J. Bob: 
Here are 2 references you might find interesting.  The 1st is a summary of the current evidence:
http://www.ucsusa.org/global_warming/science_and_impacts/science/human-contribution-to-gw-faq.html#.WOCXn_cpDqA

The 2d is a thoughtful reply to climate deniers:
https://thinkprogress.org/how-do-we-really-know-humans-are-causing-global-warming-3915e5e8d2ea