IPCC false assumptions about evaporation & clouds cause 5-fold exaggeration of global warming

A post from from the Swedish skeptics site The Stockholm Initiative explains how the incorrect assumption by the IPCC and climate models that feedback from evaporation and clouds is positive instead of negative results in a 5-fold exaggeration of climate sensitivity to CO2. 

Observations have demonstrated that feedbacks from evaporation and clouds are negative, resulting in a climate sensitivity of only ~0.64C to a doubling of CO2 levels, 5 times less than claimed by the IPCC using the false assumption of positive feedbacks from evaporation and clouds. This low estimate of climate sensitivity is in the same range as determined from observations by several papers including Lindzen & Choi, Spencer & Braswell, Bjornbom, and several others. 

[Google translation & light editing]:

How the IPCC evaporates?

03/06/2014 by CG Ribbing .

In mid-April, a guest post was published on WUWT by Richard J. Petschauer complaining of a serious fault in the climate models used by the IPCC. It is about a fundamental factor of how much water evaporation increases as water temperature increases.

In GCMs [Global Circulation Models] increased sea surface temperature increases evaporation, so that the amount of water vapor in the atmosphere increases. Since water vapor is a powerful greenhouse gas, this implies a positive feedback loop - the weak effect of increased carbon dioxide levels is enhanced through more water vapor. This is the background to the enhancement of the greenhouse effect for only CO 2 by about a factor of 3, which is assumed ​​in the models. In previous posts, this has been criticized, for example ( link). Water vapor is indeed a potent greenhouse gas, but if for example a part of it condenses into clouds is their net impact of a negative feedback loop .

The models estimated in accordance with a rule of thumb that the water vapor content increases so much that the relative humidity of the atmosphere is constant. Although this has been commented on here because it does not match the measurements (eg  link: ).

In the WUWT post by Richard J. Petschauer the criticism is the fundamental parameter for the amount evaporation increases with temperature . Evaporation depends on several factors: water temperature, air temperature just above the surface, atmospheric relative humidity, and additionally winds and waves. If the latter three factors are assumed to be constant and the water outlet temperature is set to 17 o C, the increase is 6.5% / o C. Petschauer complains that the climate models in practice apply a significantly smaller increase, about 2.5% / o C. A common AGW argument for this small increase is "energy shortage". That is the claim that a higher value requires too much energy. It is true that the heat of vaporization is high, that's what makes the evaporation of an effective cooling mechanism! The power required, is however in the heated water, which is cooled to the extent that corresponds to the heat of vaporization. As the water cools, the radiation from this is reduced accordingly. Petschauer formulates the equation of the change at a certain temperature increase in the water:

                           ΔE =  ΔD - ΔG

 where E is the heat of vaporization, ΔD reduction in downward heat radiation and ΔG increase in outward thermal radiation. Petschauer suggests that those who maintain lower evaporation did not realize that it is E which is the primary variable, and D and G adapt to the E-value.

 I can imagine that the higher evaporation and climate models that only count positive feedback leads to excessive temperature rise at 6.5% / o C - and therefore the evaporation is a knock-out in a quest for "good" results.

 In an earlier, more comprehensive post, utilizes Petschauer ( link  a higher value on evaporation to show how this affects the climate sensitivity., it is too extensive to describe the sub-steps, and I must admit I have not read the references. Nevertheless, I want to quote the final result in the form of a table that show how climate sensitivity is lowered to 0.64 o C / CO 2 -doubling when negative feedback from both cloud and evaporation are included.

At the end of the table value is thus also the cooling effect with clouds and these certainly belong to the difficulties in climate science due to the interaction of several factors. The evaporation from a liquid surface falls within the field of fundamental physics and chemistry, and it can be determined using controlled experiments. It is therefore particularly noteworthy if they choose the wrong numerical value for such a fundamental process!