THE GREENHOUSE EFFECT

There is the greenhouse theory, based on the "greenhouse effect:" When sunlight passes through glass, only the visible part of the spectrum penetrates it; the ultraviolet and infrared radiation is rejected, i.e., reflected and absorbed. (The UV comes in handy for skin cancer theories, but only the infrared is needed for the greenhouse variety of genocide.) Inside the greenhouse, the light is absorbed and re-emitted at all wavelengths, including infrared (heat radiation). The other colors get out the way they came in, but the infrared is now trapped inside the greenhouse and builds up the heat in it. ("Ain't the way my greenhouse works," a gardener may say, but we'll come to that in a moment.)

Growing technology gives rise to more and more carbon dioxide production, goes the theory, and carbon dioxide, like glass, is opaque to infrared. A carbon dioxide layer in the atmosphere would therefore act just like the glass of a greenhouse, and the remainder of the scenario merges with Ehrlichian versions of frying in our own juice.

Since carbon dioxide is produced, among man made sources, mainly by burning fossil fuels, the theory is also quite popular among some proponents of nuclear power as additional proof that nuclear is safer than fossils. This newsletter is not exactly opposed to nuclear power (our readers may have noticed), but we will not use this argument in its favor, for we believe the theory to be speculative. The proven superior safety of nuclear power has no need of such shaky arguments.

It is true that the carbon dioxide content of the atmosphere has slightly increased in the last 100 years; but the evidence that this is due to human activity is, at best, very flimsy. (As usual, man's activities are puny compared to the gigantic CO production be Mother Nature.) There is, on the contrary, some evidence (gleaned from Greenlands icesheet layers) that the atmospheric concentration of CO 2 has always fluctuated in past ages. (But won't we use up too much oxygen by burning fossils? No: For a very interesting refutation see The world doesn't end here! by Prof. J.J. McKetta. free from Council of Environmental Balance, Box 7732 Louisville KY 40307.)

The greenhouse effect is also genuine, as call be demonstrated with a piece of glass and a spectrometer. But it hardly affects the temperature of a greenhouse, which gets its warmth almost exclusively by the lack of ventilation - as proved in l909 by physicist R.W Wood, who covered one greenhouse with glass and another with rocksalt. which is transparent to all colors, including infrared. As recently reported again [Science, letters, 12/12/75], it makes little difference to a greenhouse whether it is covered with glass or infrared-transparent polyethylene; both act as a lid preventing air convection.

The earth's (cloudless) atmosphere is largely opaque to infrared already, trapping some of the earth's heat radiation, and what effect an increased concentration of carbon dioxide might have on a circulating atmosphere, nobody knows for certain. But such an effect, if any, would be superimposed on the large climatic changes that take place over decades and centuries (unknown why) anyway, and the suspicion is that the corresponding (additional) greenhouse effect would have the same effect as on a greenhouse next to none.