Water Vapour Climate Forcing
‘Up To 200 Times’ Greater,
‘Overrides Any Effect By CO2’
H. Douglas Lightfoot profile PDF
(1) Robust scientific evidence shows the sun angle controls water vapour content of the atmosphere, the main component of back radiation, as it cycles annually.
Back radiation, water vapour concentration and atmospheric temperature follow the sun angle daily and over the seasons, increasing as the sun angle increases and falling as it decreases. Water vapour concentration is measured as parts per million by volume (ppmv) or by the ratio of the number of water vapour molecules for each CO2 molecule (H2O/CO2 ratio).
The purpose of this study is to present robust evidence that the sun is working with water vapour to control the Earth’s climate and to show that the influence of CO2 on atmospheric temperature is so small as to be negligible.
(2) Water vapour content measured as the ratio of the number of water molecules to CO2 molecules varies from 1:1 near the Poles to 97:1 in the Tropics.
The H2O/CO2 ratio along the top of the plot is based on a CO2 concentration of 400 ppmv. Because water vapour is the most abundant GHG, it is reasonable to plot water vapour concentration against back radiation. … It is evident from Figure 1 that (1) the upper limit to the back radiation of GHGs is approximately 420 W m2 at water vapour concentration of approximately 32,000 ppmv, or an H2O/CO2 ratio of 80 [to 1]; (2) the lowest back radiation is 97 W m2 at the South Pole and (3) small increases in water vapour give the most increase in back radiation above the Arctic and Antarctic circles because of the steepness of the curve. These [polar] areas together are only 8.4% of the Earth’s surface and have little effect on the Earth’s average atmospheric temperature.
The CO2 baseline concentration of approximately 400 ppmv at the time of the calculation is equivalent to 0.0138 mole/kg of dry air. Thus, the H2O/CO2 ratio is 0.601/0.0138 or 43.5 molecules of water vapour for each molecule of CO2. [17,400 ppm water vapour vs. 400 ppmv CO2.]
The sun angle determines the H2O/CO2 ratio … There is little sunlight in winter above the Arctic Circle, such as at Inuvik, Canada, and the average H2O/CO2 ratio is as low as 1:1. In summer it rises to an average maximum of 29:1. … The highest sun angle corresponds to the highest H2O/CO2 ratio of 29:1 and the lowest angle to the lowest of 1:1. The H2O/CO2 values for Singapore and Nairobi also show the highest ratios occur at the highest sun angles. The difference in H2O/CO2 ratios between summer and winter is larger towards the Poles and smaller towards the equator. The levels of both the summer and winter ratios depend on whether or not there is a relatively warm ocean nearby to provide the water vapour.
(3) The effect of back radiation [water vapour] on Earth’s atmosphere is up to 200 times larger than that of CO2 and works in the opposite direction.
The actual CO2 concentration experienced at any specific location is determined by the physical gas laws discovered by Boyle and Charles. For example, the elevation of Boulder, Colorado, is 1655 m, the average July high temperature is 33°C and the average low in January is 2°C. The calculated CO2 concentrations based on 407.9 ppmv in dry air are 298.0 and 336.4 ppmv, respectively. The RF [radiative forcing] of CO2 in July at 298.0 ppmv is 5.22ln(336.4/298.0) ¼ 0.63W m2 lower than in January at 336.4 ppmv. While the RF of CO2 was falling by 0.63W m2 from January to July, the back radiation was increasing by 110 W m2 from 240 to 350 W m2. From July to January the situation reverses. This shows back radiation [water vapour] acts in opposition to the warming effect of the CO2, is larger by (110/0.63) = 174 times at the peak and overrides any effect by CO2 on atmospheric temperature.
If there is a warming effect by CO2 on the atmosphere, it is too small to measure and can be considered as being negligible. In fact, it is fair to say there is virtually a complete disconnect between the concentration of CO2 in the atmosphere and atmospheric temperature.