Here's a very clear, readable and well-researched site on how to respond to climate change skeptics. A great example of what you will find runs as follows:
So 2005 was a record year, one really warm year or two is not global warming.
This kind of objection only indicates an unfamiliarity with the actual long term temperature record and is just asking for a few good temperature facts, so let 'em have it!
2005 breaking the record is not convincing? Let's see then, how about: