Because 2 + 2 = 5

I’m done with making fun of Skeptical Science, it’s shooting fish in a barrel, so I dipped my toe into  Science of Doom again. That blog has scientific pretensions, which makes it  harder to spot the contradictions. But they put hard numbers on things, which makes it easier to nail down the sleight of hand once you’ve spotted it (which took me a couple of days this time):

Globally and annually averaged, clouds cool the planet by around 18W/m² – that’s large compared with the radiative effect of doubling CO2, a value of 3.7W/m². The net effect is made up of two larger opposite effects:
* cooling from reflecting sunlight (albedo effect) of about 46W/m²
* warming from the radiative effect of about 28W/m² – clouds absorb terrestrial radiation and reemit from near the top of the cloud where it is colder, this is like the “greenhouse” effect.

They are obsessed with ‘radiation’, It is merely one form of energy, which like most forms of energy, can turn into other forms of energy in an instant. Start with chemical energy in your muscles, throw a ball in the air and you convert chemical energy in your muscles to electrical energy to kinetic energy of the ball; then watch kinetic energy turn seamlessly into potential energy and back again; let it fall to the ground you get a bit of sound and thermal energy. There is not a fixed amount of ‘radiation’ in the atmosphere that has to be accounted for; there is a fixed amount of total energy, a lot of which is not thermal energy or radiation.

What we care about is not ‘radiation’ in itself, we care about thermal energy i.e. temperature i.e. ‘global warming’. In plain English, a net reduction of 18 W/m2 incoming radiation means that surface temperatures are about 3 degrees cooler then they would be if there were no clouds. Everyday experience and objective comparisons confirm that it’s cooler where/when it’s cloudy/moist than where/when it’s clear/dry. Three degrees seems to be on the low side (because 46 W/m2 is on the low side, the fag packet says about 60 W/m2), but let’s accept it for now.

Just as noticeable/measurable is that day-night swings are much lower where/when it’s cloudy/moist than where/when it’s clear and dry. That’s because clouds physically reflect (i.e. like a mirror) sunlight up by day and reflect radiation from the earth back down (particularly noticeable by night); also because of the latent heat released by condensation. Clouds don’t absorb and re-emit radiation, it just bounces off.

[Also worthy of note is the 'official' figure of an extra 3.7 W/m2 radiation if CO2 doubles - somebody made up this number decades ago and it is now Alarmist Gospel. This - even if were true, which it isn't - equates to about 0.7 degree of warming at the surface (and cooling higher up). Sorry, still not scared.]

By magic, they can disaggregate the 18 W/m2 (3 degrees) into minus 46 W/m2 (minus 8 degrees) of cooling (clouds reflecting sunlight back into space and casting shadows) and plus 28 W/m2 (plus 5 degrees) of warming due to the ‘top of atmosphere’ effect. While the net 18 W/m2 is probably about right, I don’t see how it is possible to disaggregate without making dozens of assumptions and guesses, seeing as both things happen simultaneously and have the same cause. But hey.

I explained the ‘top of atmosphere’ effect at point 2 here. What it boils down to is that the effective emitting altitude (in this case the upper surface of clouds) is (or would be) pushed up by about 1.5 km. That is a heck of a lot, surely airline pilots would have noticed if clouds are higher than they used to be?

The ‘top of atmosphere’ is an intellectually and mathematically pleasing theory, but complete nonsense of course. If clouds were higher, then of course they are emitting less radiation. Not just because they are cooler (being higher up), but because the radiation energy which they would otherwise emit has been converted to potential energy (the clouds are higher). Potential energy is not thermal energy and there is no warming as a result.

Common sense tells us that water vapour and clouds must dampen temperature swings, they are largely self-cancelling. The Alarmists insist that more CO2 = higher temperature = more water vapour and clouds; water vapour in turn is a ‘greenhouse gas’ so this pushes up temperatures even more in a vicious circle. This is clearly nonsense, if water vapour caused more water vapour, the oceans would have boiled dry very quickly (or more likely, never formed in the first place).

The Alarmists get round this (read the article) by saying, aha, the 46 W/m2 (8 degrees) of cooling (clouds reflecting sunlight back out to space) is fixed and unaffected by how much water vapour and clouds there are (not plausible), but the 28 W/m2 (5 degrees) of warming will increase with increasing water vapour and cloud altitudes. So above a certain level of moisture; the warming effect exceeds the cooling effect. Which is of course not borne out in real life or plausible.
———————————-
The article also get a good kicking in the comments, well worth a visit and a read.