From jbh@IDT.NET Sun Oct 19 09:45:09 EDT 1997
Article: 155900 of sci.environment
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From: Joshua Halpern <jbh@IDT.NET>
Newsgroups: alt.politics.economics,sci.econ,sci.environment
Subject: Re: minimum wage & global warming
Date: 19 Oct 1997 05:14:34 GMT
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In sci.environment jim blair <jeblair@facstaff.wisc.edu> wrote:
: jim blair:

I'm going to take an extensive quote from Richard Wayne's 
Chemistry of Atmospheres, with a few comments interspersed
by me in <brackets>  This is the paperback edition published
in 1986.  This section bears on many of the points
raised in this thread and others.  What is NOT in brackets
below is from Wayne, an elementry textbook.

START OF QUOTE:

p45. Section 2.2.4  Trapping in real atmospheres

A real atmosphere may contain several species with IR active 
modes and a full model will include their contributions to
radiation trapping produced by clouds and aerosols.  Partly
because the IR bands of the various components overlap, the
contributions of the individuals absorbers DO NOT ADD LINEARLY
<my emphasis>.  Table 2.2 shows the percentage of trapping 
that would remain if particular absorbers were removed from 
the atmosphere.  We see that the clouds on contribute 14% to
the trapping with all other species present, but would trap
50% if the other absorbers were removed.

Table 2.2  Contributions of atmospheric ratiation absorbers
to thermal trapping

Species removed		% trapped radiation remaining
All			0
H2O CO2 O3		50
H2O			64
Clouds			86
CO2			88
O3			97
None			100
Data from Rev. Geophys. & Space Sci. 16 (1978) 465

<Note: This is an astounding table.  It says that if you remove
ALL of the H2O from the atmosphere, only 36% of the radiation
currently trapped escapes.  If you remove the clouds only 14%
escapes, which is only a little more than if you remove the 
CO2>

Carbon dioxide adds 12 % to the trapping of the present atmosphere,
that is, it is a less important trapping agent than water vapor
or clouds.  On the other hand, on its own CO2 would trap three
times as much <36%> as it actually does in the Earth's atmosphere.

<Note, the relative importance would be somewhat in the ratio
H2O:Clouds:CO2...36:14:12 on this basis. Thus it is WRONG to 
say that CO2 is unimportant.>

The point is of importance in seeing how far increases in the
Greenhouse effect could provoke climatic response to changed
CO2 concentrations.  In this context, it is interesting to note
that, since the upper layers of the atmosphere leak relatively
more radiation to space than they trap, additional CO2 leads
to atmospheric cooling rather than warming for atmospheric 
layers above about 20 km.

<Note: there has been much discussion in this group about 
satellite measurements of a temperature decrease in the middle
atmosphere.  Greenhouse denialists have claimed this as a proof
that there is no anthropogenically induced warming.  Here is
a clear statement made a decade ago, well before the satellite
data was reported (maybe before the satellite was launched)
establishing the physical basis for this decrease.  Moreover,
>from  sections I will not quote, it is also clear that the same
increase in trace gas concentrations will lead to warming.
In essence this shows that Michael Tobis, Paul Farrer and
Bob Grumbine (and some others) have been committing truth,
and the greenhouse denialists have been blowing hot air.>

Many of the trace atmospheric gases, such as CH4, N2O and NH3
have infra-red modes active in the trapping region.  These
gases may therefore have a direct effect on global 
temperatures quite distinct from that exercised through
their possible modification of concentrations of major
absorbers.

<Note:  modification through reaction in the atmosphere, 
principally chains propagating through free radicals)

The influence of minor constituents is particularly marked
if they absorb where there is otherwise an atmospheric
window

<Note:  an atmospheric window is a region where there are
no strong absorptions by species found in high(er) concentrations.
For water, the window would include essentially everything
below about 1100 cm-1>

This stopping up of windows shows itself in the Venusian
atmosphere.  Over several years, doubt existed about
whether a greenhouse effect on Venus could plausibly
explain the high surface temperatures.  The problem
was in part to know how much solar radiation penetrated
below the cloud tops and in part to find the IR active
molecules that possessed an optical depth CHI= 
(732/227)^4-1= 107 

(Note:  This is what calculation would require to maintain
the high surface temperatures>

CO2 alone cannot provide the necessary depth over the 
emitting spectral region.

