I saw an awesome show on tv about this a few weeks ago. It all has to do with the amont of carbon in the air. Cars, factories, power plants and even our breathing puts tons and tons of carbon into the air. The earth can handle some of this through plants/trees which take in carbon and put out oxygen. Now, as more and more countries become industrialized, more carrs, more factories, more carbon, coupled with less plants and trees, teh earth cannot keep up with teh carbon. the carbon forms the "greenhouse" affect and the earth heats up. It seems pretty basic. I was blown away by the statistic that the earths populaiton doubled since the 1960s.
