Age: JULIA GILLARD has left open the possibility of abandoning an election promise to not introduce a carbon tax amid a concerted push by energy and mining leaders for swift action on climate change. Responding to BHP Billiton chief executive Marius Kloppers’ call for Australia to embrace a carbon price ahead of other countries, Ms Gillard yesterday refused to rule out a carbon tax, promising that a new cross-party climate change committee would look at all options “in good …