Thanks for instructing Janus and us. I did not find your post “picky” at all, but very instructive.

There are lots of species your spectroscopist needs to keep out of the sample, not just CO2. Most of the gases fingered as ‘greenhouse gases’ exhibit strong absorption of infrared at various wavelengths, most of them being **very much stronger absorbers** than CO2.

Your statement about CO2, however, that it ’simply sucks up those specific IR energy bands, and would keep doing it forever’ is not correct, since this would break the First Law of Thermodynamics, the conservation of energy.

Absorption of a photon always increases the energy of the absorber in some way. The type of energy increase depends on the wavelength of the photon. IR photons increase the vibrational energy of the absorber, in effect its temperature. At some point the absorber emits energy in the form of one or more photons, the energy of which is usually below that of the absorbed photon(s), i.e. having a longer wavelength.

Your spectroscopist would notice this as a shift or displacement: an absorption minimum that would be shadowed by an emission maximum at a lower wavelength – in other words, an emission spectrum as opposed to an absorption spectrum.

Your analogy of emitted energy becoming weaker and fizzling out after a number of absorptions and emissions also violates the First Law of Thermodynamics. The input energy has got to go somewhere, either increasing the temperature of the absorber(s) and/or emitting other photons.

‘…is that the radiation being emitted is always (99.999% of the time) going to be of a different wavelength, or is going to be at least an order of magnitude less strength than the original absorbed radiation.’ I have a particular problem with the ‘or’ in that statement.

Photons are quantum objects. Their wavelength is related to their energy. They don’t have a separate amplitude – you can’t have stronger photons and weaker photons, just more or fewer of them.

An ‘order of magnitude’ is a multiple of ten: I don’t see how this follows from your statement.

An ‘emission that goes both up and down’: have you a source for this statement?

Sorry to be so picky.

Okay so the Global Warmers believe that CO2 forcing is creating 1,120,000,000,000,000 Watts of extra heat, whereas the Solar Irradiance increase is only 348,000,000,000,000 Watts… I can see why they would think this is insignificant as 348,000,000,000,000/1,120,000,000,000,000 is a small percentage of what they feel is the real cause of global warming since the increase in solar irradiance would only account for 31% of the warming of the earth. leaving 69% attributable to CO2…

Just trying to understand. Please let me know if I am off base on this.

Timo Niroma:
Sun and Jupiter.

http://personal.inet.fi/tiede/tilmari/sunspot2.html#jupiter

His main page is here:

http://personal.inet.fi/tiede/tilmari/sunspots.html#alert

Makes me wonder if some of the planets have a direct influence on the sunspot cycle.Jupiter apelhion and Perihelion cycles seems to effect the solar cycle.

If carbon dioxide re-emitted those specific bands, then there would not be a problem, because what was being absorbed would be emitted again. The carbon dioxide does not do that. It simply sucks up those specific IR energy bands, and would keep doing it forever.

The other problem with talking about radiation being absorbed and emitted, is that the radiation being emitted is always (99.999% of the time) going to be of a different wavelength, or is going to be at least an order of magnitude less strength than the original absorbed radiation. If the emitted radiation is a different wavelength, then it is probably a wavelength which is not absorbed by carbon dioxide. If the emitted radiation is a smaller amplitude, then it will have a lot less effect the next time it is absorbed. If we assume that the wavelength remains the same, it would not take very many absorption/emittance cycles before the amplitude becomes so small as to be nonexistent.

The climate modelers really want to believe that what is absorbed will always be what is emitted. They sometimes go so far as to say that from each absorption comes an emission that goes both up and down, with both emissions being the same amplitude as the original absorption (two for the price of one).

Courtesy of [Junk Science](http://www.junkscience.com/): For sobering perspective on reality, read on [here](http://wattsupwiththat.wordpress.com/2008/06/07/some-planetary-perspective/). Also [NASA desgin a satellite](http://science.nasa.gov/headlines/…

Doh! You are not referrring to the act of darkness, but the reference to an actress in a movie that was made so long ago that it contained scenes of deep snow and therefore must have been set in a time before AGW really kicked in.

Yep, from my perspective anyone under 60 could indeed be classed as ‘younger readers’, so I apologize for being so obtuse. Memo to self: drink more coffee.

In order to make the analogy relevant to the young uns out there, who would you choose?

Peter

Steve Stip (19:13:05)
LOL. Tent? Greenhouse!

Thanks for the feedback

Peter

Great post. I learned as I lurked.

Thanks

Hi Terry

Thanks for your comments.

I can understand your problem with my rather flip explanation: I was being too brief.

I apologize in advance for the length of the current post, but you raise some interesting points and I shall try to deal with them properly.

INFRARED

Dave (10:35:41) touched on one of the keys to the solution. We have to stop thinking of radiative (heat) energy as just IR. All radiation is energy, and the higher the frequency / shorter the wavelength of a photon the more energy it contains.

When a photon is **absorbed** by a particle its energy goes into the kinetic energy of the particle and raises the quantum energies of the electrons it contains (=heating up). Under certain circumstances photon(s) of lower frequency are emitted (=cooling down). Planck’s Law describes the relationship between the temperature of a body and the energy and wavelength of the photons that are emitted.

