Joy Miller of Hallandale Beach asked Gore about carbon credits and offsets -- "buying our way out of the problem."

You won't be surprised to hear that Gore's answer was wonky and careful and came in parts. He said credits are a "good thing" if the standards and information are in place to validate their quality. "The economy can be an ally," and we know cap-and-trade systems work.

However, if used irresponsibly, as a substitute for direct reductions, they can be counterproductive. (The same issues face individuals with voluntary offsets.)

That segued into a discussion of the EU trading system and the "rocky start" of its first few years -- poor baseline calculations, over-allocation of permits, too-low initial price -- which are now being ironed out. Most of the real reductions in the world are coming from this system. "We can make this work."

He also said trade in carbon credits can serve as a bridge to build relationships between the North and South.