Environmental activists blocked the entrance to Exxon Mobil's headquarters and climbed onto the roof to protest what they said was the oil company's inaction against global warming. Police said 36 people were arrested Tuesday and would be charged with criminal trespassing. The protesters from the environmental group Greenpeace used an extension ladder to reach the roof. More protesters dressed in tiger costumes — Exxon has long used a tiger as its advertising symbol — were caught at the bottom of the ladder.