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Dan,
Thanks for your excellent post. You have touched on a number of issues
that most people are not
aware of in trying to assess the affects of additional CO2 in the
atmosphere, such as the fact that half
of the additional CO2 is being taken up by the oceans and (primarily) and
plant life, and the suturation
effect.
What I would like to see in communicating these issues to the public is a
more accurate picture of the
situation, instead of hyperbole (think Al Gore). The accurate picture is
presented based on the best
data available and by recognizing the limitations of our models. The best
data does not include the
historical thermometer record, but does include the global satellite
temperature measuresurements
since 1979, satellite sea level determination, and the recently developed
climate monitoring network
with proper instrumentation that is remotely located. We must learn much
more about forcings and
feedbacks to improve the models.
David
On 20 Feb 2012 at 11:02, Dan Schroeder wrote:
I haven't heard anything approaching a compelling response either.phys-l@carnot.physics.buffalo.edu
But there have been some fascinating incorrect and partially correct
responses, and these can at least help us better understand the physics.
The CO2 spike is in a way quite remarkable. If you had told me that
humans are adding so many gazillion tons of CO2 to the atmosphere
every year and asked me to guess what fraction of that added CO2 stays
in the atmosphere (rather than being absorbed by plants or water), I
would have guessed that the fraction is either close to zero or close
to 100%. That is, either the absorption mechanisms can easily keep up
with the emissions, or they can't keep up at all. But in fact, the
fraction is close to 50%. I find this a remarkable coincidence and
although I'm sure the experts understand the reasons in detail, I'm
not aware of any simple explanation.
There actually are some climate skeptics who deny the basic physics of
the greenhouse effect. Sadly, some of them are professional
physicists, and have even gotten a paper published in a peer-reviewed
journal. Just Google "Gerlich and Tscheuschner" if you're not already
aware of this embarrassing incident. Be sure to read Arthur Smith's
devastating rebuttal.
I think you need more than "common sense" to translate the known CO2
increase into a quantitative predicted temperature increase. An
extremely naive argument would say that if CO2 is responsible for a
third of the current 33C greenhouse effect, then doubling CO2 would
increase the average temperature by another 11C. A more sophisticated
argument would say that doubling CO2 won't have any effect at all,
because the CO2 absorption band is already "saturated" by existing CO2
concentrations and so adding more CO2 doesn't cause any additional
absorption at these wavelengths. The correct analysis acknowledges
that the middle of the absorption band is saturated but then goes on
to consider the "shoulders" of the absorption band as well as energy
transport processes in the atmosphere. The resulting prediction,
without feedbacks, is a temperature increase on the order of only
about 1C. That's for a doubling of pre-industrial CO2 levels, so I
don't think it's correct that "simple" models predict a "few-degree"
increase at current CO2 levels.
The reason why the skeptics can get away with their nonsense is
precisely because the effects are small and the correct explanations
are complicated. As a physicist, I find this situation extremely
frustrating.
Dan
On Feb 20, 2012, at 10:00 AM, phys-l-
request@carnot.physics.buffalo.edu wrote:
From: John Mallinckrodt <ajm@csupomona.edu>
Date: February 19, 2012 11:25:12 AM MST
To: Forum for Physics Educators <phys-l@carnot.physics.buffalo.edu>
Subject: Re: [Phys-l] Climate skeptic convinced by data. Was: Re:
Mike Mann _The hockey
Reply-To: Forum for Physics Educators <
Whenever debates like this get going among people who presumably CAN
be persuaded by evidence and rational argument, I like to haul out a
simple summary provided by Art Hobson a couple of years ago. I have
yet to hear anything approaching a compelling response. Maybe this
time will be different.
"The sudden atmospheric CO2 spike during only the past two centuries
is unprecedented in at least 800,000 years of alternating ice ages
and interglacials. This spike is of undeniably human origin; so far
as I know, even climate skeptics agree with this statement. The
natural greenhouse effect undeniably warms Earth´s surface by 33
degrees C, and CO2 is known to be the second strongest greenhouse
gas, after water vapor. There´s every reason to think that this CO2
spike is responsible for the temperature increase, and indeed nobody
has proposed a plausible alternative mechanism. Common sense, simple
models, and all of the computer models predict that the CO2 spike
should cause a few-degree increase in the greenhouse effect. That´s
exactly what´s been happening. Indeed, climate skeptics need to
answer the obvious question: Why wouldn´t you expect that high CO2
levels are causing high temperatures?"
--Art Hobson, The Physics Teacher, Vol. 48, pp 502-503, November 2010
John Mallinckrodt
Cal Poly Pomona
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