The International Energy Agency has developped a number of scenarios that describe the efforts needed to reduce carbon dioxide emissions. The "business-as-usual" Baseline scenario foreshadows the situation in the absence of policy change and major supply constraints leading to increases in oil demand and CO2 emissions. Other scenarios explore different technological pathways to achieve emission reductions, and, the "Energy technology perspectives" report groups the scenarios into two main subgroups, depending on emission reduction objectives: The "ACT" scenarios bring back CO2 emissions to 2005 levels by 2050 through a number of technological developpments. The "BLUE" scenarios are more ambitious, bringing emissions at 50% of the 2005 level by 2050. This implies of course higher investment costs, but also greater needs in technological and policy developments.