We've been sidetracked into a different subject, but I'm going to add to that, anyway. I think some posters fail to grasp the totality of Global Warming in an attempt to deny the impact we people have. Global Warming is the phenomenon of raising the temperature of the earth's SURFACE and its immediately-adjacent atmosphere. It has TWO major causes. One certainly is changes to the gasses and particulates in the atmosphere, and that's a more recent process. The atmosphere has two related functions here. It reflects a portion of the radiation arriving from the sun back into space, and it allows the rest to penetrate all the way to the surface. This process is selective - the split between reflected and transmitted depends on the frequency or wavelength of the radiation. In the case of infrared (heat) rays, higher-energy (shorter wavelength) rays are passed through to the earth more easily. The process is exactly the same for radiation passing the other way. That is, heat (IR) rays emitted by the earth's surface (and all its structures, etc.) will head out through the atmosphere into space, subject to the same split of transmitted out / reflected back to the surface. By far the majority of the heat energy arriving at the earth's surface (well over 90%) gets sent back out into space, but not all. What impacts the Global Warming phenomenon is what's called the "Greenhouse Effect" because it is the same thing as what the glass windows of a greenhouse do. Of all the infrared radiation passed thought the atmosphere to the surface, most is absorbed and heats thing up. Then those things re-emit infrared radiation BUT at a lower energy (longer wavelength) than the original incoming infrared. This radiation trying to p[ass through the atmosphere into space is reflected back to earth more efficiently than the original higher-energy incoming radiation. In effect, the atmosphere traps that heat on earth so it cannot be lost to space. Recent changes to the makeup of the earth's atmosphere have enhanced its tendency to trap lower-energy infrared radiation, and thus has shifted the traditional balance of infrared energy flow in the direction of keeping more of it inside the atmosphere.That shift, caused mostly by a wide variety of human activity, is a major cause of Global Warming.
However, long before that, other causes have been active. Just the use of any energy source for our benefit always produces some waste heat (as low-energy infrared radiation) of the type that is easily trapped by the atmosphere. This can include burning fuels for heat, using electrical devices for work, even our own simple daily living processes (and there are more of us, and growing!) In addition, the simple act of burning any fuel releases carbon dioxide which is one of the gasses in the atmosphere that tends to prevent the escape into space of low-energy infrared. So, even our simpler activities contribute to Global warming significantly, never mind those that release new odd chemicals into the atmosphere.
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