Why a bit more CO2 won't make any measurable difference to anything

From the motherlode:

The greenhouse effect works like this: Energy arrives from the sun in the form of visible light and ultraviolet radiation. The Earth then emits some of this energy as infrared radiation. Greenhouse gases in the atmosphere ‘capture’ some of this heat, then re-emit it in all directions – including back to the Earth’s surface. Through this process, CO2 and other greenhouse gases keep the Earth’s surface 33°Celsius (59.4°F) warmer than it would be without them.

This also means that the upper layers will be cooler than they would have been.

They have no grasp of the weather forecasters’ concept of Potential Temperature. The article is recommended reading! They show it diagrammatically as follows:

Remember – if the lapse rate is 6.6 C/km, then air which 1 km up and has an actual temperature of 25C has a potential temperature of 31.6C. If air at ground level has an actual temperature of 31.6C, then the two layers are in a neutral situation.

So if the air has the following pressure-altitude profile, where the absolute temperature falls by 6.6C for each km of altitude (the observed lapse rate), it is in a neutral situation. Each layer of air is the ‘right’ temperature for that altitude, and no layer particular wants to move up or down:

If the air higher up is warmer and the air lower down is cooler, this is a stable situation. The warmer air is quite happy where it is, the cooler air is quite happy where it is. But this situation does not hold for long, because the lower layers will warm up and the higher layers will cool down (see article), re-establishing the neutral situation:

If the air higher up is cooler and the air lower down is warmer, this is an unstable situation. The cooler air will sink and the warmer air will rise until the neutral position is re-established:

Why we can pretty much ignore CO2

We know that CO2 in an enclosed glass container in sunlight will warm up a bit more than normal air. This is because CO2 absorbs slightly more of the infra red, and more importantly, because it has a lower specific heat capacity, i.e. it takes less energy to warm CO2 by 1C.

The Alarmists say that having ‘trapped’ the warmth near the surface, the air lower down will be warmer and the air higher up will be cooler than it otherwise would be (loft insulation makes your home warmer and the loft space cooler).

OK, that’s superficially plausible. But to believe that, you must also believe that air is locked in position, and that the warmer air near the surface (and the cooler air higher up) will just stay where it is.

Well of course it won’t. We now have an unstable situation. The warmer air will rise and the cooler air will fall, it all gets mixed until we are back in the stable situation again. This will happen at the same time and at the same rate as any ‘surface warming’ happens and the will constantly cancel themselves out.

Clearly, if there is more CO2 in the air, the lapse rate will increase slightly (lapse rate = gravity ÷ specific heat capacity), warming the air at the surface and cooling the air higher up. But bearing in mind we are talking about an increases in CO2 levels of about 0.01% per century, the change in the weighted average lapse rate is going to be immeasurably small. And we know that water and water vapour will moderate that even further.