torsdag 17 juni 2010

The Atmosphere as Refrigerator

The previous posts lead us to view the thermodynamic action of the atmosphere to be similar to that of a refrigerator:
  • Evaporation at the ocean surface driven by incoming radiation generates cooling of the warm atmosphere above the surface.
  • Warm air rises by bouyancy under expansion and cooling to TOA where it releases heat by condensation for further radiation to outer space.
  • Cool air descends from TOA under compression and warming completing a thermodynamic refrigerating cyclic process.
In addition, some incoming heat is returned by radiation. If the radiation is blocked, more or less, by greenhouse gases, the refrigerator process must intensify to maintain heat balance. This requires more evaporation and thus more cooling of the atmosphere above the ocean surface. 

The atmosphere will thus act like a refrigerator giving additional cooling under increased energy input. More greenhouse gases will thus cause global cooling!

How much cooling? Assume that now 1/4 of incoming heat is returned by radiation and 3/4
by the  thermodynamic refrigerator process at a decrease of the lapse rate of 3 K/km from 10 to 7 K/km. Blocking the radiation fully would then require a further reduction of lapse by 1 K/km to 6K/km corresponding to a decrease of surface temperature by 5 K. 

If the radiation was blocked by 1% the decrease of global temperature would be 0.05 K. Climate sensitivity could thus be estimated to  - 0.05 K. To be compared with IPCC's + 1.5 to + 4.5 K.

5 kommentarer:

  1. A refrigerator moves heat from a cold part to a warmer one. The hydrological cycle moves heat from the warm surface to the colder troposphere, it is therefore not analogous to a refrigerator.

    You try to eat your cookie and keep it too. First you correctly state that evaporation (and more importantly convection) would have to increase to compensate for the loss of outgoing radiation, but then you "forget" about the radiation part and claim that the increased evaporation acts alone to cause a cooling.

    Your discussion about a drop in the lapse rate reveal your ignorance about what causes the lapse rate in the first place. It's not something that can just arbitrarily decrease, it is based on physical processes!

  2. Of course lapse rate depends on physics: turbulent thermodynamics under gravitation, what else?

    A refrigerator is a device which removes heat, which otherwise would not be removed, and so does the thermodynmaics of the atmosphere. In this sense the atmosphere acts like a refrigerator. That the TOA has a lower temp is an effect of gravitation and is irrelevant in this context.

  3. Claes, I linked to a wikipedia page to give you a very simple primer on lapse rate. Read it!

  4. I have read it. Nothing new to me.

  5. The lapse rate is determined by the onset of convection: if an air packet near the ground can rise and be lighter than the air at that altitude the atmosphere is unstable and you get convection that is very efficient at transporting heat. If the lapse rate is lower than this you don't get any convection and thus no heat transport. You can't just postulate that the lapse rate drops, it can't without shutting down the heat transport!

    You assume a linear process where heat transport is proportional to the gradient, but this is totally wrong.

    And what do you mean by "That the TOA has a lower temp is an effect of gravitation and is irrelevant in this context"?