This Research Report serves as a technical explanation of the MARKAL and MARKAL-Macro (M-M) model analysis, to be included in the 2007 Energy White Paper, of the long-term impacts and associated uncertainties of a 60 per cent reduction in CO2 emissions by 2050. It is a companion report to the policy focused DTI report 'The MARKAL energy model in the 2007 Energy White Paper' (DTI, 2007).