Anyone know of local, credible speaker on global warming issue?

My oldest son (4th grader) is involved in his school's science club/robotics club. It's competes in the FIRST LEGO League (http://www.firstlegoleague.org/default.aspx?pid=70). It's cool stuff, and teaches very good logic, problem-solving, team-working and other beneficial activities.

Last year's focus was on alternative energy.

This year's is on global warming. Last night, as part of "research," the team watched Al Gore's (supposed) documentary on global warming.

While I don't doubt global warming for the most part, I have concerns about how it's presented and how any causes are explained. So, to balance out last night's movie, I thought it be nice to look for an opposing or at least a more credible speaker to address global warming.

If anyone knows of any possibilities, either leave a comment or contact me (miked918 at Yahoo dot com).
Thank you.
-Mike