Do you accept the basic theory about how greenhouse gases trap heat?
I understand the hypothesis, yes. But there have to be numerous feedback mechanisms and external variables, otherwise, there would never be cooling periods. Since the earth is currently in a colder spell following a much warmer period before (as part of a repeated cycle), I have to assume the hypothesis has its shortcomings.
There are many things we do not understand. Why do we exist and where did the universe come from? I understand the idea that is the big bang theory, but I don't find it very convincing. The first question that one has to ask is: why would there be a big explosion and what came before that? It seems like a rather lousy attempt to have a non-creator explanation for why we are here.
It's ok to accept that we don't understand probably most things.