Andrew C. Revkin talks about the need to use visualizations to make the rather abstract problems of global warming comprehensible. He links to Global Warming Art, which has a bunch of maps and images depicting global warming in one way or another, including this map of temperature anomalies over the past decade:
And this nice map of average annual temperatures:
And this map predicting global warming for the latter part of this century:
And this map of glacier thinning:
And this map of areas at risk from rising sea levels:
And this map of areas affected by tropical storms:
And this topographic map of what an ice-free Antarctica would look like:
Lots of graphs there, too.