I have spent the last year and a half reading up on AGW theory. One after another, I have managed to iron out most of the contradictions, half-truths and flawed explanations for correct observations. Each one is a bit of an intellectual effort to overcome because it's all things that most people - Alarmists, sceptics, weather forecasters and the man in the street (i.e. me) - just take for granted.
I have spent most of that year and a half kicking myself for being sent off in the wrong direction for not having noticed something sooner, going back, rethinking and redoing my workings (and regretting many of my posts based on false - but widely held - assumptions). I hope that I have now got the bottom of it all and overcome the final false assumption, which had been nagging me for months...
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The 'inconvenient truth' is that the entire Greenhouse Effect is due to clouds (and their altitude)!
All the Alarmist pictures and diagrams just show the sunlight hitting the surface and being reflected back down by Greenhouse Gases. Clouds - when they appear at all - merely serve to reflect even more radiation back down and 'warm' (i.e. slow down the cooling of) the surface (which they clearly do during the night time).
To get back to reality, you have to draw in the cloud cover (accepted as two-thirds of the surface, so we might as well round that up to 'all of it') on all their pictures and diagrams and realize that most sunlight hits clouds first - that is the layer that absorbs sunlight. The temperature of their upper surface is determined by sunlight, and that in turn dictates the temperature of land and oceans via the gravito-thermal effect (the Greenhouse Effect = cloud altitude x lapse rate).
When you draw in the missing clouds, you realize what's causing the 'back radiation' and what's blocking terrestrial radiation from all getting to space and being measured by satellites. They are big white things that can be miles thick. They reflect sunlight, so we have to assume they reflect all EM radiation to the same extent (arguably more). It appears to be widely accepted that higher clouds mean a warmer surface than lower clouds, this is a correct observation and ties in with all this.
Another smoking gun is that on Venus and Earth, the upper surface of clouds is at the 'average emitting altitude' aka 'effective radiating layer'. This is not a coincidence - to all intents and purposes, they are the 'effective radiating layer'.
Clouds are also the 'effective absorbing layer' as far as incoming sunlight is concerned. Remember that they calculate a planet's 'effective temperature' based on 'what the sunlight hits first'. The 'effective temperature' calculation gives reliable answers, and so unsurprisingly, a planet's 'effective temperature' is pretty much the same as the actual temperature of what the sunlight hits first - namely the upper layer of clouds.
Unless a planet or satellite has no clouds (Mars, Moon) in which case the 'effective temperature' is a good approximation of the actual surface temperature. (The maths is trickier with the Moon because it revolves so slowly.)
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To sum up - there is a Greenhouse Effect warming the surface. Clouds (if high enough) mean that the surface is warmer than it otherwise would be. Nothing to do with Greenhouse Gases.
"What?" shouts the audience, "Have you gone completely, stark staring mad?
A. Don't most people say that clouds have a small overall cooling effect?
B. Doesn't it get a bit cooler when clouds pass between you and the sun?"
A. Maybe they do, but it's not true. They don't. Do the interplanetary comparison:
Venus - completely covered with very thick clouds at a very high altitude (50 km to 80 km). Hard surface gets very little sunlight, and only indirect sunlight at that. Huge Greenhouse Effect, about 500 degrees.
Mars/Moon - no clouds. Hard surface gets all the sunlight you'd expect. No Greenhouse Effect - even though the Martian atmosphere has about thirty times as much CO2 as Earth.
Earth - two-thirds moderately thick cloud cover at a few km altitude. Moderate Greenhouse Effect, accepted as 33 degrees.
Conclusion - the higher and thicker the clouds, the larger the Greenhouse Effect.
Caveat - clouds have a higher albedo (reflect more sunlight) than land or oceans, so they have to be at a certain minimum altitude for there to be net warming (so that the lapse rate effect trumps the missing sunlight). When I say 'net warming' I am comparing a hypothetical planet with and without clouds - NOT a cloudy and cloud-free area on the same planet. That minimum altitude is two-to-three km above the Earth's surface as far as I can make out, and on the whole they are much higher than that.
B. Yes, but you have to compare like-with-like.
i. Higher clouds warm the atmosphere, but it is not a local effect. The atmosphere tries to equalize temperatures around the globe (a phenomenon we refer to as 'the weather') and does a fairly good job under difficult circumstances (freezing poles, sweltering deserts). The oceans do the same thing, but that is way more complicated and poorly understood.
ii. Most of the temperature you feel - and all of the official temperature measurements - is the air temperature with no direct sunlight. Direct sunshine just gives a bit of a boost - on a hot, sunny day, it's still very warm in the shade with no direct sunlight. On a freezing cold winter day, it's still very cold even when standing in full-on direct sunlight hitting you at 90 degrees.
iii. So if you want maximum daytime temperature, you have to be a cloud-NIMBY - clouds everywhere else to warm the air (benefitting you as well as 'them'), but clear sky where you are to get the extra few degrees caused by the direct sunshine (only benefitting you and your immmediate neighbours).
iv. How many hours direct sunshine does a typical patch of land or ocean get in 24 hours? About four? Are those few hours really enough to keep the surface warm for the other twenty? Clearly not.
v. While you do feel warmer when there are no clouds between you and the sun, nearly everybody accepts that clouds tend to slow down cooling in the night time. The net effect is an overall win for clouds.
vi. If there are very low clouds (fog or mist) of course they have a direct cooling effect. That has partly to do with them blocking sunlight, partly with them being at a low altitude, but primarily because they make things damp and so the surface (and you) lose thermal energy because of the latent heat of evaporation.
vii. It is also the case that clouds often mean rain. We notice that rain cools the surface but we don't notice that this indirectly warms the atmosphere higher up - it's because of the latent heat of evaporation. So we automatically associate 'clouds' with 'cooler', not realising that most are 'high and dry'. There are clouds directly above you two-thirds of the time, but it's not raining two-thirds of the time, even in Wales or Norway.
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There. I've said it. Sue me.
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The icing on the cake is that some Alarmists say that warmer temperatures will evaporate the clouds = more direct sunlight on the surface = higher temperatures. The opposite is true! Less cloud cover would mean a) less Greenhouse Effect and b) more direct radiation from surface to space, especially at night = lower temperatures again, so entirely self-regulating = stable temperatures.
Debate Magazine
