This did pique my curiosity, so I had a look at Google Ngram viewer which gave: https://books.google.com/ngrams/graph?content=global+warming%2Cclimate+change&y

This did pique my curiosity, so I had a look at Google Ngram viewer which gave: https://books.google.com/ngrams/graph?content=global+warming%2Cclimate+change&year_start=1960&year_end=2012&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Cglobal%20warming%3B%2Cc0%3B.t1%3B%2Cclimate%20change%3B%2Cc0 https://books.google.com/ngrams/graph?content=global+warming... It looks from that like the two phrases were equally popular till 1994, when "Climate Change" suddenly took off. There was never a point where "Global Warming" was significantly more popular. Do you know of any other places I can check this?