signature climate achievement, the paris agreement? in december of 2015, in the city of light, 196 nations agreed by consensus to limit the planet's warming to two degrees celsius. that's a threshold many scientists believe will prevent disaster. >> of course, it took a long time to reach this day. one of the reasons i ran for this office was to make america a leader in this mission. >> and america is now undoubtedly a leader. perhaps the leader on climate change. clean energy is a vast and growing american industry. and more than 100 countries have signed on to the paris agreement which went into legal effect just four days before the 2016 presidential election. >> if 20, 30, 50 years from now we look back and we say we dealt