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I don't understand cycles/cm very well. The speed of light is 3e10 cm/s, so multipliy 600 to 800 cycles/cm to get 18 to 24 THz. I don't understand cycles/cm very well. The speed of light is 3e10 cm/s, so multiply 600 to 800 cycles/cm to get 18 to 24 THz.
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{{attachment:NIST2.png | | width=800 }}

This first graph shows absorption out to 3700 cycles/cm ( about 110 THz ).

The strongest and broadest peak is at 2300 cycles/cm (about 70 THz), but this peak is irrelevant; The Earth is 220K to 300K (depending on where you look) so this is well above the earth's black body emission peaks (400 to 600 cycles/cm), in the quantum-limited exponential rolloff region. It is also well below the sun's black body emission peak of 11,300 cycles/cm at 5780 K. The peak that matters to us is within the 100 to 1500 cycles/cm window, shown below.

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{{attachment:NIST5.png | | width=800 }}

The interesting aspect of this peak is that it is broad, not sharp, with long tapering tails to the side.

MoreLater

CO₂ Spectrum

From Global Warming, Understanding The Forecast by David Archer, Blackwell 2007, without permission. Buy the book for a lucid explanation of the science; perhaps the author and publisher might forgive me for posting the excerpt below.

I don't understand cycles/cm very well. The speed of light is 3e10 cm/s, so multiply 600 to 800 cycles/cm to get 18 to 24 THz.

archer4-300.png


Here's the CO₂ absorption spectrum from NIST: ( http://webbook.nist.gov/cgi/cbook.cgi?ID=C124389&Type=IR-SPEC&Index=1#IR-SPEC )

NIST2.png

This first graph shows absorption out to 3700 cycles/cm ( about 110 THz ).

The strongest and broadest peak is at 2300 cycles/cm (about 70 THz), but this peak is irrelevant; The Earth is 220K to 300K (depending on where you look) so this is well above the earth's black body emission peaks (400 to 600 cycles/cm), in the quantum-limited exponential rolloff region. It is also well below the sun's black body emission peak of 11,300 cycles/cm at 5780 K. The peak that matters to us is within the 100 to 1500 cycles/cm window, shown below.


NIST5.png

The interesting aspect of this peak is that it is broad, not sharp, with long tapering tails to the side.

MoreLater

CO2Spectrum (last edited 2016-05-31 23:33:05 by KeithLofstrom)