Scientific America: A massive climate bill has taken its first step forward in the House, its path paved by the giveaway of allowances — free greenhouse gas emission permits designed to mute the economic impact of a carbon cap-and-trade program. Free allowances — each conveying the right to pump a ton of greenhouse gases into the atmosphere — were the glue that held the sprawling bill together for Reps. Henry Waxman (D-Calif.) and Ed Markey (D-Mass.) and fellow Democrats on the Energy and Commerce …