It seems that each artist or group of artists got to pick a theme from a list, as no two themes were alike. There was one about windpower:
And one about the curse of the car:
The car one reminded me of an art car, in that it had a lot of little cars glued to it. Art cars frequently have a lot of little things--sometimes other cars--glued to them. (The Art Car is a special Houston art form, and we have a big parade and contest in the spring of Art Cars. There's also an Art Car Museum in Houston.)
This one was about biofuels. It had a nice painting of a corn stalk on it, but it didn't really examine the ethics of using corn for fuel instead of to feed people:
Usually I think that overtly didactic art doesn't work very well. This exhibit proved me right, I think. It's really hard to make something with a clear political message that doesn't beat you over the head with its message. There's so little ambiguity and room for interpretation that the Cool Globes come across more as propaganda than art, albeit propaganda for a good cause.