U.N. warns world must take “unprecedented” steps to avert worst effects of global warming

A United Nations logo is seen on a glass door in the Assembly Building at the United Nations headquarters in New York City September 18, 2015. Reuters photographer Mike Segar documented quieter moments at the famed 18-acre headquarters on Manhattan’s East Side. The U.N., established as the successor to the failed League of Nations after World War Two to prevent a similar conflict from occurring again, attracts more than a million visitors every year to its iconic New York site. The maratho