The new indispensable climate change blogger John Cook of Skeptical Science (sorry Joe, but John is blowing your doors off) just released a nice new pamphlet that simply explains some of the science behind climate change.  See his new related post here and a low-rez PDF (1.7Mb) of his awesome talk last month at the University of Queensland.

On the question of human caused global warming, there’s not just a consensus of scientists – there’s a consensus of evidence. Our understanding of climate doesn’t come from a single line of evidence. We use multiple sets of measurements, using independent methods, to further our understanding. – John Cook

Also see other wonderful resources at skeptical science including the huge list of global warming links and skeptic arguments.  The current number one argument is “It’s the sun”.