In my experience, it's usually a lack of trust. Sure, we can bombard conservatives with hard data all day long, but they'll just scoff at it because they have no way of validating whether that data is even slightly accurate. The fact that this data then seems to justify stronger federal regulation means that the average conservative will distrust it entirely, treating such research as "propaganda" or "fake news".

This is not unique to stereotypical "conservatives", either. For example, a lot of American Indian / First Nations tribes firmly believe - as they always have - that they originate from the Americas. Convincing folks otherwise (i.e. that their ancestors were more likely to have immigrated via Beringia, as current archaeological evidence suggests) is difficult; after centuries of the "white man" lying through their teeth in the name of "science", their skepticism toward some new scientific "fact" is unsurprising and understandable (and unfortunate).

Same thing with climate change deniers. They've been conditioned to distrust most outside information already; distrusting the evidence for climate change is thus unsurprising and unfortunate.

In my own experience, I've found that convincing folks that climate change is actually happening is the easy part. The hard part is convincing them that humans are causing it.