An Inconvenient Truth

root wrote in :

snip
point 1
Are you saying that we are all doomed if the atmospheric CO2 levels
double? Is that the foundation of the entire global warming warming
scare? We can see the effect using the MODTRAN atmospheric model:
http://geosci.uchicago.edu/~archer/c...radiation.html

Doubling the current level of CO2 from 375 ppm to 750 ppm would
cause a temperature rise in the tropics of 0.83K and a lesser amount
at latitudes away from the equator. The effect of atmospheric
absorbtion goes as the log of the concentration of the greenhouse
gases. The log rises very steeply at first but levels off. We are on
the leveled off part. If instead of doubling the CO2 we were to cut it
in half we would go back to the real ice age where glaciers covered
all of Canada.

snip
point 2
It seems clear to me it is the dynamics of the ocean plankton that is
responsible for the reasonable balance between the sources and sinks
of CO2. The ocean has been able to handle an atmospheric CO2 level
10 times the present
[http://www.grida.no/climate/ipcc_tar/wg1/107.htm] so there seems
little to fear for a mere doubling.

snip
point 3
I would welcome a citation for a useful IPCC report. What I have seen
is careful bookkeeping of atmosperic sources that I cannot relate
to a model which fits the ice core records. It isn't a coincidence
that sources and sinks are in relative balance historically. That
is the effect of the process. Man is a newcomer to the picture and
our effect has not been incorporated into the dynamic.


point 1
I am not saying that we are all doomed if atmospheric CO2 levels at all.
What I did say was that most reasonable scientists take doubling of
atmospheric CO2 to be the level at which no amount of remediation will
stave off adverse climatic impacts on the biosphere. This is not a
subtle distinction and if you want to continue this conversation, do not
put words in my mouth. The biosphere in total is remarkably robust and I
simply do not think mankind has the ability to "kill the planet," even
under the worst case scenario of humans triggering a runaway greenhouse
catastrophe which vaporize the oceans. Somewhere, some microbe will
survive even that. I do think that humans won't like living in a world
where atmospheric CO2 has been doubled very much, if only because of the
extra-virulent poison ivy. (http://tinyurl.com/j4cyt)

You do understand what MODTRAN is right? It's not a climatic simulation
but a radiative transfer model. That is a huge huge difference. MODTRAN
gives the change in the radiative balance due to the greenhouse gas
forcing, it does not estimate climatic effects. As near as I can tell
that implementation of MODTRAN has some really simply parameterizations
of clouds and aerosols. Estimating the global temperature rise from a
simple calculation like that, that only does the radiative balance, is
not worth discussing rationally no matter how sophisticated the radiative
transfer model. The climatic response to that change in radiative
forcing will be nonlinear, and assuming there is a one-to-one response
between the change in radiative forcing and global average temperature
increase is silly (but I will admit that if you are trying to impress
people you think don't know what you are talking, it about sounds really
convincing).

The IPCC report you linked to for Point 2 also makes the point that
atmospheric CO2 levels do not trigger ice ages. So your assertion that
reducing CO2 to half of the pre-industrial level would glaciate Canada is
as silly as using MODTRAN as a climate model.


Point 2
It is interesting to note that those epochs of high CO2 are all
contemporaneous with mass extinctions. The higher events 400,000,000
million years ago correlate nicely with the Ordovician and Cambrian
extinctions. Admittedly, that could be just coincidence or the point is
completely tangential (unless you happen to be a trilobyte or a
theropod). However, the most recent time CO2 was over 1000 ppm or so was
65,000,000 years ago or so. The flora and fauna were somewhat different
then and even assuming that they came through without any effect
(ignoring of course the mass extinction at the K-T boundary) does not
necessarily imply modern day flora and fauna will not be adversely
impacted. This is especially true since we know that corals and some
phytoplankton are already starting to show signs of acid stress. The
ocean CO2 inorganic chemistry system can handle a *lot* of atmospheric
CO2, especially on timescales of 1000s of years. There is so much
limestone around available to neutralize excess CO2 that in the long term
no amount of burning of fossil fuel will make a dent in the ocean pH.
However, I don't think we really want to wait around for 5,000 years
while the ocean and atmosphere sort this out. Again, this relation
between near-term adverse effects and long-term return to what we know as
the real chemical equilibrium is a subtle distinction, but then
anthropogenic-induced climate change is a subject of subtlety. Because
of this difference in temporal scales, it is easy to construct half-right
models that purport to show there is no problem.

point 3
I can't tell what you are talking about. It seems like you are agreeing
with my proposition that man's affect on the natural global CO2 cycle may
be important. But then again, maybe you aren't. Beats the hell out of
me.

