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[OEXCHAOS]

I was reading the comments on a post on WUWT and I came accross this bit. It's really rather voluminous but easy to read and understand. If you're curious about what some folks are referring to when they talk about climate feedbacks, this is a good start, at least on the cloud feedback aspect.

From the post:
<h1 class="entry-title">Royal Society to review climate consensus position</h1>
George E. Smith says: May 27, 2010 at 5:45 pm Well it is a good thing that they are going to do a review; but I wouldn’t hold out much hope for any reversal of their position; that would be simply too cataclysmic to countenance.

But there is good reason to review the “feedbacks” question. In some instances what is described as a feedback is nothing more than a physical system which is in transition from one state to another state, as a result of some perturbation or other; and since the transition can take some time (thermal times constants generally being large); then we get to watch intermediate unstable states pass by from one stationary state to a different one. There really isn’t any “feedback” going on at all.

Then there is this cloud gospel that evidently all climatologers embrace:-

http://books.google....A...p;q&f=false

A quick glance at the cloud fraction graph shows that at zero cloud fraction it doesn’t matter what altitude the clouds are not at; the surface temperature does not change with the amount of no cloud.

But for any amount of cloud cover greater than zero; there is one altitude; the magic cloud altitude; where the surface temperature does not change at all with the fraction of cloud cover from 0 to 100 %.

Then for any amount of non zero cloud cover percent; if you move that cloud to a lower altitude, the surface temperature falls and presumably the lower you move it, the more the temperature falls.
But if you move that cloud from the magic altitude to a higher altitude; then the surface gets hotter; and apparently the higher you move the cloud; the hotter the surface gets.

So this has generated the legend of low clouds causing negative feedback cooling while high clouds cause positive feedback heating of the surface. That is the standard gospel.

Well of course that defies both common sense and everyday observation. If you are standing out in the sun with a cloud near the sun direction at any altitude; and that cloud then moves across in front of the sun; then observation says that it ALWAYS cools down in the shadow zone. And common sense says that since the sun is a near point source (0.5 deg divergence) the shadow size is pretty much constant at the same size as the cloud regardless of how high the cloud is. Well the higher the cloud is; the wider the penumbral shadow perimeter gets; whereas at lower altitudes the shadow edge gets sharper (for a given cloud).

So we are asked to believe that if you run that cloud up and down in altitude it will get hotter and hotter the higher you move the cloud (in the shadow zone). So if you had a cloud say 1 squ km in area and that cloud reflected say 50% of the sunlight hitting the top of it; and then absorbed say 50% of the remaining sunlight that enters the cloud (we could call it a IPCC-1-50-50 cloud for Intergovernmental Propaganda Concensus Cloud) and it would have a sunlight transmittance of 25%; so presumably instead of getting a maximum ground irradiance of about 1000 W/m^2 (in the hottest places) we would only get 250 W/m^2 in that shadow zone.

Now that cloud is going to block the same amount of light in the shadow regardless of its height, so we should measure 250 W/m^2 in that zone; for all cloud heights.

But the LWIR thermal emission from the ground in that shadow zone, is of course going to be reduced by the cooling; but more importantly that surface thermal emission is going to be at least Lambertian dispersed, into a complete hemisphere. The cloud however subtends a diminisheing solid angle, as the altitude increases; and therefore the amount of thermal emission from the shadow zone that gets intercepted by the cloud goes down as the cloud altitude increases.

Now the rest of the ground outside the shadow zone, of course continues in its cloud free state; so its temperature is unaffected by the cloud; as far as solar blockage; BUT the cloud does block a small amount of the LWIR emitted from each surface element outside the shadow zone; which in this example is most of the surface.

So the cloud now intercepts a small fraction of the LWIR surface emission from everywhere outide the shadow zone; and of course at a different oblique angle for each location; so one might need to integrate all of those small contributions to get the total for the rest of the surface outside the shadow zone.

Actually you can eliminate the need for integration by just acknowledging that the problem is identical to the reverse problem where the cloud is emitting downward radiation in a Lambertian (probably) distribution pattern; and that emission will spread over the surface in exactly the same distribution as the elemental contributions from each surface element. The further away from the cloud a position is, (laterally) the smaller is the IR from the cloud at that point and also the contribution intercepted by the cloud from that location.

So actually we can just use the Lambertian Cosine distribution from a diffuse (small) source to figure out the ground emitted LWIR intercepted by the cloud; and then partially re-radiated downward to the ground. We will find that the higher the cloud is the smaller this interception is; so more of the LWIR from the surface escapes around the cloud.

Well somewhere along the line; as we look at that biblical cloud picture cited above; we will suddenly discover that it is phony; because that is not a graph of cloud cover at varying altitudes as first appears; because each of those cloud cover percent lines is actually for a totally different cloud. They are not keep ing the cloud constant as they change its altitude; they are changing the cloud as they go, and the higher they put the cloud the less dense they make the cloud thereby changing both its albedo reflectance, and it bulk absorptance. The highest cloud, and the lowest cloud are totally different clouds.

What a crock that is; if you want to know the effect of altitude on the warming effect of a cloud; you can’t go changing the cloud itself at the same time as you change the altitude.

So I would hope, that these Royal Society folks get with the program, and re-evaluate some of these biblical utterances about the effect of cloud cover. Then we shall see if clouds can cause positive feedback or not; they still result in the surface cooling inside the shadow zone; and the bigger that shadow zone cloud gets the bigger the cooler area gets; until the cloud finally is covering the entire visible sky (from that location); and I don’t see how it ever switches from being colder in the shadow zone to becoming hotter in the shadow zone; no matter how large an area the cloud covers; and I have never experienced any cloud at any height that warmed up the surface in the shadow zone, when it passes in front of the sun; it ALWAYS cools; no matter what.

So have at it Royal Society; it seems like some of the sacred cows need to be butchered.

Link to original:

http://wattsupwithth...#comment-398653

[Rogerdodger]

This article once again displays the fact that there is so much we don't known or understand about the eco-systems.

That is what makes the whole environmental/industrial/political scam so brilliant.
It's all driven by a fear that we are going to die and we must "do something" and at any cost.

The military/industrial complex with it's political payoffs has done very well since WWII on the same fear, now it's the greenies turn.

The boogie man's going to get us so we better appropriate this funding for good old General Electric with MSNBC/NBC promoting it 24/7.
BRILLIANT!


In case of environmental fear: BREAK GLASS!
(Yes, it's all about the GREEN!)

Edited by Rogerdodger, 28 May 2010 - 10:18 AM.