Because any good scientist will understand why something is the way it is before they try to predict what it will do in the future. You don't know why the earth's climate is the way it is or what that means for today's conversation.Why do you assume that my lack of knoweldge of ONE TINY PORTION of the earth's climatic history would indicate that have a profound lack of knowledge of the topic? Much less how do you thus "prove" it?
You DO know what "prove" means, correct?
In the real sciences we seldom deal in "proofs" (that's mathematics). We always couch our findings in language such as "the most likely correct hypothesis". There is always information that we don't have, errors in the measurements, etc. So the best you can do is to come asymptotically close to "proof" while never really getting there.
There's a reason that p-values are never perfectly zero.