IT WAS the Swedish scientist Svante Arrhenius (1859-1927) who made the assertion at the turn of the last century that the Earth was 30 deg warmer than could be expected because of ‘greenhouse’ gases. He based his calculations on results from the lab of the absorption in the infrared (heat) spectrum by carbon dioxide. It could not be tested, of course! You cannot remove greenhouse gases from the atmosphere to see if the temperature drops.
Not ten years later the calculation was criticised by the American physicist Professor R W Wood, often regarded as the father of infrared (IR) photography. He performed a simple experiment to assess the belief that greenhouses act as a radiation trap, that the glass (itself an absorber of IR) radiated back into the greenhouse IR heat coming from the ground causing it to warm even further.
Note on the Theory of the Greenhouse by Professor R W Wood, 1909: ‘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 this action played any very 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 the warm air heated by the ground within the enclosure. If we open the doors of a greenhouse on a cold and 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 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 in 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°C, the enclosure covered 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°C. From what we know about the distribution of energy in the spectrum of the radiation emitted by a body at 55°C, it is clear that the 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 that we gain very little from the circumstance that the 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? 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 up 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.’
This critique might have put Arrhenius’s calculation into the bin, so to speak, but as it was not a very important matter anyway (global warming was not an issue at the time) it remained as a current idea, and physics textbooks tended to repeat his hypothesis without criticism – they were doing so well into the 1970s when I was teaching physics.
This error remained undetected in the mainstream (which is not to accuse Arrhenius of any mean motive; scientists make mistakes all the time, even good ones).
But in the late 1960s and early 1970s it was revived by another Swedish scientist, Bert Bolin, because there were fears that a new Ice Age might be rapidly approaching. The hypothesis was that CO2 in the atmosphere might cause some warming and might just stave it off! Bolin speculated this possibility but even he could not be sure, and said so.
In the 1970s and 1980s temperatures started to rise. Bolin’s resuscitation of the Arrhenius hypothesis now took a more sinister turn: Global Warming, caused, of course, by the increase in the burning of fossil fuels.
Still no one was checking Arrhenius’s calculations, indeed they were actually using them! In the Apollo missions thermometers were left on the moon’s surface. The results were quietly published by NASA at the time – I suppose they thought that the moon’s surface temperatures were hardly headline news. But there was a mammoth surprise! The moon also showed a 30deg temperature excess above that expected which, by Arrhenius’s calculations, should not be there as there is no air and therefore NO greenhouse gases on the moon!
Here was a good test of the Arrhenius hypothesis, yet it showed that his calculations must be wrong. What was the mistake? Arrhenius, to simplify his calculations, had treated the Earth’s surface as ‘thin’. He ignored the fact that heat absorbed on the surface would be partly conducted (and stored) below the surface. The Earth acts as a storage heater, meaning that temperatures did not fall, at night, as far as theory predicted. The same with the moon, of course.
By now all sorts of alarm bells should have been ringing about ‘global warming’ being caused by CO2, but sadly most of the scientific community decided to ignore them. Scientists who drew attention to the issue were not listened to, but ignored, sidelined and very often personally abused. Peer reviewing ceased to be about detecting error, but rather maintaining the accepted narrative. Instead of error spotting it became heresy spotting.
So we conclude that the whole Global Warming edifice is based on an error made more than 120 years ago. Once that is realised, the edifice will collapse. Yes, reputations will be wrecked, some industries ruined, subsidy fortunes destroyed, but maybe lessons can be learned (trite, I know!) Science can maybe recover from this debacle, but it cannot be treated as some kind of infallible oracle ever again.
