We have been looking down so far. What happens when you stand on the ground and point a spectrometer up? Interesting things.
In the CO2 bands around wave number 667 a spectrometer pointed up from the ground sees radiation at very near surface temperature. In the cases above that near surface temperature was about 245 K in Barrow and 300 K at Nauru. The spectra are very different in form as a result of different humidities in the atmospheric window and ozone bands to the right. In the cold, dry air at Barrow the instrument reads near zero except for the ozone bands. Those photons are running away straight to space and there is nothing to see. In the warm, moist air of Nauru the window is very “dirty” and noisy due to scatter and radiation by water.
We can add our trusty Sahara looking down for comparison. The hot dry air is a good inverse for Barrow.
Finally we add an interesting spectrum looking up from Cerro Toco at 5 km altitude (but still on the ground) in the Atacama Desert in Chile. Notice how in the dry desert air the atmospheric window very closely matches Barrow with the photons fleeing at the speed of light and the instrument seeing next to nothing, while the higher near surface temperature shows clearly in the CO2 bands.
Note the difference between Barrow and Cerro Toco. The dip in the Barrow (Grey) CO2 bands results from a strong surface inversion. Close to the instrument, the radiance reads at a lower temperature. You essentially get an inverted altitude profile of CO2 absorption. Below is the 1 meter path at 400 ppm.
In an amazing experiment shown above, the same instrument, one pointed up from the surface of Arctic ice, and another looking down from some sort of platform at 20km took measurements of the same place at essentially the same time. In the atmospheric window the U-2 looking down sees a very chilly near surface at~267 K. The one on the ice looking up sees a much chillier 160 K. The 20 km looking down sees a very clean signal of high intensity, the ice looking up sees a noisier signal of very low intensity.
They both see a clean blackbody signal in the CO2 bands with the 15 micron/667.4 wave number “spike” pointed up towards higher intensity and temperature. No surface inversion here.
In this series we first explored the lack of correlation between temperature and CO2 at long time scales, the dependence of CO2 on temperature at Neogene scale, and the dependence of CO2 variation around the trend on temperature, but not the trend itself as the trend becomes distorted by human emission in the satellite era.
We followed up with a look at radiance on the IR earth bands and found that satellites are seeing CO2 radiance taking place between ten and twenty kilometers in the upper troposphere and lower stratosphere. We then found that the same instruments pointed up from the surface see CO2 radiating very near the surface.
The problem is that the 2 good greenhouse gas gobbles up all the surface IR within a hundred meters of the surface. This is clear from transmission.
Even at 280 ppm preindustrial levels of CO2 there is ZERO transmission of surface IR to the tropopause in the fundamental bending bending bands. Furthermore, the 667.4 band and its homologous rotational bands DEFINE the zero transmission gap.
The fundamental bend commands 89% of the Boltzmann absorptive and radiative potential of CO2. This is why it gobbles up the surface IR so fast. This is why CO2 does not drive temperature at any time scale. It has already eaten all the earth photons in its strike zone at preindustrial levels. Adding more CO2 has no effect in these bands.
It is just too good.