I actually had an opportunity to talk a climate scientist at some length about this whole "global warming" thing. Coming from a skeptical point of view, I was mainly lambasting the ability of global climate models to accurately predict temperature changes. (this guy happened to work on global climate models - oops). As it turned out, I didn't know what I was talking about.
This was a guy who works with this stuff day in and day out and he was genuinely convinced that the phenomenon is real. He wasn't taking measurements from parking lots - he was using satellite data.
We can argue all day long about the causes for the warming, but it is happening.