Re: OT - Global Warming Revisited
- From: "Eli Rabett" <EliRabett2003@xxxxxxxxx>
- Date: 2 Oct 2005 17:23:52 -0700
D Murphy wrote:
> "GayLopez69" <GayLopez69@xxxxxxxxxxxxx> wrote in
> > raylopez99 wrote:
> >> The trapping
> >> > occurs over the whole planet and when you increase the trapping,
> >> > the whole planet is affected. Bascially it happens at the boundary
> >> > of the convection layer where the chance of radiation to space of a
> >> > molecule reaches 50% ( the equipotential point ). This is where the
> >> > planet actually LOSES radiation to space. As GHGs accumulate, this
> >> > point becomes higher and thus you have a larger layer of atmosphere
> >> > trapping the heat. The lapse rate ( delta t vs delta h ) is
> >> > constant ( assured by convection ) so a larger distance means a
> >> > higher accumulated delta t to the surface. Since the equipotential
> >> > point is -18C set by necessary temperature to radiate the incoming
> >> > solar insolation in balance, the surface warms. "
> >>
> >> > Keep in mind this is only a model, a first order approximation,
> > Actually, the more CO2 in the atmosphere the more opportunities there
> > are to intercept infrared at the lowest altitudes closest to the
> > surface.
> > The visible and higher frequencies can pass through the GREENHOUSE to
> > reach the surface.
> > Some fraction is reflected and escapes out of the atmosphere again
> > because it is a frequency which is transparent to CO2.
> > A large portion of the incoming light and higher radiation is absorbed
> > at the surface and converted to longer wavelength Infrared.
> > The longer wavelength IR is intercepted by the first CO2 it meets and
> > trapped. CO2 can absorb a very large amount of IR photons -- which is
> > the definition of GREENHOUSE GASES.
>
> You were doing good until here. Trapped and absorbed are two different
> things. Once the radiation is absorbed it ceases to exist, having been
> transformed into the potential and kinetic energy of the molecules in
> the atmosphere. Since the radiation has ceased to exist, it can't be
> trapped.
>
Sorry, this process has been called radiation trapping for a long time.
See, for example http://raptor.physics.wisc.edu/talk/part_2d2.htm
Here is a definition for radiation trapping
http://www.photonics.com/dictionary/lookup/XQ/ASP/url.lookup/entrynum.4366/letter.r/pu./QX/lookup.htm
********************************************
That process by which radiation spontaneously emitted by a volume of
optical materials is resonantly reabsorbed within the same volume
before it escapes. This effect is manifested in a reduction in the
observed rate of spontaneous emission from the material relative to the
rate for single atoms or ions.
********************************************
Here is another from a talk:
http://www.up.univ-mrs.fr/~wegas99/abstracts/amolisch.htm
********************************************
When two excited atoms collide, energy can be transferred from one atom
to
the other, so that we end up with one ground-state atom, and one atom
in a
more highly excited state. Examples for these processes are energy
pooling, associative ionization, and Penning ionization. The
measurement of
the cross section for these processes is of great interest, because
they
play an important role in many situations in chemical physics.
Unfortunately, measurement of these cross sections is quite difficult
due
to radiation trapping effects: the repeated absorption and reemission
of resonance photons leads to a spatial redistribution of excited
atoms,
and influences the fluorescence radiation, which is used as a measure
for
the collision rate coefficient. This paper will investigate the
influence
of trapping on various types of experiments for cross section
measurements.
It will critically review both existing and new approximations, and
point
out the limits of validity under various circumstances. Recommendations
for
experimental setups that minimize uncertainty will be given.
**********************************************
Now there are quibbles you could quibble, but the term radiation
trapping has long been used to describe the absorption and re-emission
of light from a system.
> > These CO2 molecules continue to accumulate kinetic energy, which is
> > passed to other gases so that there is a warming.
> >
> > The IR cannot escape very high because the CO2 is thicker and the
> > statistical changes of interception are greater with increased density
> > of CO2.
> >
> > Increased kinetic energy at the surface means increased collisions
> > with land and water, which retransfers the IR which was radiated
> > previously. Cooling is delayed because the IR cycles in short loops at
> > the air-surface interface.
>
> Again close but no cigar. The IR that was radiated previously has ceased
> to exist, having been converted in the atmosphere. The atmosphere itself
> radiates because it has a finite temperature. The earth recieves twice
> as much energy from the atmosphere than from the sun. If all of the
> greenhouse gases were to disappear the earth would freeze and life would
> cease to exist. The radiation absorbed and emitted by the atmosphere are
> not made up of the same photons and aren't even in the same spectrum.
So what. See above for definitions of radiation trapping that have
been used by physicist for over a century (probably goes back to RW
Wood or earlier). What you think is radiation trapping is what happens
in a resonant cavity. It is not what people who study plasmas, atoms
and molecules call radiation trapping.
In fact what this increasingly reminds me of for futility is "the
greenhouse effect is what does not happen in a greenhouse".
Eli Rabett
.
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