Dung,
Look at the description of the greenhouse effect. It starts with some backradiation etc, occurring with the sun's rays hitting the earth, and some photons bouncing around, and culminates in 'warmth' that is detected a 100 years out, if. There is no beginning to this theory and there is no end - it is a loosely, imprecisely thrown together storyline to fit a post-ozone regulatory framework, that derives support by attributing warming that has already occurred to itself. We know how many holes there are in that one.

Greenhouse warming may be preceded by a prolonged phase of cooling, for all we care, and yet this cooling wouldn't invalidate the theory. Is that what they tell you? What they tell us, on the other hand, is that every second of warmth is because of CO2. Planetary greenhouse theory itself has problems with offering explanations, for glaciation, and for the early faint sun paradox, for example. The recent paper in Science I pointed out, which no one seems to have picked out, has Pierrehumbert claiming that nitrogen could have behaved like a greenhouse gas in the early earth (if I understood the paper correctly).