This article deals with the problem of fair sharing of a safety cumulative emissions budget up to 2050. Using climate models one may infer the temperature change due to different possible emission pathways provided by world techno-economic models. The negotiations can concentrate then on the fair sharing of the resulting budget. We use two different integrated assessment models. The first is based on TIAM-WORLD, a detailed bottom-up energy model, coupled with the climate model PLASIM-ENTS. Here the supply of quotas on the emissions trading market is decided by a benevolent planner who tries to achieve a fair sharing. In the second approach based on GEMINI-E3, a computable general equilibrium model also coupled with PLASIM-ENTS, the supply of quotas is decided strategically by the regions in- volved in the negotiations. In conclusion the article compares the results and infers some “robust” recommendations concerning the forthcoming negotiations at the next conferences of the parties.