Debate Magazine

"A Saturated Gassy Argument"

Posted on the 20 October 2020 by Markwadsworth @Mark_Wadsworth

I've been delving ever deeper into MMGW theories. Most of the common-or-garden ones are easily demolished*, their next line of argument is far more subtle and goes like this:
In the layers so high and thin that much of the heat radiation from lower down slips through, adding more greenhouse gas molecules means the layer will absorb more of the rays. So the place from which most of the heat energy finally leaves the Earth will shift to higher layers.

Those are colder layers, so they do not radiate heat as well. The planet as a whole is now taking in more energy than it radiates (which is in fact our current situation). As the higher levels radiate some of the excess downwards, all the lower levels down to the surface warm up. The imbalance must continue until the high levels get hot enough to radiate as much energy back out as the planet is receiving.

Fair enough, like most MMGW arguments it seems to stand up in isolation if you ignore the equal and opposite counter-arguments and evidence. But that claim does not square with the following statement:
In any event, modern measurements show that there is not nearly enough CO2 in the atmosphere to block most of the infrared radiation in the bands of the spectrum where the gas absorbs (1). That’s even the case for water vapor in places where the air is very dry. When night falls in a desert, the temperature can quickly drop from warm to freezing. Radiation from the surface escapes directly into space unless there are clouds to block it (2).
1) Either CO2 blocks a lot of infrared or it doesn't. You can't have it both ways. The clever diagrams show that CO2 blocks nearly all the outgoing infrared at 14 - 16 microns (terrestrial infrared goes from 4 to 100 microns). If that's not "most", I don't know what is. Then they cheerfully admit that "Radiation from the surface escapes directly to space unless there are clouds to block it".
2) Water vapour behaves in a similar fashion to CO2 as regards absorbing and re-emitting infrared (just at many more wavelengths). You cannot compare this with the effect of clouds i.e. actual water and ice droplets, which do indeed have a very strong blanket effect (cooling by day; warming by night; the overall effect is slight cooling). The acid test for all this would be to compare the rate of night time cooling where/when it's dry without clouds and times where/when it's moist without clouds.

Their maths is wrong as well:

In reality, that mere percent increase, when combined properly with the "thinning and cooling" argument, adds 4 Watts per square meter to the planets radiation balance for doubled CO2. That’s only about a percent of the solar energy absorbed by the Earth, but it’s a highly important percent to us! After all, a mere one percent change in the 280 Kelvin surface temperature of the Earth is 2.8 Kelvin (which is also 2.8 Celsius).

Nope. The "4 Watts" (often given at 3.7 Watts) was reverse engineered by assuming that the entire increase in temperature was down to increased CO2 levels over the same period, so can't be presented as evidence in support of the underlying assumption. Even if true, a one per cent increase in incoming radiation would lead to a one-quarter per cent increase in surface temperature = 0.7C.

* Such as:
(i) the IPCC energy budget diagram which does not add up or explain why the 'greenhouse effect' is negative during the day time;
(ii) claiming that the greenhouse effect adds 33C of warmth, ignoring the fact that this only applies at sea level and is entirely due to the gravito-thermal effect;
(iii) using Venus as an example of runaway global warming when its high surface temperature is also due to the extra gravito-thermal effect because its atmosphere is one-hundred times as massive as Earths;
(iv) glossing over Mars which has forty times as much CO2 per m2 but no greenhouse effect;
(v) pointing to experiments which show that CO2 warms up more than normal air under a bright light and saying it's because it traps infrared. Nope. This is because of its lower specific heat capacity - if you do the experiment with argon, it warms as much as the CO2; etc.

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