Reuters: U.S. flexibility in negotiating a global warming pact depends on passing a law to cut greenhouse gas emissions, which is not an insurmountable task, Washington’s top climate envoy said on Thursday. “We are going to fundamentally be guided by what happens in our own legislative process,” Todd Stern, the U.S. Special Envoy for Climate Change, told Reuters in an interview when asked whether there was room for maneuver in the U.S. stance at U.N. climate talks. President Barack …