Model planet, pure radiative

Posted: February 15, 2012 by tchannon in atmosphere, climate, Solar physics


This magic planet cannot exist but illustrates a simple thermal radiation only scenario, which is exactly linear, heating and cooling act the same.

The air, Sceptigen is completely transparent, unlike Politigen which is completely opaque. There is no excess atmospheric temperature.

If you don’t like the drawings, help me out, I’m struggling. Could use serious CAD but it would take a long time. Criticism is useful. FYI, OpenOffice Draw.


The situation with gravity present but still a transparent atmosphere is in late preparation.

Article by Tim Channon, co-moderator.

  1. Stephen Wilde says:

    Well if it is spinning with a hot side and a cold side where the hot side has highest temperature at the surface and the cold side has lowest temperature at the surface the centrifugal and coriolis forces and uneven and constantly changing temperature differentials would cause a vigorous air circulation of some sort even without any gravity induced change of pressure between top and bottom of atmosphere, wouldn’t they ?

    There would be considerable conduction between molecules in the atmosphere as they are being constantly mixed by powerful lateral winds.

  2. tchannon says:

    Seems reasonable. Given the magical lack of gravity I suspect all bets are off but the primary point of the same day and night should hold good.

  3. Would the radiation out not be omnidirectional with the red shift from incoming to outgoing being a function of disc to sphere ratio?

  4. tchannon says:

    I’m showing omnidirectional as a flow shorthand, emission will be spatially some kind of distorted circle or somesuch.

    This particular diagram is mostly scene setting, should be uncontroversial, is the model suggested by warmists who claim can be no excess air temperature. I agree. What comes next is a much longer post and likely to lead to contention. I’m sticking my neck out.

  5. Brian H says:

    With no gravity the atmosphere will simply disperse into space; the warmer it is, the faster that happens.

    [Grin. Why it is a magic planet. No way to illustrate pure conduction with gravity present. –T]

  6. gbaikie says:

    “With no gravity the atmosphere will simply disperse into space; the warmer it is, the faster that happens.

    [Grin. Why it is a magic planet. No way to illustrate pure conduction with gravity present. –T]”

    And the spin would throw entire surface into space.

    Perhaps there some magical magnetic force holding it together.

    One could just have a hollow sphere, with it’s skin strong enough to withstand the rotation. And anything on the surface would would to be nailed down.
    Now if the hollow sphere wasn’t spinning it’s weak gravity could keep some atmosphere- though it seem the atmosphere would migrate to the dark side. Denser atmosphere on darkside, would flow from bottom to sunlit side and flow at top from sunlit side.
    Though seems rather unrealistic.

    How about something exotic but plausible?
    The dwarf planet “Eris, about 2400 km in diameter” which heated by nuclear reactors. You use it to transport millions of people to a different star system.

    Relevant because there is no reason to heat upper atmosphere, so you heat it in such manner that limits convection. So you have surface temperature of around 10 C, and don’t heat surface higher than this. You have as big of an atmosphere which reasonable- and such atmosphere would block high energy particles [GCRs] and also block some meteorites from hitting the surface.
    The planet would have resources which keep “the +million crew” busy. With oxygen mask any crew could work or play outdoor, under star lit sky.
    For propulsion you use nuclear bombs [it’s a massive Orion nuclear starship]. The expensive part is nuclear reactors needed to keep the atmosphere warm- the inhabitant would have massive amount energy available for use [and energy used also adds to the warmth of atmosphere. Higher population or use of the energy means less nuclear power used to simply heat the atmosphere.
    So could 1 million people or 100 million people. With 100 million people it’s still sparsely populated- it twice land area as US- so with 100 million it’s 1/6th the US population per square kilometer.
    Downside is one only has 1/10th gravity- with dwarf planet you some gravity [with starship you need to spin the ship to get gravity. But a planet would safer- most starship [without reflector shields:) would destroyed if 10 meter rock hit it- a planet could survive such impact- even 100 meter diameter rock could be more or less survivable.

  7. Hans says:

    Hallo Tim!

    Gravity is needed or there wouldn´t be any atmosphere at all. This means that your model atmosphere is useless if it is meant to lead to conclusions about any real atmosphere. But there might be benefits to discuss inferior modelling, too.

    To make it even more unphysical you stipulate “there is no convection” assuming a day and night side can still occur. Convenction is THE major physical process tranfering energy to polar areas (all areas with energy deficits) during winter time. 150 W/m^2 is sent to space from Arctic areas just now. Day and night. Integrate this power over the polar areas between 60-90 north latitude and it is turns up to be a gigantic power equivalent to an enormous amount of nuclear reactors.

    I am afraid that this model is just spreading confusion, similar to what IPCC is doing. It might be used as an illustration of bad modelling similar to the one used by Trenberth + IPCC when inventing the +300 W/m^2 unphysical “backradiation” model.
    Bad modelling does not help in understanding existing physical realities.

    The best that can be said about it is that it so clearly shows that gravity is the king (major physical process) and dismissing its impact in the atmosphere must always be wrong! It is true that the explicit use of gravity in meteorology is very limited. Its impact is mostly hidden. Pressue and temperature are tha major concepts in use. But pressure is equal to atmospheric mass per unit area times gravity. This is one reason why the formula of the dry adiabatic temperature lapse rate is so important where you can see gravity explicitly: dT/dz = -g/Cp. Gravity is the major process deciding a lapse rate in any dense atmosphere (in the troposphere).

  8. Genghis says:

    In your model the atmosphere will help average the surface temperature, cooling the surface directly warmed by the sun and warming the surface elsewhere.

    Apparently the question the model poses is how does this non lapsing atmosphere affect the average surface temperature compared to an atmosphere with a lapse rate?

    I am guessing that an atmosphere with a lapse rate with colder air at the top and warmer denser air at the bottom will be a better conductor and distribute the surface energy more evenly, than an atmopsphere with no lapse rate.

    Hence the average surface temperature will be warmer with an atmosphere with a lapse rate.

  9. Michael Hart says:

    If I have read the post correctly, I don’t think you need gravity for convection. Not even if you were to restrict the thought experiment to a ‘two-dimensional’ one with no gravity and no night-time. On the insolated day-side of a planet the insolation is not homogeneous due to the obliquity of the sun’s rays. So differential heating occurs by conduction>>differential atmospheric expansion>>pressure differences>>air movements=convection.

    A heated parcel of “sceptigen” will expand [and contract] in three dimensions, with or without gravity.

  10. Michael Hart says:

    I should qualify my above statement by saying
    1) that it could not be a true 2-D model on a spherical planet, and
    2) even if one posits a steady-state, the system is still a dissipative one that is inherently unstable. So motion in the atmosphere could be triggered by virtually any number of different stimuli.