Dr. John Holdren on Late Show with David Letterman

"There is a huge difference between how much climate change we can expect if we do nothing, and how much climate change we can expect if we do a lot in the way of reducing our emissions...It gets more and more difficult to cope with the impacts of climate change the higher we go. And there is a huge difference between being at, let us say, 3.6°F above pre-industrial — we're around 1.5°F now above pre-industrial — huge difference between that and 10°F above pre-industrial. We're much better off at the lower number, and we can get there."

- Dr. John Holdren, Director of the White House Office of Science and Technology Policy