In this campaign video, Sen. John McCainJohn McCainBush biographer: Trump has moved the goalpost for civilized society White House to pressure McConnell on ObamaCare McCain: Trump needs to state difference between bigots and those fighting hate MORE (R-Ariz.) said he'd be a leader in global warming reform if he's elected president.

"Americans, I don't think, appreciate the fergility of our environment nor do they understand completely how vulnerable we are in our dependency of foreign oil," McCain said.