http://www.scotese.com/climate.htm
This shows clearly a geological history of global temperature.
Note the plateau at 22 degrees C. These times included ANY time when
the atmospheric CO2 exceeded approximately 600 ppm, including millions
of years when it ixceeded 2000 ppm with no additional corresponding
warming whatsoever. What source to you use to imply that that is
either innacurate or irrelovent? If we are planning to expend the
herculean efforts involved in a 550 ppm stabilization (again, I am
sceptical that 25% current emissions would produce that) and 600 ppm is
the response cieling, then what's the point??
That's an awfully crude diagram to be basing that much importance on. The paleoclimate
evidence isn't really that obliging regarding global mean surface temperature.
You may want to have a look at an alternative representation of this data.
http://www.globalwarmingart.com/wiki/Image:Phanerozoic_Climate_Change_Rev_png
Note that image only claims a rough proxy for tropical sea surface temperature.
You may also wish to consider that events that may be too short to capture on a half-billion year time scale graph (never mind one obviously drawn freehand, more of a cartoon than data) can be plenty long enough to make matters very nasty for humans.
Finally, if your model of things is correct, we really ought to stop emitting immediately, because a 7 C rise in mean surface temperature is not something to shrug off.
> Simply because there are a great deal of factors at
> > work other than carbon. Venus isn't a fair comparison due to several
> > factors, among them, 1) it is closer to the sun.
> Not close enough. Do you understand the relationship between the
> Stefan-Boltzmann law and planetary surface temperature? Again this is
> first-year stuff.
Yes, I understand the concepts involved in blackbody radiation,
and in radiative forcing. It is nonetheless a fact that once the
atmosphere is completely opaque at the indicated range of wavelengths,
adding more opacifier doesn't result in additional warming.
Then why is Venus warmer than Mercury?
> Us old guys are partial to Wallace and Hobbs, "Atmospheric Science, an
> Introductory Survey" 1977 but there are plenty of alternatives. I understand
> that there is a new edition of W&H as of 2006.
> 2) Our moon has
> > been shown to have gravitationally "skimmed" our atmosphere such that
> > there is a very great deal less total volatile volume to work with on
> > earth.
> News to me. Are you making that up? What does that have to do with anything
> if so? And what do you mean by "volatile"?
No. gasses leak from the atmosphere when the average temperature
velocity is greater tthan 1/10 of escape velocity. For the earth, the
moon produces a very significant reduction (circa 15%) in that escape
velocity which in turn increases the amount of atmospheric leakage.
Supposing I grant this point. I find it plausible but not especially relevant. You didn't explain why it has anything to do with the matter at hand.
> I'd just as soon you dropped this unpromising hodge-podge and followed up on
> optical depth and Stefan-Boltzmann, but feel free to defend it if you can.
> > Okay, adult, present the alternate source of energy you are
> > supporting. Or present some evidence that 25% of current emissions
> > would produce a stable carbon cycle.
> Let's try to take our time here. I will just answer this one question, and
> then we can see how it impacts the rest of your opinions.
>
> I refer you to IPCC WG1 TAR 3, section 2.3.2.2; you can find it at
> http://www.grida.no/climate/ipcc_tar/wg3/075.htm .
The TAR generally bothers me as a source. It tends toward
political motivation and for the most part presents as a collection of
statements without the bulk of the evidence to support them.
To claim that the IPCC WGI is political will not win you friends among people who know people on the committee.
Leaving that aside, the reports summarize the primary literature and present the statements as well as the references to the relevant primary literature.
However,
accepting it as a valid source, I still don't see a stabilization
mechanism defined in your reference, merely a comparison of different
"stabilization scenarios", and a bald assertion that these are indeed
stabilization scenarios. What mechanism produces the carbon
sequestration that you and they assert will remove the annually added
co2 from the atmosphere?
The equilibration is similar to the preindustrial equilibration to mean volcanic sources. Many processes speed up when a reagent's concentration is increased. It's not surprising; eventually the concentration settles to where it would be if there were more volcanos.
the global land use currently in play
prevents that mechanism from being the addition of more forest land,
and the ocean under warming conditions is a source of co2, not a sink.
Ah, only if you hold atmospheric CO2 constant. It's a sink if you increase CO2 holding temperature constant. Eventually concentration wins.
I am oversimplifying here and don't want to get into it any further.
The trouble with your approach is you put too many balls in the air for me to pursue all of them.
It seems to me your argument (which peculiarly seems perfectly happy with a 7 C increase in mean temperature, albeit on an unspecified time scale) remains based on the idea that the greenhouse effect saturates. It seems to me that a reasonable discussion will take one point at a time.
Suppose we postulate that the CO2 "saturated" temperature of the Earth is 22C, ie, 295 K. Now the orbit of Venus is at 67/93 of the earth's orbit, so that by the square law it receives (93/67)^2 as much irradiation per unit area. Even leaving aside albedo, which would incline in favor of the argument, by Stefan-Boltzmann law the temperature of Venus should go as the fourth root of the irradiation, or as the square root of (93/67) * 295 = 347 K, not even enough to boil water, less than 100C. So what then would account for the actual surface temperature in excess of 400C?
mt
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