RKS

You cannot determine the conditions of an airless Earth using the same albedo etc as if it had an atmosphere and oceans.

That's not what I'm saying, please read this carefully.

N&Z say that since clouds are an artefact of the atmosphere, to compare airless with airless you have to remove the earth's almospeher,and in doing so, you remove the clouds, so you bring the albedo down to the same as the moon (from 0.3 down to 0.12).

They then go on to work out, using their particular brand of unrotating physics, that the SB temperature of the earth is some 150K cooler than current observed temperature... and THEREFORE the GHE/ATE has to make up this 150K.

This is not true, the re-application of an atmosphere means you have to re-apply the cloudy albedo again. NOT all of that 150K is down to the GHE/ATE, some of it, a large chunk, is down to the return of the cloud albedo. They can claim that GHE/ATE + increased albedo effect = 150K, if they like. But it's not accurate to pin all of it on GHE/ATE, that's having their cake and eating it.

It was more an example of what I would call... creative polemics. Using a number which is not all GHE to demonstrate how 'obviously' it can't all be GHE. Appeals to the populum using dodgy numbers has no place in what puports to be a scientific paper.

Dung, some scientific effects only happen in the macro, and you can't reduce them in scale to make them happen in a lab experiment, I suspect GHE only happens in the wild.

By all means try, but as I said way back at the start of this thread... you're on a hiding to nothing. If you design an experiment and run it and it shows GHE, you've lost the bet. If it doesn't show it, there's endless scope for critics to point out that your experiment does not reflect reality in some dimension (size, voume, amount of insolation, lapse rate, etc) - so you wouldn't get the difinitive 'disproof' you were after. Trying to prove a negative is hard, which is why science doesn't often try it.

But the good news is you can try the experiment in the wild. Build your insulated container open to the sky, put your IR detector in the container, wait til night and measure the IR. If you get any, then it must be coming from the atmosphere. Job done. If you have a handy spectrum analyser, you can repeat the experiment and draw a graph of the mixtures of IR wavelengths in there to see what kind of thing emitted them.

Surprisingly you will see large peaks for H2O, CO2 and lesser peaks for other molecules.

This experiment has, in fact, been done. Here are the results.

So please, no more of this 'it hasn't been proved in a lab'. It's been proved in the wild, which is even better.

Sorry, sometimes all this trying to disprove the GH theory gets me annoyed, because I think it's distracting from the main show, and I think it's unfortunate that a faction of 'skepticism' has got itself to a point that it feels it has to deny the existence of something there is a decent amount of evidence for, in order to say that AGW is wrong.

The GHE can be real and as large as claimed and AGW still be wrong

This is because where AGW is wrong is going to be in areas like the delayed temperature effects of increased levels of solar flux, badly modelled feedback mechanisms such as cloud albedo, inflated temperature records due to UHI and introduced statistical bias, reliance on unproven positive feedbacks... etc.

This used to be where the bread and butter of skepticism was - attacking poor statistical handling of temperature records, attacking UHI, attacking the models for not modelling clouds or solar flux.

I think the development of a strain of 'skepticism' which is attacking core physics is distracting, divisive, and in my opinion wrong and harmful to our cause. If the physics is wrong, it will become apparent, but we're going to get no traction on AGW by going there, instead driving up the one-way-street of fringedom leading to being sidelined.

This is a very good example of what I said earlier, an experiment not being able to prove a negative. So what if the balloons don't change temperature? As you said yourself, mylar is transparent to IR, so any extra IR absorbed and re-emitted by the CO2 in the balloon will have gone out one of the other sides of it.

Consider (keep it in 1 dimension for simplicty)

Case 1: CO2 doesn't backscatter IR:
100 photons enter the balloon from the left, 100 from the right.
Nothing interferes with the IR.
Result: 100 photons exit from the right, 100 photons exist from the left

Case 2: CO2 backscatters the radiation
100 photons enter the balloon from the left, 100 from the right.
50 from the left are scattered and go back out the left, 50 keep going
50 from the right are scattered and go back out the right, 50 keep going
Result: 100 photons exit from the right, 100 photons exist from the left

Expand that for the remaining 2 dimensions.

