In the sentence "I hope you are all paying attention, here is a sentence I made earlier", is here an adverb or a noun? I think it is a noun, but if I substitute a noun or a pronoun for here, the sentence loses its intended meaning.
John Lawler notes in a comment on a different answer here:
Alas, no. It's still an adverb. The construction Here/There is/are
Noun Phraseallows the adverb to be fronted, with the subject
Noun Phrasemoved to the end, as the new information. It's said either referring to a physical place (pointing is appropriate), or metaphorically to refer to things that are being said in the conversation. Here is
Xgenerally means 'The next thing I say is
the sentence, "I hope you are all paying attention, here is a sentence I made earlier" is a type of run-on sentence known as a comma splice. correctly written it should read. "I hope you are all paying attention. Here is a sentence I made earlier." Rewritten correctly, "Here" becomes the subject of the second sentence and thus, a noun
looking at it a different way, an adverb is a word that modifies a verb. In either the original sentences or my rewritten version "Here" is not modifying a verb or anything else for that matter and thus is not an adverb.