Mike M. answered 11/15/21
Experienced public speaking coach and mentor
The field of political science, particularly about public opinion, should have lots of hypotheses as to why some deny climate change. There is even quite a bit of research on the public opinion of climate change specifically.
First off, I'd say there are lots of shade of denial: there is denying there is climate change at all, there is accepting that it is happening but it's not caused by humans, there is accepting we are causing it but denying that it's as serious as some of the more serious/alarmist prognosticators are saying, there's denying that we can do anything to stop it, and there is denying that what we can do to stop it is worth the cost.
Assuming you are speaking about the first few types, I'd say this: none of us directly experience global climate, we directly experience local weather. Individual weather events (a hurricane, a fire, a drought, etc.) are not evidence of a trend, and weather can be hard to measure from our everyday sensory perceptions (I'm still surprised at how dark it gets every winter, for example). So ALL of us depend on the experts and the media to tell us what's going on with the Earth's climate. That said, it's easy to understand why some don't believe it's happening: they haven't encountered the information, they don't understand the information, they don't trust the sources to be correct, unbiased, or honest. This last one is I think a major reason in the US today why many don't believe this is a "real" problem.
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