Models need data
Lenny Smith makes a number of important points concerning the consequences of overselling the results from climate models, but he omits an important one (6 December 2008, p 42).
Those who overstate the present capability of climate models risk creating the perception that models can substitute for measurement and so undermine the case for adequate observation and monitoring.
It is only through these measurements and observations that we can reduce the models’ uncertainties, by improving our understanding of the processes driving both natural and anthropogenic climate change. Excessive reliance on models can also result in reduced support for critical long-term observations against which the models’ climate projections are validated and their accuracy determined.
As Smith says, climate models provide useful information about plausible risks. Only carefully planned systematic observation and monitoring will permit us to properly understand what is happening to our climate and the elucidation of the processes at work in determining any future long-term change.
Going off-grid
One important item was missing from your power-saving suggestions (6 December 2008, p 30) in the article “Life unplugged”. Home heating takes a lot of power, especially when it comes to getting fresh air into the house.
Could we not virtually eliminate energy use for heating (or cooling) incoming air by using a counter-flow heat exchanger? Cold incoming air would be heated by warm air going out through the heat exchanger, and vice versa when it is hot outside. Counter-flow heat exchangers are so effective that they are used industrially. Why they are not used domestically baffles me.
From David Clarke
Chris Knapton may be right to put some of the blame on the utilities and government for the slow growth of small-scale generation (20/27 December 2008, p 18), but we should not underestimate the potential problems with this technology.
As the amount of small-scale generation grows, with each little generator doing its own thing, it will become difficult to maintain system stability 鈥� something that the big utilities and the operators controlling the electricity grid at present do pretty well. Maintaining local voltage stability may be a particular problem.
We need technology to automatically control the output of small-scale generation in response to system conditions. With luck the “smart grid” initiatives will deal with this problem, but I do not think we’re there yet.
Royston, Hertfordshire, UK
From Steve Plater
Gaia Vince should have used the estimator of solar energy yields published by the Renewable Energy Unit at the European Union’s Joint Research Centre (): it would have told her that in the UK 8 square metres of panel are required to gain 1 kilowatt peak output and 800 or so kilowatt-hours per year (“For the record”, 3 January, p 17).
Vince also tells us that in Germany “homeowners selling back renewably generated power are guaranteed to get four times the market rate charged to consumers for electricity”.
The German feed-in tariff is indeed admirable, but it is not that generous. The market rate to consumers is at present 20 to 21 cents per kilowatt-hour. The feed-in tariff for electricity generated by a small rooftop photovoltaic array this year is just over 46 cents, and for arrays installed next year it will be 43 cents.
The starting rate will drop by 8 to 10 per cent each year. Rates for electricity from other renewables are lower.
Sevenoaks, Kent, UK
From Vivienne Mugford
I have just had eight solar panels installed on my roof, occupying 10.2 square metres.
I now realise, too late, that the average output is dramatically less than the peak output. My system, with a grant, cost me 拢7200 鈥� and will take 37 years to break even, under the current arrangements with electricity suppliers.
Though the return on my money is better than I would now get from a savings account, I feel misled by the supplier, who gave me only peak values at point of sale.
Ottershaw, Surrey, UK
From Rolfe Bridson
Reading of the generous price premium offered in Germany for selling surplus electricity generated to the power companies (6 December 2008, p 30), I was struck by the possibility of people fraudulently buying in power from the grid at the lower cost and then selling it back at the higher rate.
Has anyone thought about how to plug this loophole?
Alton, Hampshire, UK
Why menopause?
Alison Motluk makes no mention of the opportunity an early menopause offers to pass on culture, and the great advantage this provides (13 December 2008, p 41). It is obvious that we are separated from other primates by culture 鈥� and by being hugely more successful in evolutionary terms than they.
Pregnancy is a life-threatening condition which, in societies that have no access to modern medicine, sees off many a grandmother before she has the leisure time to educate her grandchildren. Rachel Caspari, now , and Sang-Hee Lee , make a convincing case that with grandparents came civilisation (10 July 2004, p 14). Assuming that male grandparents tended towards the autistic end of the personality spectrum and preferred power struggles and sitting around to being educators of the younger generations, a genetic variation that allowed an early menopause looks as if it conferred a huge evolutionary advantage.
From Marco Overdale
You report Michael Cant saying that the lack of overlap in the fertility of mothers and daughters is striking, and that this can explain why human women experience the physical switch of menopause, rather than a slow decline in fertility.
What is equally striking is the commonality in the age of menopause across several species of primates with different average lifespans.
One factor that would, in evolutionary terms, result in the physical cessation of fertility at a particular age is a decline in the viability of offspring conceived after that age. In a longer-lived species this could initially tend to terminate fertility at a set age independent of lifespan.
As a mother’s age increases, the likelihood her offspring will survive or be healthy decreases. She is also likely to be less able to care for more young children.
The reproductive viability of later offspring is thus likely to decrease. If this fall-off with mother’s age at conception is sufficiently steep, those who continue to conceive successfully as age increases will be selected against because their later offspring will not reproduce.
Other factors would also need to operate to push reproduction into a younger age group, so that a greater proportion of a women’s offspring will end up reproducing. Those identified by Cant would be such a possible driving force.
