Frank,

The common wavelength distribution is also drawn to have equal areas underneath to represent equal power. Distortion of the areas is thus not the misleading factor in having the 15 µm peak significantly off the maximum. The misleading factor is in not noticing that the absorption peaks get broader with increasing wavelength. The widths of the peaks are less dependent on the wavenumber (inverse of wavelength) when considered as function of wavenumber. For that reason the spectrum vs. wavenumber gives a more correct view of the importance of absorption of various absorption peaks than the spectrum vs. wavelength. The CO2 absorption peak of 667 1/cm (15 µm) is close to the maximum of the wavenumber spectrum of the Earth surface.

The power of emission at a fixed wavelength grows exponentially (with decreasing 1/T) at low temperatures, when the wavelength is a small fraction of that at the maximum point of the energy spectrum for the temperature. Far on the other side the power grows linearly with temperature. Thus the power grows always over the whole temperature range and for all wavelengths, but the faster growth at shorter wavelengths leads to Wien’s displacement law and also to the Stefan-Boltzmann’s law of fourth power that’s between the linear and exponential behaviors in speed of growth.

]]>CO2’s 15 um band absorbs where LWR is near its maximum and doesn’t absorb SWR at all. CO2’s 2.7 um band absorbs where SWR is ONLY about 1% of its peak intensity in the visible and it doesn’t absorb LWR. CO2’s 4.3 um band absorbs little SWR and LWR. For the earth to maintain a constant temperature, “post-albedo” incoming SWR (after reflection by clouds) must be equal to outgoing LWR. So CO2 has a bigger effect on outgoing LWR than incoming SWR.

When you associate 15 um radiation and 193 degK, you are using Wien’s displacement law, which tells you the relationship between a blackbody’s temperature and the wavelength of peak emission. Unfortunately, Wien’s displacement law causes much confusion, because a blackbody also emits more power at EVERY WAVELENGTH as its temperature rises. (Check the plots above and elsewhere.) So CO2 emits far more power at 15 um when its temperature is 300 degC than when it is 193 degC. To a first approximation: 1) Absorption of radiation is independent of the absorber’s temperature. 2) Total emission increases with the 4th power of temperature, the Stefan-Boltzman Law. Technically, the S-B law applies to only blackbodies; gases are more complicated. 3) Don’t use Wien’s law for anything (except the emission maximum.)

You can see a clearer picture with the log of wavelength on the x-axis at the link below (the last graph in the post). Note the vertical axis has been “normalized” so that the areas underneath are equal.

http://noconsensus.wordpress.com/2010/04/19/radiative-physics-yes-co2-does-create-warming/

]]>Rosco,

I don’t think you understood the article at all.

The solar radiation absorbed by the earth is approximately equal to the terrestrial radiation emitted by the climate system. How can this possibly be when sun is so much hotter? It’s some kind of mystery..

Then let’s pick one point, the 15um band..

Under the text “*If we take the average of 30% of solar reflected, and at an angle from the zenith of 45°, we will have these curves:*”

– we have a graph which shows that the terrestrial radiation at 15 μm is much higher than solar radiation. I’m travelling and don’t have a computer to hand but it’s at least 100x greater.

If you can find a way to get solar radiation at 15um greater than terrestrial radiation at 15um on or around the earth’s climate system you will have either disproved Planck’s law or the inverse square law.

So I’m not sure what your point was except to demonstrate that you haven’t read the article and didn’t try to follow the basic maths.

]]>Rosco,

You seem to forget that the Sun is far away.

The Sun emits about 2 billion times more than the Earth surface, but the distance of the Earth from the Sun is large and the amount of solar radiation that hits the Earth is less than the radiation from the Earth surface. The emission from the Earth to the space must be nearly equal to the amount of solar radiation absorbed by by the Earth. Part of the solar radiation is reflected, and the radiation from the Earth to space is less than the emission from the surface. For this reason the radiation from the Earth surface can be larger.

Only 1.5% of the energy of solar radiation is at wavelengths of more than 2.3 µm. Therefore the absorption of the 2.7 µm band has only a small effect. Changes in that absorption from added CO2 are really minimal.

At 4 µm the solar radiation is much weaker in the atmosphere than the radiation from the atmosphere itself or from the Earth surface.

]]>The Earth’s radiation will not impact the 2.7 and 4.3 bands – effectively zero absorption – whilst they will absorb significant amounts from the solar insolation as it is significantly more powerful.

You show a scale factor of 10 to the minus 6 in your posts.

All the literature I can find states ~50% of the solar radiation is infrared.

The 2.7 band coincides with a calculated temperature of ~1073 K and the 4.3 band coincides with a calculated temperature of ~673 K whilst the 15 band coincides with a temperature of ~193 K.

Why would absorbing radiation with a peak generated by 193 K have more thermal effect than radiation with peaks of 1073 and 673 K ?

It doesn’t make sense.

The solar radiation is heating CO2 on the way in far more than the feeble outgoing radiation ever could.

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