IS THE GREENHOUSE EFFECT A MISNOMER? Before I proceed, let me admit that this is largely speculation from an amateur climatologist, and I may be talking out of my butt. If you can shoot me down, please do so. I will have learned and gained from the experience. On average the earth receives 1361 watts per square meter energy from the sun at top of atmosphere. Because the earth is not a perfect black body absorber, about thirty per cent of this is reflected back into space. The reflectivity of a planet is known as albedo. During the earth’s annual orbit around the sun the amount of incoming energy varies quite considerably. This is because the orbit is not perfectly circular, but elliptical. The difference in incoming energy between perihelion (the closest point to the sun) and aphelion (when earth is furthest away) is about seven per cent. According to standard energy models, this should result in a temperature swing of over four degrees C at earth’s surface. But not even the slightest corresponding pattern of temperature variation is discernible over the course of a year. This means partly that energy models are wrong, and partly that there is another factor than greenhouse gases that determines the earth’s temperature. What this other factor may be, at this moment nobody can say for sure. Variations in albedo are the prime suspect. Only recently have satellites been launched to measure the earth’s cloud cover, and perhaps in time NASA will tell us what the results are, provided the information is not damaging to the CAGW creed. If albedo varies by thirteen per cent over a year, and its highs and lows coincide with perihelion and aphelion, this would account for the earth’s stable temperature. Another explanation, and here I’m talking heresy that no self-respecting warmist would begin to entertain, is that greenhouse gases are not solely responsible for the greenhouse effect*. Atmospheric mass and pressure may also play a substantial part. This hypothesis appears to be supported by the surface temperature of Venus. Standard energy models based on the greenhouse effect undercalculate Venus’s temperature by around one hundred degrees C. The difference is probably due to Venus’s extremely thick and heavy atmosphere. If greenhouse gases are less important in determining temperature than previously believed, a change in albedo in sync with the earth’s orbit would not need to be so great in order to explain earth’s stable temperature over the course of a year. *The greenhouse effect is defined as the difference between (a) the earth’s temperature if it had no greenhouse gases, and (b) the temperature actually measured, albedo somehow remaining the same with or without cloud cover. Acknowledgements to Derek Alker for teaching me about the atmospheric pressure effect, and to Steve Goddard for getting me thinking about this.
Posted on: Mon, 01 Dec 2014 06:06:07 +0000
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