I don’t get ‘the gravito-thermal effect’

Lately there’s been a bit of back-and-forth discussion going on on the so-called ‘Gravito-Thermal Effect’ (GTE) at a few notable climate blogs, like The Hockey Schtick, Tallbloke’s Talkshop, Clive Best and even Judith Curry’s Climate Etc. (in fact, this is where the lengthiest discussion thread on the subject is to be found).

To me the whole thing appears to arise from a fundamental misunderstanding of the adiabatic process (see the end of the post).

Something called the ‘Loschmidt Effect’, after a proposal in the 1870s by the Austrian scientist Josef Loschmidt, seems to lie at the heart of the GTE argument. Tallbloke brought it out from relative obscurity in a post in early 2012. A quote from a textbook describes the proposed effect as follows: Continue reading


On Heat, the Laws of Thermodynamics and the Atmospheric Warming Effect

On average, Earth’s solar-heated global surface is warmer than the Moon’s by as much as 90 degrees Celsius! This is in spite of the fact that the mean solar flux – evened out globally and across the diurnal cycle – absorbed by the latter is almost 80% more intense than the one absorbed by the former.

The Earth’s global surface, absorbing on average 165 W/m2 from the Sun, has a mean temperature of ~288K (+15°C).

The Moon’s global surface, absorbing on average 295 W/m2 from the Sun, has a mean temperature of >200K (-75°C).

A pure solar radiative equilibrium for each of the two bodies (according to the Stefan-Boltzmann equation: Q = σT4, assuming emissivity (ε) = 1) would provide them with maximum steady-state mean global temps of 232K (-41°C) and 269K (-4°C) respectively.

As you can well gather from this, the Earth’s surface is 56 degrees warmer than its ideal solar radiative equilibrium temperature, while the lunar surface is at least 70 degrees colder than its ideal solar radiative equilibrium temperature. That’s a spread of no less than 126 degrees! On average …

Still, these two celestial bodies are at exactly the same distance from the Sun: 1AU.

So what could possibly account for this astounding difference between such close neighbours?

Very simple: The Earth has an atmosphere. The Moon doesn’t. Continue reading