2011-07-09 04:32:40Radiative forcing in the troposphere -- DeWitt Payne
John Hartz
John Hartz
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The following was just posed on the comment thread to SoD's "Models, On – and Off – the Catwalk – Part Three."

Is it an accurate statement? Is Payne blowing smoke?

DeWitt Payne

Comparing radiative forcing at the tropopause for an instantaneous change in CO2 before equilibration of the lower atmosphere and surface to the change in surface emission after equilibration of the atmosphere and surface is comparing apples to oranges. It demonstrates a fundamental misunderstanding of the physics of the atmospheric ‘greenhouse’ effect. For starters, it fails completely to consider the change in downward atmospheric radiation at the surface after equilibration.


2011-07-11 17:54:04
Tom Curtis

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I assume DeWitt Paynes comment is a response to RW (RW1 on SS), and it is absolutely correct.

 

In fact, RW1 made exactly that comparison on the Lindzen and Choi thread (among others).

 

In essence the radiative forcing for a doubling of CO2 is 3.7 W/m^2.  That figure does not include feedbacks, and represents a change in forcing at the effective altitude of OLR of 1.2 degrees C.  It is, moreover, a reduction in OLR.  After feedbacks have kicked in and equilbrium has been reached, the change in OLR at the effective altitude of radiation is zero, but the surface radiation will have increased by 16.6 W/m^2 for a climate sensitivity of 3 degrees for 2xCO2.  Comparing those two figures (3.7 and 16.6) as if there is some kind of contradiction between them shows you do not understand the greenhouse effect, even slightly.

The most important fact about this is that the change in net energy flux at the TOA is zero at equilbrium, and the change in net energy flux at the surface is also zero.  Whatever the combined changes in increased surface radiation, evapo/transpiration and thermal fluxes are, they will be compensated for by equal changes in energy returned to the surface from the atmosphere (almost entirely as increase back radiation).  Thus there is no change in net energy flux.   There is more energy stored at the surface, hence the elevated temperature, but that energy comes from the reduced energy leaving the top of the atmosphere as a result of the disequilbrium, during which period more energy enters the system from the sun than leaves as IR energy.  For that energy to not be stored somewhere, and hence for there to be no region of elevated temperature would require a  violation of the first law of thermodynamics.

2011-07-12 00:00:58Tom Curtis
John Hartz
John Hartz
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98.122.98.161

Thanks for the clarification.

BTW, RW/RW1 is defintely a climate denier drone. He/she has been spreading poppycock on quite a few comment threads recently.