The National ship owning associations of five shipping nations have published a discussion paper about the possibilities of introducing a carbon trading scheme. The paper, which was published yesterday, does not set any targets for cutting emissions, but it suggests that shipping lines could purchase existing permits created for other schemes. The permits would be auctioned and sold to the highest bidder; this would tend to drive up the price of permits, and therefore provide an incentive to reduce emissions. This idea was endorsed by the UK, Australia, Belgium, Norway and Sweden but the shippers organisation in Denmark favours a levy on ships’ fuel.