Everyman needs a hobby (1)....
I think I may take up Essex and McKitrick, or at least share it with Tim Lambert. I should say at the beginning that I have a very different point of view than Tim, more physically based for one, but Essex and McKitrick sticks in my craw, and keeps on coming up, so I need a place to point to rather than posting the same comments a zillion different times.
Chris Essex and Ross McKitrick have written a book entitled "TAKEN BY STORM
The Troubled Science, Policy and Politics Of Global Warming" in it they make a large number of troubled claims.
The book itself is not on line, but a briefing pamphlet is at http://www.takenbystorm.info/TBSbriefing.pdf. They should know better. The briefing alone is an invitation to a fisking, with so many dubious claims that one hardly knows where to begin. For example, starting at the bottom of page 6 they say:
"Temperature is not energy. It is a thermodynamic variable with some special properties that make it far more interesting than it usually gets credit for."
True enough, but then they start going off the rails
"Consider that an ordinary laser pointer, powered by small flashlight batteries, generates peak temperatures of about 10^11 Kelvin. Yet you can shine it on your hand and not feel any warmth! This can happen because temperature represents the distribution of energy across physical states, and the fewer the states the higher the peak temperature, even at low energies."
Which is absolute garbage. A system with any number of states can have any temperature. You would think Essex would know better. What matters is the distribution of population in the various states. The simplest example is the two level system, which is described at any number of web sites. The temperature is determined by the relative populations in the two states, or alternatively the temperature determines what the relative population in each state is. Chicken/egg.
Here is a neat little applet that lets you play around with a two level system http://physchem.ox.ac.uk/~rkt/tutorials/heatcap/heatcap.html. The energy slider changes the separation between the two states, the temperature slider increases the temperature of the system.
The degeneracy slider is a bit more complicated. If the degeneracy is greater than one, the upper state rather than being composed of a single state, is built out of two or more states with equal energy. Leave that at one for now.
The relative populations in each state are shown by the green bars on top of each level. The blue arrow indicates how much population is shifted into the upper level if the temperature is increased 1 K (same as a 1 C change).
If Essex and McKitrick are right, how come the population of the system can be cooled to ~ 0K if most of the population is in the lower state.
The paragraph above is really a twofer. The statement about the laser temperature is another goody. More about that next time. As homework, go look up what the temperature describing the distribution of energy across states in a system which lases is.
Thursday, October 27, 2005
Everyman needs a hobby (1)....