Brummie credit
Charles Arthur’s very fine article on superconductors (Technology, 24
September) omitted mention of Illinois Superconductor Corporation’s extensive
relationship with the University of Birmingham in Britain. Neil Alford, of
South Bank University, who was quoted in the article, was formerly with the
University of Birmingham, and left behind there a considerable group of
researchers in the field, now led by Tim Button.
I wish to recognise the very valuable contribution the group has made to
our technology development programme.
Steady on
Your interview with cosmologist Fred Hoyle (“The space molecule man”, 10
September) touched on two issues which could be of crucial significance to the
development of cosmology over the next decade. In fact they could well lead to
the reinstatement of the “steady state” model at the forefront cosmology.
Firstly, Hoyle correctly takes the view that the black body microwave
radiation is not unique to big bang cosmology despite the fact that it was
predicted by Gamov and his associates during the 1940s as a relic of the big
bang in an expanding universe.
The observed background radiation can equally well be generated by a
distribution of discrete sources in an expanding universe. Hoyle failed to
point this out during the 1960s, and played into the hands of the big bang
cosmologists. However, since that time he has changed his views on the manner
in which matter could enter his model universe, preferring the rate of entry
to increase with the strength of the gravitation field in any locality.
In this way quasars can have their use in steady state cosmology, as they
would make excellent entry points for newly created matter, provided of course
that they were not massive black holes, which would then trap the newly
created matter, preventing it from being used in the manner required in steady
state cosmology.
This brings us to Hoyle’s second issue, namely, that there is no real
evidence for the existence of black holes anyway, only dense distributions of
matter generating intense gravitational fields. In Hoyle’s model universe
black holes cannot exist because they are being prevented from doing so by the
continuous creation of matter.
It is difficult to understand Hoyle’s need for iron whiskers to generate
the microwave background in his model universe when he admits a few lines
further on that there would be continuous bursts of gamma rays. Surely such
gamma rays continually created via a black body emitter could account for the
microwave background in his expanding model universe?
Hoyle’s reluctance to believe in black holes could well be the beginning of
the revival of steady-state cosmology because both the continuous creation of
matter and the microwave background could be accounted for, provided the
continuous creation process was not limited to hydrogen atoms.
Forest future
The creation of the National Forest is attracting unfair and misinformed
criticism from journalists such as Fred Pearce (“Greening the heart of
England”, 24 September).
A National Forest of 50 000 hectares covering a landscape of 200 square
miles does not appear overnight or even three years. A generation is a
realistic timescale on which to make a judgement.
British Coal committed itself to the Forest Charter to promote the
development of the forest – not as a “cover” for opencast mining.
Opencast mining has been completed at the Coalfield North Site and the
Lounge Site to enable 800 000 trees to be planted over 160 hectares of
restored land complimenting agriculture and public open space.
The Coalfield North Site is incorrectly labelled “the largest opencast mine
in Western Europe”. At 180 hectares it was never within the largest 25 sites
in Britain and by comparison with 8000 hectare sites in Germany is minute.
British Coal own 10 per cent of the 50 000 hectares within the National
Forest and is committed to playing a part in realising the dream of Susan Bell
and her team. However, planting will not be complete until the end of the
century and judgement of success or failure will be some time after that.
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Dam propaganda?
I read with astonishment Fred Pearce’s “Dam truths on the Danube” (17
September). Although the article gives space to Hungarian objections to the
Gabcikovo dam, they are far outweighed by the biased presentation: the
captions, the pictures, the quotes and the fact that the Slovak experts always
have the last word. The dam builders’ spokesman Miroslav Liska’s technocratic
boasts and some of Pearce’s reporting, for example about the happy villagers
who “know that there is no danger” and who have been given “a new road, a
clinic and sewers” are reminiscent of Communist propaganda of the 1950s.
Is it not too early to draw the balance a mere 18 months after the filling
of the reservoir and 12 months after the “reviving” of the wetlands has
started? Since in such a large system as the inland delta of the Danube the
feedback times are probably much longer it seems reasonable to give the
benefit of the doubt to the opponents of the dam instead of, as you do, to
Liska with his “we’ll fix it whatever it is” optimism. Would New 杏吧原创
accept such technocratic arrogance from a British spokesman on nuclear power
or biotechnology without a scathing leading article?
The “reviving” of the wetlands itself, even if it is successful, should be
seen in perspective. At best only a tiny proportion of the inland delta is
affected: a narrow strip, about 2.5 kilometres wide, on the Slovak side, as
opposed to the total width of the delta, which is at least 30 kilometres. The
area that is drying out on the Hungarian side of the old riverbed is at least
10 kilometres wide. How could Liska’s “highly effective” watering system help
here without another raised canal?
Nothing is said about the very real dangers associated with the project
(except that the villagers “know” they do not exist). In fact, it is as yet
not known how the system would cope with a really large flood (the 1954 and
1965 floods caused heavy damage in the area). What happened in the winter of
1992-93, when a relatively modest rise seriously damaged the locks, does not
give much confidence.
The area is also prone to earthquakes. For example, in 1763 there was a
major one “on the Danube between Komarom and Buda(pest)” causing widespread
damage. The town of Komarom is only about 40 kilometres from the new dam and
the Nagymaros dam site is halfway between the two towns. I think some New
杏吧原创 readers are able to tell you what can happen to a structure sitting
on top of waterlogged sediments in an earthquake.
