Both the UK and the EU have pinned much of their climate change policy on the effective operation of the EU emissions trading system (ETS). Now in its second year the scheme has yet to demonstrate that it can deliver the substantial greenhouse gas emission reductions that will form the yardstick of its success. This report examines the proposed revisions to the ETS, which would take effect in the scheme’s third trading period, scheduled to last from 2013 to 2020. It is ultimately felt that if the ETS is to live up to its full potential, the aim must be to link it up with emissions trading schemes in other parts of the world so as to make the most of emission reduction opportunities in additional countries and sectors. However, the establishment of such links could prove arduous. It is anticipated that the EU may eventually face stark trade-offs between maintaining the environmental integrity of the ETS and extending its reach.