Kev,
Al Gore is playing the role of scientific journalist and bringing the findings of the worldwide community of climatologists to the attention of the public. Al Gore did not invent the science that supports the AGW concern, and neither did he contribute to it in any way. Al Gore is a self-appointed messenger, but he did not originate the message himself.
Al Gore is doing what he has done for his entire career, which is to attempt to affect public policy based on the implications of science and technology. An example of previous work by Al Gore when he was a Senator is
The High Performance Computing and Communications Act of 1991, where he took the initiative to advocate and popularize the idea that a public worldwide network of computers would be a boon to all areas of life. He created the bill and wrote articles in the popular press and spoke to congress to raise people's awareness of the implications of the technology and the value of funding it.
Later on, he lectured and spoke often about the value of an "Information Super Highway" when he was VP. His early advocacy led directly to the funding of the technologies that went into the present day Internet. And his later advocacy led to the public awareness and eventual public adoption of the Internet.
At the time, it might have been appropriate to debate Al Gore on his recommendations for funding high speed computer networks, but it would have been ridiculous to suggest that anyone should debate Al Gore on network design theory itself. Would you suggest that we should have debated Al Gore on the merits of Token Ring networks vs Ethernet networks, or the merits of the TCP/IP stack?
Al Gore was following in the footsteps of his father who, as a Senator, was instrumental in convincing congress to fund the development of a National Highway System in the 1950s. I wonder if at the time, people were calling for a debate with Al Gore Sr. over whether asphalt was better than cement for a highway? I don't think so.
Al Gore's role, then and now, is to advocate for changing public policy based on the findings of the technical or the scientific community. Al Gore did not invent the technology of networks nor did he invent the science of AGW.
Debating Al Gore on the science of AGW makes as much sense as debating any other journalist who reports on the the findings of the scientific community.