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March 18, 2012
Warmism in theory and in practice
Skeptics are divided into two camps on the greenhouse effect. The larger camp say it does exist but is of trivial importance for policy and the smaller camp says it does not exist at all.
Being just a humble social scientist with minimal background in physics, it is of no importance for me to take a stand on the question but I have recently been trying to get the issues clear in my head in pursuit of a most unlikely goal: Expressing the theory entirely in plain words so that those of us who are uncomfortable with algebra and technical terms from physics can get a handle on the whole thing.
I think the biggest barrier to understsanding for me has been the old law of the conservation of energy (Yes: I know about Einstein). This law does, I suspect, feel intuitively wrong for almost all of us. It states that energy is neither created nor destroyed. It just bounces around at different times in different places.
Most of us, I think, experience energy as something that gets used up -- as when the gas bottle on our BBQ runs out. But in fact energy is only changed into another form, which may or may not be of any benefit to us.
Lubos Motl, my favourite Pilsener, has been very kind in trying to show me how that works in the atmosphere. This is what I get from it:
When radiation from the sun hits the earth, it warms the earth. But a warm body also gives off heat so the earth warms its atmosphere by convection (contact) but also by radiation. It's not only the sun but also the earth that gives off energy in the form of radiation.
But since the earth is much cooler than the sun it gives off energy in largely different wavelengths. The energy that bounces off the earth is largely in the infrared (IR). But different surfaces respond differently to IR. IR passes right through some gases but gets soaked up by others. Some gases, principally water vapour, soak it up and therefore become hotter. So they become hot bodies too. And what do hot bodies do? They radiate energy in all directions, some of which is downwards toward the earth. And that is the storied Greenhouse effect: The heat that is bounced back towards the earth.
And CO2 is a minor partner in that process. Like water vapour, it too absorbs and subsequently emits IR radiation. Because it is such a tiny fraction of the "greenhouse" process, however, variations in its levels have negligible heating effect on the earth. It's levels of water vapour that matter.
So that's it! That's my attempt to explain greenhouse theory in words only. Partly in response to my desire for a really simple explanation of Greenhouse theory, Roy Spencer has put up his own, much more sophisticated explanation.
And don't blame Lubos for any errors above. Blame my shaky understanding.
I put up on GREENIE WATCH writings by both mainstream skeptics (who believe that a greenhouse effect exists but is trivial) and ultra skeptics who think that no such effect exists at all.
And one of the reasons for that is that the greenhouse effect is a complete red herring. It does not matter whether it is true or not. The real issue is the "amplifications" that Warmists add into their predictions.
What matters above all is of course the facts and the BIG fact in climate is that warming has happened over the last 150 years but at a very slow rate. So the cause of that warming is unimportant. It is clearly so slight (less than one degree Celsius) that it is obviously no problem as it stands. A projection of the known trend into the future is no cause for alarm in any way. Another fraction of a degree of warming by the year 2100 would hardly be noticed.
But the Warmists are unlike other scientists in that they refuse to project from the known to produce the most likely prediction. They postulate that there are "amplifying" factors which will cause the trend suddenly to change and temperature will shoot upwards -- and that claim is sheer guesswork and speculation.
A crucial element in their amplification theory (such as it is) is the effect of clouds. Clouds are the main amplifier that they rely on. With absolutely no proof other than correlations that can be interpreted in completely opposite ways, they say that warming will cause increased cloudiness and that this increased cloudiness will suddenty have a catastrophic warming effect. It is all assumption and imagination, not science. It does not proceed from the known but rather from speculation
For what it is worth I think that greenhouse theory can be expressed in a coherent and plausible way but whether the theory is true or not I don't know. I see evidence for it and evidence against it and am not at all sure that all the influences at work are even known, let alone those we know being well understood.
But looking at the theory as we have it, it is difficult to see how CO2 could have any effect worth attending to. Why? 1). The major source of heating for the earth's surface is radiation from the sun so any greenhouse effect is marginal to that. 2). CO2 is an extremely minor greenhouse gas, with water vapour being the principal player. 3). As a heated molecule, CO2 will radiate heat in all directions, just as the sun does. Only a small fraction of that heat will arrive at the terrestrial surface. So CO2 heating of the earth will be a minor fraction of a minor fraction of a minor fraction of the total heat hitting the earth -- and as such must be totally inconsequential even in theory.
And reality confirms that theory. Fluctuations in CO2 are not followed by similar fluctuations in heating. Even Hume's stringent theory of causation requires that the effect regularly follows the cause and CO2 fluctuations over the last 150 years (and indeed in paleohistory) have not regularly been followed by similar fluctuations in temperatures.
It is only the incessant "adjustments" of the temperature record of the last century or so by Jim Hansen (and Michael Mann's false "hockeystick" record) that seem to show some semblance of the two factors moving in tandem. And having a fierce advocate of global warming in charge of the data on global warming is even in theory having the fox guard the henhouse. And the obvious prediction from that theory is confirmed by Hansen's regular alterations of the temperature record to suit his theory. Even he however has not been able to adjust out of existence the temperature standstill of the last 15 years or so -- at a time when CO2 levels (a record out of his control) have been rising steadily. Hume's minimal conditions for CO2 levels to be a cause of terrestrial temperature fluctuations are therefore not met.
But as I have pointed out, the greenhouse effect is simply not the issue. Even given all they want from greenhouse theory, Warmists still cannot predict anything alarming. They have to add on "amplifications" to predict any temperature rise worth attending to. And those amplifications are the real weak point in alarmism -- amplifications that are sheer speculation. And improbable speculations based on very partial knowledge are no basis for public policy.
CODA: I suppose I should add in a small coda about Venus. Warmists often assert that the high surface temperature of Venus is an example of "runaway" global warming caused by high levels of CO2. It is of course no such thing. The high Venusian surface temperature is the result of a simple adiabatic process. The huge Venusian atmosphere leads to huge atmospheric pressure at the surface which in turn leads to a very high temperature.
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