Hill: The National Park Service (NPS) is walking back comments that showcased doubts about whether natural gas development can help battle climate change, acknowledging they did not receive appropriate review. NPS Director Jonathan Jarvis, in a letter to a House Republican, withdrew the unsigned comments that the service sent months ago to a separate federal agency crafting regulations on hydraulic fracturing. Jarvis, in his mid-November letter to Rep. Rob Bishop (R-Utah), said nobody in management...