At the heart of the anthropogenic global warming (or AGW) hypothesis is the so-called "greenhouse effect", which is widely discussed on the internet (so I won't go over what is readily available elsewhere). Climate scientists have, apparently, all been taught that the carbon dioxide greenhouse effect is a long-known fact, and confirmed by overwhelming experimental observations along many lines of evidence. Physicists, however, tend to have independent opinions and more critical views (which are spread out over the range from total acceptance to total rejection). A few of the current articles, available online, by physicists critical of the greenhouse effect, are: Prof. Claes Johnson, "Climate Thermodynamics"; Gerhard Gerlich and Ralf Tscheuschner, "On the Barometric Formulas and Their Derivation from Hydrodynamics and Thermodynamics"; and Tom Vonk, "CO2 Heats the Atmosphere...A Counter View." The first two are math intensive, while the third is more narrowly focused and clearly physical in tone. I would not ordinarily feel the need to write an article on the subject myself, but I have to discuss openly the incompetence I see being played out in many sciences, across the board. I have lately found myself posting on forums I have come across, where the physicist's view of the greenhouse effect seems to be neglected, or even haughtily dismissed by climate scientists; and I might as well say here, in my own backyard so to speak, what I have said elsewhere -- particularly because I haven't seen anyone voice my own understanding of the physics of it, in a clear, strong manner.
Putting my position succinctly, I have come to consider the greenhouse effect completely wrong, the more I have read about it. The following is basically a copy of one of my most recent posts on the subject.
The imaginary character of the atmospheric greenhouse effect is most readily seen in the energy budget diagrams that are derived from it (look up "Trenberth energy budget", or see my last post here), where the surface of the Earth is shown as emitting more energy than is provided by the Sun (the sole power source for the global climate system). This is a clear violation of the conservation of energy (never mind the "laws of thermodynamics" that others talk about), but today's climate scientists as a whole seem to have been taught otherwise, and are simply incompetent.
So forget what even the AGW skeptics who believe in the greenhouse effect are putting out, it is all flawed, as the obvious violation of energy conservation should make clear. CO2 and other IR absorbing gases cannot "trap" or even "slow down" heat transport through the atmosphere. The radiation they absorb and emit is simply heat energy, and that heat flows from warmer regions to colder, by whichever path (convection, conduction, or radiation) is available and is the most efficient.
[In fact, to make it simple, I suggest that heat radiation should probably be considered as "heat conduction by radiation," and perhaps treated as an effective thermal conductivity of the atmosphere, rather than radiation per se, since climate scientists, and thermodynamicists in general, have stumbled badly trying to deal with it as the latter. This is my own, recent idea, which I have noticed an echo of in the article by Prof. Johnson, so it is certainly not a new idea in the world of science, although the IPCC and those who believe in the greenhouse effect (including many physicists) don't seem to have heard of it. The physics behind it can be stated as, the IR radiation from molecules in a cooler region cannot be absorbed by the molecules in a warmer region, because the "cooler" IR photon does not have enough energy to excite the "warmer" molecule to its next higher energy level. Heat, including heat radiation, can only flow from warmer to cooler regions.]
The temperature profile of the atmosphere is dictated solely by gravity acting on the ocean of air and the specific heat of the air, which imposes a temperature "lapse rate" (a declining temperature) with height given by -g/c, a constant rate, where g is the acceleration due to gravity and c is the specific heat. Note that this is entirely independent of the presence of any IR absorption by gases in the atmosphere. The available heat energy must be distributed in accordance with that constant lapse rate, and IR radiation is just one pathway for the heat to be distributed. Thus, IR absorption and emission in the atmosphere can only enable more efficient (faster) heat transport through the atmosphere, they cannot trap heat, or slow it down. And as you can read elsewhere on the internet (see, for example, www.appinsys.com/globalwarming/), the evidence from climate science itself is that the co2 greenhouse effect cannot explain the global temperature record, particularly over the last ten years or so, when atmospheric co2 has substantially increased, while the temperature has levelled off or declined very slightly.
The only thing that has kept the greenhouse theory alive, even after the lapse rate was observed and explained by simple thermodynamics, has been the breathtaking magnitude of the entrenched incompetence among climate scientists. It can be traced, to a substantial degree, back to Carl Sagan's popular appeal, around 1960, to a "runaway greenhouse effect" for the extremely high surface temperature of Venus. But he was wrong (and a bad, self-serving scientist), and the lapse rate for the huge ocean of air on Venus (providing a surface pressure 90 times that on the Earth) explains that too, although again, you will find climate scientists referencing Venus to "prove" the greenhouse effect. This is not just your usual scientific discussion or genteel disagreement, then, it is the tip of a world-sized incompetence in science. Indeed, it involves a religious belief among climate scientists in the greenhouse theory, a belief up to now immune to even the clearest logical and evidential arguments.