Basis of CO2 Alarmism = Modtran = 0

As CO2 global warming alarmism is losing momentum in the absence of any warming since 15 years with politicians turning to other nobel causes, it may now be possible to question the very basis of this movement which has threatened to throw humanity back to stone-age by tough regulations to  "decarbonize" society.

The scientific evidence of the warming effect of the trace gas CO2 consists of theoretical predictions of the "radiative forcing" effect using models for radiative transfer such as Modtran based on spectral data from the data base Hitran. A version of Modtran can be run on the web, which makes it possible to test its performance, as we did in a previous post.

Modtran gives a "radiative forcing" of 3.7 W/m2 upon doubling of atmospheric CO2 from 300 ppm to 600 ppm. This serves as the starting point of CO2 global warming alarmism by giving the trace gas CO2 a substantial warming effect as a powerful "greenhouse gas" GHG. Experimental evidence of this is effect is lacking. Without the 3.7 W/m2 produced by Modtran, there would be no IPCC and no CO2 alarmism.

Can we then trust the Modtran prediction of radiative forcing of 3.7 W/m2?

Well, Modtran as radiative transfer model is a very simplistic model of the complex atmosphere. Modtran is further supposed to model the effect of a very small cause since CO2 is an atmospheric trace gas, and to capture a small cause requires high accuracy. The scientific warning signs are thus blinking for Modtran.

Let us here check how Modtran reacts to very low concentrations of CO2 from 0.001 ppm to 1 ppm as an extension of previous posts. We get for a standard atmosphere with CO2 as the only greenhouse gas present, the following total outgoing long wave radiation OLR in W/m2 for different ppm of CO2:

• OLR = 397.524 for 0 (ppm CO2)
• OLR = 397.524 for 0.001
• OLR = 397.21 for 0.01 
• OLR = 396.582 for 0.05 
• OLR = 395.64 for 0.1
• OLR = 392.814 for 0.5
• OLR = 390.616 for 1 (ppm CO2).   

We see a radiative forcing of  0.3 W/m2 from 0 to 0.01 ppm, 2 W/m2 from 0 to 0.1 ppm and  7 W/m2 from 0 to 1 ppm. This is a substantial effect from a cause as small as one part in 100 million. It is hard to believe that this effect can be viewed as a scientifically evidenced real effect.

This test gives yet another reason to question Modtran as the basic scientific evidence of a global warming effect of CO2, for both climate alarmists and skeptics who have accepted Modtran as truth.

If climate skeptics would dare to take the step to question Modtran, that could very well be the final nail in the coffin of IPCC.