The report assesses the options for ambitious GHG reduction targets for the Nordic countries in 2050. The options and associated costs for CO2 emission reductions in the Nordic energy and transport sectors and for reduction of non-CO2 climate gases, based on known technologies, are assessed. The energy model Markal-Nordic is used for a system approach analysis of the Nordic energy sector, whereas emission reductions in other sectors are based on individual, existing technologies and associated costs. With the assumptions used in the analysis the Nordic GHG emissions in 2050 are reduced to approximately 40% of the 1990 emissions (e.g. 60% reduction) at costs corresponding to 0.5-1% of GDP. While an 80% reduction is obtained in the Nordic energy sector it is difficult to reach same targets in transport CO2 emissions and in emissions of other gasses, particularly in the agricultural sector. Rather conservative assumptions have been applied, and additional reductions may be obtained by import of biomass and development of improved technologies.   Rapporten vurderer ambitiøse reduktioner af udledningerne af klimagasser fra de nordiske lande i 2050. Mulighederne for, med kendte teknologier, at reducere udledningen af CO2 fra den nordiske energisektor og transportsektor samt udledningerne af andre klimagasser end CO2 analyseres og de tilhørende omkostninger for samfundet vurderes. Energimodellen Markal-Nordic anvendes til en samlet systemanalyse af den nordiske energisektor, mens der for øvrige reduktionsmuligheder identificeres eksisterende reduktionsteknologier med tilhørende omkostninger. Med de anvendte forudsætninger reduceres de nordiske emissioner i 2050 til 40% af 1990 emissionen (ca. 60% reduktion) ved omkostninger på 0,5-1% af BNP. Mens der opnås 80% reduktion i energisektoren er det vanskeligere at nå tilsvarende reduktioner i transportsektoren og landbrugssektoren. Der er anvendt relativt konservative forudsætninger, og yderligere reduktioner kan opnås, bl.a. ved import af biomasse og udvikling af nye teknologier.