The book describes the rationale and implications of the lEA's BLUE Map Scenario, which explores the energy policy and technology options needed to achieve a 50% reduction in global energy-related C02 emissions by 2050. The analysis indicated that achieving such reductions would require maximum implementation of energy efficiency worldwide and a virtually decarbonised power sector (Figure ES.l). The decarbonisation of the power sector, in particular, poses a major challenge. The goal was to refine the ETP2008 scenarios and to assess their viability in greater detail.