--
Bill Asher

William Asher wrote:
point 1
I am not saying that we are all doomed if atmospheric CO2 levels at all.
What I did say was that most reasonable scientists take doubling of
atmospheric CO2 to be the level at which no amount of remediation will
stave off adverse climatic impacts on the biosphere. This is not a
subtle distinction and if you want to continue this conversation, do not
put words in my mouth.

Asking what you mean is not putting words in your mouth.


You do understand what MODTRAN is right? It's not a climatic simulation
but a radiative transfer model.

Of course I understand that, and I never represented MODTRAN as anything
else.

it does not estimate climatic effects.

It is the pure physics of the atmosphere and the radiation passing
through it.

As near as I can tell
that implementation of MODTRAN has some really simply parameterizations
of clouds and aerosols.

In fact most of my uses have had "no cloud cover". What the UChicago site
offers is several types of clouds in addition.

Estimating the global temperature rise from a
simple calculation like that, that only does the radiative balance, is
not worth discussing rationally no matter how sophisticated the radiative
transfer model. The climatic response to that change in radiative
forcing will be nonlinear, and assuming there is a one-to-one response
between the change in radiative forcing and global average temperature
increase is silly (but I will admit that if you are trying to impress
people you think don't know what you are talking, it about sounds really
convincing).

One starts with the physics, from that point is becomes less and less
science. When an atmospheric effect suggests a surface temperature change
less than 0.1K, say, it is pretty hard to get excited, but people do.


The IPCC report you linked to for Point 2 also makes the point that
atmospheric CO2 levels do not trigger ice ages. So your assertion that
reducing CO2 to half of the pre-industrial level would glaciate Canada is
as silly as using MODTRAN as a climate model.


Overall there has to be global balance between the solar input and
the re-radiation from the earth. If the CO2 level were halved the
absorbtion of the atmosphere would be reduced, the radiation from
the earth would be increased, and the earth would cool. That is
physics. Now, using silly MODTRAN we find that if the CO2 level
were halved the temperature in the tropics would fall by 17K. As
shown on the ice core site:

http://carto.eu.org/article2481.html

the temperature change from the present to the last major ice
age is about 10K.

Whether or not that means a new ice age, wouldn't you agree that
the consequence of halving the CO2 would be worse than doubling
the CO2?


Point 2
It is interesting to note that those epochs of high CO2 are all
contemporaneous with mass extinctions. The higher events 400,000,000
million years ago correlate nicely with the Ordovician and Cambrian
extinctions. Admittedly, that could be just coincidence or the point is
completely tangential (unless you happen to be a trilobyte or a
theropod). However, the most recent time CO2 was over 1000 ppm or so was
65,000,000 years ago or so. The flora and fauna were somewhat different
then and even assuming that they came through without any effect
(ignoring of course the mass extinction at the K-T boundary) does not
necessarily imply modern day flora and fauna will not be adversely
impacted. This is especially true since we know that corals and some
phytoplankton are already starting to show signs of acid stress. The
ocean CO2 inorganic chemistry system can handle a *lot* of atmospheric
CO2, especially on timescales of 1000s of years. There is so much
limestone around available to neutralize excess CO2 that in the long term
no amount of burning of fossil fuel will make a dent in the ocean pH.
However, I don't think we really want to wait around for 5,000 years
while the ocean and atmosphere sort this out. Again, this relation
between near-term adverse effects and long-term return to what we know as
the real chemical equilibrium is a subtle distinction, but then
anthropogenic-induced climate change is a subject of subtlety. Because
of this difference in temporal scales, it is easy to construct half-right
models that purport to show there is no problem.


Step back and look at what you have said and tell me how much of that
is science and how much is speculation?


point 3
I can't tell what you are talking about. It seems like you are agreeing
with my proposition that man's affect on the natural global CO2 cycle may
be important. But then again, maybe you aren't. Beats the hell out of
me.


I am a scientist (physicist) and have no dog in this fight. I am trying
to sort out the arguments for myself.