RKS

You say insolation cannot interact with the majority of the air molecules - N&Z, after years of refining their theory, say that it does.

If N&Z actually do say that*, then their paper is junk, plain and simple. Thanks for clearing it up, it means I don't have to consider it again.

* a citation would be nice for complete closure

RKS

my problem with the N&Z paper are statements such as:

"Equations (5) and (6) imply that pressure directly controls the kinetic energy and temperature...." (taken directly from N&Z

"The more molecules per unit volume the higher the temperature and the less molecules per unit volume the lower the temperature." RKS 2.53pm

These are simply wrong statements. Pressure does not control the kinetic energy of molecules. The energy distribution of molecules is a function of temperature alone. One can have 10 molecules per unit volume, or 10^n molecules per unit volume with the volume of gas at the same temperature. The temperature is not based on the total energy in the volume but on the average molecular kinetic energy.

I'm trying to come to some understanding of the N&Z work but it's difficult when some elementary concepts such as the kinetic theory of gases, ideal gases, work, energy etc. are not presented as they should.

My position at the moment is that in an atmosphere that is not radiatively active. i.e. one that contains say just N2 then the atmosphere will attain an isothermal state. It can't lose heat to space by radiation, if it picks up heat through conduction by contact with the planetary surface at it's base then any movement will serve to bring the atmosphere to it's isothermal state. I belive this is also the position of Roy Spencer, Richard Lindzen amongst others. There is a 'GHE'. The real question is what is the climate sensitivity. Empirical data on time scales ranging from 10^7 years, through to 10^-1 year (8 orders of magnitude) tend to suggest that it is on the low side (1-1.5K per doubling of CO2).

I'm prepared to spend some time on the N&Z work but at this stage I have my doubts. My own calculation of the S-B temperature, accounting for the geometry of a sphere, with incoming radiation coming from one direction only and outgoing radiation in all directions shows little difference from the standard S-B calculation presented by the IPCC and others. Tonight I'll redo the calculation using an analytical integration and check it agains my numerical approach I outlined earlier.

Paul,

Reading the paper, N&Z say their analysis is consistent with the Ideal Gas Law, which is stated and examined further. After years of work they now have (what they say is) a definitive paper under peer reviiew (I wonder who the peers are - they must have balls of steel!).

I agree that numerical integration and analytical integration should yield the same result (I remember thinking this a year ago). I bet you £100 that they do - do you accept?

BigYen and RKS, please shake hands and make up like gentlemen. - whatever your differences. You are both capable physicists. If we were all right all of the time what fun would there be? I am wrong so often that I insist that my greatest detractors check all of my work before I submit it (but then, I work in industry...).

Absolutely, consider the N&Z topic closed.

Now back to the GHE...

Roger

your offer of a sporting bet is tempting but before I accept I need to check my own numerical calculation, to carry out my own integration and to check what the implications of the N&Z integration is.

Once I've established the integrity of my own result I might just accept.

Have a good evening.

Thanks Paul, I'll wait to hear.

If you like we could transfer the bet to a dinner in London - winner pays. I would like to meet you.

(Same goes for BigYin, but probably a different occasion...)

RKS,

Back to the subject of the thread and your experiment, why don't we work it up and propose it to a university. I am clearly biased in this and and while I have contacts in many universities, and contracts with some, I have no business at all with Imperial - one of the foremost physics departments in the world (along with MIT and Stanford). I feel sure that Imperial would never impeach their credibility.

What do you think?

And me too, not a physicist just a working engineer, I did one year of pure Physics and two years of pure mathematics, as part of an electronics course back in the 80s (the pre-Calculator age) and quite a lot of QED as part of an electronics materials course later.

Do you ever get the feeling that the faceless nature of this lends itself to a rather impersonal confrontational approach? If we were all sitting round a table in a pub discussing this, I bet these sorts of to-and-fros would be much more congenial. I have no ill-feeling towards RKS at all, I'd buy him a pint in the genial pub. As a Scotsman, that is a grand compliment.

Me too, too. Degrees in physics but a chartered engineer for most of my career (I gave up paying the fees a while back).

We need to find a pub. Any of you get to London? (Bish - feel free to give RKS, BigYin and Paul my email if they ask).

RKS - do you want to start a new thread, either here or at Tallbloke's, to try to define an experiment?

Thanks lapogus - and an excellent point! Also, you can't get sunburnt at sundown on a clear day, so that takes care of the UV as well as the IR.

lapogus,

I'm abstaining from the N&Z discussion, but your points seem to be back on the general GH discussion again.

I see you understand that the poles are colder because the insolation is spread across a greater area, so we won't go into that.

