Associated Press: German Chancellor Angela Merkel marked the 20th anniversary of the fall of the Berlin Wall by exhorting the world in a speech to Congress on Tuesday to “tear down the walls of today” and reach a deal to combat global warming. Frequently interrupted by robust applause, Merkel reiterated her country’s commitment to fostering security in Afghanistan and also said that a nuclear bomb in the hands of Iran “is not acceptable.” In the first address by a German chancellor to Congress …