Tim Flannery was just on the daily show promoting his new book on the topic . Feynman is one of the experts in the field. I like reading science books and many of them mention global warming and other things mentioned in this article. For the most part I believe from what I read global warming is a geological process, but things like astronomy (the wobble of the earth, the tilt of the earth also effect how much sunlight the earth receives) and human processes can also effect global temperature. I believe the article was misleading in saying that co2 were high at the dawn of the cambrian age because it was the co2 put into the air by a series of valconoes that helped to end that billion year ice age (actually scientist don't know that for sure, unlike evolution which has a ton of evidence, this is just the most plausible theory given the evidence in existence) and made earth more modern by our standards. It wasn't there were high level of c02 during the ice age, it was that the co2 helped end that ice age and the start of the tetonic rumblings obviously shared a small amount of period in time with the ice age it was causing to come to an end.
Most global warming and cooling takes place because of geolgoical processes like volcanoes putting co2 into the air, for example the severe ice age 10 million years ago that ended only 10,000 year ago was caused by the rise of the himalyas when india collided with asia, the himalyas are tall and changed wind direction in a ton of important ways, furthermore, the isthumus of panama rose out of the sea and that changed the ocean routes because before that the pacific and atlantic meant, whenever oceans patterns are thrown off it vastly changes the weather. When those two things happened at roughly the same time, lots of things changed (including large parts of africa turning from jungle to savannah and apes learning to walk to deal with the changed environment).
For the past 40 million years or so we have been in a bit of ice age in that there are places on earth with ice year round, something that didn't happen for most of the time dinosaurs were on the earth for example (the dinosaurs did endure their own 50 million year ice age though), and during the past 40 million years we have varied from moderate ice age, like today, to severe ice age like the one that ended 10 million years ago. I think I saw the number somewhere that humans are producing 3 to 4 % of the co2 in the air, co2 is a greenhouse gas which has the short term effect of causing global warming. How important a 3 to 4% increase is and what the long term effects are relatively unknown, but its very dangerous to say the least to mess with geologic processes because we might be throwing it off the earths natural processes and lead the world to become a dried desert or it might lead to a huge ice age or might not be enough of an influence to really mess with the earth's natural processes at all-from what I understand, nobody really knows.