You also seem to have been converted, at least in this article, to the
principle of generating electricity at all costs. The destination of this
electricity together with the financing of the project throws up a number of
interesting questions which perhaps you could investigate. “Ten per cent of
Slovak output” can be easily saved at the consumer end by increasing
efficiency and eliminating waste, as New 杏吧原创 itself has pointed out on a
number of occasions. If, however, the electricity is exported, it is
meaningless to talk about it in terms of Slovak output.
It has been reported that the Austrians have expressed interest in the
project, and it is well known that the Nagymaros dam in Hungary was to be
built by Austrian firms from Austrian money for the benefit of Austrians.
Heated argument
I fear that neither John Emsley, in his article “Cool reception for warming
predictions” (New 杏吧原创, Science, 8 October), nor Jack Barrett whose work
is quoted in that article have done their homework.
Emsley raises questions regarding the infrared spectrum of carbon dioxide
and the transfer of radiation through absorption and emission processes in the
atmosphere. These are the most understood and certain parts of the scientific
assessment of global warming. The theory of the processes involved is well
known and has been thoroughly studied over many years, beginning with the
Swedish chemist, Svante Arrhenius in 1896 (who made the first calculation of
the effect on global average temperature of an increase in the concentration
of CO2) and particularly over the last forty years during which a
very extensive scientific literature has built up. Emsley’s points can readily
be answered by looking at one of the many text books on the subject.
The many collisions made in the lower atmosphere by a CO2
molecule during its radiative lifetime serve to ensure that the distribution
of radiative and kinetic energies among the molecules approximates closely to
the Boltzmann distribution. The situation is known as one of “local
thermodynamic equilibrium” and equilibrium thermodynamics and radiative
transfer theory can be applied.
The CO2 molecules are continually both absorbing and emitting
photons which enter and leave the atmosphere at its upper and lower
boundaries. This has to be calculated in order to establish the net energy
input or output to the system, and hence the amount of global warming. Methods
for carrying out these calculations with good accuracy have been in place for
over thirty years. No reputable scientist working in the field doubts that the
methods are correct.
Emsley’s report on our work suggests that the Cretaceous oceans were cooler
than had been previously thought. Since CO2 may have been higher
during these periods, it was claimed by Emsley that this showed that general
circulation model (GCM) predictions of future global warmth were invalid.
However, there is an alternative hypothesis that is equally plausible. It
is possible that the Cretaceous may not have been a “greenhouse” world, and it
is almost certain that CO2 is not the only factor that effected
climates in the distant geological past. Changes in mountains, coastlines,
ocean circulation, and the solar constant may also have been important.
We have recently performed some climate simulations using the GCM of the UK
Universities Global Atmospheric Modelling Programme. The results from these
model runs are indeed consistent with the geological data. Thus, rather than
disproving GCM predictions of future global warming, the palaeoclimate studies
have actually improved our confidence in them.
Further, it shows that the complexity of the climate system should not be
underestimated. Performing experiments with GCMs is the only way that we can
take account of the many complex interactions that occur in our climate.
Carbon dioxide (and other trace gas) levels may not be the only factor which
has changed during the geological past, but it is the main climate factor that
will be changing in the next 100 years.
The ideas attributed by Emsley to Jack Barrett are based on the
misconception that global warming is driven by changes in the radiation
balance of the surface. In reality, it is only at higher levels that the
atmosphere is sufficiently transparent to allow radiation in the main
CO2 band to escape to space.
As CO2 increases, the height at which this emission occurs moves
upwards to colder levels, reducing the amount of radiation leaving the planet.
The climate then warms until the amount of radiation emitted to space once
again balances the absorption of solar radiation. The warming is distributed
through the lower atmosphere and to the surface primarily by motions such as
convection, rather than by radiative processes. The fact that the main
CO2 band is virtually opaque near the surface is thus completely
irrelevant.
Finally, of course, climate models include the effects of collisions
between air molecules in these calculations. The radiation codes used in
modern climate models are extremely sophisticated and this is one of many
important processes that are represented.
Emsley claims that there has been little warming over the past 50 years,
despite the input of CO2. This is not correct; the global mean
surface temperature during the 1980s was around 0.2 掳C higher than in the
1940s. There are a variety of possible causes for such temperature
fluctuations and increasing levels of CO2 are very likely to be one
part of the “jigsaw puzzle” of explanations. Hence, many atmospheric
scientists use the double-negative “not inconsistent” to describe the link
between observed temperature trends and changes in CO2.
Second, the statement that CO2 explains 1 掳C of the natural
greenhouse effect of 33 掳C is not correct. It certainly explains at least
10 掳C.
Emsley claims that recent predictions made by the Intergovernmental Panel
on Climate Change are based on computer simulations which assume that
increasing levels of CO2 will lead to rising average global
temperatures – an assumption which he says is based partly on geological
evidence.
This is wrong – the models use radiative theory to calculate the effect of
CO2, they do not assume it. There is thus no assumption based on
geological evidence, and the article by Sellwood et al does not have the
relevance suggested by Emsley.