Many possible causes of global warming have been raised by old men with long beards and white lab coats. These people study data about stuff (often to do with things) and come up with theories about the causes of Global Warming, including; greenhouse gasses, ocean currents, increased solar activity, changes in lifestyle choices by the northern reticulated monk squirrel, cosmic rays and a reduction in natural levels of freemasonite in the earths crust. Candidates include;