here is something i learned in college, besides how to drink:
relativly new data colleceted from "frozen air pockets in glaciers" contain perfectly preserved air from a given time period when it was originally trapped there. these air samples were dated and show that CO2 levels naturally increase over time, and then result in a sudden "ice age", which drops CO2 levels, and then gradually rise again. this repeats its self over and over. some scientist think that the increased CO2 levels actually cause the ice age.
back in the 80s scientists thaught that these green house gasses would decrease the globle temperature. caused by teh gasses creating more clouds and inturn decrease the temperature. (thats why areas like miami have a higher overall temperature than areas like equador). but now, many of those same scientists think the exact oposite, that green house gasses increase the globle temperatures. so thats something else to think about.
increasing CO2 levels has been shown to be a natural process on earth. but after the industrial revolution, there has a "dramatic" increase in CO2 levels. basically increasing the levels faster than they naturally would. so you could say that global warming is a NATURAL process, slightly speed up by man. and will result in a ice age. so, for example, if its natural for the earth to gradually heat up 1 degree every 1000 years, with man's help we've cut that to 1 degree every 100 years. (but you can look up the exact number, remember im lazy.)
but dont freak about the ice age thing, its only a 10 degree drop in average world temperatures, and those close to the equator would hardly notice. though the polar ice caps may drop down as far as tennessee.