Originally Posted by
cwatters
As I understand it CO2 is such a good absorber of IR that (even at pre industrialisation levels of C02) it only takes about 25 meters of the atmosphere to scatter most of the IR radiated by the earth (
http://clivebest.com/blog/?p=1169 ). This means energy is only radiated into space from high up in the atmosphere, where the air and CO2 is thin enough.
Its been suggested that adding CO2 raises the effective height from which IR energy is radiated. Unfortunately the higher you go the colder it gets and IR radiation is proportional to the fourth power of temperature (T^4).
If less energy is radiated into space the temperature of the planet must increase until the energy lost from the earth once again matches that arriving from the sun.
Except that most energy radiated is carried past this theoretical effective height by convection. A significantly long way as those who have flown through the Intertropical convergence zone will attest - these are the convective Hadley cells at the equator. Even the tops of Cb in cold fronts in the temperate zone are well above the 'effective height' and these are the Ferrel cells. As the water in these clouds first condense and then freeze heat is released a long way above the altitudes at which CO2 is an issue,
You should also remember that the absorption of infrared by CO2 is logarithmic so each doubling of CO2 has half the effect of the previous. At 400ppm the absorption in the 3 narrow IR wavelength bands are almost saturated. Two of the bands are in any case overlapping with water vapor absorption.
Note:
* There is no correlation between CO2 and atmospheric temperature at geologic timescales where CO2 has been tens to hundred times higher concentrations in the atmosphere. The brief 20 year correlation in the last decades of the 20th century do not imply causation. See this spurious correlation
NONE of the forecasts made by climate scientists' models have been correct. Normally in science if the forecast made based on your hypothesis is falsified n the real world the hypothesis is abandoned.