer is a-immunotherapy, in which antibodies bearing short-lived a emitters are used to seek and destroy cancer cells. 

This work has already reached clinical trials. I reason that much of the chemical work that was needed for super heavy element research will facilitate the development of a-immunotherapy, for example the skills required to rapidly separate different elements would be of great use when trying to prepare these radiopharmaceuticals. 

I am sure that radiochemical research started out as blue skies research with no obvious use. It is unlikely that Henri Becquerel or the Curies had considered uses of radioactivity such as cancer treatment, industrial radiography or nuclear power when they started their research. However, the lack of an application did not make the research they conducted any less valid or useful.

The study of fossils (and other old objects) offers a deep insight into how radioactive and other hazardous waste stores will behave over millions of years. Like it or not, we have long-lived radioactive waste (and infinitely long-lived nonradioactive hazardous wastes), and one of the needs of today’s society (and of future generations) is to manage this waste. While the dinosaurs did not have hazardous waste landfills that we can examine, we can study the retention of substances in some fossils such as the Oklo prehistoric nuclear reactors and thus gain 

an insight into how the waste stores we have created will behave in the future.

M Foreman CChem MRSC 

Nuclear Chemistry, Chalmers University of Technology, Sweden

Kirchhoff’s quantum contribution

From Michael Jewess

Andrea Sella states that Gustav Robert Kirchhoff ‘[laid] the groundwork for the black body concept and its practical realisation’. This understates the matter. Kirchhoff specifically identified the black body as worthy of intensive experimental study and thereby became the grandfather of quantum theory.

In 1860, Kirchhoff proved that the radiation emitted per unit area by a completely absorptive (‘black’) body was dependent on the absolute temperature of the body, T, but not on the material from which it was constructed; between frequency n and frequency (n +dn), it was J(n, T)dn in which J was an, as then, unknown universal function. (Otherwise, it would be possible to make a perpetual motion machine of the second kind, in contravention of the second law of thermodynamics.) 

Kirchhoff asserted that J (being universal, applying to all matter) had to be important; he challenged experimentalists to overcome the great difficulties that stood in the way of obtaining the experimental data from which the algebraic form of J could be inferred. 

Only in 1900 was the experimental data sufficient to provoke Max Planck into deriving an expression for J including just three parameters: the speed of light in vacuo, plus the two key fundamental constants relating specifically to atomic and molecular behaviour, namely the Boltzmann constant and the constant h which now carries Planck’s name. 

M Jewess CChem FRSC

Harwell, UK 

Gunpowder plot

From Clifford Jones

On reading David Jones’ article ‘Explosive mixtures’, I am minded to make the following contribution to his discussion. 

Gunpowder was being used as an explosive in the mines in Victoria, Australia, in the mid-19th century. It was sourced in the UK and in the US. In my book The Sherlock Holmes stories and combustion science, I suggest that not all of it was legally imported but that some might have been illegally smuggled. 

J C Jones FRSC

University of Aberdeen, UK

Chemistry World welcomes letters, which should be concise (normally fewer than 300 words) and timely. Those selected for publication are subject to editing for clarity and length. Letters should be marked ‘for publication’ and sent to chemistryworld@rsc.org

Letters are not routinely acknowledged.