he's fun to argue with
Bill Clinton was known for taking on positions completely at odds with his actual views and arguing them behind closed doors in front of his staff, to force them to know their stuff as well as he did. Nelder is good for that - in as much as he argues for an imminent clean energy revolution right now (as opposed to 20 years from now). He's making lots of predictions that are going to look silly in another 5 years though .... the US energy numbers are changing by a lot, and pretending they aren't doesn't promote credibility.