Your point about angling your hand to be perpendicular to the sun is an interesting one, though, and I hope I can explain it to your satisfaction.

When I say that the atmosphere is transparent to solar radiation, it's not quite true. It's that most of the atmosphere is mostly transparent to solar radiation. Obviously sunlight isn't a coherent source of shortwave IR, it's a Planck curve as shown in this graph. This means that sunlight contains *some* LW radiation (not much compared with SW, but still some)

By a curious coincidence (but not really) this is the exact band that our skin temperature receptors are able to pick up. This is why you feel your skin heat up in direct sunlight. It's not the SW you feel, but a tiny little bit of LW contained in the Planck curve spread of frequencies.

In winter, the light has to pass through more atmosphere, as you pointed out. Let's say for example, it has to pass through twice as much air to get to your hand. That means the small bit of LW you can feel as heat on your skin has to pass through twice as much air, containing twice as many GHG molecules as before. Some of this energy is absorbed by the GHGs and sent out onmi-directionally.

So meanwhile, while you feel 'intuitively' that the sun has less strength in winter, this is not because the atmosphere can stop SW. What you are experiencing is actually the scattering effect of GH gases on the little bit of the sunlight your skin could feel anyway - the LW part of the sun's Planck curve.

I hope you can see what I mean.

BigYin,

But what about the SW (UV)?

(a genuine question - NOT confrontational)

At sunset, sunrise, or in winter, the UV insolation as part of general insolation, is spread over a larger area, so has a correspondingly less power. It's not that you *cant* get sunburn at sunset, it's just that it would take twice or three times as long.. and sunsets don't last long enough.

Think about it.... if you've ever been skiing in a northern country in winter in the sun. You can absolutely get sunburnt, for two reasons (1) because the weakened power of UV is reflected by the snow, so you get double (2) you stay outdoors for much longer than you would normally.

Roger,

dinner and a drink in London would be great. Or perhaps if you are ever in East Anglia dinner in Norwich and I'll throw in a visit and tour of my labs. I should be in London sometime in the new Year, probably February as I'm giving a lecture at UCL sometime.

The same invitation goes for anyone else too.

Now back to the N&Z integration!

As further information about how little UV we're talking about:

good old ozone layer

Ozone, being in a thin layer rather than distributed throughout the atmosphere, doesn't really increase its influence when we are talking about longer path lengths in winter. The majority of the reduction in UV intensity is down to the geometry.

Many thanks Paul - I'd like to take you up on it!

BigYin, I was thinking about ozone, when at sundown the UV has to pass through much more of it due to the geometry. Like many mad dogs I have been burned to a crisp under the midday sun, but I have enjoyed many happy hours drinking "sundowners" while facing it at the end of the day.

EM radiation can only be either transmitted, reflected (scattered) or absorbed by any medium, such as the atmosphere. It is clear that all frequencies are attenuated in a plane normal to the source when the elevation of the sun is low to the horizon. Is it all triatomic molecules, or are there other factors (again, a genuine question).

lapogus,

But the opacity of the atmosphere applies to the short wave UV radiation - why else do Govt agencies and skin cancer specialists stress that only midday direct sunlight should be avoided?

Because at mid-day the sun is directly overhead and is at its maximum intensity, or put another way, spread over the smallest area. At the start and end of the day, we're round the side a little, and the intensity is spread over a larger area only this time in terms of longitude, in the same way as at the poles in terms of latitude. At sunset we're receiving exactly the same insolation as the north pole because to the sun, we're right on the edge of the disc of the earth. It's got nothing to do with path length through the atmosphere.

But I have not finished with LW. You agree that LW incoming radiation is intercepted by the GHG molecules. I thought the settled science was that CO2 and other GHG molecules could only reflect outward IR radiation? If humans are increasing atmospheric concentrations of CO2 then surely these extra molecules will also reflect more incoming LW radiation back out to space? Ergo the CO2 concentration is irrelevant?

I'm not sure what you mean by GHG only reflecting outward radiation. Greenhouse gasses absorb and re-emit photons in the correct LW band, no matter where they came from directionally. So yes, more GHG means more of the LW from the sun will be reflected (reabsorbed and reemitted in a random direction, but generally half of them back out to space)

Unfortunately, the amount of LW in general insolation is small anyway. The extra number of photons GHGs manage to get rid of is dwarfed by photons coming from the ground. This is because the ground 'converts' SW photons into LW photons, so the total number of LW photons bouncing around is dominated by this effect rather than the little bit of LW directly from the sun.

So yes, increasing GH gases reflect away a fraction of a small number of incoming LW photons, but unfortunately reflects the same fraction of a much larger number of LW photons coming out of the earth back towards it.