What I have observed in many people is that they DO understand, but not deeply. That is, they might understand that CO2 is causing problems for us, but if you then go on to talk about ways to reduce that, they understand that part, but can't make a strong "then we obviously need to" connection. It's like you've given them ice cubes to build a wall but it's hot and the ice is melting as they try to build it.

Or a train of logic: A to B to C to D. Each step is understood, but by the time you reach D, And B are melting away. They've become fuzzy facts, things they aren't sure of anymore.

Connections are everything. Connections let us see answers even when we have no experience with the question. That's called creativity by some, but at it's heart it is strong connections.