Plot: 2012/08/28 Headlines: Tropical Storm Isaac Threatens Gulf Coast on Katrina's 7th Anniversary; Arctic Sea Ice Melts to Lowest Point as "Worst-Case Scenario" Appears Real; Greenpeace Activists Confront Russian Oil Drilling in Arctic; Israeli Judge Clears Military for 2003 Killing of Rachel Corrie; Syrian Regime Launches Air Strikes Around Damascus; Scores Killed in Taliban Attacks in Afghanistan; No Criminal Charges for U. S