A discussion on WUWT over the past few days led to the following question to me, and my answer just below. The topic is, once again, whether the Greenhouse Effect (GHE) is real, and carbon dioxide in the atmosphere can and does warm the Earth's surface below.
One commenter asked me to comment on this statement in italics below. My reply is below that.
"[There is ] not even a semblance of a testable hypothesis regarding the GHE, GHGs, and all the rest of the claptrap spouted by those who should (but obviously don’t) know better."
I must disagree on this one. My knowledge squares with the statement by Professor Richard Lindzen (MIT), that GHG warming is trivially true but numerically insignificant.
As proof of GHE, or better expressed, radiant heat absorbed and re-radiated by CO2 and water vapor, my chemical engineering colleagues and I refer to the well-known properties of luminous gases in fired heaters. It turns out that furnace design (for industrial fired heaters that burn coal, oil, natural gas, or other such carbonaceous fuels) requires an adjustment for the combustion products' composition. Otherwise, the furnace does not work as expected.
The basic textbooks on chemical engineering, and heat transfer, all have a comprehensive section on this. The key parameters are gas composition, gas pressure (and hence the CO2 and water vapor partial pressures), flame temperature, and mean beam length. Here, beam length is the radiating distance. That distance is not far in a furnace, typically measured in inches. see e.g. Perry's Chemical Engineers' Handbook, 8th Edition (2008) pg 5-15 et. seq. The same material is in the same Handbook, 5th Edition (1973) (that I used in undergrad) starting on pg 10-48 et. seq.
The upper atmosphere where the CO2 and water vapor radiate energy back to Earth, aka TOA or top of atmosphere, has far different properties compared to a fiery furnace's interior. It turns out that heat radiated is far less for colder temperatures, lower partial pressures, and longer beam length. TOA is at approximately minus 50 deg C, CO2 partial pressure is very, very low at 400 ppm and (probably) one-tenth bar total pressure, and the beam length is measured in miles, not inches. In contrast, a furnace's radiant heat section is at approximately 2600 degrees F, partial pressures are much, much higher at one atmosphere and several percent (10 to 15 percent, not ppm), and the beam length is a few inches.
And that is why (I am certain) that Dr. Lindzen says the GHE is trivially true (we know for a fact that CO2 and water vapor can absorb and re-radiate), but numerically insignificant. The values are so small as to be meaningless.
The absorption and re-radiation of IR by CO2 and water vapor absolutely is true. It's all a matter of degree.
The chemical engineers have known this for decades. It is why our fired furnaces work, in the countless millions, around the globe, 24/7. And, it is also why global warming due to man's production of greenhouse gases, GHG, (primarily CO2 is blamed) is absolutely a false alarm.
To believe that a tiny few ppm of CO2 at very cold temperatures and miles up in the atmosphere can measurably increase the Earth's average temperature requires chemical engineers to dis-believe what we know to be true about fired furnaces.