14 Jun (PRINCIPIA SCIENTIFIC) – You may be surprised to learn that there are many “Old Wives’ Tales” apparently circulating among climatologists that are quite contrary to valid physics. Some will be discussed below.
Air cools when it expands and warms when it is compressed.
The Ideal Gas Law in physics basically tells us that pressure is proportional to the product of absolute temperature and the density of the gas. But the density usually varies with pressure, and so we cannot deduce any direct causal relationship in which pressure might affect temperature. In fact Kinetic Theory tells us that temperature is proportional to the mean kinetic energy of the molecules and is not dependent upon anything else. In other words, temperature only changes if the mean kinetic energy changes. Indeed this can happen when air rises and kinetic energy is converted to extra potential energy, but the resulting temperature change has nothing to do with whether or not the air expanded. It can happen in totally still air, even in a sealed container, where molecules simply collide with each other and share their kinetic energy, as discussed in my paper Planetary Core and Surface Temperatures.
Greenhouse gases (mostly water vapour) have raised temperatures by over 30 degrees
If water vapour did in fact raise surface temperatures by about 30 degrees on average, then we would expect significant variations in different locations, because there may be only 10% as much water vapour in a dry area as in a moist area. So we would expect perhaps 5 degrees of warming in a dry area and maybe 50 degrees in a similar but moist area. In fact, real world data shows us (in studies such as that in the Appendix of my paper cited above) that moist areas have cooler mean daily maximum and minimum temperatures than similar but dry areas. The paper explains why this is the case.
Water vapour and carbon dioxide increase the insulating effect of the atmosphere.
Those in the building industry know that double glazed windows should be filled with dry air, not moist air. The insulating effect is reduced by water vapour (and carbon dioxide) because these radiating molecules assist thermal energy to traverse the gap at the speed of light, rather than at the speed of the much slower process of molecular diffusion of kinetic energy. Of course there would be “back radiation” headed for the warmer pane of glass, but the evidence is that the overall insulation is more effective with dry air, and presumably better still with pure nitrogen that would not radiate like the carbon dioxide in the dry air. The atmosphere acts like the air or gas in the space between the double glazing, and so water vapour and carbon dioxide assist the cooling process.
The Earth’s surface would be far cooler in the absence of water vapour.
No it would not be. As we saw in the previous section, water vapour actually cools the surface. In fact it probably reduces the mean surface temperature from something over 20°C back to the observed 15°C. Without water vapour, the gravitational influence in the atmosphere would create a steeper thermal gradient and this leads to a higher mean surface temperature when radiative equilibrium is established. For more detail and evidence, please see the above paper.
The atmosphere is transparent to incident radiation and opaque to surface radiation
No it’s not. The NASA net energy diagram below shows that more incident Solar radiation is absorbed by the clouds and atmosphere on the way down (namely, 19%) than the 15% absorbed from surface radiation.
Most of the energy transferred from the surface to the atmosphere is by radiation
The NASA diagram shows 23% by latent heat (evaporative cooling) and 7% by conduction and rising air. This total of 30% for non-radiative processes is double the 15% for radiation.
The effect of carbon dioxide is more significant than that of water vapour
Like water vapour, carbon dioxide also absorbs some incident Solar radiation, particularly in the 2.7 micron band. So it prevents this radiation from reaching and warming the surface. However, the atmosphere has only about 0.04% carbon dioxide, compared with about 1% to 4% water vapour. Each water vapour molecule absorbs and radiates in a far wider range of wavelengths than each carbon dioxide molecule and so, as some have estimated, the overall effect of all the carbon dioxide could be as little as 0.1% that of all the water vapour. And that effect is likely to be a net cooling effect anyway.
Radiation from the cooler atmosphere slows the rate of non-radiative cooling
No, it can only slow radiative cooling and cannot slow non-radiative cooling, because the electromagnetic energy in such radiation is not converted to thermal energy in the warmer surface. Hence such “back radiation” cannot affect the rates of conduction and evaporative cooling which, in total, transfer about twice as much thermal energy from the surface to the atmosphere as does radiation. Furthermore, there is nothing to stop non-radiative processes accelerating or lasting longer into the night if radiative cooling is slowed. For more detail please see my paper Radiated Energy and the Second Law of Thermodynamics.
Temperatures have increased at a more rapid rate in the last century
As shown in the Appendix of the paper just cited, the underlying rate of increase has actually reduced from a mere 0.06 C degree per decade about 100 years ago to about 0.05 C degree per decade in current times. This is still quite consistent with a long term rise of slightly less than 0.5 C degree per century over the last 300 to 400 years or so. The world probably saw similar rises between the Dark Ages and the Medieval Warming Period and, just as there was then a natural fall in temperatures for about 500 years until the Little Ice Age, so too can we expect a similar fall to commence within the next 100 to 200 years I would suggest. Mean temperatures are very unlikely to rise by more than a degree before such cooling sets in. In the short term, the fairly level trend since 1998 is likely to last for about 30 years before another 30 years of rising temperatures. The reasons for the apparent natural variations in climate may have something to do with processes not yet fully understood, but probably related mostly to the planetary orbits of Jupiter, Saturn and Venus. Above all, we need to recognise that there is no valid physics which can prove that carbon dioxide plays any significant role in affecting the climate of our planet.