It all boils down to money. Period. Money has made a real scientific phenomenon political.
The fossil fuel industry's profits are at the center of this issue. Exxon Mobile sets record profits in the billions of dollars nearly monthly and a lot of this is based on speculation and potential (i.e., worth based on fossil fuels that they have access to and still in the ground). Imagine what happens to them if carbon-based fuels are discontinued?
Therefore these industries and their friends throw untold amounts of $$ into misinformation campaigns and think tanks in order to protect "business as usual" (i.e, their enormous profits).
If you think I'm wrong, consider another natural issue that was caused by man's activities and this time it didn't threaten huge profits...The Ozone Hole. There wasn't this sort of backlash since there wasn't a fraction of the $$ involved. And you could pretty much continue to live "business as usual" with fairly minor adjustments (i.e, spray cans without CFC's in them, etc)
My point - the greater the amount of a certain industries' money is threatened - the louder and better the funding for misinformation and the perpetuation of "doubt".
If you want to learn more about what motivates a skeptic, check out: