I remember my reaction the first time I met John Holdren: my jaw was on the floor. Once I picked it up, I wrote to a friend:
I saw John Holdren speak last night on global warming. It was one of the greatest technical talks I've ever seen. Without slides or anything, he simply walked through the whole subject, explaining every piece of the logic and the implications, taking every counterclaim and quietly dismantling it with cogent reason -- and doing the same in response to any questions, with apparently exhaustive knowledge of the subject. The audience was captivated. I can see why he's president of the AAAS [the main professional organization for scientists].
I've since had several more chances to talk to him and while my opinion has grown more nuanced, I can't think of anyone better to be Obama's science advisor and head of the Office of Science and Technology Policy. John Holdren has spent his career trying to save the planet: recently, that's meant doing everything he can to stop global warming. Before that, he accepted a Nobel Peace Prize on behalf of Pugwash for their attempts to stop nuclear proliferation.
But he's also a brilliant scientist. He won a MacArthur "genius" grant, has written dozens of books, and teaches at Harvard. It will be great having a President who takes his science advice from someone who truly knows and cares.