Chicago Tribune: It wasn’t long ago that Marco Rubio and Tim Pawlenty, two of the brightest fresh faces in the Republican Party, supported legislation to limit the greenhouse gas emissions that are blamed for global warming. But in recent weeks both have suddenly begun to express doubts about whether burning coal, powering cars with gasoline and other human activities in fact have anything to do with a warming Earth. The shifts by Rubio and Pawlenty — as well as other prominent Republicans — reflect …