People in Greenhouses Shouldn't Throw Stones - Guest Post

People in Greenhouses Shouldn't Throw Stones

Edward Spalton

Belief in man-made global warming caused by so-called greenhouse gases – carbon dioxide (CO2), methane (CH4), water vapour (H2O), ozone (O3) and nitrous oxide (N20) has produced enormous public concern and a huge structure of very costly political, financial and technical measures to cope with it. Even religion is invoked.

This whole edifice depends on a belief in the greenhouse hypothesis – the way in which a greenhouse is thought to produce a much higher temperature inside than in the surrounding atmosphere. If that hypothesis is shown to be false, then everything else collapses completely.

The hypothesis is an old one, dating as far back as 1824 (Fourier). Glass is opaque to some radiation in the infra-red (IR) part of the spectrum – the part we call heat radiation. Direct sunlight passes through the glass, losing a little of its infra-red on the way in. The remaining radiation from the sun is absorbed by the ground in the greenhouse and re-emitted in the lower frequencies of infra-red. The glass traps these rays and re-emits them back into the greenhouse, stoking up the heat. The greenhouse is a radiation trap – or so the hypothesis states. The “greenhouse gases” mentioned above have some similar properties to the glass.

It is assumed that nearly all the sun's radiation (such as light) is turned to heat radiation at the ground – called a transformation of wavelength. That the infra-red radiated back by the glass further warms the ground and therefore the air in the greenhouse. Physics teachers and textbooks have taught this for more than a century and so it is considered an established fact. Hardly anybody has tested the hypothesis by experiment.

One man did, a very eminent American scientist Professor R.W. Wood (1868-1955), who is sometimes called “the father of both infra-red and ultra-violet photography”. Wood earned numerous degrees from Harvard, MIT and the University of Chicago. He became full time professor of “optical physics” at John Hopkins University from 1901 until his death and is credited with many patents and experimental techniques. His notes from a very elegant experiment which he did in 1909 should be better known. They come from an age before scientists dressed up their work in impenetrable jargon and are easy to understand.

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“Notes on the Theory of the Greenhouse by Professor R.W. Wood

There appears to be a widespread belief that the comparatively high temperature produced within a closed space covered with glass, and exposed to solar radiation, results from a transformation of wave-length, that is, that the heat waves from the sun, which are able to penetrate the glass, fall upon the walls of the enclosure and raise its temperature: the heat energy is re-emitted by the walls in the form of much longer waves, which are unable to penetrate the glass, the greenhouse acting as a radiation trap.

I have always felt some doubt as to whether the action played any large part in the elevation of temperature. It appeared much more probable that the part played by the glass was the prevention of the escape of warm air heated by the ground within the enclosure. If we open the doors of a greenhouse on a cold, windy day, the trapping of radiation appears to lose much of its efficacy. As a matter of fact I am of the opinion that a greenhouse made of a glass transparent to waves of every possible length would show a temperature nearly, if not quite, as high as that observed in a glass house. The transparent screen allows the solar radiation to warm the ground, and the ground in turn turn warms the air, but only the limited amount within the enclosure. In the open, the ground is continually brought into contact with cold air by convection currents.

To test the matter I constructed two enclosures of dead black cardboard, one covered with a glass plate, the other with a plate of rock salt of equal thickness. The bulb of a thermometer was inserted into each enclosure and the whole packed in cotton with the exception of the transparent plates which were exposed. When exposed to sunlight the temperature rose gradually to 65 degrees centigrade, the enclosure with the salt plate keeping a little ahead of the other, owing to the fact that it transmitted the longer waves from the sun, which were stopped by the glass. In order to eliminate this action the sunlight was first passed through a glass plate.

There was now scarcely a difference of one degree between the temperatures of the two enclosures. The maximum temperature reached was about 55 degrees. From what we know about the distribution of energy in the spectrum of the radiation emitted by a body at 55 degrees it is clear that a rock salt plate is capable of transmitting practically all of it, while the glass plate stops it entirely. This shows us that the loss of temperature of the ground by radiation is very small in comparison to the loss by convection. , in other words we gain very little from the circumstance that radiation is trapped.

Is it therefore necessary to pay attention to trapped radiation in deducing the temperature of a planet as affected by its atmosphere?.

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The solar rays penetrate the atmosphere, warm the ground which in turn warms the atmosphere by contact and by convection currents. The heat received is thus stored in the atmosphere, remaining there on account of the very low radiating power of a gas. It seems to me very doubtful if the atmosphere is warmed to any great extent by absorbing the radiation from the ground, even under the most favourable conditions”.

So, even if the “greenhouse gases” really do behave like the glass in a greenhouse, the effect is negligible. Until somebody conducts a real experiment (not a computer model) to disprove Professor Wood's experiment, we can stop building wind turbines, sack the carbon traders and busybody officials and tear up the silly claims for “climate compensation” from Third World countries – because carbon dioxide is not causing anything except increased plant growth to feed a hungry world. Al Gore and the other investors in “green” technologies can only thrive when the law compels us to use their products or our taxes subsidise them. That is what drives their campaign. They can vote themselves rich. Now they are like the people who made the Emperor's new clothes – and we can see through them.

Of course, there is every economic reason to improve the insulation of our buildings and the efficiency with which we use expensive fuels. Neither should we stop improving control over real pollutants – but carbon dioxide is not one of them. According to best scientific estimate , on a scale of 300 million years it is at a very low level. So a rise of 40% from this low level is nothing to get excited about and it is a marvellous, non-polluting fertiliser.

I am indebted to The Revd Philip Foster MA (Nat. Sci. & Theol) for drawing Professor Wood's paper to my attention)

I also recommend his book “While the Earth Endures: Creation, Cosmology and Climate Change” and

“Climategate: the CRUtape Letters” by Stephen Mosher & Thomas Fuller

both published in the UK by

SMP Ltd, 1 Barnfield, Common Lane, Hemingford Abbots, Huntingdon, PE28 9AX

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