Or they don't want the truth. Or like dad used to say "never argue with an idiot".
snip
And here’s what’s odd. In 1989, I could fit just about every scientific study on climate change on top of my desk. The science was still thin. If my reporting made me think it was nonetheless convincing, many scientists were not yet prepared to agree.
Now, you could fill the Superdome with climate-change research data. (You might not want to, though, since Hurricane Katrina demonstrated just how easy it was to rip holes in its roof.) Every major scientific body in the world has produced reports confirming the peril. All 15 of the warmest years on record have come in the two decades that have passed since 1989. In the meantime, the Earth’s major natural systems have all shown undeniable signs of rapid flux: melting Arctic and glacial ice, rapidly acidifying seawater, and so on.
http://www.alternet.org/environment/145838/how_the_mountain_of_climate_change_evidence_is_being_used_to_undermine_the_cause