Massive greenhouse gas emission reductions are needed in order to mitigate climate change. The reductions will pose dramatic changes in today's mainly fossil fuel based energy system. Improving energy efficiency and increasing the use of renewable energy sources and nuclear energy are significant means to reduce emissions. Technology plays an important role in enabling deep greenhouse gas emission reductions. This report presents scenario calculations for the Finnish energy system using the TIMES energy system model available at VTT. The calculations provide estimates, which technologies would be economically optimal to apply in order to reach the emission reduction targets. Scenarios have been developed for alternative development pathways of technology, the Finnish energy system and international emissions trading. The aim of the scenarios was to estimate, how Finland could respond to the recent IPCC estimate that effective mitigate climate change mitigation requires global emissions reductions in the order of 50-85% by the year 2050, and to the EU goal of reducing emissions by 60-80% by the year 2050. In Finland, GHG emissions can be reduced by 60-66% from 1990 to 2050, if emission allowance prices remain less than 80 €/t(CO 2-ekv.) Increased energy use efficiency becomes an important factor in emissions reductions by 2050. Key reduction technologies in energy production are bioenergy technologies, wind power and nuclear power. The cost-efficient amount of these technologies in the Finnish energy system varies depending on assumptions of emissions trading price development, technology development and other possible constraints. A major part of the technology opportunities are already on the market and therefore immediately applicable. The adoption is restricted by costs and long investment cycles in many of the applications. By the year 2050, also the Finnish climate will change considerably. Besides the major general harmful effects, heating requirements decrease, cooling needs increase, and wind power and hydro power potentials are estimated to increase.