Canie...you were correct...it was 0.3% 50 years ago. It is 0.4% now (or will be in 10 years). This is one of the main arguments that Michael Crichton used in the appendix of his fiction novel about evil environmentalists and the hoax of climate change, for which he won the "journalism" award from the American Association of Petroleum Geologists...which is both appalling and interesting at the same time. Crichton used a football field to explain this...I guess 80 yards of nitrogen, 19 of oxygen, and about a foot of CO2. While I don't understand in any detail how exactly how it works that CO2 at 380 ppm has such a huge effect, it has been known for 200 years that it does. This is just atmospheric physics. The CO2 concentration on Mars and Venus are known, and I'm sure that adjusting for distance from the sun they can determine what part of the surface temperature is due to CO2: freeze butt off vs. melt tin. So, we need some atmospheric scientist to explain this is some detail, but simply. Maybe HW is bored and will Google this. As for your link, I started to read it but my 9 neurons all started screaming "make it stop". The author pretty much discredited himself with various rants about Gore being uglier than Bush, etc.
Chris