Interestingly, the key to understanding this issue of the amount of warming does not actually lie in greenhouse gas theory. Most scientists, skeptics and alarmists alike, peg the warming directly from CO2 at between 0.3 and 1.0 degrees Celsius for a doubling in CO2 levels ... If this greenhouse gas warming was the only phenomenon at work, we would expect man-made warming over the next century even using the most dire assumptions to be less than 1C, or about the same amount we have seen (non-catastrophically) over the last century.
As I said before, man-produce greenhouse gases (CO2) may produce a small, minuscule, amount of warming, which is insignificant, quantitatively, among the natural variations. The catastrophic predictions aren't based on this minuscule warming. They are based on "positive feedback loops".
This theory hypothesizes that small changes in temperature from greenhouse gas increases would be multiplied 3,4,5 times or more by positive feedback effects, from changes in atmospheric water vapor to changing surface albedo.
Let me emphasize again: The catastrophe results not from greenhouse gas theory, but from the theory of extreme climactic positive feedback. In a large sense, all the debate in the media is about the wrong thing! When was the last time you saw the words "positive feedback" in a media article about climate?
Now, this positive feedback has absolutely no scientific base or proof, it's just a guess based on nothing - well, based on the ideological bias of the"scientists". It is not based on scientific data or theory.
Here is what Christopher Monckton writes about it:
The feedback factor f accounts for at least two-thirds of all radiative forcing in IPCC (2007); yet it is not expressly quantified, and no “Level Of Scientific Understanding” is assigned either to f or to the two variables b and κ upon which it is dependent....
Indeed, in IPCC (2007) the stated values for the feedbacks that account for more than two-thirds of humankind’s imagined effect on global temperatures are taken from a single paper. The value of the coefficient z in the CO2 forcing equation likewise depends on only one paper. The implicit value of the crucial parameter κ depends upon only two papers, one of which had been written by a lead author of the chapter in question, and neither of which provides any theoretical or empirical justification for the IPCC’s chosen value. The notion that the IPCC has drawn on thousands of published, peer-reviewed papers to support its central estimates for the variables from which climate sensitivity is calculated is not supported by the evidence.
As I said, there is absolutely no scientific basis to the alarmist scare mongering. The IPCC, including the dubious positive feedbacks, predicts (i.e. guesses) a rise of 2-4 deg C in temperature, and 60-100 cm in sea levels for the year 2100. Even these predictions aren't yet catastrophic.
The chief scare mongers, Al Gore and Dr. James Hanson speak of 8-10 degrees, 10 m sea level rise and "tipping points" within 30 years. This scare mongering is based on absolutely nothing, not even on the exaggerated IPCC numbers.