Politico: Black police vans, with sirens screaming and occupants clutching semiautomatic rifles, barreled past the iconic Marble Church here Sunday, rattling the nerves of climate change conferees trying to enjoy a final break before this week’s intense finale. That collective flinch — after a weekend of mass protests and arrests — summed up the unsettled mood heading into an unpredictable week of negotiations, demonstrations and speeches by a diverse group of leaders including Al Gore, …