On Tue, 7 Nov 2006 20:56:11 +0000, John Beardmore
wrote:

http://www.profc.udec.cl/~gabriel/tu...cp1/1-11-2.gif

Clearly these different gases have different absorption spectra, and
can never be "equivalent to CO2"...

They can have a net thermal effect similar to CO2.

They absorb at different wavelengths, and they absorb at different
efficiencies. No, they are not similar.

They are similar in that they are greenhouse gasses.

Ozone (O3) is a greenhouse gas. CO2's spectral response is quite
unlike Ozone.

Or perhaps we can say that CO2 is equivalent to O3, and therefore we
needn't worry about an ozone hole, because there is this "equivalent
gas" present?...

They are similar in they cause net amounts of energy to be retained
which affects temperature. That they absorb different amounts at
different wave lengths doesn't mean that different amounts of various
green house gasses can't achieve the same energy retention / temperature
increase as some particular amount of CO2.

Gosh, and that also allows one to pretend that these gases have the
same spectral response, especially when we discover that the solar
flux has increased... (which it has)

The technique demonstrated by claiming "equivalence" is called
"begging the question" (a well known logical fallacy).

Well - you begged it - you got an answer.

Nonsense. The question being begged is "How is CO2 equivalent to
those other gases?"... Answer: it isn't.

BTW, have you stopped beating your wife?

But if "net thermal effect" is what the comparison is all about, why
don't you compare it to something people can see and touch -- say, a
burning candle?

Could do, but it interesting to compare the 'potency' of various
greenhouse gasses, and if CO2 is the one with the biggest effect, it's
not surprising that people adopt it as a bench mark, but contribution to

Why not compare it to water, which is the biggest?

heat retention and heat flows are calculated. Candle power would be
rather a small unit to use though.

Why is that?

http://en.wikipedia.org/wiki/Candle

"A candle typically produces about 13 lumens of visible light and 40
watts of heat,..."

The IPCC is claiming that CO2 contributes an "equivalent" of 1.5
W/m^2.

So the candle would be a bit large, but managable. But it wouldn't be
nearly as frightening to claim it's the equivalent of 1 burning
candle, every 27 square meters (after all, 1/27th is such a small
number, and 430 looks so much larger and scarier...).

"This is equivalent to XXX extra candles burning per
square mile of Earth's surface"... Oh, but then you wouldn't be able
to fold in the CO2 boogeyman...

Not a matter of any particular bogey - just causes, effects and
mitigation.

Mitigation implies a good understanding of the system, a controllable
cause, and a certainty that the changes being observed are not due to
natural variations.

The sun behaves approximately as a black body. If the sun increases
in temperature (and output), the spectrum shifts towards the blue (and
increased UV).

OK - and how significant do you claim this is ?

The solar data was in the link below:

And NOAA notes that the solar emission spectrum has changed:
http://www1.ncdc.noaa.gov/pub/data/p...irradiance.txt

and thus those gases are NOT
_equivalent_ to CO2. Their behavior is qualitatively and quantitively
different.

Yes - they all cause different amounts of heat to be retained per
amount of greenhouse gas released, but that doesn't mean that the total
heat retained can't be represented as being equivalent to a particular
amount of carbon dioxide.

Only if your desire is to disguise the true cause(s) of the changes.

Indeed! Why do we believe that increasing CO2 will be any more
catastrophic than it was a million years ago?

Well, you mentioned a figure of 6000 ppm I believe. How well would you
cope physiologically at that concentration ?

Let's see, 6000 ppm is 0.6%.

What is the concentration of CO2 in my breath? My recollection is
that we breathe in air with 21% O2, and exhale air with about 16% O2
-- the missing balance is CO2.

Again, current CO2 levels are exceptionally low, compared to past
history.

Geological history yes, but as I understand it, not human history.

And?... That is no way changes the observation that the current time
is for some reason at an exceptionally low CO2 concentration. And
claiming "human history" will not prevent any sources of natural
variation from occurring.

And we note that those high levels did not exterminate life
on Earth.

Which doesn't mean humanity would have survived. I suggest that if,
warming aside, 6000 ppm CO2 concentrations pose a major physiological
challenge to us and other animals, that in itself is a global catastrophe.

You will have to provide some data to support this claim...
We currently exhaust rather high levels of CO2 in our breath.

Retief