According to Joseph Romm at ClimateProgress, this is "Obama’s strongest message on climate yet".
"I have known Holdren for over a decade and have discussed energy/climate issues with him many times. He probably has more combined expertise on both climate science and clean energy technology than any other person who could plausibly have been named science adviser."
“I am one of those who believes that any reasonably comprehensive and up-to-date look at the evidence makes clear that civilization has already generated dangerous anthropogenic interference in the climate system,” Dr. Holdren said. “What keeps me going is my belief that there is still a chance of avoiding catastrophe.”
Great to see another scientist aware of the importance of addressing climate change (and another physicist!) appointed to Obama's cabinet. It's certainly looking like he's serious about addressing climate change, and not just talk.