Originally Posted by StuM
Well, I would think it obvious from the question that I had looked.
"Can you explain what you mean by 'Co2 has almost reached its thermal absorption maximum anyway.' I can find no reference to this anywhere."
"I can find no reference anywhere" should infer to a sharp reader that I had
looked. Or were you just being facetious?
Of course, it was a mostly rhetorical question, though I did hope 33 would explain what he meant by thermal absorption maximum.
It's actually basic 'denier science 101', and has been around in varying forms since the early 20th century. Usually it's called 'CO2 saturation', and its' root is usually in not understanding the system completely or misapplication of data (or just an agenda, either open or hidden). In one word about saturation (which leaves out all the complexities of gas formulas) there is always this 'Venus'.
Just to be sure, I read (and reread) the article you suggested at the wanna be MSM site WUWT, where I found reverse-alarmist statements like this:
"Plant growth shuts down at 150 ppm, so the Earth was within 30 ppm of disaster. Terrestrial life came close to being wiped out by a lack of CO2 in the atmosphere. If plants were doing climate science instead of us humans, they would have a different opinion about what is a dangerous carbon dioxide level."
Now contrast that with this statement about the same thing:
"Studies addressing the effects of low [CO2] on plants are also fundamental for understanding plant evolution in response to changes in resource availability through time – primarily since changing [CO2] has been shown to have major implications for plant fitness (Ward et al., 2000
). Modern plants grown at low [CO2] (150–200 ppm) exhibit highly compromised survival (Ward & Kelly, 2004
) and reproduction (Dippery et al., 1995
) at conditions that occurred only 18 000–20 000 yr ago. Such findings beg the question of how glacial plants survived during low-[CO2] periods, especially considering the lack of evidence for plant extinctions during these times. Furthermore, past work has demonstrated that low [CO2] has the potential to act as a strong selective agent on plants, and therefore evolutionary responses may have ameliorated some of the negative effects of low [CO2] in the past (Ward et al., 2000
). However, the full suite of mechanisms accounting for these adaptive responses is currently unknown, as well as how adaptive processes may have been influenced by other interactions with climate change (for a discussion of possibilities see Sage, 1994
; Sage & Cowling, 1999
; Ward et al., 2000
; Beerling, 2005
). Furthermore, it is also important to consider that any genetic changes that occurred in the recent geologic past as a result of low [CO2] may continue to affect the responses of plants to rising [CO2] throughout the next century (Strain, 1991
; Sage & Cowling, 1999
There were also the usual manipulated, uninforming and/or unreferenced graphs. I can entirely understand how someone who thought the 'information' here was accurate or factual would deny the work of thousands of scientists and hundreds of years experimentation. What's harder to understand is how anyone would think it is
accurate and informative.
One can find virtually the same article on another wanna be MSM sight:
4. Carbon dioxide is already absorbing almost all it can « JoNova
For a more in depth
, but still a layman's explanation one could read this:
A Saturated Gassy Argument « RealClimate
Open minds are optional for reading this, verifiable measurements tend to be more reliable.
And finally, I just like this shredding of the 'Saturation Myth' better.
How does the Earth’s blanket of air impede the outgoing heat radiation? Fourier tried to explain his insight by comparing the Earth with its covering of air to a box with a glass cover. That was a well-known experiment
— the box's interior
warms up when sunlight enters while the heat cannot escape.(10)
This was an over simple explanation, for it is quite different physics that keeps heat inside an actual glass box, or similarly in a greenhouse. (As Fourier knew, the main effect of the glass is to keep the air, heated by contact with sun-warmed surfaces, from wafting away. The glass does also keep heat radiation from escaping, but that's less important.) Nevertheless, people took up his analogy and trapping of heat by the atmosphere eventually came to be called "the greenhouse effect."(11*)
Not until the mid-20th century would scientists fully grasp, and calculate with some precision, just how the effect works. A rough explanation goes like this. Visible sunlight penetrates easily through the air and warms the Earth’s surface. When the surface emits invisible infrared heat radiation, this radiation too easily penetrates the main gases of the air. But as Tyndall found, even a trace of CO2
vapor, no more than it took to fill a bottle in his laboratory, is almost opaque to heat radiation. Thus a good part of the radiation that rises from the surface is absorbed by these gases in the middle levels of the atmosphere. Its energy transfers into the air itself rather than escaping directly into space. Not only is the air thus warmed, but also some of the energy trapped there is radiated back to the surface, warming it further.
=> Radiation math
That’s a shorthand way of explaining the greenhouse effect — seeing it from below, from "inside" the atmosphere. Unfortunately, shorthand arguments can be misleading if you push them too far. Fourier, Tyndall and most other scientists for nearly a century used this approach, looking at warming from ground level, so to speak, asking about the radiation that reaches and leaves the surface of the Earth. So they tended to think of the atmosphere overhead as a unit, as if it were a single
sheet of glass. (Thus the "greenhouse" analogy.) But this is not how global warming actually works, if you look at the process in detail. What happens to infrared radiation emitted by the Earth's surface? As it moves up layer by layer through the atmosphere, some is stopped in each layer. (To be specific: a molecule of carbon dioxide, water
vapor or some other greenhouse gas absorbs a bit of energy from the radiation. The molecule may radiate the energy back out again in a random direction. Or it may transfer the energy into velocity in collisions with other air molecules, so that the layer of air where it sits gets warmer.) The layer of air radiates some of the energy it has absorbed back toward the ground, and some upwards to higher layers. As you go higher, the atmosphere gets thinner and colder. Eventually the energy reaches a layer so thin that radiation can escape into space. What happens if we add more carbon dioxide? In the layers so high and thin that much of the heat radiation from lower down slips through, adding more greenhouse gas means the layer will absorb more of the rays. So the place from which most of the heat energy finally leaves the Earth will shift to higher layers. Those are colder layers, so they do not radiate heat as well. The planet as a whole is now taking in more energy than it radiates (which is in fact our current
situation). As the higher levels radiate some of the excess downwards, all the lower levels down to the surface warm up. The imbalance must continue until the high levels get warmer and radiate out more energy. As in Tyndall's analogy of a dam on a river, the barrier thrown across the outgoing radiation forces the level of temperature everywhere beneath it to rise until there is enough radiation pushing out to balance what the Sun sends in. While that may sound fairly simple once it is explained, the process is not obvious if you have started by thinking of the atmosphere from below as a single
slab. The correct way of thinking eluded neary all scientists for more than a century after Fourier. Physicists learned only gradually how to describe the greenhouse effect. To do so, they had to make detailed calculations of a variety of processes in each layer of the atmosphere. (For more on absorption of infrared by gas molecules, see this discussion in the essay on Basic Radiation Calculations.)
<= Radiation math
Despite Fourier's exceptional prowess in mathematics and physics, he lacked the knowledge to make even the simplest numerical calculation of how radiation is absorbed in the atmosphere.(12*)
A few other 19th-century scientists attempted crude calculations and confirmed that at the Earth’s distance from the Sun, our planet would be frozen and lifeless without its blanket of air .(13)
Tyndall followed with rich Victorian prose, arguing that water vapor "is a blanket more necessary to the vegetable life of England
is to man. Remove for a single summer-night the aqueous vapour from the air... and the sun would rise upon an island held fast in the iron grip of frost."(14)
Tyndall needed no equations, but only simple logic, to see what many since him overlooked: it is at night that the gases are most important in blocking heat radiation from escape, so it is night-time temperatures that the greenhouse effect raises the most.
You can read the whole story here:
(And yes there is information on the subject at SkepticalScience, though it too is under 'saturation' not 'thermal absorption maximum'.)