No he's not and let me give you a technical answer why. If you let the entire video load, and jump around with your mouse to different area's, you'll see that the background lighting on the trees get's lighter and darker. Now, that doesn't automatically mean it's not a green screen - it just means that the background is not a static picture - it could be a moving video shot that is running on the green screen. However, also look at Obama's head, forehead and podium the lighting also changes with the background (there are probably lights facing him as well so the give away is the side and top of his head and shoulders). So I don't think he's in front of a green screen.
Interesting.... I had no idea what to look for to know if it was a green screen or not.