Below is a screen shot for the Academic OneFile database. It shows a Basic Search by Keyword using the search term "global warming."  The Keyword option of a Basic Search lets you search on significant fields in documents, including titles, introductory text, authors, and subject terms.  This option searches a broader range of fields than more specific searches by title or subject.  Keyword searches work well for less common terms such as proper nouns.

 Let's look at the results from this search to see if there are any helpful articles about global warming.