Most people believe what they want to believe or their beliefs follow political party lines. Some tend to follow the crowd or believe what seems to be the trendiest at any one time. You don't need to be a scientist or watch a movie to see whats going on. Just open your eyes and look around........
This figure shows the variations in concentration of carbon dioxide (CO2) in the atmosphere during the last 400 thousand years from ice cores and direct measurements (since 1950). Throughout most of the record, the largest changes can be related to glacial/interglacial cycles within the current ice age. Although the glacial cycles are most directly caused by changes in the Earth's orbit (i.e. Milankovitch cycles), these changes also influence the carbon cycle, which in turn feeds back into the glacial system.
Since the Industrial Revolution, circa 1800, the burning of fossil fuels has caused a dramatic increase of CO2 in the atmosphere, reaching levels unprecedented in the last 400 thousand years. This increase has been implicated as a primary cause of global warming.
http://en.wikipedia.org/wiki/Global_warming