If you're not from the U.S. you have to understand the background of mendacity that flows through nearly the entire culture. That's a big part of the backdrop for fairly deep levels of distrust, whether it's of a company, one's colleague, the gov't, etc.
For example-- I was watching a political show where the question was something about global warming. One of the guests gave a reply that sounded vaguely reasonable but wasn't clear. The host tried to rephrase the question, and the same respondent again gave a suspiciously confusing reply. This caused the host to drill down on a simpler question-- did the guest believe that global warming was real and that human activity has contributed to this global warming? This time the guest answered a different question, addressing the reality of global warming but ducking the issue of causes. This went on for about 45 seconds before the host finally forced the guest to give a response that revealed the guest was in fact a climate denier. Honestly, it was like watching that scene in Blade Runner with the Voight-Kampff test, except on humans.
Being an American myself, I could immediately tell what the guest's purpose was: to sound like they agreed with the other (sensible) panelists, in order to give more credibility to a climate denial talking point that their job depends on. It's a planned strategy essentially of "denial-in-depth"-- try to sneak FUD into an otherwise good faith discussion, and if that doesn't then reveal your crude talking points for what they are.
In a weird way, the process of figuring out someone's level of earnestness makes me think of the "Sie" to "du" journey in German. Except here in the U.S., it's a slow slog of figuring out exactly how a friend spouts bullshit and under what circumstances, and then figuring out if there's enough earnestness left to become close friends.
That's not a good yes or no question, because it not only unites two different points together, but also really depends on your definition of global warming, and also ties a lot of other different issues into it. You could for example believe that humanity affects climate to some extent, but still think that it's not bad enough to support environmentalists from economics point of view. You could also believe that this climate change is real, but is not caused by human activity and is just a part of a natural process.
I just don't think that boxing a complex issue into a boolean is a good idea.