Re: Christopher Booker: "2008 Was The Year Man-Made Global Warming Was Disproved"

On Sat, 3 Jan 2009 01:46:18 +0000 (UTC), Paul J Gans <gans@xxxxxxxxx>
wrote:

Eric Stevens <eric.stevens@xxxxxxxxx> wrote:

An explanation I have seen is that once the CO2 level rises
sufficiently it will close the particular IR radiation window and that
once that point is reached the addition of more CO2 will make no
further difference. Of course the actual argument is much more
complicated than that.

I think you misunderstand. Light comes in from the sun
in the visible region of the spectrum. It gets reradiated
mostly in the infrared.

CO2 blocks a bunch of wavelengths in the infrared. Thus
the reradiation is slowed down by a percentage that depends
on the amount of CO2 in the atmosphere.

To be more accurate, it is the "transmission" that matters.
If a gas blocks 10% of the radiation the transmission is
90% If the amount of that gas is doubled, the transmission
is now 90% of 90%, or 81%.

Thus the reradiation is *never* totally cut off. Al that
happens is that each increment of that gas in the air becomes
less efficient than previous increments.

That is my general understanding also. However your explanation is
oversimplified and as the limit is approached the simple relation
between gas concentration and IR absorbtion no longer stands.

That has nothing to do with the assumptions in atmospheric
modelling. It has primarily to do with basic physics.

And by the way, our climate models are not so much hampered
by lack of understanding the basic science (though there is
some of that) as they are by our inability to do the complex
computations needed to arrive at answers.

It is of concern that the models are unsuccessful at making even
qualitative predictions of the nature of changes in the earth's
atmosphere, let alone quantitative predictions.

Each model's success depends on its assumptions. Its assumptions
are limited by the amount of computing power available. For
instance, does including cloud cover in the equatorial regions
make a real difference? The only way to tell is to do two
computations, one including it and one not. But if you can't
do the one including it, well...

But the knowlege of global warming does NOT come from models
alone. Indeed, they are a minor part of it.


I recall a discussion with one modeller about 10+ years ago when the
thermal properties of the sea were just beginning to be taken into
account (but no currents, no waves and no interaction with the
atmosphere). But even then models were predicting global warming. I
described my experiences with complicated models of engineering
systems and their sensitivity to _minute_ changes in the input data.
Even a stable model was lucky to get within 20% of real world
behaviour. The flapping of butterfly wings was rampant.

My friend agreed that climate models suffered from the same kind of
problems and, even then, they were so complicated that it was almost
impossible to track down where things were going off the rails. I
asked him "How can you tell a good model from a bad model?" I was
shaken by his reply "It all depends on whether or not it predicts
global warming". In this case it seems the map _is_ the territory, but
its not the world I live on.

It should be. You see, global warming is a FACT. You have
got to wrap your head around that.

Are you arguing that all that is needed to confirm a model is that it
predicts global warming? How much global warming? Does more predicted
global warming mean that it is a better model?

What your friend was talking about was the ability of a given
model to predict the past 20 or 40 or whatever years of
climate history. That history shows warming. Scream all
you want, it is fact.

We were discussing _future_ predictions.

The problem is to determine how much of that is human caused.
I've given the example of CO2 in the air. We *know* that it
causes warming. And we *know* that humans have caused a huge
increase in the CO2 in the air.

You raise an interesting point. You _are_ a chemist (and I am not
trying to denigrate you by this in any sense - quite the opposite).
What do you know of atmospheric CO2 analysis in the 19th century?
Surely these must give some meaningful insight into trends well before
1930.

Those that would deny human effects have to explain why the
CO2 is NOT causing warming. So far, nobody has even come
close.

Do you start to see what we are talking about?

There is a response I wish to make to this but the book I need has
vanished. I will return to this when the thing turns up again.



Eric Stevens
.

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