EBSCO maintains a thesaurus of keywords to help you make sure that your search is more specific.
For example, if you search for articles with 'global warming' in the title you will find over 3000 results appear.
From your search results list, use the drop-down option on the left of the screen Subject
You'll see a selection of subject terms based on the search you ran. Tick the ones that are relevant to your search and then Update. You will now have a smaller set of results to consider.