This is a great post on Gristmill (courtesy Brad DeLong):
How to Talk to a Climate Skeptic
Below is a complete listing of the articles in “How to Talk to a Climate Skeptic,” a series by Coby Beck containing responses to the most common skeptical arguments on global warming. There are four separate taxonomies; arguments are divided by:
What follows is a very detailed outline under each heading. The post notes that the same article may appear in multiple listings.