0Jeffrey SachsAs Obama addresses the U.N. climate summit, Jeffrey Sachs warns that dangerous changes are happening much faster than politicians have even begun to grasp.Updated Jul. 14, 2017 5:25PM EDT / Published Sep. 21, 2009 12:17PM EDT AP Photo AP Photo Bill Pugliano / Getty Images Alex Wong / Getty Images DEA, C. SAPPA / De Agostini/Getty Images Rodrigo Baleia / Getty Images Denis Balibouse / Reuters Roberto Schmidt / Newscom TSVANGIRAYI MUKWAZHI Elise Amendola / AP Photo Daniel Berehulak / Getty Images
AP Photo Bill Pugliano / Getty Images Alex Wong / Getty Images DEA, C. SAPPA / De Agostini/Getty Images Rodrigo Baleia / Getty Images Denis Balibouse / Reuters Roberto Schmidt / Newscom TSVANGIRAYI MUKWAZHI Elise Amendola / AP Photo Daniel Berehulak / Getty Images