Re: Global warming deniers

In article <1145830209.541154.163130@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
Robert Carnegie <rja.carnegie@xxxxxxxxxx> wrote:
Robert Grumbine wrote:
In article <e247ba$27c$4@xxxxxxxxxxxxxxxxx>,
Paul J Gans <gans@xxxxxxxxx> wrote:
Robert Grumbine <bobg@xxxxxxxxx> wrote:
In article <1145393941.108159.218350@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
Kermit <unrestrained_hand@xxxxxxxxxxx> wrote:

[snipping away to commit a little pedantry]

Have any evidence? We have
significantly altered CO2, the main greenhouse gas, in the atmosphere.

It's actually number 2, behind water vapor. It is the number one
greenhouse gas that does not condense under terrestrial conditions,
and that is an important qualifier. If water vapor were the sole,
or strongly dominant, greenhouse gas, then we'd be a very cold place.
Any decline in temperature (say because it's night) would precipitate
water from the atmosphere, leading to further cooling, and a runaway
that direction. The noncondensing greenhouse gases, lead by CO2,
provide a floor for that process and prevent the runaway cooling.

[excellent stuff snipped to make a point that Robert of course
already knows]

The surface of the earth is about 70% covered by water.
The meaning of this is that there is no way that we can
control the amount of water in the atmosphere.

The maximum amount of water in the atmosphere is governed
by the temperature. The higher the temperature, the larger
the maximum.

When the maximum is exceeded, it rains. But very often the
maximum is not exceeded. The actual percent of the maximum
we have at any time is called the humidity (which is exactly
that percent.)

The humidity is controlled by many things including amount
of surface water, rates of evaporation, and so on.

But the point is that we humans are NOT directly influencing
the amount of water vapor in the atmosphere. We *are*
directly influencing the amount of CO2 in the atmosphere.

A good point to keep in mind, thanks for adding it.

For trivial trivia to memorize: average relative humidity is 70%.
You can do some amazingly good climate modeling by simply fixing it
there. (It's about 40 years since we did do so in a serious model,
but after running the big hairy complicated models, models that
would be quite happy to say 95% or 25%, 70% still pops out.)

The nontrivial trivia to know: Water cycles through the atmosphere
on about a 2 week time scale. (Maybe it's 1 week, the important
point is, it's a small number and the time unit is week.) This
means that in addition to it being beyond human ability (at least
currently) to influence directly, it is something which _responds_
rapidly to the rest of the climate system. It is, for this
additional reason, a responder, not a driver.

Carbon dioxide, once in the atmosphere, is up there for
decades to centuries to millennia (it's not very meaningful
to put a single number down for time scale, due to the multiple
source/sink interactions) -- up for a long time. As such,
it is a driver of climate. Also means that if we decide that
380 ppm is a bad concentration to have, and it should be 280
instead, it will be a long time (millennia in this case) before
the system can pull that much carbon out of the atmosphere on
its own, even if we immediately stopped emitting more.

Might I trouble you for the addresses of some respectable Web pages
setting this out clearly to laymen, for purpose of pursuing the same
argument elsewhere? Particularly how long it takes to get the CO2 down
again - from what you say, much longer than it took us to send it up.
Thank you! I'm assuming, of course, that you didn't slip a zero,
although I did - I quoted you from memory (and without attribution) as
saying 100 years to get rid of the excess CO2, not 1000.

I may at one time have mentioned the figure as low as 100, but
learned better. Millennia is the time scale for return to preindustrial.
Centuries is more the time scale for notable change.

I think the IPCC lays it out fairly well for laymen, at least
in the policy maker summary side. www.ipcc.ch ... ok, maybe
it's an earlier edition (the third is the one shown, and it might
be the second which has the description I like for this).
http://www.grida.no/climate/ipcc_tar/wg1/096.htm has some description,
but not all that I'd want.

I dare say it depends on assumptions:
1. Limit industrial carbon dioxide emissions (i.e. fossil fuel
consumption) to present annual levels
2. Terminate all industrial fossil fuel emissions
3. Terminate all industrial CO2 emissions
4. Eliminate the human race
5. Eliminate all animal species

Of course I merely could point to your article on Google Groups, or if
you've written something on a personal Web site, I should be able to
dig it up if I know what to look for.

For the time to remove all anthropogenic CO2, it's a calculation
assuming (from some date) no further CO2 emission. Stabilization
strategies involve some continuing emission -- 10% or less of current
emissions. The thing being, any level can be a stabilization target,
but at stability the emissions can only be about 10% of current.
(Ch 3. is the prime one to go through on this. It isn't spelled out
this way there, but you can infer it ok from the relevant figures.)

http://www.radix.net/%7Ebobg/faqs/scq.CO2rise.html is a nice (if old)
description, with cites to the scientific literature about how CO2
has risen, and how we know that it's anthropogenic.

--
Robert Grumbine http://www.radix.net/~bobg/ Science faqs and amateur activities notes and links.
Sagredo (Galileo Galilei) "You present these recondite matters with too much
evidence and ease; this great facility makes them less appreciated than they
would be had they been presented in a more abstruse manner." Two New Sciences

.

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