Carson made a name for himself in politics: first as press secretary for the Howard Dean and Hillary Clinton presidential campaigns in 2004 and 2008, then as chief deputy mayor of Los Angeles. Now, he's become a force in climate action: As CEO of the C40 Cities Climate Leadership Group and Senior Advisor to Bloomberg Philanthropies, Carson has overseen the strategic alliance of Mayor Michael Bloomberg and President Bill Clinton's work on climate action to run a robust, international group helping cities go green and prepare for the realities of adapting to climate conditions. (Carson also helped inspire Ryan Gosling's character in the current major motion picture, "The Ides of March.")

Environment,