Changes in Heating Rates

In the previous post, I shared how changes in radiative forcing profiles imply changes to stability for various greenhouse related scenarios. I depicted the changes in net radiance but not the changes in the heating rate.

The theory of radiative forcing is that the net radiance change imposed by greenhouse gasses change the radiative energy for the tropospheric layer as a whole. The Column Radiative Model calculates the radiative changes for each individual layer of an atmospheric profile. This can be a source of some confusion because the rationale for the cooling applied to the stratosphere is due to the intense decline in heating rate for the individual layers, especially in the upper stratosphere. Here is a depiction of the changes in radiative forcing as well as the changes in heating rate for the various scenarios:

Change in Net Radiance Change in Heating Rate

2xCO2,

Instantaneous





2xCO2,Strat Adjusted





2xCO2,

Strat Adjusted,

Trop Humidifed





2xCO2,

Strat Adjusted,

Trop Warmed





2xCO2,

Strat Adjusted,

Trop Warmed,

& Trop Humidified





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3 Responses to Changes in Heating Rates

  1. I did what you did and found that the upper atmosphere becomes more efficient at loosing heat, because the CO2 is emitting it, but not trapping as much because it is blocked below.

    So with more CO2, we have a cooler stratosphere. I have been trying to find out what happens to the Ozone layer when it is colder. Also, stratospheric water vapor should reduce.

    Below the tropopause, the heat transport is unchanged, because thermal equilibrium requires convection to make up the difference. This means that the whole effect is happening in the tropopause and above. There is very little water vapor there. That is why we don’t see any amplification of the basic CO2 effect due to increased water vapor. (Regression values for transient climate response are on the order of 1.3 degC and 1.7 degC for equilibrium climate response, much below the 2.4 deg C you use).

    I have wanted to build a model that iterates temperature while maintaining the pre-existing convective equilibrium and also modifies the ozone densities and absorption as a function of temperature. This model should also keep the relative humidity the same (to be fair). My hunch is that we will see the tropopause come down slightly along with the stratospheric location of maximum temperature. Upper atmosphere water vapor will decrease. TCS and ECS will be reduced and become consistent with regression values (Lewis and Curry) and satellite global temperature trajectories.

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    • Thanks for your comment.
      I’m glad you are investigating these effects which are taken for granted.
      I hope to have some follow ups in the future.
      One thing I’ve wondered about is water vapour in the upper troposphere.
      When I computed RF for constant RH, I did so for the entire troposphere.
      But much of the troposphere has an RH closer to zero than to saturation.
      It may be that a humidity response is not uniform.

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  2. I think you did it right. The profile RH is representative of convection cells that have near 100% RH in the rising column and much lower RH in the surrounding air. This mechanism could change slowly with temperature. For example, if the shape of the convection cells is changed when the water content goes up (they become wider and flatter). Wouldn’t know how to address this. Don’t think the climate community has figured it out either.

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