There's one more factor, though, that makes our world extra confusing. On reflection, virtually everything you know is based on trust in other people! Life's too short to personally verify more than a sliver of facts. Unless you actually replicate the experiments in your physics textbook, even your knowledge of "hard science" rests on your unproven - and often false - belief that big groups of people don't converge on shared lies.
.. Under such circumstances, doubts aren't just defensible; they're a strong symptom of truth-seeking.
Global warming is a case in point. The vast majority of people who believe in global warming have only one real piece of evidence: Climatologists believe in global warming. In fact, most believers don't even have that. All they really know is that many non-climatologists say that climatologists believe in global warming. As far as most non-experts are concerned, the real issue is simply, "Are big groups of people lying?"
If this sounds paranoid, recall the plight of Ivan Ilych. Big groups of people often lie. Maybe you have enough first-hand knowledge to say, "Not in this case." Yet most people - even people who agree with you - lack such first-hand knowledge. Ridiculing skeptics may make them shut up. But when you do so, you're promoting not truth, but mere conformity.