## söndag 25 juli 2010

### What the 2nd Law Tells about the "Greenhouse Effect"

To check if the basic postulate of climate alarmism (= "greenhouse effect" of
"backradiation" from "greenhouse gases"), violates the 2nd Law of thermodynamics, it is useful to understand what the 2nd Law says.

But if there is a mystery in science, then the 2nd Law has the first place: It comes in many forms and nobody seems to know which one is the right one and why it should be valid. Some of the formulations of the 2nd Law read:
• heat cannot by itself flow from cold (but what is "heat" and  "by itself"?)
• entropy cannot decrease (but what is "entropy"?)
• disorder is always increasing (but what is "disorder")
• a heat engine cannot be more efficient than a Carnot engine (but what is a "heat engine" and a "Carnot engine"?).
To come grips with this mess I propose in Computational Thermodynamics a resolution of the mystery in terms of finite precision computation, where the 2nd Law states that
• a system evolving in time with finite precision necessarily has to destroy fine details or high frequency information in order to move ahead,
• which effectively means grinding high frequency details into heat.
This version of the 2nd Law is presented in understandable form in the knol The 2nd Law of Thermodynamics.

Next, recall that "backradiation" is supposed to mean that a blackbody B of a certain temperature (top of the atmosphere) can radiatively heat another blackbody  A of higher temperature (Earth surface).

But Planck's Radiation Law including Wien's Displacement Law tells us that a blackbody radiation spectrum has a cut-off of high frequencies proportional to the temperature, which means that the high-frequency end of the spectrum of A is missing in the spectrum of B, which means that B cannot heat A. The fine details in the spectrum of A cannot be created out of the coarser details in the spectrum of B, because a blackbody spectrum has a unique form (up to cut-off).

On the other hand A can heat B because the (coherent) fine details in the spectrum of A can be grinded to heat (= decoherent fine details) increasing the temperature of B.

In short: coherent fine details can be destroyed by a coarse process (into heat), but a coarse process cannot create coherent fine details (from decoherent heat).

We conclude that backradiation violates the 2nd Law and thus is non-physical.

#### 2 kommentarer:

1. What people refer to when they claim that a cold object can warm a hot object is probably the effect of increased pressure and heat capacity which results from adding mass to the system. However, by definition it cannot increase the temperature.