John Schellnhuber is one of the world's most influential climate scientists, advising politicians, governments, and influential figures on the numbers behind our warming planet. Not only was he the principal climatologist to the pope for the Encyclical, he’s also the mind who first forwarded the now internationally accepted 2 degree target as the global red-line that shouldn’t be crossed. We speak about the birth of the 2 degree target, what it was like working with the Pope, and what it would mean for the world if Donald Trump became president.