Skepticism: Taking a look at the available evidence and following it to the result.

Denial: Taking a look at the available evidence and then arguing against the it ad nauseam because you don't like what you see.

If you've never heard anything about global warming before (no idea how that should have happened, but let's give you the benefit of the doubt here) you can be skeptical. Then you look at the available evidence and well, that's that. The conclusion is clear. From then on it's denial to run around "sorry, I haven't reached the conclusion yet, please convince me".