Obama under fire for Air Force One's big carbon footprint on Earth Day

CBS News reporter Mark Knoller called into question Monday on the use of Air Force One on Earth Day at the White House Press Secretary's daily briefing delivered by Josh Earnest:

[Transcript below]

"Mark, I'll give you the last one.
Q    Thanks.  On the Everglades trip, does the president risk undermining his message when he flies to the Everglades on a 747 hundreds of miles to make a statement about climate change?  (Laughter.) 
Q    He could drive.  (laughter.)
MR. EARNEST:  It's a provocative question.
Q    Take a van. 
MR. EARNEST:  But, no, he doesn't.  The president believes that there are important changes that we can make to reduce carbon pollution in this country, and we can do it in a way that will be good for our economy.  That is precisely the case that the president will be making at the Everglades.  And he's looking forward to the trip.
Q    Does he try to minimize the carbon footprint that he leaves whenever he goes anywhere?
MR. EARNEST:  Well, obviously, the Department of Defense and the Presidential Airlift Group at the United States Air Force is responsible for the president's transportation.  So you can talk to them about any steps that they may have taken.
I can say as a general matter that the Department of Defense has acknowledged that climate change does pose a national security threat to the United States.  And there are a lot of practices that the Department of Defense has taken to try to reduce their carbon footprint.  I don't know how that intersects with the use of Air Force One, but you could check with the Air Force on that.
All right?  Thanks, everybody.  Have a good Monday.

Video of the exchange can be seen here: YouTube

Knoller also tweeted an interesting calculation on Earth Day: