Its not much different to Gillard saying there would be no carbon tax 2010, then introducing a carbon tax because the Greens made her, then Shorten shooting Gillard and installing Rudd, and Rudd promising to scrap the tax if he won in 2013.
I don't know what Shorten's policy is - I don't think even he does, but no doubt Labor would introduce a carbon tax to pay welfare to the Muslim refugees who would flood the country at a rate of 1,000 a week like last time they mismanaged the country.