Is Cosmic Microwave Background Radiation Measurable?

Temperature fluctuations of CMB measured by COBE satellite. 

Pierre-Marie Robitaille leading the development of the 8 Tesla Ultra High Field human MRI (Magnetic Resonance Imaging) scanner, used his deep knowledge of electromagnetic resonance to question the measurement of the Cosmic Microwave Background Radiation (CMB) by NASA's COBE satellite, awarded the Nobel Prize in 2008. 

This was not well received by the physics community and Robitaille was effectively cancelled academically (as far as I understand), but his very informative youtube channel Sky Scholar (with 50k subscribers and 145 videos) has survived. Take a look and compare with previous post on Man Made Universality of Black Body Radiation.

CMB is supposed to be the "cooled remnant of the first light that could ever travel freely throughout the Universe" at the very low temperature of 2.726 K above ultimate 0 K. Very cold indeed. More precisely, it is claimed that measured CMB spectrum is very close to a blackbody spectrum at 2.726 K. 

In previous posts I have posed the question if the spectrometer involved in measuring CMB is effectively measuring temperature or radiative flux, with the answer that temperature can be measured at distance by radiative equilibrium in the same way a thermometer in contact measures temperature and not heat flux by establishing radiative equilibrium. This is supported by the fact that it is a measured temperature of 2.726 K, which is the main characteristic of the postulated CMB, not its unknown radiative heat emission as a (small) possible contribution to global warming. Recalling previous posts and Robitaille, we know that the blackbody spectrum is a fiction only met by graphite and so one may ask why CMB could behave the same. 

In the view presented on Computational Blackbody Radiation the temperature measurement by NASA's COBE satellite as main evidence of the existence of CMB, is based on resonance between apparatus and cosmic background, which has to be singled out from all other resonances. Robitaille here presents the Oceans of the Earth as a possible source overwhelming CMB, thus questioning the existence of CMB.  

When your brain registers a sound arising from resonance between a sound source and eardrum, the direction to the source can be decided because you have two ears, but the distance to the source and so the origin of the sound is more difficult to determine in the presence of other possibly stronger sources.  Robitaille questions the possibility to single out CMB from the radiation from the Oceans.  Do you?

How to Interprete an Atmospheric Radiance Spectrum

The thermal emisson spectrum of the Earth + atmosphere measured by the IRIS Michelson interferometer instrument on the Nimbus 4 space craft over three different regions, takes the following form:

The curves shows the radiance (in mW/m2 and 1/cm) per unit wave number as function of wavenumber, and are computed from interferometer measurements of temperature using Planck's law of blackbody radiation.

The basic measurement thus concerns temperature and not radiance, but the computed radiance spectra  are commonly taken as observed rates of emission of energy. For example, the dip in the spectrum around wavenumber 700 is interpreted as "blocking" energy transfer or "trapping" energy by atmospheric CO2 as a Greenhouse Gas Effect GHE causing global warming, and the size of the dip is used to suggest alarm. We argue below that this inflates the role of the trace gas CO2.

But sticking to the true the measurements of temperature gives the following somewhat different interpretation:

The temperature of 220 K at the bottom of the dip around wavenumber 700 is the temperature of the tropopause, suggesting that the Earth + tropopause can be be viewed as a blackbody with a spectrum following the 220 K curve with total radiation of 140 W/m2. The radiation above the 220 K curve of a total of 100 W/m2  would then correspond to 40 W/m2 directly radiated to outer space from the Earth surface through the atmospheric window (wave numbers larger than 800), and 60 W/m2 from water vapor in the atmosphere (wave numbers smaller than 550).

The total would be 240 W/m2 absorbed by the Earth+troposphere with 180 W/m2 absorbed by the Earth surface. The role of combined thermodynamics and radiation within the troposphere would then be to transport 140 W/m2 from the Earth surface to the tropopause, with an estimated 120 by thermodynamics of convection and evaporation/condensation, thus mainly by thermodynamics.

The effect of the thermodynamics would then be a reduction of the dry adiabatic lapse rate of 10 C/km to the observed 6.5 C/km, with the drop increasing with the vigor of the thermodynamics.

A change of the radiative properties of the atmosphere could then have an effect on (i) the temperature of the tropopause as the outer boundary of the Earth + atmosphere system, and (ii) the lapse rate, which together would determine the Earth surface temperature.

A decrease of the transparency of the atmosphere would decrease the atmospheric window and thus demand an increase of the temperature of the tropopause, while at the same time demand more vigorous thermodynamics decreasing the lapse. The net effect could be interpreted as radiative warming with negative feedback cooling from thermodynamics, thus with potentially a small net effect. In other words, the climate sensitivity could very well be small.

The purpose of the argument is to seek to assess the Earth surface temperature from lapse rate and temperature of the tropopause as an (effective) outer boundary of the Earth + atmosphere as a blackbody, without more precise (difficult) modeling of the combined thermodynamics/radiation within the atmosphere. This analysis indicates that the Earth surface temperature may be insensitive to even quite large perturbations of atmospheric composition and insolation.

It is also an attempt to get away from the notions of "effective emission altitude" (at 5 km) and "effective emission temperature" (255 K) as fictitious entities which cannot be measured and have no physical correspondence (as compared to the tropopause which has a physical reality).

Notice that with an ideal blackbody as a universal thermometer, the temperature of a given body would be measured by radiative equilibrium with the universal thermometer at a certain temperature defined by no radiative transfer of energy between the body and the thermometer. The absorptivity/emissivity of the body would then not affect the temperature reading, but would be directly connected to the radiance of the body. Without knowing the absorptivity/emissivity, it would thus be impossible to tell the effective radiance of a body from its temperature. The above radiance plots constructed from temperature readings assuming absorptivity = emissivity = 1, may thus not represent reality. In particular, the emissivity of CO2 as a trace gas must be very small, and the radiation from the troposphere even within the 550-800 band of CO2, must emanate from the whole atmosphere, not only CO2. In other words, the radiance dip between 550 and 800 would be due to CO2 only to a small extent, and the alarm balloon would collapse.