Wellington, New Zealand
From Carole Karan
As a woman of happily post-menopausal age, I can think of several additional things that encourage menopause. Anything a new birth does that increases the likelihood of one or more previous children dying would encourage a cut-off of late fertility. For example, the higher rate of defects in births from older women would mean wasting resources on some pregnancies that will never lead to another adult at the expense of older offspring.
Older women are also much more likely to be widowed, and the food that mates supply should not be underestimated.
Mebane, North Carolina, US
Less is Moore
杏吧原创s and engineers have indeed done an impressive job in realising Moore’s law over the years (6 December 2008, p 35). What a pity that the average PC user has not seen the equivalent leap in “user experience”.
A combination of operating system bloat, poorly configured and maintained networks, and overzealous virus checkers means that for many, PCs today seem little faster than a 1980s model running pre-Windows software.
The assumption that Moore’s law will compensate for inefficiently designed systems leads to Prior’s conjecture: sloppy software losses will negate Moore’s law gains.
Greeks' gifts
You speculate on what the Greeks might have achieved had the Romans not supplanted their culture (13 December 2008, p 5). This rather misunderstands the role of the Romans, who were great admirers of the Greeks and eagerly adopted much of Greek thought and culture. The Romans might not have been particularly original thinkers or inventors, but adapted and used whatever they found in the societies they conquered.
The failure of the Greeks to take their technology further was more likely due to the chaotic rivalry between their city-states. This effectively crippled them, both in their resistance to Rome and in adapting technology to everyday life.
Even so, much knowledge might still have survived to allow further advances had the rise of Christianity not got in the way.
From the outset, Christianity regarded learning, in particular inquiry into the nature of the physical world, as positively dangerous. All that passed for learning for over 1000 years in the west was the narrow interpretation of religious texts.
Only when Greek texts rescued and translated by the Arabs from the moribund Byzantine empire found their way to the west, and the shackles on learning were eased, did advances become possible again.
From Stuart Leslie
Jo Marchant asks why the Greeks did not use their science to create useful technology (13 December 2008, p 36). Could it be because Greek civilisation was based on slavery? Plato and Aristotle both wrote that civilisation was impossible without slaves.
This implies the answer to her second question: to what better use could technology be put than understanding and demonstrating the nature of the universe? I suggest that improving the lot and lessening the suffering of human beings takes first place every time.
Dorrigo, New South Wales, Australia
Dangerous sex in a pill
Bernd Brunner is “terrified” by Clare Wilson saying an “intelligent and well-informed” gay man “sometimes” has unsafe sex. He sees this as a contradiction, and believes this kind of behaviour to be unusual (20/27 December 2008, p 18).
If his reasoning were correct, then intelligent, informed people would never smoke, take drugs, drink to excess or be overweight. Smart people do dumb things, especially for sex. Human nature often contradicts common sense.
Canine calculus
Marcus du Sautoy opines that we have the innate mathematics skills needed to survive things being thrown at us and gauge enemies’ sizes (29 November 2008, p 44). My dog can compute the trajectory and velocity of an object far better than I can. Does this mean that she is better at mathematics than I am? In contrast, small yappy dogs seem not to realise how small they are. Are they therefore both vertically and mathematically challenged?
Gunner Copernicus
Copernicus may have expelled us in principle from the centre of the universe (15 November 2008, p 32), but I am reminded of an incident in Spike Milligan’s memoirs of the British army:
Officer (shouting): “You there, what are you doing over there?”
Milligan: “Uh, everybody gotta be somewhere, sir.”
For the record
鈥� Scud missiles are not intercontinental ballistic missiles: they have a range of only 1000 kilometres and are classed as intermediate-range ballistic missiles (13 December 2008, p 26).
Going off-grid
A life unplugged is an idea close to my heart (6 December 2008, p 30). Since discovering the at Machynlleth in mid-Wales, near my ancestral home of Dolgellau, 28 years ago, I have frequently flirted with the dream. But two flaws have held back a full commitment.
As “simple” as the lifestyle is, participants are still dependent on high-tech alloys, energy inputs, R&D, advanced education, the market and of course hard cash. Without these requirements we would have already seen full-blown application in developing nations where it is more appropriate and needed the most. So in the real sense of the concept, disconnection is not possible.
The second flaw is that such action does not change the economic growth philosophy and infrastructure that is the root cause. Instead it takes people who know its flaws out of the system. So by all mean drop out in Surbiton (The Good Life, BBC television, 1975) but remember it will not stop the icebergs melting alone (John Mortimer’s play The Other Side, BBC television, 1967 鈥� see ).
Stirling service
One thing has been puzzling me about the hybrid cars being rolled out by the car industry (20 September 2008, p 26): why don’t they use Stirling engines to drive the generators?
The point is that this would be much cleaner than any internal combustion engine, much more fuel-efficient and perfectly capable of running on just about anything that would burn.
I can understand why a Stirling engine cannot be used directly to drive a car 鈥� it’s the world’s worst possible prime mover 鈥� but that does not explain why it cannot be used to drive a generator.
For the record
鈥� We reported the European Court of Human Rights ruling that “the UK’s national DNA database… must remove more than 800,000 of roughly 4.5 million profiles” (online news, 9 December 2008). In fact, the judgment applied to England, Wales and Northern Ireland; Scottish law already insisted that DNA samples taken when people are arrested must be destroyed if the individual is not charged or convicted.