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The logic of global warming theory
« on: July 28, 2013, 10:27:24 PM »
The logic of global warming

Global warming theory makes a claim: there is more heat entering the earth than radiating from it, and we caused this through carbon dioxide emissions. What is the justification for this claim?

1) In the laboratory an increase in carbon dioxide concentrations increases infrared absorption. Carbon dioxide can be shown to absorb certain wavelengths and to re-radiate this heat in all directions, including back towards the planet, thus warming it.

2) We assume this works in the atmosphere just as it does in the laboratory. The assumption is an essential one if any knowledge is to be transferred from laboratory to nature. Secondly, we have no reason to doubt it, no suggestion of an explanation for why this would not be so out in the world.

3) Evidence shows a correspondence between increased carbon dioxide levels and increases in climate temperature. Where this does not happen plausible explanations-- primarily increases in airborne particulate matter-- account for the failure. Thus the predicted effect is actually taking place.

4) By burning fossil fuels we have added a large amount of carbon dioxide to the atmosphere.

A denialist must counter this solidly-supported claim. Surely points 1, 2, and 4 are unassailable, certainly 1 and 4 are. To attack 2 would be to attack the entire scientific enterprise. To be sure the trip from laboratory to world must be taken cautiously, for in the world there are factors of which we know nothing. But the argument for the validity of this leap is that the predicted result appears, and no better explanation is at hand. This is all science can ever offer.

So the attack must be at 3. But since the correspondence holds, the only way to attack 3 would be to offer a better correspondence with some other factor. Otherwise we have no cause to doubt 3. Since greenhouse gas concentrations, if the identifiable counter-causes don't interfere, correspond to warming temperatures, the scientific case is solid, though of course vulnerable to some alternative theory. But it is the denialist who must come up with this alternative theory with explanatory evidence.

One note: the idea of “natural variation” is bogus. It is just a device to allow yourself to doubt where there is no cause for doubt. “Natural variations” require causal explanations just as do human produced variations. It is not enough to attribute some variation to “nature.” That is just a way of relieving oneself of the obligation of providing an explanation.

Glenn Tamblyn

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Re: The logic of global warming theory
« Reply #1 on: August 01, 2013, 05:59:44 AM »
Some general points.
2. We don't just assume it. We can calculate what patterns of emission and radiation we expect to see at different heights in the atmosphere column, from the ground all the way to space, looking up or down, under different states for the atmospheric column.
Then compare our calculations based on theory with actual observations. And this has been done. Repeatedly, under all sorts of conditions. With exceptional agreement between theory and observations.

The earliest of these studies, using the Nimbus 3 satellite in 1969 that I know of was Conrath et al 1970 here
(Nasa used to have a non-paywalled copy but it is off line at the moment. If anyone has an accessible copy please link it here

The key graph from the paper (Fig 5) shows the Earth's OLR spectrum from theory and observation. The two curves had to be shifted vertically on the graph to separate them since they matched almost perfectly. Theory had nailed the radiative physics of the GH Effect by the time Neil and Buzz were walking on the moon!!


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Re: The logic of global warming theory
« Reply #2 on: August 08, 2013, 10:16:38 AM »
One additional big evidence for CO2 greenhouse effect, which is often forgotten, is Venus. Planet Venus, i mean. Venus' athmosphere is entirely made out of CO2, concentration is about 96%. And, we know from direct observations (including probes) that Venus' average surface temperature is much, much higher than one of any other planet in Solar system:

 - mean surface temperature, Venus = ~462 degrees C;
 - mean surface temperature, Mercury = ~47 degrees C;
 - mean surface temperature, Earth = ~15 degrees C;
 - mean surface temperature, Mars and other planets = below 0 degrees C.

If this doesn't prove greenhouse effect, then probably nothing would. Especially if one does know, from physics, that amount of energy emitted by any hot body is proportional to FOURTH power of temperature difference between the body and environment - thus that 462 is INSANE thing. In kelvins, Venus has more than 2,5 times higher temperature than other inner planets; 4th power of 2,5 is 39,0625; so Venus is some 40+ times more efficient at holding ("capturing") heat as any other planet of our solar system.