The paper uses the framework of the IPAT equation, as applied to CO2 emission, to decompose the various driving forces in the global energy use. Data from recent history are superimposed on projections of SRES IPCC scenarios to determine if enough sustainable capacity can be built to prevent irreversible ecological deterioration. The conclusion from the analysis is that, in agreement with the IPCC 4th report, until about 2030 there are no large differences between a sustainable scenario and the one that resembles “business as usual”. The sharp divergence that follows stems from different estimates in population growth and in the percentage of use of fossil fuels in the total energy mix. Decomposition of alternative energy options indicate that the rate of increase of alternatives such as hydroelectric and nuclear start with a relatively high base but a growth rate too short for major contribution to a timely replacement of fossil fuels while wind and solar starts from a much lower base but rate of growth, if maintained, that can satisfy a timely replacement.