To be 33C or not to be 33C
There is a popular fantasy that the earth is 33C warmer with an atmosphere than without due to the radiative greenhouse effect, RGHE and 0.04% atmospheric CO2.
Let’s start at the very beginning, a very good place to start – or so I hear.
The 33C difference is between an alleged average surface temperature of 288K/15C and 255K/-18C, the alleged surface temperature without an atmosphere. Let’s take a closer look.
Just which average surface temperature? The two extremes? (71C + -90C) / 2 = -10C? Or the average of all the real actual (adjusted, homogenized, corrupted) measurements 90% of which are in the US, Canada, Europe and Australia? What about the sea surface? Satellite data? Over thirty years?
Per IPCC AR5 glossary the average land surface temperature is measured 1.5 meters above the ground, but 80% of the land (Africa, Siberia, South America, SE Asia) doesn’t even have reliable weather instrumentation or data.
The average sea surface temperature is a combination of buckets and thermometers, engine cooling intakes, buoys, satellites, etc.
This composite “global” surface average temperature, one number to rule them all, must represent: both lit and dark sides, both poles, oceans, deserts, jungles and a wide range of both land and sea surfaces. The uncertainty band must be YUGE!
The 255K is a theoretical calculation using the S-B ideal BB temperature associated with the 240 W/m^2 radiative balance at the top of the – wait for it – atmosphere, i.e. 100 km.
So what would the earth be like without an atmosphere?
The average solar constant is 1,368 W/m^2 with an S-B BB temperature of 390 K or 17 C higher than the boiling point of water under sea level atmospheric pressure, which would no longer exist. The oceans would boil away removing the giga-tons of pressure that keeps the molten core in place. The molten core would push through the floor flooding the surface with dark magma changing both emissivity and albedo. With no atmosphere a steady rain of meteorites would pulverize the surface to dust same as the moon. The earth would be much like the moon with a similar albedo (0.12) and large swings in surface temperature from lit to dark sides. No clouds, no vegetation, no snow, no ice a completely different albedo, certainly not the current 30%. No molecules means no convection, conduction, latent energy and surface absorption/radiation would be anybody’s guess. Whatever the conditions of the earth would be without an atmosphere, it is most certainly NOT 240 W/m^2 and 255K.
The alleged 33C difference is between a) an average surface temperature composed of thousands of WAGs that must be +/- entire degrees and b) a theoretical temperature calculation 100 km away that cannot even be measured and c) all with an intact and fully functioning atmosphere.
The surface of the earth is warm because the atmosphere provides an insulating blanket, a thermal resistance, no different from the insulation in the ceiling and walls of a house with the temperature differential determined per the equation Q = U * A * dT, simple to verify and demonstrate. (Explains why 250 km thick atmosphere of Venus with twice the irradiance heats surface bigly compared to earth.)
A voltage difference is needed for current to flow through an electrical resistance.
A pressure difference is needed for fluid to flow through a physical resistance.
A temperature difference is needed for energy to flow, i.e. heat, through a thermal resistance.
RGHE upwelling/downwelling/”back” radiation is a fictional anti-thermodynamic non-explanation for the “33C without an atmosphere” phenomenon that doesn’t actually exist.