Greenwire: Rep. Collin Peterson, the outspoken House Agriculture Committee chairman who has emerged as a key figure in the climate debate, is used to rocking the house. He has done so, guitar in hand, at night clubs, the Grand Ole Opry and Farm Aid as the leader of rock-country bands. And with gavel in hand, he has often rocked the boat in Congress, frequently going against his party on key votes and fighting for fiscal restraint as a founding member of the conservative “Blue Dog” …