The presentation will focus on post-2012 options to reduce greenhouse gas (GHG) emissions, putting special emphasis on the need to abate world emissions. The presentation will focus on post-2012 options to reduce greenhouse 27 gas (GHG) emissions, putting special emphasis on the need to abate world emissions at least cost, which in turn requires the need to select a least-cost set of policy instruments. In particular, model simulations will be presented to discuss whether and how price instruments should be combined with technology- support policies in order to reduce overall mitigation costs. On a more speculative note, the potential implications for climate policy design of the uncertainties surrounding both future damages from climate change and mitigation costs will be discussed.