It also bears mentioning that simply because the earth has warmed in the past does not necessarily mean that the warming we are seeing now is necessarily caused by the same factors. Thats what science is about, not just reporting "this is what happens" but also trying to get under the hood of what goes on.
To use a gun example:
THe problem that antigunners make oftentimes is that they apply preconcieved notions to the data, a la "crime went up when people had guns, therefore guns must cause crime". In fact, it may be spurious. Are climatologists doing this? Well, looking at alot of the popular "OMG TEH CLIMATE IZ GONNA KILL US!!! OH NOEZZ!!" stuff that you see in the media, yes, you hear "co2 concentrations went up, temp went up, therefore co2 conecntrations are the cause." However, read into the literature and you'll see that there are mechanisms that link between stuff like CO2 and climate warming.
You can do the math for yourself and see. . . if it wasn't for global warming, it would be really really cold. The link between CO2 and a warming effect is not disputed. The question is, how much warming is due to the CO2 that we've put into the atmosphere, and are there any indirect effects, and (as I said before), what happens in the next 100 or so years.
About the "we can't predict the weather, how can we predict the climate" - there's some validity to this statement, of all "climate change" issues, i think its certainly not crazy to challenge those models. But this doesn't mean that we can't know anything about the atmosphere, or about what causes different stuff to occur. Much of our understanding of the atmosphere does have its basis in concrete equations, believe it or not. . . but the applicaton is difficult in a complex system, with variables that might not be anticipated. I'm pretty sure there are some engineers at nasa who would argue that engineering is not straightforward in a complex and changing system, either.
Honestly, scientists are not in the game to make money. . . its just not a good return on the investment. Five to six years of making 25,000 dollars a year, and then maybe an entry level position at a university, and six years later, if you are lucky, you might get tenure, and if you work your butt off, at the end of the job, you'll be making about as much as the guy who went straight from undergrad to working for a "green energy company" was making 15 years ago.
I think there's a lot of people who believe in global warming mostly because it confirms their values about "saving the environment". ANd this turns other people off. And it seems like this anti-global-warming attitude has caused many in the scientific community to be suspicious of anyone who argues against global warming, and then the unfortunate cycle occurs where you have the pro global warming people who allow no room for argument or the complete skeptics, who call anyone who believes a "joiner" , "liberal" or "hippy".
Last comment - what someone else said here is exactly true: we shouldn't forget the forest for the tree of global warming. There are more important things out there than just atmospheric CO2, both in terms of caring for the earth, and in terms of caring for other humans.
IN 50 years, i know i'll look back and laugh at how dumb I was, either for believing in the crock that was global warming, or for not believing it enough to buy that beach chalet in on baffin island.