David is just a moron.
I'm not so sure. Gore, like most politicians, is incredibly intellectually shallow. He never even waded through a first semester physics or chemistry class. I don't know how he can make any judgment, except by recourse to authority. The problem with "recourse to authority" is that you can become susceptible to choosing authorities who confirm your prejudices.
My personal take is that a small amount man-made (anthroprogenic, if you will) global warming is probably real, but benign at worst.