In what universe would having CO2 in a balloon make it warm up, or the surrounding air, the air under it, or the ground beside the balloons warm up?

The CO2 inside the balloon and the CO2 outside the balloon don't behave any differently.

I'm trying to think of an analogy.

Imagine a football field of people, all at arms length from each other, equally spread across the field.

Now at one end, say the on the right hand goal-line (the goal has been removed for this experiment), a line of officials start handing out footballs to the people closest to the goaline. Say 1 football every 10 seconds when a bell rings.

When the next bell rings, each person chooses one of the 6 or 7 people around them to hand the football to, but are instructed to choose a different person each time, to make sure the distribution is random.

Over time, the footballs make their way down the length of the pitch.

At any snapshot in time, many, approximately half, of the footballs will be going backwards towards the goal line again. At the goal line, some of the people may choose to give the football back to the officials, that's ok.

Eventually, balls reach the left hand goal line, where they can be handed off to another line of officials, if that last person so chooses on the bell ring. So eventually, footballs start leaving the pitch on the left.

This is a model of GH gases in the atmosphere as people, and IR photons as footballs. The balls being handed back to the original officials is the ground 'heating up' (i.e. having more photons than they started out with, and having to give away teice as many as before) - the steady state at the end is the IR escaping from the top of the atmosphere

All your balloon experiment did was to say, lets put a circular fence up on the pitch somewhere and cram in as many people as we can. Not at arms length, shoulder to shoulder. The ones at the edge of this tight circle can still hand out footballs to those outside and inside the ring. Yes, there may more footballs inside the fenced off area, but does it make any real difference to the number of footballs leaving on the left hand side of the pitch averaged over time?

The answer is... during the initial 'fill up', it will. A greated number of balls will enter thie tight fenced area than leave it.. at first. But over time, the balls will be coming out of the area only as fast as they went in, on average.

This is the same as the atmophere and your balloon.

A mylar balloon with 100% CO2 should therefore be warming more than the Mylar ballon with normal levels of CO2 or did I miss something?

Air has a notoriously small heat capacity at the temperatures we're talking about (graph). This means when it's making the decision about whether to vibrate or emit, it almost always chooses to emit. The CO2 probably did go up by a thousandth of a degree.

Close, but no cigar.

Atmospheric heating by direct LW is not important, because it's tiny. As you saiy.

That's not where atmospheric heat comes from. All that interchange of footballs or IR photons means more hit the ground than are emitted. The ground heats to get rid rid of the extra energy. It heats by IR emission, and also by kinetic warming of the air. Warm air rises, we have a lapse rate. Voila.

Which is why it's always described as a 'back radiation' - the photons are omnidirctional but it's only the backscattered IR photons hitting the ground, which CAN vibrate and heat up which is the problem. 'Back radiation' is one of those misleading terms, like Greenhouse, which makes people doubt it.

If it was kinetic heating of the air that was important, there would be no lapse rate, because the CO2 would be heating all through the atmosphere equally. It's only photons which bounce back and hit the earth which cause kinetic heating, and then convective through the air to make a lapse rate.

Hard one to say with any accuracy because CO2 contribution is only a small part, H2O content is highly variable and it dominates the signal, but in theory, if you had hundreds of spectrum analysers pointing at clear skies all over the world for say 20 years, you could work out this figure and trend. But nobody is doing that. The only reason we have temp records is because they were useful for other things, nobody would propose measuring temperature either if we hadn't already done it.

Saying that, you can do a rough estimate. the DLR is about 290 W/m^2 on average. There is a debate going on about the exact contributions CO2 makes, but 25% of the whole effect in a dry sky seems to be the generally agreed quantity. Which would make CO2 contributing about 75 Watts.

That's true Dung. Unfortunately, the temperature to which conduction and convection attempts to heat it IS governed by greenhouse gases. It's not warmed by greenhouses gases, but the ground is heated by the extra photons that happen to be aimed downwards out of the thin layer of air near the ground, and the ground then heats ALL of the air.

I'm sorry I didn't explain, we can't ignore H2O - it is the major greenhouse gas, its effect is 2.5 times the size of CO2's effect. Both H2O and CO2 backscatter IR, warming the surface.