"Clouds are said to be the largest uncertainty in climate models, and I can believe that.
Their representation in the models is highly parameterized, each model uses different parameters as well as different values for the same parameters, and so of course, different models give very different results.
Or to quote from the IPCC, the Intergovernmental Panel on Climate Change:
"In many climate models, details in the representation of clouds can substantially affect the model estimates of cloud feedback and climate sensitivity.
Moreover, the spread of climate sensitivity estimates among current models arises primarily from inter-model differences in cloud feedbacks.
Therefore, cloud feedbacks remain the largest source of uncertainty in climate sensitivity estimates."
The question of importance is this—if the earth heats up, will clouds exacerbate the warming or will they act to reduce the warming?
The general claim from mainstream climate scientists and the IPCC is that the clouds will increase the warming, viz:
"All global models continue to produce a near-zero to moderately strong positive net cloud feedback."
My own theory is that clouds and other emergent climate phenomena generally act to oppose any increases in surface temperature.
... I’d expect the opposite of what the models show.
I figured that there should be a negative cloud feedback that opposes the warming.
So I thought I’d take a look at answering the question using the CERES satellite dataset.
... Clouds have two effects on the surface radiation balance, and thus on the surface temperature.
On the one hand, they reflect sunlight (shortwave radiation, “SW”) back out to space, cooling the surface.
And on the other hand, clouds block and absorb upwelling thermal (longwave, “LW”) radiation from the surface, and they re-radiate about half of what is absorbed back down towards the surface.
This additional downwelling radiation leaves the surface warmer than it would be in the absence of the clouds.
We can actually physically perceive both of these effects.
During a clear summer day, a cloud comes over and instantly cools us down.
And during a clear winter night, a cloud comes over and we immediately feel warmer.
These two changes, cooling and warming from different phenomena, are lumped together under the term “CRE”, which stands for the Cloud Radiative Effect.
... it has a shortwave (SW) and a longwave (LW) component, and when added together these give us the “Net CRE”.
Planetwide ... the net CRE averages out to a surface cooling effect of about -20 watts per square metre (W/m2).
... clouds cool the surface more than they warm it.
... clouds have a net cooling effect everywhere except over some deserts and at the poles.
At the poles, clouds actually warm the surface.
And on average, the cooling is much greater over the oceans (-25 W/m2) than over the land (-8 W/m2).
In short, the clouds are cooling the hot tropics and warming the cold poles, just as my theory predicts.
... what happens as the planet warms?
... I calculated the changes in the net CRE with respect to surface temperature for each 1° latitude x 1° longitude grid cell.
... As predicted by my theory that clouds are a major part of the thermo-regulatory system keeping the planet from overheating, we find that almost everywhere on earth, as surface temperature increases, cloud cooling also increases (negative values).
This is true in both hemispheres, in the tropics, on land, on the ocean, and in both the Arctic and the Antarctic.
Only in isolated patches of the ocean does cloud cooling decrease with increasing surface temperature.
I’m currently in the process of writing up my theory that emergent phenomena act to keep the surface temperature within narrow bounds, for submission to some as-yet-undecided scientific journal."
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Thursday, March 18, 2021
"Clouds From Both Sides Now"
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