High energy, short wavelength photons (visible light and higher) tend to interact with matter by causing the emission of lower energy, longer wavelength photons (IR). Returning to Dave’s example, a black object absorbs visible light, heats up and in turn radiates perceptible heat (=IR).

The spectrum of the solar irradiance – that is, the light that arrives at the earth – can be approximated to the radiation of a blackbody at a temperature of 5780°K. You have to look at the curve to see the full implications of this, but for our purposes we can note that the majority of the energy we receive from the Sun is mostly in the visible range of the spectrum, roughly in the wavelength range of 0.4µm (=approx. violet visible light)..1.0µm (=approx. near IR).

The photons arriving at the surface of the atmosphere – which, if we include the thermosphere, can be 150km+ thick – may or may not interact with the particles of the atmosphere in the way I sketched in my previous post. They may even survive the descent and be reflected at the Earth’s surface, only to suffer and interaction on the way out again. Interactions can be with gas molecules, aerosol particles, condensates etc. Photons can not only be scattered and absorbed, they can also trigger important photolytic reactions in the atmosphere whilst being absorbed. With so many possibilities available, describing the process numerically is a tremendously complex business.

The atmosphere is also a complex structure. I nearly jumped into the post about the beneficial effects of CO2 in the atmosphere to point out that it depends very much on where the CO2 is. In the boundary layer next to the surface (approx. 1km thick) CO2 will probably have some effect on plant life; in the troposphere or stratosphere, none at all. An aircraft that discharges its CO2 into the lower stratosphere is not going to help the beans in my garden one bit. I was so entertained by MA and Anthony, though, that I thought my trivia would be out of place.

But I digress. If you look at a graph of temperature against height of the atmosphere (here’s an example ) you will see that the temperature of the atmosphere at the top of the stratosphere has almost reached surface values. At the top of the thermosphere – although the atmosphere here is barely dense enough to be able to speak of a ‘top’ – the temperature can be well in excess of 1000°C. All this energy comes from solar irradiance.

My point is that you cannot just take visible light as – well, just light – and ignore it by just focusing on the absorption of IR. It’s all energy, and things happen when it interacts with matter at all levels of the atmosphere. In consequence, it is not terribly important for the overall energy balance for us to know which bit of the spectrum a particular gas absorbs. O3, for example, is fortunately for us a strong absorber of UV, although the interaction in this case leads principally to photodissociation. All kinds of things in the atmosphere – dust, vapours, aerosols, condensates – absorb a wide range of light wavelengths, which is why the AGW focus on CO2 is just obsessive. If a particle absorbs a photon of visible light and emits a photon of IR that seems to me to be just as important as a particle that absorbs a photon of IR (which it may have got from the first particle).

BLANKETS

The blanket keeping the Earth warm is, like greenhouses, an analogy too far in my opinion. A blanket is a device that interrupts convection effectively. A simple thought experiment will make this clear.

Imagine you are lying naked next to Julie Christie under a thick woollen blanket in the snowed-in dacha in the movie ‘Dr Zhivago’, discussing, say, convective forcing in the troposphere. Body heat would rise to the blanket, but because of the poor heat transfer through the blanket, the air above would be only slightly warmed and only a weak convective flow would be established above it.

How unpleasant this would soon become! – and how much better a simple thin silken bedsheet would be!

In this case, body heat would convect to the sheet, the sheet would heat up and establish a strong convection in the cold night air of the dacha above it, transporting the heat away and enabling us to continue our discussions in comfort far into the night.

There is no comparable blanket effect in the atmosphere – not even clouds. There is nothing that acts as a barrier to convection. As I pointed out in my first post on this subject, if the atmosphere heats up during the day it returns heat to the surface and continues absorbing a portion of heat radiated from the surface.

The absorption of energy in the atmosphere is the role played by the so called greenhouse gases. One of the principal gases is water vapor. A dry desert becomes blazingly hot on the surface during the day and freezingly cold at night because dry, clear air is a poor thermal reservoir, not because there are no clouds to blanket it and keep the heat in. You would need an awful lot of CO2 to achieve the same result.

A ‘greenhouse gas’ cools the surface during the day and warms it at night, so I think we are broadly in agreement.

I apologize once more for this windbaggery – just imagine what an earful Julie Christie would get…

Peter

Your Greenhouse Effect lesson stands what I thought I knew about GHGs on it’s head.

I was under the impression that:

The energy of the sun that reaches us surface dwellers is mostly in the range to which the atmosphere is transparent causing the surface to heat.

The surface then emits its heat as IR and convection.

Greenhouse gasses are good absorbers of IR and when they re-emit some of this will be downward making them act like a blanket.

Is it back to school for me?

PS
I appreciate your efforts.

Regards
Terry

In Colorado, at 2000+ meters above sea level, we get a lot more from that big orange thing as well. Flatlanders who nap in the sun learn the hard way.

Perhaps you could try some hot tea, a cinnamon stick, a spoonful of honey and a shot a Apricot brandy. Keep you warm until the ics caps melt…:)

Probably a bit late, about the perspective and scales I keep in my bookmarks a link to a flash animation that goes scaling down from the universe to a proton. Really good.

http://www.nikon.com/about/feelnikon/universcale/index.htm

Gorka Ion.

REPLY: No problem – stay warm. – Anthony