<Note:  Given the higher temperature of Venus, this will be
blue shifted wrt the emitting regions from the Earth>

However, the Pioneer Venus and Venera 11/12 probed of 1978 
have now shown that no only does enough sunlight reach the
surface to fuel the effect, but that also the small H2O
and SO2 concentrations are sufficient, together with
pressure induced transitions in CO2 to close the
spectral window.

END OF QUOTE

<Note to Uncle Al the role of pressure broadening, a 
somewhat subtle effect.  There is more to IR spectroscopy
that unresolved vibrational bands of the fundamental 
active modes>

<Note:  This shows directly that contrary to the claims of
the greenhouse denialist community one 
can successfully model the atmospheric temperature profile
based on absorption of major (CO2) and minor (H2O, SO2)
species and radiative transfer codes. The same is true for 
the earth.  Compare this to the misleading and false claims
of Blair>

: But quite apart from all this consider the following:
: One of the "examples" of a runaway greenhouse effect, which is 
: supposedly what Earth will become if we do not "do something" is Venus.
: But there is a problem, more precisely three problems with comparing
: Venus to Earth.
: 1. Venus of course lies only ~2/3 AU from the Sun receving a lot more
: heat, since the amont of heat diminishes in a geometric progression with
: distance.

Accounted for in the calculations.  Any Venus atmospheric model
includes this.  The common way of expressing this is that the
intensity decreases as 1/r^2  

: 2. the athmospere on Venus is thick with clouds ranging from 45 to 60
: kilometers above the surface; those clouds trap heat as well as the CO2

See section from Wayne quoted above as to why this is misleading.
The models include this at a high enough level to provide reliable
predictions of temperature profiles.

: 3. and most importantly the upper level of venusian athmosphere
: *superrotates* - the athmosphere above the clouds moves 60 times faster
: than the planet rotates. This crates an athmosperic layer which reflects
: heat downward, because it is impenetrable to air from below (much like
: the Antarctic polar vortex, which is responsible for the peridocal
: thinning of ozone over Antarctica).

It appears that you are confusing convections with radiation here.
This should not effect radiative losses.

: None of the above exist on Earth, nor indeed will exist as a result of
: release of the CO2 into the athmosphere, even allowing that CO2 is
: being released in substantial amounts, a claim which as I pointed out
: before fails to meet the rigor of scientific iqnquiry.
: Thus a global warming, or indeed a runaway greenhouse effect is 
: extremely unlikely on Earth, _in any circumstance_.
: Like I said: a sense of proportion is lacking.--DN

The next to last sentence is fundamentally dishonest.  It
puts global warming on the same basis as a runaway greenhouse
effect.  AFAIK the best predictions predict warming in the 
range of 1.5-4.5 C in the next century.  NONE predict a 
runaway greenhouse effect.  

As a matter of fact, the next section of Wayne's book explains
why  there cannot be a runaway greenhouse effect on the
earth (although there is apparently on Venus), however, I
am tired of typing and Richard could use the income.

One also gains confidence in the atmospheric models because of
their relative success in matching temperature profiles on
Venus and other planets besides the Earth (note: models of
other planets AFAIK are all one-dimensional vertical models)

As Tobis pointed out to you there is no doubt that CO2 and 
trace gas concentrations are increasing.  Long searches
for additional non-anthrogenic sources, or unknown sinks
have failed.  Calculations of anthrogenic releases of 
CO2 and other trace gases such as NH3 and CH4 agree
with measured increases.  Basically, denying this makes
you look like an idiot with his thumb up his nose.   
What Tobis was telling you is

1.  It is not hard to measure CO2 concentration changes
    at the ppm level.

2.  The technology to do so has existed for many years.

3.  Measurements have been made for many years.

4.  CO2 concentrations are increasing.  You should be able
    to find long term data at the IPCC site, or in any 
    textbook on atmospheric chemistry.  There is a clear
    increase of 25 ppm btw 1958 and 1984 for example 
    shown in a graph on p 20 of Wayne.

The same is true for other trace gases including methane, the
CFCs, etc. although, given their lower concentrations, the
measurement series do no extend as far back.  Give this
one up.

Apologies to all for the length of this post

josh halpern