The Triptych approach is a method for allocating future greenhouse gas (GHG) emission reductions among countries under a post-2012 international climate mitigation regime based on technological criteria at the sector level, and accounting for structural differences. The emission allowances are decomposed according to sectors, thereby enabling the link to real-world emission reduction strategies to be more concrete. The new Triptych approach presented here is a refinement of an earlier version in terms of an increased transparency and allowing a delayed participation for developing countries (initial participation of developing countries with incentives but no penalties through 'no lose' targets or sustainable development policies and measures). For this article we calculated the emission reductions for countries for two technology-oriented scenarios, which stabilize GHG concentrations at 450 and 550 ppm CO2-eq, respectively. The reductions are ambitious, but nonetheless compatible with existing technical reduction potentials as growth is allowed but efficiency has to be improved. (C) 2007 Elsevier Ltd. All rights reserved.