you'd need to explore the connotations of the noun 'warning' it connotes deterrence and message . the purpose of an author is usually to spread a message so the author has deliberately started the passage with 'warning' to reassure the reader that they are here to bring the message , it could also be used to emphasise the dramatic his intended audience are as the warning also holds dramatic connotations , it could also allow the reader to relate with the author as they could both be seen as overly dramatic
