I was just watching an educational program called South Park and according to their writers the true cause of global warming is...farts.
According to their expert Randy Marsh-Son of a Bitch, this presents a real dilemma as his research shows that farting is releasing too much methane into the air which is causing global warming, but holding in your farts can lead to spontaneous combustion.
At this point in time the best solution seems to be only to fart in moderation and only when it's really really funny.