måndag 9 augusti 2010

Energy Budgets Without Backradiation

The Hockeyschtick displays 4 similar Earth Energy Budgets without backradiation from different sources including the above from NASA Langley Research Center. 

What do we see? Out of 51% absorbed by the Earth from incoming 100%, 
  • 30% is transported to the Atmosphere by convection/latent heat = thermodynamics
  • 15% is radiated to the Atmosphere = radiation
  • 6% is radiated directly to outer space.
The 45% transported from the Earth to the Atmosphere is radiated to outer space together 
with the 19% of incoming absorbed by the Atmosphere = 64%.

The Atmosphere acts an air conditioner cooling/warming the Earth by combination of thermodynamics and radiation,  with the following basic specifications:
  • Earth temperature T_E = 15 C 
  • Atmosphere temperature T_A = -18 C (at 5 km altitude)
  • lapse rate = 6.5 C/km.
Here T_A = -18 C is the Stefan-Boltzmann temperature required to radiate 64%. The lapse rate is set by the thermodynamics, and the lapse rate determines T_E = + 15 C. The temperature drop from + 15 C to -18 C determines the 15 % radiated from Earth to Atmosphere. 

Thermodynamics and radiation thus together act as an air conditioner, with thermodynamics setting the lapse rate and T_E which determines the cooling by radiation. 

We see that in this analysis "backradiation" does not appear, and thus can be dismissed to 
the realm of fiction, without any role to play in climate science nor at NASA.  

Suppose now that absorption properties of the Atmosphere changes so that instead of 6% 
only 5% is radiated directly, that is a 20% change of Atmosphere absorption by some 
"greenhouse gas", a large change. To compensate, either thermodynamics or radiation, or a combination thereof, will have to take care of that extra 1% to be transported away from the Earth, with the following basic options:

Increasing thermodynamics from 30% to 31%:
  • more convection/latent heat
  • tends to decrease the lapse rate and thus T_E
  • decreasing T_E decreases radiation.  
Increasing radiation from 15% to 16%:
  • requires increasing lapse rate
  • increasing lapse rate = less/more convection/latent heat
  • less/more convection/latent heat decreases/increases thermodynamics,
where increasing T_E may correspond to both decreasing (bigger lapse rate) and increasing (more vigorous) thermodynamics.

We thus see a dynamics of competing forces to balance the extra 1%: 
  • more thermodynamics with decreasing T_E and decreasing radiation
  • more radiation with increasing T_E and decreasing/increasing thermodynamics.
Which mechanism will win? Will T_E decrease or increase? Cooling or warming?  Only a more careful analysis can tell. 

As a first guess, it is tempting to put the money on thermodynamics with little/no increase of T_E , because of the starting point with 30% thermodynamics and 15% radiation, and the fact that increasing T_E may stimulate compensating more vigorous thermodynamics.

Again: radiation-only cannot give any scientifically based indication of global warming (or cooling) from a marginal increase of "greenhouse gases". CO2 alarmism is based on radiation-only including "backradiation" and thus lacks scientific rationale.

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