It's almost impossible to have a reasoned debate on this topic; since it's become a presumed "moral" issue, and also is shaping up to be a wedge issue for the U.S. Presidential election.
One thing I've found effective is to challenge "Goreian" global-warming chicken-littles to put their money where their mouth is. Gore bought "Certified Emission Reduction Credits" to make his air travel promoting his slide show and movie "carbon neutral". Tell anyone who insists that this is a crisis and that we have to "do something"; that they can copy Gore; and refer them to the "Survey of Offset Services" at this site:
http://www.freerepublic.com/perl/post?id=1658580%2C1
The price of these "offsets" is about what we would be paying Russia, etc. under Kyoto. Tell them to "put up or shut up". Most won't put up (or shut up either, unfortunately) -- those who do are deluded; but, at least they gain my respect for demonstrating their sincerity. I don't care if they waste their money -- just so long as they don't force me to waste my money too (as Kyoto would have done).
My apologies -- that was clearly the wrong URL. Here's the right one:
http://www.treehugger.com/files/2006/03/survey_of_carbo.php
As you can see by the name; it's a "treehugger" site -- your moonbat friends won't be able to accuse you of referring them to some sort of "oil cabal sponsored, right-wing propaganda site". (Not that I mind such sites :-) )