Hard Evidence of CO2 Warming Inflated by a Factor of 20

Dr. Claes Johnson, KTH Professor of Applied Mathematics, has a post today demonstrating that computer models of radiation transmitted by the atmosphere attribute a warming effect of CO2 which is at least 20 times more powerful than that of water vapor. This is despite water vapor being a more powerful greenhouse gas, with a much wider absorption interval that also significantly overlaps the CO2 interval to further trivialize the effect of CO2. Climate models also assume that increased CO2 will increase water vapor, despite observations showing that water vapor has decreased. Furthermore, there is no evidence to support the global warming theory that outgoing longwave radiation [OLR] has decreased due to increased CO2, since satellite observations instead show an increase in OLR.

From a prior post demonstrating that the CO2 absorption interval is already significantly overlapped by water vapor:

Region of interest of CO2 LWIR (long wave infrared) absorption indicated by circle. Note also the much wider absorption interval of water vapor in comparison to CO2, and overlap with CO2 absorption.

Blowup of region of interest showing overlap between CO2 and water vapor
shaded area is absorbed by CO2 only

Blowup of above figure. Area with asterisk is absorbed by CO2 only.

From Dr. Claes Johnson:

Hard Evidence of CO2 Warming Inflated by a Factor of 20

The hard scientific evidence of the warming effect of atmospheric CO2 consists of radiation spectra computed by the atmospheric radiation model Modtran, predicting a "radiative forcing" of 3.7 W/m2 from doubling of the concentration of CO2 to 0.06% from preindustrial level of 0.03%.

To get perspective, let us use the online model of Modtran to compare the present 0.039% of CO2 with a typical value of 2% water vapor. We get the following OLR spectrum for a 1976 USA standard atmosphere with 1.7 ppm CH4, trop. ozone 28 ppb, strat ozone scale 1:

We see the effect of water vapor as the area between the blue to the red curve for wave numbers smaller than 550 and the effect of CO2 as the comparable area between 550 and 800, thus with an effect of 0.039% of CO2 comparable to that of 2% water vapor. More precisely, Modtran gives the following OLR numbers:

• CO2 = 390, water vapor 2%: 248 W/m2
• CO2 = 0, water vapor 0%: 337 W/m2
• CO2 = 390, water vapor 0%: 304 W/m2
• CO2 = 0, water vapor 2%: 273 W/m2

which shows an effect of 0.039% CO2 which is about half of that of 2% water vapor.

Modtran thus attributes a warming effect of CO2 which is at least 20 times more powerful than that of water vapor!!

We can now summarize the recent posts on Modtran as the hard evidence of CO2 alarmism:

• Modtran is supposed to be the hard scientific evidence of the warming effect of CO2.
• Modtran appears to inflate the warming effect of CO2 by factor more than 20.